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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jl7EV-0001kQ-7n; Tue, 16 Jun 2020 08:46:15 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jl7ES-0001js-0u for linux-arm-kernel@lists.infradead.org; Tue, 16 Jun 2020 08:46:13 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 79EB91FB; Tue, 16 Jun 2020 01:46:10 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.1.157]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5E24B3F71F; Tue, 16 Jun 2020 01:46:09 -0700 (PDT) Date: Tue, 16 Jun 2020 09:45:48 +0100 From: Mark Rutland To: Will Deacon Subject: Re: [PATCH] arm64: pgtable: Clear the GP bit for non-executable kernel pages Message-ID: <20200616084548.GA11780@C02TD0UTHF1T.local> References: <20200615154642.3579-1-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200615154642.3579-1-will@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200616_014612_112388_008B3B37 X-CRM114-Status: GOOD ( 15.34 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Brown , kernel-team@android.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jun 15, 2020 at 04:46:42PM +0100, Will Deacon wrote: > Commit cca98e9f8b5e ("mm: enforce that vmap can't map pages executable") > introduced 'pgprot_nx(prot)' for arm64 but colliding silently with the > BTI support during the merge window, which endeavours to clear the GP > bit for non-executable kernel mappings in set_memory_nx(). > > For consistency between the two APIs, clear the GP bit in pgprot_nx(). > > Cc: Mark Rutland > Cc: Mark Brown > Signed-off-by: Will Deacon > --- > arch/arm64/include/asm/pgtable.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 6dbd267ab931..758e2d1577d0 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -416,7 +416,7 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd) > __pgprot((pgprot_val(prot) & ~(mask)) | (bits)) > > #define pgprot_nx(prot) \ > - __pgprot_modify(prot, 0, PTE_PXN) > + __pgprot_modify(prot, PTE_MAYBE_GP, PTE_PXN) Since this is just used to clear the bit, we could use PTE_GP directly and allow the compiler to constant fold this. Either way: Acked-by: Mark Rutland Mark. > > /* > * Mark the prot value as uncacheable and unbufferable. > -- > 2.27.0.290.gba653c62da-goog > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel