linux-kernel - Re: [PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and efi=old

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Date:   Thu, 11 May 2017 11:44:17 -0700
From:   Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri@...el.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ravi Shankar <ravi.v.shankar@...el.com>
Subject: Re: [PATCH] x86/efi: Add EFI_PGT_DUMP support for x86_32, kexec and
 efi=old_map

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@...el.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@...el.com>
> > Cc: Borislav Petkov <bp@...en8.de>
> > Cc: Ricardo Neri <ricardo.neri@...el.com>
> > Cc: Matt Fleming <matt@...eblueprint.co.uk>
> > Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Cc: Ravi Shankar <ravi.v.shankar@...el.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