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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=5K2KfWGbdPDvciUxJWKmXs8jymeyhVJTI52mBn5Jn2U=; b=pQ84ziRlapHWkg3TeATfzD6PADzPxKwY27zM3yRmTiRzFZer2cDA6Lru2UwGPZtFFL ctZLAd26zuZWj9i1vLkIGGxKOFi+4z9WtZzVshax7UZi0CLBBn28onukYiKaLHSw6YSJ Vk/XarhkKJFFE0741W+1Pppyu8rN20BaxFd2iPySj7l6PAMFNSrVE6KwBmcxjtFldUoy DHSifgKZ/6wc8tkUVtLprQAVJCtGsv3sUGvfxqGaJnS6NH1vrYPJMKQ3tnzB8h525GK2 9H9puk3dTqqKHVymsbNS4t8MY1OgGKf4RauQy/4miM8dFRaftxj/x+wi8A+YQ5oY8xQP uMOw== X-Gm-Message-State: AGi0PuYiQvQjidAEnT1VsX3+gTsd1gKm++mxpE8gHIAAofI18DKmrTsC j2mhvDpnKAaDScJPw2wyk6QXu0Eh4T+jD9y6Zn0= X-Google-Smtp-Source: APiQypKZHPN6pHK1vtX6gJq9lobiR8zzmYnoXCSFDICaarTBdgedlZVYx+cSajiHci65J+75kJpbiA+ZLbes2n1w/OI= X-Received: by 2002:a0c:bec4:: with SMTP id f4mr23363061qvj.26.1588003248063; Mon, 27 Apr 2020 09:00:48 -0700 (PDT) Date: Mon, 27 Apr 2020 09:00:13 -0700 In-Reply-To: <20200427160018.243569-1-samitolvanen@google.com> Message-Id: <20200427160018.243569-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200427160018.243569-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.2.303.gf8c07b1a785-goog Subject: [PATCH v13 07/12] arm64: efi: restore x18 if it was corrupted From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200427_090050_239400_60B9932B X-CRM114-Status: GOOD ( 11.27 ) 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: Kees Cook , Jann Horn , Marc Zyngier , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , Masami Hiramatsu , Sami Tolvanen , clang-built-linux@googlegroups.com, Laura Abbott , Dave Martin , 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 If we detect a corrupted x18, restore the register before jumping back to potentially SCS instrumented code. This is safe, because the wrapper is called with preemption disabled and a separate shadow stack is used for interrupt handling. Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook Acked-by: Will Deacon --- arch/arm64/kernel/efi-rt-wrapper.S | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S index 3fc71106cb2b..6ca6c0dc11a1 100644 --- a/arch/arm64/kernel/efi-rt-wrapper.S +++ b/arch/arm64/kernel/efi-rt-wrapper.S @@ -34,5 +34,14 @@ ENTRY(__efi_rt_asm_wrapper) ldp x29, x30, [sp], #32 b.ne 0f ret -0: b efi_handle_corrupted_x18 // tail call +0: + /* + * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a + * shadow stack pointer, which we need to restore before returning to + * potentially instrumented code. This is safe because the wrapper is + * called with preemption disabled and a separate shadow stack is used + * for interrupts. + */ + mov x18, x2 + b efi_handle_corrupted_x18 // tail call ENDPROC(__efi_rt_asm_wrapper) -- 2.26.2.303.gf8c07b1a785-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel