Re: [PATCH v4 01/30] mm: Introduce ARCH_HAS_USER_SHADOW_STACK

[Carlos Bilbao <carlos.bilbao.osdev@gmail.com>]

On 9/12/24 18:16, Deepak Gupta wrote:

> From: Mark Brown <broonie@kernel.org>
>
> 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>
> Acked-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Reviewed-by: Deepak Gupta <debug@rivosinc.com>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> ---
>  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 007bab9f2a0e..320e1f411163 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1957,6 +1957,7 @@ 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 5f171ad7b436..0ea49725f524 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -984,7 +984,7 @@ 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
>  #ifdef CONFIG_64BIT
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 147073601716..e39796ea17db 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -346,7 +346,7 @@ 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 b72e7d040f78..3167be663bca 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1263,6 +1263,12 @@ config IOMMU_MM_DATA
>  config EXECMEM
>  	bool
>  
> +config ARCH_HAS_USER_SHADOW_STACK
> +	bool
> +	help
> +	  The architecture has hardware support for userspace shadow call
> +          stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
> +
>  source "mm/damon/Kconfig"


Reviewed-by: Carlos Bilbao <carlos.bilbao.osdev@gmail.com>


>  
>  endmenu


Thanks, Carlos