diff mbox series

[v4,09/26] x86/boot: Remove mapping from page fault handler

Message ID dd39dfd18bcae4e5116597d4e9c186249aa15850.1671098103.git.baskov@ispras.ru
State New
Headers
Series x86_64: Improvements at compressed kernel stage |

Commit Message

Evgeniy Baskov Dec. 15, 2022, 12:38 p.m. UTC 
  After every implicit mapping is removed, this code is no longer needed.

Remove memory mapping from page fault handler to ensure that there are
no hidden invalid memory accesses.

Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
---
 arch/x86/boot/compressed/ident_map_64.c | 26 ++++++++++---------------
 1 file changed, 10 insertions(+), 16 deletions(-)

Comments

Ard Biesheuvel March 10, 2023, 2:49 p.m. UTC | #1 
On Thu, 15 Dec 2022 at 13:40, Evgeniy Baskov <baskov@ispras.ru> wrote:
>
> After every implicit mapping is removed, this code is no longer needed.
>
> Remove memory mapping from page fault handler to ensure that there are
> no hidden invalid memory accesses.
>
> Tested-by: Mario Limonciello <mario.limonciello@amd.com>
> Tested-by: Peter Jones <pjones@redhat.com>
> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  arch/x86/boot/compressed/ident_map_64.c | 26 ++++++++++---------------
>  1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
> index fec795a4ce23..ba5108c58a4e 100644
> --- a/arch/x86/boot/compressed/ident_map_64.c
> +++ b/arch/x86/boot/compressed/ident_map_64.c
> @@ -386,27 +386,21 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
>  {
>         unsigned long address = native_read_cr2();
>         unsigned long end;
> -       bool ghcb_fault;
> +       char *msg;
>
> -       ghcb_fault = sev_es_check_ghcb_fault(address);
> +       if (sev_es_check_ghcb_fault(address))
> +               msg = "Page-fault on GHCB page:";
> +       else
> +               msg = "Unexpected page-fault:";
>
>         address   &= PMD_MASK;
>         end        = address + PMD_SIZE;
>
>         /*
> -        * Check for unexpected error codes. Unexpected are:
> -        *      - Faults on present pages
> -        *      - User faults
> -        *      - Reserved bits set
> -        */
> -       if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD))
> -               do_pf_error("Unexpected page-fault:", error_code, address, regs->ip);
> -       else if (ghcb_fault)
> -               do_pf_error("Page-fault on GHCB page:", error_code, address, regs->ip);
> -
> -       /*
> -        * Error code is sane - now identity map the 2M region around
> -        * the faulting address.
> +        * Since all memory allocations are made explicit
> +        * now, every page fault at this stage is an
> +        * error and the error handler is there only
> +        * for debug purposes.
>          */
> -       kernel_add_identity_map(address, end, MAP_WRITE);
> +       do_pf_error(msg, error_code, address, regs->ip);
>  }
> --
> 2.37.4
>
diff mbox series

Patch

diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index fec795a4ce23..ba5108c58a4e 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -386,27 +386,21 @@  void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
 	unsigned long address = native_read_cr2();
 	unsigned long end;
-	bool ghcb_fault;
+	char *msg;
 
-	ghcb_fault = sev_es_check_ghcb_fault(address);
+	if (sev_es_check_ghcb_fault(address))
+		msg = "Page-fault on GHCB page:";
+	else
+		msg = "Unexpected page-fault:";
 
 	address   &= PMD_MASK;
 	end        = address + PMD_SIZE;
 
 	/*
-	 * Check for unexpected error codes. Unexpected are:
-	 *	- Faults on present pages
-	 *	- User faults
-	 *	- Reserved bits set
-	 */
-	if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD))
-		do_pf_error("Unexpected page-fault:", error_code, address, regs->ip);
-	else if (ghcb_fault)
-		do_pf_error("Page-fault on GHCB page:", error_code, address, regs->ip);
-
-	/*
-	 * Error code is sane - now identity map the 2M region around
-	 * the faulting address.
+	 * Since all memory allocations are made explicit
+	 * now, every page fault at this stage is an
+	 * error and the error handler is there only
+	 * for debug purposes.
 	 */
-	kernel_add_identity_map(address, end, MAP_WRITE);
+	do_pf_error(msg, error_code, address, regs->ip);
 }