linux-kernel - Re: [PATCH v2] fs/proc/task_mmu: add VM_SHADOW

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Message-ID: <ebaa1561-eb42-43f6-ba33-e59982f6b359@redhat.com>
Date: Sat, 7 Jun 2025 20:17:01 +0200
From: David Hildenbrand <david@...hat.com>
To: wangfushuai <wangfushuai@...du.com>, akpm@...ux-foundation.org,
 andrii@...nel.org, osalvador@...e.de, Liam.Howlett@...cle.com,
 christophe.leroy@...roup.eu
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] fs/proc/task_mmu: add VM_SHADOW_STACK for arm64 when
 support GCS

On 07.06.25 15:15, wangfushuai wrote:
> The recent commit adding VM_SHADOW_STACK for arm64 GCS did not update
> the /proc/[pid]/smaps display logic to show the "ss" flag for GCS pages.
> This patch adds the necessary condition to display "ss" flag.
> 
> Fixes: ae80e1629aea ("mm: Define VM_SHADOW_STACK for arm64 when we support GCS")
> Signed-off-by: wangfushuai <wangfushuai@...du.com>
> ---
>   fs/proc/task_mmu.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 27972c0749e7..2c2ee893a797 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -994,6 +994,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>   #ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
>   		[ilog2(VM_SHADOW_STACK)] = "ss",
>   #endif
> +#if defined(CONFIG_ARM64_GCS)
> +		[ilog2(VM_SHADOW_STACK)] = "ss",
> +#endif

Which makes me wonder why we don't select 
CONFIG_ARCH_HAS_USER_SHADOW_STACK for CONFIG_ARM64_GCS?

>   #if defined(CONFIG_64BIT) || defined(CONFIG_PPC32)
>   		[ilog2(VM_DROPPABLE)] = "dp",
>   #endif


-- 
Cheers,

David / dhildenb