diff mbox series

[v4,1/2] riscv: Add remaining module relocations

Message ID	20231017-module_relocations-v4-1-937f5ef316f0@rivosinc.com
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33; From: Charlie Jenkins <charlie@rivosinc.com> Date: Tue, 17 Oct 2023 22:34:16 -0700 Subject: [PATCH v4 1/2] riscv: Add remaining module relocations MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20231017-module_relocations-v4-1-937f5ef316f0@rivosinc.com> References: <20231017-module_relocations-v4-0-937f5ef316f0@rivosinc.com> In-Reply-To: <20231017-module_relocations-v4-0-937f5ef316f0@rivosinc.com> To: linux-riscv@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Eric Biederman <ebiederm@xmission.com>, Kees Cook <keescook@chromium.org>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Charlie Jenkins <charlie@rivosinc.com> Precedence: bulk
Series	riscv: Add remaining module relocations and tests \| [v4,0/2] riscv: Add remaining module relocations and tests [v4,1/2] riscv: Add remaining module relocations [v4,2/2] riscv: Add tests for riscv module loading

Commit Message

Charlie Jenkins Oct. 18, 2023, 5:34 a.m. UTC

  Add all final module relocations and add error logs explaining the ones
that are not supported.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
 arch/riscv/include/uapi/asm/elf.h |   5 +-
 arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
 2 files changed, 186 insertions(+), 26 deletions(-)

Comments

Emil Renner Berthing Oct. 18, 2023, 12:17 p.m. UTC | #1

Charlie Jenkins wrote:
> Add all final module relocations and add error logs explaining the ones
> that are not supported.
>
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
>  arch/riscv/include/uapi/asm/elf.h |   5 +-
>  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
>  2 files changed, 186 insertions(+), 26 deletions(-)
>
> diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> index d696d6610231..11a71b8533d5 100644
> --- a/arch/riscv/include/uapi/asm/elf.h
> +++ b/arch/riscv/include/uapi/asm/elf.h
> @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_TLS_DTPREL64	9
>  #define R_RISCV_TLS_TPREL32	10
>  #define R_RISCV_TLS_TPREL64	11
> +#define R_RISCV_IRELATIVE	58
>
>  /* Relocation types not used by the dynamic linker */
>  #define R_RISCV_BRANCH		16
> @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_ALIGN		43
>  #define R_RISCV_RVC_BRANCH	44
>  #define R_RISCV_RVC_JUMP	45
> -#define R_RISCV_LUI		46
>  #define R_RISCV_GPREL_I		47
>  #define R_RISCV_GPREL_S		48
>  #define R_RISCV_TPREL_I		49
> @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_SET16		55
>  #define R_RISCV_SET32		56
>  #define R_RISCV_32_PCREL	57
> +#define R_RISCV_PLT32		59
> +#define R_RISCV_SET_ULEB128	60
> +#define R_RISCV_SUB_ULEB128	61
>
>
>  #endif /* _UAPI_ASM_RISCV_ELF_H */
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index 7c651d55fcbd..e860726352ac 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -7,6 +7,7 @@
>  #include <linux/elf.h>
>  #include <linux/err.h>
>  #include <linux/errno.h>
> +#include <linux/kernel.h>
>  #include <linux/moduleloader.h>
>  #include <linux/vmalloc.h>
>  #include <linux/sizes.h>
> @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
>  	return -EINVAL;
>  }
>
> +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location += (u8)v;
> +	return 0;
> +}
> +
>  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
>  				    Elf_Addr v)
>  {
> @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
>  	return 0;
>  }
>
> +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location -= (u8)v;
> +	return 0;
> +}
> +
>  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
>  				    Elf_Addr v)
>  {
> @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
>  	return 0;
>  }
>
> -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> -				Elf_Addr v) = {
> -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> +					 Elf_Addr v)
> +{
> +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> +	       me->name, location);
> +	return -EINVAL;
> +}
> +
> +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> +	       me->name, location);
> +	return -EINVAL;
> +}
> +
> +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (u8)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u16 *)location = (u16)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> +				       Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	/*
> +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> +	 * R_RISCV_SUB_ULEB128 so do computation there
> +	 */
> +	return 0;
> +}
> +
> +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	if (v >= 128) {
> +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> +		       me->name, (unsigned long)v, location);
> +		return -EINVAL;
> +	}
> +
> +	*location = v;
> +	return 0;
> +}
> +
> +/*
> + * Relocations defined in the riscv-elf-psabi-doc.
> + * This handles static linking only.
> + */
> +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> +				    Elf_Addr v) = {
> +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> +	/* 12-15 undefined */
> +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> +	/* 41-42 reserved for future standard use */
> +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> +	/* 46-50 reserved for future standard use */
> +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> +	/* 62-191 reserved for future standard use */
> +	/* 192-255 nonstandard ABI extensions  */
>  };

Hi Charlie,

This is not a critique of this patch, but all these callbacks take a
u32 *location and
because of the compressed instructions this pointer may not be
aligned, so a lot of
the callbacks end up doing unaligned access which may fault to an
M-mode handler on
some platforms.

I once sent a patch to fix this:
https://lore.kernel.org/linux-riscv/20220224152456.493365-2-kernel@esmil.dk/

Maybe that's something you want to look into while touching this code anyway.

/Emil
>
>  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  	unsigned int i, type;
>  	Elf_Addr v;
>  	int res;
> +	bool uleb128_set_exists = false;
> +	u32 *uleb128_set_loc;
> +	unsigned long uleb128_set_sym_val;
> +
>
>  	pr_debug("Applying relocate section %u to %u\n", relsec,
>  	       sechdrs[relsec].sh_info);
> @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  				  me->name);
>  				return -EINVAL;
>  			}
> +		} else if (type == R_RISCV_SET_ULEB128) {
> +			if (uleb128_set_exists) {
> +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> +				       me->name);
> +				return -EINVAL;
> +			}
> +			uleb128_set_exists = true;
> +			uleb128_set_loc = location;
> +			uleb128_set_sym_val =
> +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> +					ELF_RISCV_R_SYM(rel[i].r_info))
> +					->st_value +
> +				rel[i].r_addend;
> +		} else if (type == R_RISCV_SUB_ULEB128) {
> +			if (uleb128_set_exists && uleb128_set_loc == location) {
> +				/* Calculate set and subtraction */
> +				v = uleb128_set_sym_val - v;
> +			} else {
> +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> +				       me->name, location);
> +				return -EINVAL;
> +			}
>  		}
>
>  		res = handler(me, location, v);
>
> --
> 2.34.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Samuel Holland Oct. 18, 2023, 6:28 p.m. UTC | #2

On 2023-10-18 12:34 AM, Charlie Jenkins wrote:
> Add all final module relocations and add error logs explaining the ones
> that are not supported.
> 
> Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
>  arch/riscv/include/uapi/asm/elf.h |   5 +-
>  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
>  2 files changed, 186 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> index d696d6610231..11a71b8533d5 100644
> --- a/arch/riscv/include/uapi/asm/elf.h
> +++ b/arch/riscv/include/uapi/asm/elf.h
> @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_TLS_DTPREL64	9
>  #define R_RISCV_TLS_TPREL32	10
>  #define R_RISCV_TLS_TPREL64	11
> +#define R_RISCV_IRELATIVE	58
>  
>  /* Relocation types not used by the dynamic linker */
>  #define R_RISCV_BRANCH		16
> @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_ALIGN		43
>  #define R_RISCV_RVC_BRANCH	44
>  #define R_RISCV_RVC_JUMP	45
> -#define R_RISCV_LUI		46
>  #define R_RISCV_GPREL_I		47
>  #define R_RISCV_GPREL_S		48
>  #define R_RISCV_TPREL_I		49
> @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
>  #define R_RISCV_SET16		55
>  #define R_RISCV_SET32		56
>  #define R_RISCV_32_PCREL	57
> +#define R_RISCV_PLT32		59
> +#define R_RISCV_SET_ULEB128	60
> +#define R_RISCV_SUB_ULEB128	61
>  
>  
>  #endif /* _UAPI_ASM_RISCV_ELF_H */
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index 7c651d55fcbd..e860726352ac 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -7,6 +7,7 @@
>  #include <linux/elf.h>
>  #include <linux/err.h>
>  #include <linux/errno.h>
> +#include <linux/kernel.h>
>  #include <linux/moduleloader.h>
>  #include <linux/vmalloc.h>
>  #include <linux/sizes.h>
> @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
>  	return -EINVAL;
>  }
>  
> +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location += (u8)v;
> +	return 0;
> +}
> +
>  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
>  				    Elf_Addr v)
>  {
> @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
>  	return 0;
>  }
>  
> +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location -= (u8)v;
> +	return 0;
> +}
> +
>  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
>  				    Elf_Addr v)
>  {
> @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
>  	return 0;
>  }
>  
> -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> -				Elf_Addr v) = {
> -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> +					 Elf_Addr v)
> +{
> +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> +	       me->name, location);
> +	return -EINVAL;
> +}
> +
> +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> +	       me->name, location);
> +	return -EINVAL;
> +}
> +
> +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (u8)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u16 *)location = (u16)v;
> +	return 0;
> +}
> +
> +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;

You don't need to cast the pointer, since it's already a `u32 *`.

