[PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and efi=old_map

[PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and efi=old_map

[Sai Praneeth Prakhya]

From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

EFI_PGT_DUMP, as the name suggests dumps efi page tables to dmesg during
kernel boot. This feature is very useful while debugging page
faults/null pointer dereferences to efi related addresses. Presently,
this feature is limited only to x86_64, so let's extend it to other efi
configurations like kexec kernel, efi=old_map and to x86_32 as well.
This doesn't effect normal boot path because this config option should
be used only for debug purposes.

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
---
 arch/x86/platform/efi/efi.c    | 2 ++
 arch/x86/platform/efi/efi_32.c | 9 ++++++++-
 arch/x86/platform/efi/efi_64.c | 5 ++++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 217dc166c649..a6d6cd8fe78a 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -890,6 +890,8 @@ static void __init kexec_enter_virtual_mode(void)
 	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
 		runtime_code_page_mkexec();
 
+	efi_dump_pagetable();
+
 	/* clean DUMMY object */
 	efi_delete_dummy_variable();
 #endif
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 9b1abcf6e7bb..9477653c78f8 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -44,7 +44,14 @@ int __init efi_alloc_page_tables(void)
 }
 
 void efi_sync_low_kernel_mappings(void) {}
-void __init efi_dump_pagetable(void) {}
+
+void __init efi_dump_pagetable(void)
+{
+#ifdef CONFIG_EFI_PGT_DUMP
+	ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+#endif
+}
+
 int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 {
 	return 0;
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 76e1cd6b74dd..3bde2589fdb9 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -510,7 +510,10 @@ void __init efi_runtime_update_mappings(void)
 void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
-	ptdump_walk_pgd_level(NULL, efi_pgd);
+	if (efi_enabled(EFI_OLD_MEMMAP))
+		ptdump_walk_pgd_level(NULL, swapper_pg_dir);
+	else
+		ptdump_walk_pgd_level(NULL, efi_pgd);
 #endif
 }
 
-- 
2.1.4

Re: [PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and efi=old_map

[Borislav Petkov]

On Wed, May 10, 2017 at 03:49:05PM -0700, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
> 
> EFI_PGT_DUMP, as the name suggests dumps efi page tables to dmesg during
> kernel boot. This feature is very useful while debugging page
> faults/null pointer dereferences to efi related addresses. Presently,
> this feature is limited only to x86_64, so let's extend it to other efi
> configurations like kexec kernel, efi=old_map and to x86_32 as well.
> This doesn't effect normal boot path because this config option should
> be used only for debug purposes.
> 
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Ricardo Neri <ricardo.neri@intel.com>
> Cc: Matt Fleming <matt@codeblueprint.co.uk>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Ravi Shankar <ravi.v.shankar@intel.com>
> ---
>  arch/x86/platform/efi/efi.c    | 2 ++
>  arch/x86/platform/efi/efi_32.c | 9 ++++++++-
>  arch/x86/platform/efi/efi_64.c | 5 ++++-
>  3 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 217dc166c649..a6d6cd8fe78a 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -890,6 +890,8 @@ static void __init kexec_enter_virtual_mode(void)
>  	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
>  		runtime_code_page_mkexec();
>  
> +	efi_dump_pagetable();

You can call that only once at the end of efi_enter_virtual_mode()
instead of adding it here and leaving it in __efi_enter_virtual_mode().

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and efi=old_map

[Sai Praneeth Prakhya]

On Thu, 2017-05-11 at 13:18 +0200, Borislav Petkov wrote:
> On Wed, May 10, 2017 at 03:49:05PM -0700, Sai Praneeth Prakhya wrote:
> > From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
> > 
> > EFI_PGT_DUMP, as the name suggests dumps efi page tables to dmesg during
> > kernel boot. This feature is very useful while debugging page
> > faults/null pointer dereferences to efi related addresses. Presently,
> > this feature is limited only to x86_64, so let's extend it to other efi
> > configurations like kexec kernel, efi=old_map and to x86_32 as well.
> > This doesn't effect normal boot path because this config option should
> > be used only for debug purposes.
> > 
> > Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: Ricardo Neri <ricardo.neri@intel.com>
> > Cc: Matt Fleming <matt@codeblueprint.co.uk>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: Ravi Shankar <ravi.v.shankar@intel.com>
> > ---
> >  arch/x86/platform/efi/efi.c    | 2 ++
> >  arch/x86/platform/efi/efi_32.c | 9 ++++++++-
> >  arch/x86/platform/efi/efi_64.c | 5 ++++-
> >  3 files changed, 14 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> > index 217dc166c649..a6d6cd8fe78a 100644
> > --- a/arch/x86/platform/efi/efi.c
> > +++ b/arch/x86/platform/efi/efi.c
> > @@ -890,6 +890,8 @@ static void __init kexec_enter_virtual_mode(void)
> >  	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
> >  		runtime_code_page_mkexec();
> >  
> > +	efi_dump_pagetable();
> 
> You can call that only once at the end of efi_enter_virtual_mode()
> instead of adding it here and leaving it in __efi_enter_virtual_mode().
> 

Thanks for the suggestion Boris,
Sure! will roll out v2 with this change

Regards,
Sai