linux-kernel - Re: [PATCH v9 12/13] mm: smaps: Report arm64 guarded pages in smaps

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Date:   Thu, 12 Mar 2020 17:00:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Paul Elliott <paul.elliott@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Amit Kachhap <amit.kachhap@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Marc Zyngier <maz@...nel.org>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        "H . J . Lu " <hjl.tools@...il.com>,
        Andrew Jones <drjones@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Richard Henderson <richard.henderson@...aro.org>,
        Kristina Martšenko <kristina.martsenko@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Florian Weimer <fweimer@...hat.com>,
        Sudakshina Das <sudi.das@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Daniel Kiss <daniel.kiss@....com>
Subject: Re: [PATCH v9 12/13] mm: smaps: Report arm64 guarded pages in smaps

On Wed, Mar 11, 2020 at 07:26:07PM +0000, Mark Brown wrote:
> From: Daniel Kiss <daniel.kiss@....com>
> 
> The arm64 Branch Target Identification support is activated by marking
> executable pages as guarded pages.  Report pages mapped this way in
> smaps to aid diagnostics.
> 
> Signed-off-by: Daniel Kiss <daniel.kiss@....com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> Signed-off-by: Mark Brown <broonie@...nel.org>
> ---
>  Documentation/filesystems/proc.txt | 1 +
>  fs/proc/task_mmu.c                 | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
> index 99ca040e3f90..ed5465d0f435 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -519,6 +519,7 @@ manner. The codes are the following:
>      hg  - huge page advise flag
>      nh  - no-huge page advise flag
>      mg  - mergable advise flag
> +    bt  - arm64 BTI guarded page
>  
>  Note that there is no guarantee that every flag and associated mnemonic will
>  be present in all further kernel releases. Things get changed, the flags may
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 3ba9ae83bff5..1e3409c484d1 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -668,6 +668,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>  		[ilog2(VM_ARCH_1)]	= "ar",
>  		[ilog2(VM_WIPEONFORK)]	= "wf",
>  		[ilog2(VM_DONTDUMP)]	= "dd",
> +#ifdef CONFIG_ARM64_BTI
> +		[ilog2(VM_ARM64_BTI)]	= "bt",
> +#endif
>  #ifdef CONFIG_MEM_SOFT_DIRTY
>  		[ilog2(VM_SOFTDIRTY)]	= "sd",
>  #endif
> -- 
> 2.20.1
> 

-- 
Kees Cook