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

Kees Cook
2020-03-13T00:00:33Z

On Wed, Mar 11, 2020 at 07:26:07PM +0000, Mark Brown wrote:
> From: Daniel Kiss <daniel.kiss@arm.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@arm.com>

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

-Kees

> Signed-off-by: Mark Brown <broonie@kernel.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