[1/2] x86/paravirt: Use relative reference for original instruction
Commit Message
Similar to the alternative patching, use relative reference for original
instruction rather than absolute one, which saves 8 bytes for one entry
on x86_64. And it could generate R_X86_64_PC32 relocation instead of
R_X86_64_64 relocation, which also reduces relocation metadata on
relocatable builds. And the alignment could be hard coded to be 4 now.
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
arch/x86/include/asm/paravirt.h | 10 +++++-----
arch/x86/include/asm/paravirt_types.h | 8 ++++----
arch/x86/kernel/alternative.c | 8 +++++---
arch/x86/kernel/callthunks.c | 2 +-
4 files changed, 15 insertions(+), 13 deletions(-)
@@ -742,16 +742,16 @@ extern void default_banner(void);
#else /* __ASSEMBLY__ */
-#define _PVSITE(ptype, ops, word, algn) \
+#define _PVSITE(ptype, ops) \
771:; \
ops; \
772:; \
.pushsection .parainstructions,"a"; \
- .align algn; \
- word 771b; \
+ .align 4; \
+ .long 771b-.; \
.byte ptype; \
.byte 772b-771b; \
- _ASM_ALIGN; \
+ .align 4; \
.popsection
@@ -759,7 +759,7 @@ extern void default_banner(void);
#ifdef CONFIG_PARAVIRT_XXL
#define PARA_PATCH(off) ((off) / 8)
-#define PARA_SITE(ptype, ops) _PVSITE(ptype, ops, .quad, 8)
+#define PARA_SITE(ptype, ops) _PVSITE(ptype, ops)
#define PARA_INDIRECT(addr) *addr(%rip)
#ifdef CONFIG_DEBUG_ENTRY
@@ -5,7 +5,7 @@
#ifndef __ASSEMBLY__
/* These all sit in the .parainstructions section to tell us what to patch. */
struct paravirt_patch_site {
- u8 *instr; /* original instructions */
+ s32 instr_offset; /* original instructions */
u8 type; /* type of this instruction */
u8 len; /* length of original instruction */
};
@@ -270,11 +270,11 @@ extern struct paravirt_patch_template pv_ops;
#define _paravirt_alt(insn_string, type) \
"771:\n\t" insn_string "\n" "772:\n" \
".pushsection .parainstructions,\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR " 771b\n" \
+ " .align 4\n" \
+ " .long 771b-.\n" \
" .byte " type "\n" \
" .byte 772b-771b\n" \
- _ASM_ALIGN "\n" \
+ " .align 4\n" \
".popsection\n"
/* Generate patchable code, with the default asm parameters. */
@@ -1364,20 +1364,22 @@ void __init_or_module apply_paravirt(struct paravirt_patch_site *start,
{
struct paravirt_patch_site *p;
char insn_buff[MAX_PATCH_LEN];
+ u8 *instr;
for (p = start; p < end; p++) {
unsigned int used;
+ instr = (u8 *)&p->instr_offset + p->instr_offset;
BUG_ON(p->len > MAX_PATCH_LEN);
/* prep the buffer with the original instructions */
- memcpy(insn_buff, p->instr, p->len);
- used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len);
+ memcpy(insn_buff, instr, p->len);
+ used = paravirt_patch(p->type, insn_buff, (unsigned long)instr, p->len);
BUG_ON(used > p->len);
/* Pad the rest with nops */
add_nops(insn_buff + used, p->len - used);
- text_poke_early(p->instr, insn_buff, p->len);
+ text_poke_early(instr, insn_buff, p->len);
}
}
extern struct paravirt_patch_site __start_parainstructions[],
@@ -245,7 +245,7 @@ patch_paravirt_call_sites(struct paravirt_patch_site *start,
struct paravirt_patch_site *p;
for (p = start; p < end; p++)
- patch_call(p->instr, ct);
+ patch_call((void *)&p->instr_offset + p->instr_offset, ct);
}
static __init_or_module void