> +	return 0;
> +}
> +
> +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> +				       Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;

This expression should be:

    *location = v - location;

matching the other PC-relative relocations.

(BTW, recent clang generates these relocations for module alternatives.)

> +	return 0;
> +}
> +
> +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> +				    Elf_Addr v)
> +{
> +	*(u32 *)location = (u32)v;

This should look like apply_r_riscv_32_pcrel_rela(), but with the PLT entry
emission code from apply_r_riscv_call_plt_rela(). See the psABI commit[1].

[1]:
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/c3f8269c56d8a2f56c2602f2a44175362024ef9c

> +	return 0;
> +}
> +
> +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	/*
> +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> +	 * R_RISCV_SUB_ULEB128 so do computation there
> +	 */
> +	return 0;
> +}
> +
> +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	if (v >= 128) {
> +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> +		       me->name, (unsigned long)v, location);
> +		return -EINVAL;
> +	}
> +
> +	*location = v;
> +	return 0;
> +}
> +
> +/*
> + * Relocations defined in the riscv-elf-psabi-doc.
> + * This handles static linking only.
> + */
> +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> +				    Elf_Addr v) = {
> +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> +	/* 12-15 undefined */
> +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> +	/* 41-42 reserved for future standard use */
> +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> +	/* 46-50 reserved for future standard use */
> +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> +	/* 62-191 reserved for future standard use */
> +	/* 192-255 nonstandard ABI extensions  */
>  };
>  
>  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  	unsigned int i, type;
>  	Elf_Addr v;
>  	int res;
> +	bool uleb128_set_exists = false;
> +	u32 *uleb128_set_loc;
> +	unsigned long uleb128_set_sym_val;
> +

Extra blank line.

>  
>  	pr_debug("Applying relocate section %u to %u\n", relsec,
>  	       sechdrs[relsec].sh_info);
> @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>  				  me->name);
>  				return -EINVAL;
>  			}
> +		} else if (type == R_RISCV_SET_ULEB128) {
> +			if (uleb128_set_exists) {
> +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> +				       me->name);
> +				return -EINVAL;
> +			}
> +			uleb128_set_exists = true;
> +			uleb128_set_loc = location;
> +			uleb128_set_sym_val =
> +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> +					ELF_RISCV_R_SYM(rel[i].r_info))
> +					->st_value +
> +				rel[i].r_addend;
> +		} else if (type == R_RISCV_SUB_ULEB128) {
> +			if (uleb128_set_exists && uleb128_set_loc == location) {
> +				/* Calculate set and subtraction */
> +				v = uleb128_set_sym_val - v;

You need to set uleb128_set_exists back to false somewhere, or you can only
handle one R_RISCV_SET_ULEB128 relocation per module.

Regards,
Samuel

> +			} else {
> +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> +				       me->name, location);
> +				return -EINVAL;
> +			}
>  		}
>  
>  		res = handler(me, location, v);
>

Charlie Jenkins Oct. 18, 2023, 6:31 p.m. UTC | #3

On Wed, Oct 18, 2023 at 05:17:44AM -0700, Emil Renner Berthing wrote:
> Charlie Jenkins wrote:
> > Add all final module relocations and add error logs explaining the ones
> > that are not supported.
> >
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> >  arch/riscv/include/uapi/asm/elf.h |   5 +-
> >  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
> >  2 files changed, 186 insertions(+), 26 deletions(-)
> >
> > diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> > index d696d6610231..11a71b8533d5 100644
> > --- a/arch/riscv/include/uapi/asm/elf.h
> > +++ b/arch/riscv/include/uapi/asm/elf.h
> > @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_TLS_DTPREL64	9
> >  #define R_RISCV_TLS_TPREL32	10
> >  #define R_RISCV_TLS_TPREL64	11
> > +#define R_RISCV_IRELATIVE	58
> >
> >  /* Relocation types not used by the dynamic linker */
> >  #define R_RISCV_BRANCH		16
> > @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_ALIGN		43
> >  #define R_RISCV_RVC_BRANCH	44
> >  #define R_RISCV_RVC_JUMP	45
> > -#define R_RISCV_LUI		46
> >  #define R_RISCV_GPREL_I		47
> >  #define R_RISCV_GPREL_S		48
> >  #define R_RISCV_TPREL_I		49
> > @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_SET16		55
> >  #define R_RISCV_SET32		56
> >  #define R_RISCV_32_PCREL	57
> > +#define R_RISCV_PLT32		59
> > +#define R_RISCV_SET_ULEB128	60
> > +#define R_RISCV_SUB_ULEB128	61
> >
> >
> >  #endif /* _UAPI_ASM_RISCV_ELF_H */
> > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > index 7c651d55fcbd..e860726352ac 100644
> > --- a/arch/riscv/kernel/module.c
> > +++ b/arch/riscv/kernel/module.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/elf.h>
> >  #include <linux/err.h>
> >  #include <linux/errno.h>
> > +#include <linux/kernel.h>
> >  #include <linux/moduleloader.h>
> >  #include <linux/vmalloc.h>
> >  #include <linux/sizes.h>
> > @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
> >  	return -EINVAL;
> >  }
> >
> > +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location += (u8)v;
> > +	return 0;
> > +}
> > +
> >  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
> >  				    Elf_Addr v)
> >  {
> > @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
> >  	return 0;
> >  }
> >
> > +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location -= (u8)v;
> > +	return 0;
> > +}
> > +
> >  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
> >  				    Elf_Addr v)
> >  {
> > @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
> >  	return 0;
> >  }
> >
> > -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> > -				Elf_Addr v) = {
> > -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> > -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> > -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> > -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> > -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> > -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> > -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> > -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> > -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> > -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> > -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> > -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> > -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> > -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> > -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> > -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> > -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> > -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> > -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> > -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> > -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> > -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> > -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> > +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> > +					 Elf_Addr v)
> > +{
> > +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> > +	       me->name, location);
> > +	return -EINVAL;
> > +}
> > +
> > +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> > +	       me->name, location);
> > +	return -EINVAL;
> > +}
> > +
> > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (u8)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u16 *)location = (u16)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> > +				       Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	/*
> > +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> > +	 * R_RISCV_SUB_ULEB128 so do computation there
> > +	 */
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	if (v >= 128) {
> > +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> > +		       me->name, (unsigned long)v, location);
> > +		return -EINVAL;
> > +	}
> > +
> > +	*location = v;
> > +	return 0;
> > +}
> > +
> > +/*
> > + * Relocations defined in the riscv-elf-psabi-doc.
> > + * This handles static linking only.
> > + */
> > +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> > +				    Elf_Addr v) = {
> > +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> > +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> > +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> > +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> > +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> > +	/* 12-15 undefined */
> > +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> > +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> > +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> > +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> > +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> > +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> > +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> > +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> > +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> > +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> > +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> > +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> > +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> > +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> > +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> > +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> > +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> > +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> > +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> > +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> > +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> > +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> > +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> > +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> > +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> > +	/* 41-42 reserved for future standard use */
> > +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> > +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> > +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> > +	/* 46-50 reserved for future standard use */
> > +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> > +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> > +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> > +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> > +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> > +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> > +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> > +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> > +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> > +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> > +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> > +	/* 62-191 reserved for future standard use */
> > +	/* 192-255 nonstandard ABI extensions  */
> >  };
> 
> Hi Charlie,
> 
> This is not a critique of this patch, but all these callbacks take a
> u32 *location and
> because of the compressed instructions this pointer may not be
> aligned, so a lot of
> the callbacks end up doing unaligned access which may fault to an
> M-mode handler on
> some platforms.
> 
> I once sent a patch to fix this:
> https://lore.kernel.org/linux-riscv/20220224152456.493365-2-kernel@esmil.dk/
> 
> Maybe that's something you want to look into while touching this code anyway.
> 
> /Emil

Oh nice, I will pick up that patch and change the "native-endian"
wording to be "little-endian" in the commit.

