linux-kernel - Re: [PATCH RFT v3 1/5] mm: Introduce ARCH_HAS_USER_SHADOW

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Date: Sun, 4 Feb 2024 12:56:41 +0100
From: Mike Rapoport <rppt@...nel.org>
To: Mark Brown <broonie@...nel.org>
Cc: "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
	Deepak Gupta <debug@...osinc.com>,
	Szabolcs Nagy <Szabolcs.Nagy@....com>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Florian Weimer <fweimer@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Kees Cook <keescook@...omium.org>,
	jannh@...gle.com, linux-kselftest@...r.kernel.org,
	linux-api@...r.kernel.org, David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH RFT v3 1/5] mm: Introduce ARCH_HAS_USER_SHADOW_STACK

On Mon, Nov 20, 2023 at 11:54:29PM +0000, 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@...hat.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Mark Brown <broonie@...nel.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..6713bb3b0b48 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 or RISC-V Zicfiss).

The whitespace looks suspicious, I think there should be a leading tab.
Otherwise

Reviewed-by: Mike Rapoport (IBM) <rppt@...nel.org>

> +
>  source "mm/damon/Kconfig"
>  
>  endmenu
> 
> -- 
> 2.30.2
> 

-- 
Sincerely yours,
Mike.