Message-ID: <6ccc8d30-336a-12af-1179-5dc4eca3048d@redhat.com>
Date:   Mon, 20 Feb 2023 13:58:38 +0100
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Subject: Re: [PATCH v6 22/41] mm/mmap: Add shadow stack pages to memory
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To:     Rick Edgecombe <rick.p.edgecombe@intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Andy Lutomirski <luto@kernel.org>,
        Balbir Singh <bsingharora@gmail.com>,
        Borislav Petkov <bp@alien8.de>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Eugene Syromiatnikov <esyr@redhat.com>,
        Florian Weimer <fweimer@redhat.com>,
        "H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Kees Cook <keescook@chromium.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Weijiang Yang <weijiang.yang@intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        John Allen <john.allen@amd.com>, kcc@google.com,
        eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com,
        dethoma@microsoft.com, akpm@linux-foundation.org,
        Andrew.Cooper3@citrix.com, christina.schimpe@intel.com,
        debug@rivosinc.com
Cc:     Yu-cheng Yu <yu-cheng.yu@intel.com>
References: <20230218211433.26859-1-rick.p.edgecombe@intel.com>
 <20230218211433.26859-23-rick.p.edgecombe@intel.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20230218211433.26859-23-rick.p.edgecombe@intel.com>
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On 18.02.23 22:14, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@intel.com>
> 
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
> 
> Account shadow stack pages to stack memory.
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Tested-by: John Allen <john.allen@amd.com>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: Kees Cook <keescook@chromium.org>
> 
> ---
> v3:
>   - Remove unneeded VM_SHADOW_STACK check in accountable_mapping()
>     (Kirill)
> 
> v2:
>   - Remove is_shadow_stack_mapping() and just change it to directly bitwise
>     and VM_SHADOW_STACK.
> 
> Yu-cheng v26:
>   - Remove redundant #ifdef CONFIG_MMU.
> 
> Yu-cheng v25:
>   - Remove #ifdef CONFIG_ARCH_HAS_SHADOW_STACK for is_shadow_stack_mapping().
> ---
>   mm/mmap.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 425a9349e610..9f85596cce31 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -3290,6 +3290,8 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
>   		mm->exec_vm += npages;
>   	else if (is_stack_mapping(flags))
>   		mm->stack_vm += npages;
> +	else if (flags & VM_SHADOW_STACK)
> +		mm->stack_vm += npages;

Why not modify is_stack_mapping() ?

-- 
Thanks,

David / dhildenb