Re: [PATCH RFC RFT v2 1/5] mm: Introduce ARCH_HAS_USER_SHADOW_STACK

David Hildenbrand
2023-11-15T15:12:58Z

On 14.11.23 21:05, Mark Brown wrote:
> Since multiple architectures have support for shadow stacks and we need to
> select support for this feature in several places in the generic code
> provide a generic config option that the architectures can select.
>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> arch/x86/Kconfig | 1 +
> fs/proc/task_mmu.c | 2 +-
> include/linux/mm.h | 2 +-
> mm/Kconfig | 6 ++++++
> 4 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 3762f41bb092..14b7703a9a2b 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1952,6 +1952,7 @@ config X86_USER_SHADOW_STACK
> depends on AS_WRUSS
> depends on X86_64
> select ARCH_USES_HIGH_VMA_FLAGS
> + select ARCH_HAS_USER_SHADOW_STACK
> select X86_CET
> help
> Shadow stack protection is a hardware feature that detects function
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ef2eb12906da..f0a904aeee8e 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -699,7 +699,7 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> [ilog2(VM_UFFD_MINOR)] = "ui",
> #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
> -#ifdef CONFIG_X86_USER_SHADOW_STACK
> +#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
> [ilog2(VM_SHADOW_STACK)] = "ss",
> #endif
> };
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 418d26608ece..10462f354614 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -341,7 +341,7 @@ extern unsigned int kobjsize(const void *objp);
> #endif
> #endif /* CONFIG_ARCH_HAS_PKEYS */
>
> -#ifdef CONFIG_X86_USER_SHADOW_STACK
> +#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
> /*
> * VM_SHADOW_STACK should not be set with VM_SHARED because of lack of
> * support core mm.
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 89971a894b60..b8638da636e1 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1270,6 +1270,12 @@ config LOCK_MM_AND_FIND_VMA
> bool
> depends on !STACK_GROWSUP
>
> +config ARCH_HAS_USER_SHADOW_STACK
> + bool
> + help
> + The architecture has hardware support for userspace shadow call
> + stacks (eg, x86 CET, arm64 GCS, RISC-V Zisslpcfi).
> +

Probably less controversial if we start with one example we have in
place: "e.g., x86 CET". That should be sufficient to understand what
this is about :)

Acked-by: David Hildenbrand <david@redhat.com>

--
Cheers,

David / dhildenb