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References: <20231122-arm64-gcs-v7-0-201c483bd775@kernel.org>
 <20231122-arm64-gcs-v7-13-201c483bd775@kernel.org>
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From:   Thiago Jung Bauermann <thiago.bauermann@linaro.org>
To:     Mark Brown <broonie@kernel.org>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Arnd Bergmann <arnd@arndb.de>, Oleg Nesterov <oleg@redhat.com>,
        Eric Biederman <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>,
        "Rick P. Edgecombe" <rick.p.edgecombe@intel.com>,
        Deepak Gupta <debug@rivosinc.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
        "H.J. Lu" <hjl.tools@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Florian Weimer <fweimer@redhat.com>,
        Christian Brauner <brauner@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
        kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH v7 13/39] arm64/mm: Map pages for guarded control stack
In-reply-to: <20231122-arm64-gcs-v7-13-201c483bd775@kernel.org>
Date:   Mon, 04 Dec 2023 00:01:49 -0300
Message-ID: <87a5qqisbm.fsf@linaro.org>
MIME-Version: 1.0
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Hello,

Mark Brown <broonie@kernel.org> writes:

> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
> index 645fe60d000f..605d4e6edc1d 100644
> --- a/arch/arm64/mm/mmap.c
> +++ b/arch/arm64/mm/mmap.c
> @@ -79,9 +79,20 @@ arch_initcall(adjust_protection_map);
>  
>  pgprot_t vm_get_page_prot(unsigned long vm_flags)
>  {
> -	pteval_t prot = pgprot_val(protection_map[vm_flags &
> +	pteval_t prot;
> +
> +	/* If this is a GCS then only interpret VM_WRITE. */
> +	if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) {
> +		if (vm_flags & VM_WRITE)
> +			prot = _PAGE_GCS;
> +		else
> +			prot = _PAGE_GCS_RO;
> +	} else {
> +		prot = pgprot_val(protection_map[vm_flags &
>  				   (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);
> +	}
>  
> +	/* VM_ARM64_BTI on a GCS is rejected in arch_valdiate_flags() */

s/valdiate/validate/

>  	if (vm_flags & VM_ARM64_BTI)
>  		prot |= PTE_GP;


-- 
Thiago