- Charlie

> >
> >  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >  	unsigned int i, type;
> >  	Elf_Addr v;
> >  	int res;
> > +	bool uleb128_set_exists = false;
> > +	u32 *uleb128_set_loc;
> > +	unsigned long uleb128_set_sym_val;
> > +
> >
> >  	pr_debug("Applying relocate section %u to %u\n", relsec,
> >  	       sechdrs[relsec].sh_info);
> > @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >  				  me->name);
> >  				return -EINVAL;
> >  			}
> > +		} else if (type == R_RISCV_SET_ULEB128) {
> > +			if (uleb128_set_exists) {
> > +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> > +				       me->name);
> > +				return -EINVAL;
> > +			}
> > +			uleb128_set_exists = true;
> > +			uleb128_set_loc = location;
> > +			uleb128_set_sym_val =
> > +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> > +					ELF_RISCV_R_SYM(rel[i].r_info))
> > +					->st_value +
> > +				rel[i].r_addend;
> > +		} else if (type == R_RISCV_SUB_ULEB128) {
> > +			if (uleb128_set_exists && uleb128_set_loc == location) {
> > +				/* Calculate set and subtraction */
> > +				v = uleb128_set_sym_val - v;
> > +			} else {
> > +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> > +				       me->name, location);
> > +				return -EINVAL;
> > +			}
> >  		}
> >
> >  		res = handler(me, location, v);
> >
> > --
> > 2.34.1
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

Emil Renner Berthing Oct. 18, 2023, 6:38 p.m. UTC | #4

Charlie Jenkins wrote:
> On Wed, Oct 18, 2023 at 05:17:44AM -0700, Emil Renner Berthing wrote:
> > Charlie Jenkins wrote:
> > > Add all final module relocations and add error logs explaining the ones
> > > that are not supported.
> > >
> > > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > > ---
> > >  arch/riscv/include/uapi/asm/elf.h |   5 +-
> > >  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
> > >  2 files changed, 186 insertions(+), 26 deletions(-)
> > >
> > > diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> > > index d696d6610231..11a71b8533d5 100644
> > > --- a/arch/riscv/include/uapi/asm/elf.h
> > > +++ b/arch/riscv/include/uapi/asm/elf.h
> > > @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > >  #define R_RISCV_TLS_DTPREL64	9
> > >  #define R_RISCV_TLS_TPREL32	10
> > >  #define R_RISCV_TLS_TPREL64	11
> > > +#define R_RISCV_IRELATIVE	58
> > >
> > >  /* Relocation types not used by the dynamic linker */
> > >  #define R_RISCV_BRANCH		16
> > > @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > >  #define R_RISCV_ALIGN		43
> > >  #define R_RISCV_RVC_BRANCH	44
> > >  #define R_RISCV_RVC_JUMP	45
> > > -#define R_RISCV_LUI		46
> > >  #define R_RISCV_GPREL_I		47
> > >  #define R_RISCV_GPREL_S		48
> > >  #define R_RISCV_TPREL_I		49
> > > @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > >  #define R_RISCV_SET16		55
> > >  #define R_RISCV_SET32		56
> > >  #define R_RISCV_32_PCREL	57
> > > +#define R_RISCV_PLT32		59
> > > +#define R_RISCV_SET_ULEB128	60
> > > +#define R_RISCV_SUB_ULEB128	61
> > >
> > >
> > >  #endif /* _UAPI_ASM_RISCV_ELF_H */
> > > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > > index 7c651d55fcbd..e860726352ac 100644
> > > --- a/arch/riscv/kernel/module.c
> > > +++ b/arch/riscv/kernel/module.c
> > > @@ -7,6 +7,7 @@
> > >  #include <linux/elf.h>
> > >  #include <linux/err.h>
> > >  #include <linux/errno.h>
> > > +#include <linux/kernel.h>
> > >  #include <linux/moduleloader.h>
> > >  #include <linux/vmalloc.h>
> > >  #include <linux/sizes.h>
> > > @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
> > >  	return -EINVAL;
> > >  }
> > >
> > > +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	*(u8 *)location += (u8)v;
> > > +	return 0;
> > > +}
> > > +
> > >  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
> > >  				    Elf_Addr v)
> > >  {
> > > @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
> > >  	return 0;
> > >  }
> > >
> > > +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	*(u8 *)location -= (u8)v;
> > > +	return 0;
> > > +}
> > > +
> > >  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
> > >  				    Elf_Addr v)
> > >  {
> > > @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
> > >  	return 0;
> > >  }
> > >
> > > -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> > > -				Elf_Addr v) = {
> > > -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> > > -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> > > -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> > > -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> > > -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> > > -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> > > -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> > > -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> > > -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> > > -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> > > -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> > > -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> > > -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> > > -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> > > -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> > > -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> > > -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> > > -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> > > -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> > > -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> > > -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> > > -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> > > -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> > > +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> > > +					 Elf_Addr v)
> > > +{
> > > +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> > > +	       me->name, location);
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> > > +	       me->name, location);
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	*(u8 *)location = (u8)v;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> > > +				    Elf_Addr v)
> > > +{
> > > +	*(u16 *)location = (u16)v;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> > > +				    Elf_Addr v)
> > > +{
> > > +	*(u32 *)location = (u32)v;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> > > +				       Elf_Addr v)
> > > +{
> > > +	*(u32 *)location = (u32)v;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> > > +				    Elf_Addr v)
> > > +{
> > > +	*(u32 *)location = (u32)v;
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	/*
> > > +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> > > +	 * R_RISCV_SUB_ULEB128 so do computation there
> > > +	 */
> > > +	return 0;
> > > +}
> > > +
> > > +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > +{
> > > +	if (v >= 128) {
> > > +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> > > +		       me->name, (unsigned long)v, location);
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	*location = v;
> > > +	return 0;
> > > +}
> > > +
> > > +/*
> > > + * Relocations defined in the riscv-elf-psabi-doc.
> > > + * This handles static linking only.
> > > + */
> > > +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> > > +				    Elf_Addr v) = {
> > > +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> > > +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> > > +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> > > +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> > > +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> > > +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> > > +	/* 12-15 undefined */
> > > +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> > > +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> > > +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> > > +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> > > +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> > > +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> > > +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> > > +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> > > +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> > > +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> > > +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> > > +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> > > +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> > > +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> > > +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> > > +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> > > +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> > > +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> > > +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> > > +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> > > +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> > > +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> > > +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> > > +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> > > +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> > > +	/* 41-42 reserved for future standard use */
> > > +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> > > +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> > > +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> > > +	/* 46-50 reserved for future standard use */
> > > +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> > > +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> > > +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> > > +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> > > +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> > > +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> > > +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> > > +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> > > +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> > > +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> > > +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> > > +	/* 62-191 reserved for future standard use */
> > > +	/* 192-255 nonstandard ABI extensions  */
> > >  };
> >
> > Hi Charlie,
> >
> > This is not a critique of this patch, but all these callbacks take a
> > u32 *location and
> > because of the compressed instructions this pointer may not be
> > aligned, so a lot of
> > the callbacks end up doing unaligned access which may fault to an
> > M-mode handler on
> > some platforms.
> >
> > I once sent a patch to fix this:
> > https://lore.kernel.org/linux-riscv/20220224152456.493365-2-kernel@esmil.dk/
> >
> > Maybe that's something you want to look into while touching this code anyway.
> >
> > /Emil
>
> Oh nice, I will pick up that patch and change the "native-endian"
> wording to be "little-endian" in the commit.

