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[173.198.77.92]) by smtp.gmail.com with ESMTPSA id x18sm44832674pfr.26.2020.01.21.07.51.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 07:51:50 -0800 (PST) Subject: Re: [PATCH v2 3/5] linux-user/i386: Emulate x86_64 vsyscalls To: =?UTF-8?Q?Alex_Benn=c3=a9e?= References: <20200116194341.402-1-richard.henderson@linaro.org> <20200116194341.402-4-richard.henderson@linaro.org> <87v9p62vt5.fsf@linaro.org> <87r1zt15jg.fsf@linaro.org> From: Richard Henderson Message-ID: Date: Tue, 21 Jan 2020 05:51:46 -1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <87r1zt15jg.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::642 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: , Cc: Paolo Bonzini , qemu-devel@nongnu.org, laurent@vivier.eu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 1/21/20 12:13 AM, Alex Bennée wrote: > > Richard Henderson writes: > >> On 1/20/20 1:48 AM, Alex Bennée wrote: >>>> + default: >>>> + sigsegv: >>> >>> this label looks a little extraneous. >>> >>> Otherwise: >>> >>> Reviewed-by: Alex Bennée >>> >> >> Look a little further down: >> >>> + default: >>> + sigsegv: >>> + /* Like force_sig(SIGSEGV). */ >>> + gen_signal(env, TARGET_SIGSEGV, TARGET_SI_KERNEL, 0); >>> + return; >>> + } >>> + >>> + /* >>> + * Validate the return address. >>> + * Note that the kernel treats this the same as an invalid entry point. >>> + */ >>> + if (get_user_u64(caller, env->regs[R_ESP])) { >>> + goto sigsegv; >>> + } > > Wouldn't this read better: > > /* > * Validate the entry point. We have already validated the page > * during translation, now verify the offset. > */ > switch (env->eip & ~TARGET_PAGE_MASK) { > case 0x000: > syscall = TARGET_NR_gettimeofday; > break; > case 0x400: > syscall = TARGET_NR_time; > break; > case 0x800: > syscall = TARGET_NR_getcpu; > break; > default: > syscall = -1; > break; > } > > /* > * If we have an invalid entry point or an invalid return address we > * generate a SIGSEG. > */ > if (syscall < 0 || get_user_u64(caller, env->regs[R_ESP])) { > gen_signal(env, TARGET_SIGSEGV, TARGET_SI_KERNEL, 0); > return; > } > Only if you have a violent goto allergy. r~