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Tue, 24 Nov 2020 09:18:16 -0800 (PST) Received: from [192.168.1.11] ([71.212.141.89]) by smtp.gmail.com with ESMTPSA id m11sm3065240pfa.24.2020.11.24.09.18.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Nov 2020 09:18:15 -0800 (PST) Subject: Re: simple aarch64 binary can cause linux-user QEMU to segv in zero_bss() To: Peter Maydell , QEMU Developers , Laurent Vivier , =?UTF-8?Q?Alex_Benn=c3=a9e?= References: From: Richard Henderson Message-ID: <8e6cbc1f-82a5-1cd7-cdf3-59ab45c6d189@linaro.org> Date: Tue, 24 Nov 2020 09:18:12 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::42c; envelope-from=richard.henderson@linaro.org; helo=mail-pf1-x42c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 11/23/20 11:52 AM, Peter Maydell wrote: > Somebody reported this on stackoverflow. Before I spend too > much time thinking about how this ought to work, does anybody > have the elfload.c intended operation in their head still? > Bug description and analysis of what goes wrong below: > > https://stackoverflow.com/questions/64956322/alignment-requirements-for-arm64-elf-executables-run-in-qemu-assembled-by-gas > > Given this trivial asm: > > ===begin program.s=== > // GNU Assembler, ARM64 Linux > > .bss > > .lcomm ARRAY, 16 > > .text > > .global _start > > _start: > mov x8, 93 // exit sys num > mov x0, 0 // success > svc 0 > ===endit=== ... > Should we try to get the SEGV handler working earlier in initialization > (it's pretty hairy machinery so that could be tricky) or should > elfload.c be mprotect()ing things appropriately itself? elfload should be handling this. I believe this should be fixed by https://patchew.org/QEMU/20201118165206.2826-1-steplong@quicinc.com/ r~