Great, thanks. You'll probably also want the reads to be wrapped in
le16_to_cpu() and similar when writing now that it's decided that the parcels
are always in little-endian byteorder.

/Emil

>
> - Charlie
>
> > >
> > >  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > > @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > >  	unsigned int i, type;
> > >  	Elf_Addr v;
> > >  	int res;
> > > +	bool uleb128_set_exists = false;
> > > +	u32 *uleb128_set_loc;
> > > +	unsigned long uleb128_set_sym_val;
> > > +
> > >
> > >  	pr_debug("Applying relocate section %u to %u\n", relsec,
> > >  	       sechdrs[relsec].sh_info);
> > > @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > >  				  me->name);
> > >  				return -EINVAL;
> > >  			}
> > > +		} else if (type == R_RISCV_SET_ULEB128) {
> > > +			if (uleb128_set_exists) {
> > > +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> > > +				       me->name);
> > > +				return -EINVAL;
> > > +			}
> > > +			uleb128_set_exists = true;
> > > +			uleb128_set_loc = location;
> > > +			uleb128_set_sym_val =
> > > +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> > > +					ELF_RISCV_R_SYM(rel[i].r_info))
> > > +					->st_value +
> > > +				rel[i].r_addend;
> > > +		} else if (type == R_RISCV_SUB_ULEB128) {
> > > +			if (uleb128_set_exists && uleb128_set_loc == location) {
> > > +				/* Calculate set and subtraction */
> > > +				v = uleb128_set_sym_val - v;
> > > +			} else {
> > > +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> > > +				       me->name, location);
> > > +				return -EINVAL;
> > > +			}
> > >  		}
> > >
> > >  		res = handler(me, location, v);
> > >
> > > --
> > > 2.34.1
> > >
> > >
> > > _______________________________________________
> > > linux-riscv mailing list
> > > linux-riscv@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-riscv
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Andreas Schwab Oct. 18, 2023, 6:47 p.m. UTC | #5

On Okt 17 2023, Charlie Jenkins wrote:

> +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> +{
> +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;

I think that should use *(u8*) on both sides.

Charlie Jenkins Oct. 18, 2023, 8:19 p.m. UTC | #6

On Wed, Oct 18, 2023 at 11:38:39AM -0700, Emil Renner Berthing wrote:
> Charlie Jenkins wrote:
> > On Wed, Oct 18, 2023 at 05:17:44AM -0700, Emil Renner Berthing wrote:
> > > Charlie Jenkins wrote:
> > > > Add all final module relocations and add error logs explaining the ones
> > > > that are not supported.
> > > >
> > > > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > > > ---
> > > >  arch/riscv/include/uapi/asm/elf.h |   5 +-
> > > >  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
> > > >  2 files changed, 186 insertions(+), 26 deletions(-)
> > > >
> > > > diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> > > > index d696d6610231..11a71b8533d5 100644
> > > > --- a/arch/riscv/include/uapi/asm/elf.h
> > > > +++ b/arch/riscv/include/uapi/asm/elf.h
> > > > @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > >  #define R_RISCV_TLS_DTPREL64	9
> > > >  #define R_RISCV_TLS_TPREL32	10
> > > >  #define R_RISCV_TLS_TPREL64	11
> > > > +#define R_RISCV_IRELATIVE	58
> > > >
> > > >  /* Relocation types not used by the dynamic linker */
> > > >  #define R_RISCV_BRANCH		16
> > > > @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > >  #define R_RISCV_ALIGN		43
> > > >  #define R_RISCV_RVC_BRANCH	44
> > > >  #define R_RISCV_RVC_JUMP	45
> > > > -#define R_RISCV_LUI		46
> > > >  #define R_RISCV_GPREL_I		47
> > > >  #define R_RISCV_GPREL_S		48
> > > >  #define R_RISCV_TPREL_I		49
> > > > @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > >  #define R_RISCV_SET16		55
> > > >  #define R_RISCV_SET32		56
> > > >  #define R_RISCV_32_PCREL	57
> > > > +#define R_RISCV_PLT32		59
> > > > +#define R_RISCV_SET_ULEB128	60
> > > > +#define R_RISCV_SUB_ULEB128	61
> > > >
> > > >
> > > >  #endif /* _UAPI_ASM_RISCV_ELF_H */
> > > > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > > > index 7c651d55fcbd..e860726352ac 100644
> > > > --- a/arch/riscv/kernel/module.c
> > > > +++ b/arch/riscv/kernel/module.c
> > > > @@ -7,6 +7,7 @@
> > > >  #include <linux/elf.h>
> > > >  #include <linux/err.h>
> > > >  #include <linux/errno.h>
> > > > +#include <linux/kernel.h>
> > > >  #include <linux/moduleloader.h>
> > > >  #include <linux/vmalloc.h>
> > > >  #include <linux/sizes.h>
> > > > @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
> > > >  	return -EINVAL;
> > > >  }
> > > >
> > > > +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	*(u8 *)location += (u8)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > >  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
> > > >  				    Elf_Addr v)
> > > >  {
> > > > @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
> > > >  	return 0;
> > > >  }
> > > >
> > > > +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	*(u8 *)location -= (u8)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > >  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
> > > >  				    Elf_Addr v)
> > > >  {
> > > > @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
> > > >  	return 0;
> > > >  }
> > > >
> > > > -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> > > > -				Elf_Addr v) = {
> > > > -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> > > > -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> > > > -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> > > > -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> > > > -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> > > > -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> > > > -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> > > > -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> > > > -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> > > > -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> > > > -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> > > > -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> > > > -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> > > > -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> > > > -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> > > > -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> > > > -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> > > > -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> > > > -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> > > > -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> > > > -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> > > > -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> > > > -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> > > > +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> > > > +					 Elf_Addr v)
> > > > +{
> > > > +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> > > > +	       me->name, location);
> > > > +	return -EINVAL;
> > > > +}
> > > > +
> > > > +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> > > > +	       me->name, location);
> > > > +	return -EINVAL;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	*(u8 *)location = (u8)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> > > > +				    Elf_Addr v)
> > > > +{
> > > > +	*(u16 *)location = (u16)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> > > > +				    Elf_Addr v)
> > > > +{
> > > > +	*(u32 *)location = (u32)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> > > > +				       Elf_Addr v)
> > > > +{
> > > > +	*(u32 *)location = (u32)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> > > > +				    Elf_Addr v)
> > > > +{
> > > > +	*(u32 *)location = (u32)v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	/*
> > > > +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> > > > +	 * R_RISCV_SUB_ULEB128 so do computation there
> > > > +	 */
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > > +{
> > > > +	if (v >= 128) {
> > > > +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> > > > +		       me->name, (unsigned long)v, location);
> > > > +		return -EINVAL;
> > > > +	}
> > > > +
> > > > +	*location = v;
> > > > +	return 0;
> > > > +}
> > > > +
> > > > +/*
> > > > + * Relocations defined in the riscv-elf-psabi-doc.
> > > > + * This handles static linking only.
> > > > + */
> > > > +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> > > > +				    Elf_Addr v) = {
> > > > +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> > > > +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> > > > +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> > > > +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> > > > +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> > > > +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> > > > +	/* 12-15 undefined */
> > > > +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> > > > +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> > > > +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> > > > +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> > > > +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> > > > +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> > > > +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> > > > +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> > > > +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> > > > +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> > > > +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> > > > +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> > > > +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> > > > +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> > > > +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> > > > +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> > > > +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> > > > +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> > > > +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> > > > +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> > > > +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> > > > +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> > > > +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> > > > +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> > > > +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> > > > +	/* 41-42 reserved for future standard use */
> > > > +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> > > > +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> > > > +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> > > > +	/* 46-50 reserved for future standard use */
> > > > +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> > > > +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> > > > +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> > > > +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> > > > +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> > > > +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> > > > +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> > > > +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> > > > +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> > > > +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> > > > +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> > > > +	/* 62-191 reserved for future standard use */
> > > > +	/* 192-255 nonstandard ABI extensions  */
> > > >  };
> > >
> > > Hi Charlie,
> > >
> > > This is not a critique of this patch, but all these callbacks take a
> > > u32 *location and
> > > because of the compressed instructions this pointer may not be
> > > aligned, so a lot of
> > > the callbacks end up doing unaligned access which may fault to an
> > > M-mode handler on
> > > some platforms.
> > >
> > > I once sent a patch to fix this:
> > > https://lore.kernel.org/linux-riscv/20220224152456.493365-2-kernel@esmil.dk/
> > >
> > > Maybe that's something you want to look into while touching this code anyway.
> > >
> > > /Emil
> >
> > Oh nice, I will pick up that patch and change the "native-endian"
> > wording to be "little-endian" in the commit.
> 
> Great, thanks. You'll probably also want the reads to be wrapped in
> le16_to_cpu() and similar when writing now that it's decided that the parcels
> are always in little-endian byteorder.
> 
> /Emil

I believe that le16_to_cpu() is only needed when instructions are being modified, and
the relocations that only touch data can be left alone. Is this correct?

- Charlie

> 
> >
> > - Charlie
> >
> > > >
> > > >  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > > > @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > > >  	unsigned int i, type;
> > > >  	Elf_Addr v;
> > > >  	int res;
> > > > +	bool uleb128_set_exists = false;
> > > > +	u32 *uleb128_set_loc;
> > > > +	unsigned long uleb128_set_sym_val;
> > > > +
> > > >
> > > >  	pr_debug("Applying relocate section %u to %u\n", relsec,
> > > >  	       sechdrs[relsec].sh_info);
> > > > @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > > >  				  me->name);
> > > >  				return -EINVAL;
> > > >  			}
> > > > +		} else if (type == R_RISCV_SET_ULEB128) {
> > > > +			if (uleb128_set_exists) {
> > > > +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> > > > +				       me->name);
> > > > +				return -EINVAL;
> > > > +			}
> > > > +			uleb128_set_exists = true;
> > > > +			uleb128_set_loc = location;
> > > > +			uleb128_set_sym_val =
> > > > +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> > > > +					ELF_RISCV_R_SYM(rel[i].r_info))
> > > > +					->st_value +
> > > > +				rel[i].r_addend;
> > > > +		} else if (type == R_RISCV_SUB_ULEB128) {
> > > > +			if (uleb128_set_exists && uleb128_set_loc == location) {
> > > > +				/* Calculate set and subtraction */
> > > > +				v = uleb128_set_sym_val - v;
> > > > +			} else {
> > > > +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> > > > +				       me->name, location);
> > > > +				return -EINVAL;
> > > > +			}
> > > >  		}
> > > >
> > > >  		res = handler(me, location, v);
> > > >
> > > > --
> > > > 2.34.1
> > > >
> > > >
> > > > _______________________________________________
> > > > linux-riscv mailing list
> > > > linux-riscv@lists.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-riscv
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

Emil Renner Berthing Oct. 18, 2023, 8:28 p.m. UTC | #7

Charlie Jenkins wrote:
> On Wed, Oct 18, 2023 at 11:38:39AM -0700, Emil Renner Berthing wrote:
> > Charlie Jenkins wrote:
> > > On Wed, Oct 18, 2023 at 05:17:44AM -0700, Emil Renner Berthing wrote:
> > > > Charlie Jenkins wrote:
> > > > > Add all final module relocations and add error logs explaining the ones
> > > > > that are not supported.
> > > > >
> > > > > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > > > > ---
> > > > >  arch/riscv/include/uapi/asm/elf.h |   5 +-
> > > > >  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
> > > > >  2 files changed, 186 insertions(+), 26 deletions(-)
> > > > >
> > > > > diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> > > > > index d696d6610231..11a71b8533d5 100644
> > > > > --- a/arch/riscv/include/uapi/asm/elf.h
> > > > > +++ b/arch/riscv/include/uapi/asm/elf.h
> > > > > @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > > >  #define R_RISCV_TLS_DTPREL64	9
> > > > >  #define R_RISCV_TLS_TPREL32	10
> > > > >  #define R_RISCV_TLS_TPREL64	11
> > > > > +#define R_RISCV_IRELATIVE	58
> > > > >
> > > > >  /* Relocation types not used by the dynamic linker */
> > > > >  #define R_RISCV_BRANCH		16
> > > > > @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > > >  #define R_RISCV_ALIGN		43
> > > > >  #define R_RISCV_RVC_BRANCH	44
> > > > >  #define R_RISCV_RVC_JUMP	45
> > > > > -#define R_RISCV_LUI		46
> > > > >  #define R_RISCV_GPREL_I		47
> > > > >  #define R_RISCV_GPREL_S		48
> > > > >  #define R_RISCV_TPREL_I		49
> > > > > @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> > > > >  #define R_RISCV_SET16		55
> > > > >  #define R_RISCV_SET32		56
> > > > >  #define R_RISCV_32_PCREL	57
> > > > > +#define R_RISCV_PLT32		59
> > > > > +#define R_RISCV_SET_ULEB128	60
> > > > > +#define R_RISCV_SUB_ULEB128	61
> > > > >
> > > > >
> > > > >  #endif /* _UAPI_ASM_RISCV_ELF_H */
> > > > > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > > > > index 7c651d55fcbd..e860726352ac 100644
> > > > > --- a/arch/riscv/kernel/module.c
> > > > > +++ b/arch/riscv/kernel/module.c
> > > > > @@ -7,6 +7,7 @@
> > > > >  #include <linux/elf.h>
> > > > >  #include <linux/err.h>
> > > > >  #include <linux/errno.h>
> > > > > +#include <linux/kernel.h>
> > > > >  #include <linux/moduleloader.h>
> > > > >  #include <linux/vmalloc.h>
> > > > >  #include <linux/sizes.h>
> > > > > @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
> > > > >  	return -EINVAL;
> > > > >  }
> > > > >
> > > > > +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	*(u8 *)location += (u8)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > >  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
> > > > >  				    Elf_Addr v)
> > > > >  {
> > > > > @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
> > > > >  	return 0;
> > > > >  }
> > > > >
> > > > > +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	*(u8 *)location -= (u8)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > >  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
> > > > >  				    Elf_Addr v)
> > > > >  {
> > > > > @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
> > > > >  	return 0;
> > > > >  }
> > > > >
> > > > > -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> > > > > -				Elf_Addr v) = {
> > > > > -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> > > > > -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> > > > > -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> > > > > -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> > > > > -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> > > > > -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> > > > > -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> > > > > -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> > > > > -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> > > > > -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> > > > > -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> > > > > -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> > > > > -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> > > > > -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> > > > > -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> > > > > -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> > > > > -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> > > > > -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> > > > > -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> > > > > -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> > > > > -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> > > > > -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> > > > > -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> > > > > +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> > > > > +					 Elf_Addr v)
> > > > > +{
> > > > > +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> > > > > +	       me->name, location);
> > > > > +	return -EINVAL;
> > > > > +}
> > > > > +
> > > > > +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> > > > > +	       me->name, location);
> > > > > +	return -EINVAL;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	*(u8 *)location = (u8)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> > > > > +				    Elf_Addr v)
> > > > > +{
> > > > > +	*(u16 *)location = (u16)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> > > > > +				    Elf_Addr v)
> > > > > +{
> > > > > +	*(u32 *)location = (u32)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> > > > > +				       Elf_Addr v)
> > > > > +{
> > > > > +	*(u32 *)location = (u32)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> > > > > +				    Elf_Addr v)
> > > > > +{
> > > > > +	*(u32 *)location = (u32)v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	/*
> > > > > +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> > > > > +	 * R_RISCV_SUB_ULEB128 so do computation there
> > > > > +	 */
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > > > > +{
> > > > > +	if (v >= 128) {
> > > > > +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> > > > > +		       me->name, (unsigned long)v, location);
> > > > > +		return -EINVAL;
> > > > > +	}
> > > > > +
> > > > > +	*location = v;
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * Relocations defined in the riscv-elf-psabi-doc.
> > > > > + * This handles static linking only.
> > > > > + */
> > > > > +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> > > > > +				    Elf_Addr v) = {
> > > > > +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> > > > > +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> > > > > +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> > > > > +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> > > > > +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> > > > > +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> > > > > +	/* 12-15 undefined */
> > > > > +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> > > > > +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> > > > > +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> > > > > +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> > > > > +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> > > > > +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> > > > > +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> > > > > +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> > > > > +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> > > > > +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> > > > > +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> > > > > +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> > > > > +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> > > > > +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> > > > > +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> > > > > +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> > > > > +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> > > > > +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> > > > > +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> > > > > +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> > > > > +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> > > > > +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> > > > > +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> > > > > +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> > > > > +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> > > > > +	/* 41-42 reserved for future standard use */
> > > > > +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> > > > > +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> > > > > +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> > > > > +	/* 46-50 reserved for future standard use */
> > > > > +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> > > > > +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> > > > > +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> > > > > +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> > > > > +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> > > > > +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> > > > > +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> > > > > +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> > > > > +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> > > > > +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> > > > > +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> > > > > +	/* 62-191 reserved for future standard use */
> > > > > +	/* 192-255 nonstandard ABI extensions  */
> > > > >  };
> > > >
> > > > Hi Charlie,
> > > >
> > > > This is not a critique of this patch, but all these callbacks take a
> > > > u32 *location and
> > > > because of the compressed instructions this pointer may not be
> > > > aligned, so a lot of
> > > > the callbacks end up doing unaligned access which may fault to an
> > > > M-mode handler on
> > > > some platforms.
> > > >
> > > > I once sent a patch to fix this:
> > > > https://lore.kernel.org/linux-riscv/20220224152456.493365-2-kernel@esmil.dk/
> > > >
> > > > Maybe that's something you want to look into while touching this code anyway.
> > > >
> > > > /Emil
> > >
> > > Oh nice, I will pick up that patch and change the "native-endian"
> > > wording to be "little-endian" in the commit.
> >
> > Great, thanks. You'll probably also want the reads to be wrapped in
> > le16_to_cpu() and similar when writing now that it's decided that the parcels
> > are always in little-endian byteorder.
> >
> > /Emil
>
> I believe that le16_to_cpu() is only needed when instructions are being modified, and
> the relocations that only touch data can be left alone. Is this correct?

Yes, that sounds right to me. I only meant in the riscv_insn_rmw() function of
my patch and the callbacks modifying a compressed instruction, but I haven't
gone through all the other reloc types to check if they have a set endianess.

/Emil

Charlie Jenkins Oct. 18, 2023, 10:19 p.m. UTC | #8

On Wed, Oct 18, 2023 at 01:28:45PM -0500, Samuel Holland wrote:
> On 2023-10-18 12:34 AM, Charlie Jenkins wrote:
> > Add all final module relocations and add error logs explaining the ones
> > that are not supported.
> > 
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
> > ---
> >  arch/riscv/include/uapi/asm/elf.h |   5 +-
> >  arch/riscv/kernel/module.c        | 207 +++++++++++++++++++++++++++++++++-----
> >  2 files changed, 186 insertions(+), 26 deletions(-)
> > 
> > diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
> > index d696d6610231..11a71b8533d5 100644
> > --- a/arch/riscv/include/uapi/asm/elf.h
> > +++ b/arch/riscv/include/uapi/asm/elf.h
> > @@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_TLS_DTPREL64	9
> >  #define R_RISCV_TLS_TPREL32	10
> >  #define R_RISCV_TLS_TPREL64	11
> > +#define R_RISCV_IRELATIVE	58
> >  
> >  /* Relocation types not used by the dynamic linker */
> >  #define R_RISCV_BRANCH		16
> > @@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_ALIGN		43
> >  #define R_RISCV_RVC_BRANCH	44
> >  #define R_RISCV_RVC_JUMP	45
> > -#define R_RISCV_LUI		46
> >  #define R_RISCV_GPREL_I		47
> >  #define R_RISCV_GPREL_S		48
> >  #define R_RISCV_TPREL_I		49
> > @@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
> >  #define R_RISCV_SET16		55
> >  #define R_RISCV_SET32		56
> >  #define R_RISCV_32_PCREL	57
> > +#define R_RISCV_PLT32		59
> > +#define R_RISCV_SET_ULEB128	60
> > +#define R_RISCV_SUB_ULEB128	61
> >  
> >  
> >  #endif /* _UAPI_ASM_RISCV_ELF_H */
> > diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> > index 7c651d55fcbd..e860726352ac 100644
> > --- a/arch/riscv/kernel/module.c
> > +++ b/arch/riscv/kernel/module.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/elf.h>
> >  #include <linux/err.h>
> >  #include <linux/errno.h>
> > +#include <linux/kernel.h>
> >  #include <linux/moduleloader.h>
> >  #include <linux/vmalloc.h>
> >  #include <linux/sizes.h>
> > @@ -268,6 +269,12 @@ static int apply_r_riscv_align_rela(struct module *me, u32 *location,
> >  	return -EINVAL;
> >  }
> >  
> > +static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location += (u8)v;
> > +	return 0;
> > +}
> > +
> >  static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
> >  				    Elf_Addr v)
> >  {
> > @@ -289,6 +296,12 @@ static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
> >  	return 0;
> >  }
> >  
> > +static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location -= (u8)v;
> > +	return 0;
> > +}
> > +
> >  static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
> >  				    Elf_Addr v)
> >  {
> > @@ -310,31 +323,149 @@ static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
> >  	return 0;
> >  }
> >  
> > -static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
> > -				Elf_Addr v) = {
> > -	[R_RISCV_32]			= apply_r_riscv_32_rela,
> > -	[R_RISCV_64]			= apply_r_riscv_64_rela,
> > -	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
> > -	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
> > -	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
> > -	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
> > -	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
> > -	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
> > -	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
> > -	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
> > -	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
> > -	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
> > -	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
> > -	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
> > -	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
> > -	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
> > -	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
> > -	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
> > -	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
> > -	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
> > -	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
> > -	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
> > -	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
> > +static int dynamic_linking_not_supported(struct module *me, u32 *location,
> > +					 Elf_Addr v)
> > +{
> > +	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
> > +	       me->name, location);
> > +	return -EINVAL;
> > +}
> > +
> > +static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
> > +	       me->name, location);
> > +	return -EINVAL;
> > +}
> > +
> > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (u8)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u16 *)location = (u16)v;
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> 
> You don't need to cast the pointer, since it's already a `u32 *`.
> 
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
> > +				       Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> 
> This expression should be:
> 
>     *location = v - location;
> 
> matching the other PC-relative relocations.
> 
> (BTW, recent clang generates these relocations for module alternatives.)
> 
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
> > +				    Elf_Addr v)
> > +{
> > +	*(u32 *)location = (u32)v;
> 
> This should look like apply_r_riscv_32_pcrel_rela(), but with the PLT entry
> emission code from apply_r_riscv_call_plt_rela(). See the psABI commit[1].
> 
> [1]:
> https://github.com/riscv-non-isa/riscv-elf-psabi-doc/commit/c3f8269c56d8a2f56c2602f2a44175362024ef9c
> 

Thank you for pointing out these issues.

> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	/*
> > +	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
> > +	 * R_RISCV_SUB_ULEB128 so do computation there
> > +	 */
> > +	return 0;
> > +}
> > +
> > +static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	if (v >= 128) {
> > +		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
> > +		       me->name, (unsigned long)v, location);
> > +		return -EINVAL;
> > +	}
> > +
> > +	*location = v;
> > +	return 0;
> > +}
> > +
> > +/*
> > + * Relocations defined in the riscv-elf-psabi-doc.
> > + * This handles static linking only.
> > + */
> > +static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
> > +				    Elf_Addr v) = {
> > +	[R_RISCV_32] =			apply_r_riscv_32_rela,
> > +	[R_RISCV_64] =			apply_r_riscv_64_rela,
> > +	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
> > +	[R_RISCV_COPY] =		dynamic_linking_not_supported,
> > +	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
> > +	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
> > +	/* 12-15 undefined */
> > +	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
> > +	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
> > +	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
> > +	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
> > +	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
> > +	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
> > +	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
> > +	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
> > +	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
> > +	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
> > +	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
> > +	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
> > +	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
> > +	[R_RISCV_TPREL_HI20] =		tls_not_supported,
> > +	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
> > +	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
> > +	[R_RISCV_TPREL_ADD] =		tls_not_supported,
> > +	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
> > +	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
> > +	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
> > +	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
> > +	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
> > +	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
> > +	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
> > +	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
> > +	/* 41-42 reserved for future standard use */
> > +	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
> > +	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
> > +	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
> > +	/* 46-50 reserved for future standard use */
> > +	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
> > +	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
> > +	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
> > +	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
> > +	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
> > +	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
> > +	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
> > +	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
> > +	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
> > +	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
> > +	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
> > +	/* 62-191 reserved for future standard use */
> > +	/* 192-255 nonstandard ABI extensions  */
> >  };
> >  
> >  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> > @@ -348,6 +479,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >  	unsigned int i, type;
> >  	Elf_Addr v;
> >  	int res;
> > +	bool uleb128_set_exists = false;
> > +	u32 *uleb128_set_loc;
> > +	unsigned long uleb128_set_sym_val;
> > +
> 
> Extra blank line.
> 
> >  
> >  	pr_debug("Applying relocate section %u to %u\n", relsec,
> >  	       sechdrs[relsec].sh_info);
> > @@ -425,6 +560,28 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
> >  				  me->name);
> >  				return -EINVAL;
> >  			}
> > +		} else if (type == R_RISCV_SET_ULEB128) {
> > +			if (uleb128_set_exists) {
> > +				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
> > +				       me->name);
> > +				return -EINVAL;
> > +			}
> > +			uleb128_set_exists = true;
> > +			uleb128_set_loc = location;
> > +			uleb128_set_sym_val =
> > +				((Elf_Sym *)sechdrs[symindex].sh_addr +
> > +					ELF_RISCV_R_SYM(rel[i].r_info))
> > +					->st_value +
> > +				rel[i].r_addend;
> > +		} else if (type == R_RISCV_SUB_ULEB128) {
> > +			if (uleb128_set_exists && uleb128_set_loc == location) {
> > +				/* Calculate set and subtraction */
> > +				v = uleb128_set_sym_val - v;
> 
> You need to set uleb128_set_exists back to false somewhere, or you can only
> handle one R_RISCV_SET_ULEB128 relocation per module.
> 

I guess that never made it out of my thoughts and into the code...

- Charlie

> Regards,
> Samuel
> 
> > +			} else {
> > +				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
> > +				       me->name, location);
> > +				return -EINVAL;
> > +			}
> >  		}
> >  
> >  		res = handler(me, location, v);
> > 
>

Charlie Jenkins Oct. 18, 2023, 10:19 p.m. UTC | #9

On Wed, Oct 18, 2023 at 08:47:58PM +0200, Andreas Schwab wrote:
> On Okt 17 2023, Charlie Jenkins wrote:
> 
> > +static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
> > +{
> > +	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
> 
> I think that should use *(u8*) on both sides.

Yep, thank you.

- Charlie

> 
> -- 
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> "And now for something completely different."

diff mbox series

Patch

diff --git a/arch/riscv/include/uapi/asm/elf.h b/arch/riscv/include/uapi/asm/elf.h
index d696d6610231..11a71b8533d5 100644
--- a/arch/riscv/include/uapi/asm/elf.h
+++ b/arch/riscv/include/uapi/asm/elf.h
@@ -49,6 +49,7 @@  typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_TLS_DTPREL64	9
 #define R_RISCV_TLS_TPREL32	10
 #define R_RISCV_TLS_TPREL64	11
+#define R_RISCV_IRELATIVE	58
 
 /* Relocation types not used by the dynamic linker */
 #define R_RISCV_BRANCH		16
@@ -81,7 +82,6 @@  typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_ALIGN		43
 #define R_RISCV_RVC_BRANCH	44
 #define R_RISCV_RVC_JUMP	45
-#define R_RISCV_LUI		46
 #define R_RISCV_GPREL_I		47
 #define R_RISCV_GPREL_S		48
 #define R_RISCV_TPREL_I		49
@@ -93,6 +93,9 @@  typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_SET16		55
 #define R_RISCV_SET32		56
 #define R_RISCV_32_PCREL	57
+#define R_RISCV_PLT32		59
+#define R_RISCV_SET_ULEB128	60
+#define R_RISCV_SUB_ULEB128	61
 
 
 #endif /* _UAPI_ASM_RISCV_ELF_H */
diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 7c651d55fcbd..e860726352ac 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -7,6 +7,7 @@ 
 #include <linux/elf.h>
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/kernel.h>
 #include <linux/moduleloader.h>
 #include <linux/vmalloc.h>
 #include <linux/sizes.h>
@@ -268,6 +269,12 @@  static int apply_r_riscv_align_rela(struct module *me, u32 *location,
 	return -EINVAL;
 }
 
+static int apply_r_riscv_add8_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	*(u8 *)location += (u8)v;
+	return 0;
+}
+
 static int apply_r_riscv_add16_rela(struct module *me, u32 *location,
 				    Elf_Addr v)
 {
@@ -289,6 +296,12 @@  static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
 	return 0;
 }
 
+static int apply_r_riscv_sub8_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	*(u8 *)location -= (u8)v;
+	return 0;
+}
+
 static int apply_r_riscv_sub16_rela(struct module *me, u32 *location,
 				    Elf_Addr v)
 {
@@ -310,31 +323,149 @@  static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
 	return 0;
 }
 
-static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
-				Elf_Addr v) = {
-	[R_RISCV_32]			= apply_r_riscv_32_rela,
-	[R_RISCV_64]			= apply_r_riscv_64_rela,
-	[R_RISCV_BRANCH]		= apply_r_riscv_branch_rela,
-	[R_RISCV_JAL]			= apply_r_riscv_jal_rela,
-	[R_RISCV_RVC_BRANCH]		= apply_r_riscv_rvc_branch_rela,
-	[R_RISCV_RVC_JUMP]		= apply_r_riscv_rvc_jump_rela,
-	[R_RISCV_PCREL_HI20]		= apply_r_riscv_pcrel_hi20_rela,
-	[R_RISCV_PCREL_LO12_I]		= apply_r_riscv_pcrel_lo12_i_rela,
-	[R_RISCV_PCREL_LO12_S]		= apply_r_riscv_pcrel_lo12_s_rela,
-	[R_RISCV_HI20]			= apply_r_riscv_hi20_rela,
-	[R_RISCV_LO12_I]		= apply_r_riscv_lo12_i_rela,
-	[R_RISCV_LO12_S]		= apply_r_riscv_lo12_s_rela,
-	[R_RISCV_GOT_HI20]		= apply_r_riscv_got_hi20_rela,
-	[R_RISCV_CALL_PLT]		= apply_r_riscv_call_plt_rela,
-	[R_RISCV_CALL]			= apply_r_riscv_call_rela,
-	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
-	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
-	[R_RISCV_ADD16]			= apply_r_riscv_add16_rela,
-	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
-	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
-	[R_RISCV_SUB16]			= apply_r_riscv_sub16_rela,
-	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
-	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
+static int dynamic_linking_not_supported(struct module *me, u32 *location,
+					 Elf_Addr v)
+{
+	pr_err("%s: Dynamic linking not supported in kernel modules PC = %p\n",
+	       me->name, location);
+	return -EINVAL;
+}
+
+static int tls_not_supported(struct module *me, u32 *location, Elf_Addr v)
+{
+	pr_err("%s: Thread local storage not supported in kernel modules PC = %p\n",
+	       me->name, location);
+	return -EINVAL;
+}
+
+static int apply_r_riscv_sub6_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	*(u8 *)location = (*location - ((u8)v & 0x3F)) & 0x3F;
+	return 0;
+}
+
+static int apply_r_riscv_set6_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	*(u8 *)location = (*(u8 *)location & 0xc0) | ((u8)v & 0x3F);
+	return 0;
+}
+
+static int apply_r_riscv_set8_rela(struct module *me, u32 *location, Elf_Addr v)
+{
+	*(u8 *)location = (u8)v;
+	return 0;
+}
+
+static int apply_r_riscv_set16_rela(struct module *me, u32 *location,
+				    Elf_Addr v)
+{
+	*(u16 *)location = (u16)v;
+	return 0;
+}
+
+static int apply_r_riscv_set32_rela(struct module *me, u32 *location,
+				    Elf_Addr v)
+{
+	*(u32 *)location = (u32)v;
+	return 0;
+}
+
+static int apply_r_riscv_32_pcrel_rela(struct module *me, u32 *location,
+				       Elf_Addr v)
+{
+	*(u32 *)location = (u32)v;
+	return 0;
+}
+
+static int apply_r_riscv_plt32_rela(struct module *me, u32 *location,
+				    Elf_Addr v)
+{
+	*(u32 *)location = (u32)v;
+	return 0;
+}
+
+static int apply_r_riscv_set_uleb128(struct module *me, u32 *location, Elf_Addr v)
+{
+	/*
+	 * Relocation is only performed if R_RISCV_SET_ULEB128 is followed by
+	 * R_RISCV_SUB_ULEB128 so do computation there
+	 */
+	return 0;
+}
+
+static int apply_r_riscv_sub_uleb128(struct module *me, u32 *location, Elf_Addr v)
+{
+	if (v >= 128) {
+		pr_err("%s: uleb128 must be in [0, 127] (not %ld) at PC = %p\n",
+		       me->name, (unsigned long)v, location);
+		return -EINVAL;
+	}
+
+	*location = v;
+	return 0;
+}
+
+/*
+ * Relocations defined in the riscv-elf-psabi-doc.
+ * This handles static linking only.
+ */
+static int (*reloc_handlers_rela[])(struct module *me, u32 *location,
+				    Elf_Addr v) = {
+	[R_RISCV_32] =			apply_r_riscv_32_rela,
+	[R_RISCV_64] =			apply_r_riscv_64_rela,
+	[R_RISCV_RELATIVE] =		dynamic_linking_not_supported,
+	[R_RISCV_COPY] =		dynamic_linking_not_supported,
+	[R_RISCV_JUMP_SLOT] =		dynamic_linking_not_supported,
+	[R_RISCV_TLS_DTPMOD32] =	dynamic_linking_not_supported,
+	[R_RISCV_TLS_DTPMOD64] =	dynamic_linking_not_supported,
+	[R_RISCV_TLS_DTPREL32] =	dynamic_linking_not_supported,
+	[R_RISCV_TLS_DTPREL64] =	dynamic_linking_not_supported,
+	[R_RISCV_TLS_TPREL32] =		dynamic_linking_not_supported,
+	[R_RISCV_TLS_TPREL64] =		dynamic_linking_not_supported,
+	/* 12-15 undefined */
+	[R_RISCV_BRANCH] =		apply_r_riscv_branch_rela,
+	[R_RISCV_JAL] =			apply_r_riscv_jal_rela,
+	[R_RISCV_CALL] =		apply_r_riscv_call_rela,
+	[R_RISCV_CALL_PLT] =		apply_r_riscv_call_plt_rela,
+	[R_RISCV_GOT_HI20] =		apply_r_riscv_got_hi20_rela,
+	[R_RISCV_TLS_GOT_HI20] =	tls_not_supported,
+	[R_RISCV_TLS_GD_HI20] =		tls_not_supported,
+	[R_RISCV_PCREL_HI20] =		apply_r_riscv_pcrel_hi20_rela,
+	[R_RISCV_PCREL_LO12_I] =	apply_r_riscv_pcrel_lo12_i_rela,
+	[R_RISCV_PCREL_LO12_S] =	apply_r_riscv_pcrel_lo12_s_rela,
+	[R_RISCV_HI20] =		apply_r_riscv_hi20_rela,
+	[R_RISCV_LO12_I] =		apply_r_riscv_lo12_i_rela,
+	[R_RISCV_LO12_S] =		apply_r_riscv_lo12_s_rela,
+	[R_RISCV_TPREL_HI20] =		tls_not_supported,
+	[R_RISCV_TPREL_LO12_I] =	tls_not_supported,
+	[R_RISCV_TPREL_LO12_S] =	tls_not_supported,
+	[R_RISCV_TPREL_ADD] =		tls_not_supported,
+	[R_RISCV_ADD8] =		apply_r_riscv_add8_rela,
+	[R_RISCV_ADD16] =		apply_r_riscv_add16_rela,
+	[R_RISCV_ADD32] =		apply_r_riscv_add32_rela,
+	[R_RISCV_ADD64] =		apply_r_riscv_add64_rela,
+	[R_RISCV_SUB8] =		apply_r_riscv_sub8_rela,
+	[R_RISCV_SUB16] =		apply_r_riscv_sub16_rela,
+	[R_RISCV_SUB32] =		apply_r_riscv_sub32_rela,
+	[R_RISCV_SUB64] =		apply_r_riscv_sub64_rela,
+	/* 41-42 reserved for future standard use */
+	[R_RISCV_ALIGN] =		apply_r_riscv_align_rela,
+	[R_RISCV_RVC_BRANCH] =		apply_r_riscv_rvc_branch_rela,
+	[R_RISCV_RVC_JUMP] =		apply_r_riscv_rvc_jump_rela,
+	/* 46-50 reserved for future standard use */
+	[R_RISCV_RELAX] =		apply_r_riscv_relax_rela,
+	[R_RISCV_SUB6] =		apply_r_riscv_sub6_rela,
+	[R_RISCV_SET6] =		apply_r_riscv_set6_rela,
+	[R_RISCV_SET8] =		apply_r_riscv_set8_rela,
+	[R_RISCV_SET16] =		apply_r_riscv_set16_rela,
+	[R_RISCV_SET32] =		apply_r_riscv_set32_rela,
+	[R_RISCV_32_PCREL] =		apply_r_riscv_32_pcrel_rela,
+	[R_RISCV_IRELATIVE] =		dynamic_linking_not_supported,
+	[R_RISCV_PLT32] =		apply_r_riscv_plt32_rela,
+	[R_RISCV_SET_ULEB128] =		apply_r_riscv_set_uleb128,
+	[R_RISCV_SUB_ULEB128] =		apply_r_riscv_sub_uleb128,
+	/* 62-191 reserved for future standard use */
+	/* 192-255 nonstandard ABI extensions  */
 };
 
 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
@@ -348,6 +479,10 @@  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 	unsigned int i, type;
 	Elf_Addr v;
 	int res;
+	bool uleb128_set_exists = false;
+	u32 *uleb128_set_loc;
+	unsigned long uleb128_set_sym_val;
+
 
 	pr_debug("Applying relocate section %u to %u\n", relsec,
 	       sechdrs[relsec].sh_info);
@@ -425,6 +560,28 @@  int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 				  me->name);
 				return -EINVAL;
 			}
+		} else if (type == R_RISCV_SET_ULEB128) {
+			if (uleb128_set_exists) {
+				pr_err("%s: riscv psABI requires the next ULEB128 relocation to come after a R_RISCV_SET_ULEB128 is an R_RISCV_SUB_ULEB128, not another R_RISCV_SET_ULEB128.\n",
+				       me->name);
+				return -EINVAL;
+			}
+			uleb128_set_exists = true;
+			uleb128_set_loc = location;
+			uleb128_set_sym_val =
+				((Elf_Sym *)sechdrs[symindex].sh_addr +
+					ELF_RISCV_R_SYM(rel[i].r_info))
+					->st_value +
+				rel[i].r_addend;
+		} else if (type == R_RISCV_SUB_ULEB128) {
+			if (uleb128_set_exists && uleb128_set_loc == location) {
+				/* Calculate set and subtraction */
+				v = uleb128_set_sym_val - v;
+			} else {
+				pr_err("%s: R_RISCV_SUB_ULEB128 must always be paired with the first R_RISCV_SET_ULEB128 that comes before it. PC = %p\n",
+				       me->name, location);
+				return -EINVAL;
+			}
 		}
 
 		res = handler(me, location, v);