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[173.198.77.218]) by smtp.gmail.com with ESMTPSA id ns18sm18705755pjb.31.2021.08.09.14.00.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Aug 2021 14:00:46 -0700 (PDT) Subject: Re: [PATCH for 6.2 28/49] bsd-user: Move stack initializtion into a per-os file. To: Warner Losh , qemu-devel@nongnu.org References: <20210807214242.82385-1-imp@bsdimp.com> <20210807214242.82385-29-imp@bsdimp.com> From: Richard Henderson Message-ID: <5ac9c3db-b7e0-9439-b2b5-a6ff3ed38b18@linaro.org> Date: Mon, 9 Aug 2021 11:00:43 -1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210807214242.82385-29-imp@bsdimp.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::102c; envelope-from=richard.henderson@linaro.org; helo=mail-pj1-x102c.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: , Cc: kevans@freebsd.org, Warner Losh , Stacey Son Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/7/21 11:42 AM, Warner Losh wrote: > +static inline int setup_initial_stack(struct bsd_binprm *bprm, > + abi_ulong *ret_addr, abi_ulong *stringp) > +{ > + int i; > + abi_ulong stack_hi_addr; > + size_t execpath_len, stringspace; > + abi_ulong destp, argvp, envp, p; > + struct target_ps_strings ps_strs; > + char canary[sizeof(abi_long) * 8]; > + > + stack_hi_addr = p = target_stkbas + target_stksiz; > + > + /* Save some space for ps_strings. */ > + p -= sizeof(struct target_ps_strings); > + > +#ifdef TARGET_SZSIGCODE > + /* Add machine depedent sigcode. */ > + p -= TARGET_SZSIGCODE; > + if (setup_sigtramp(p, (unsigned)offsetof(struct target_sigframe, sf_uc), > + TARGET_FREEBSD_NR_sigreturn)) { > + errno = EFAULT; > + return -1; > + } > +#endif Hmm. The x86 version you just added always returns -EOPNOTSUPP. Therefore I conclude that TARGET_SZSIGCODE is unset. Perhaps a better interface would be p = setup_sigtramp(p, ...); if (p == 0) { // fail } then you don't need to expose TARGET_SZSIGCODE or have conditional compilation here. Perhaps for the to-do list... > + /* Add canary for SSP. */ > + arc4random_buf(canary, sizeof(canary)); You should use qemu_guest_getrandom_nofail here. > + /* > + * Deviate from FreeBSD stack layout: force stack to new page here > + * so that signal trampoline is not sharing the page with user stack > + * frames. This is actively harmful in qemu as it marks pages with > + * code it translated as read-only, which is somewhat problematic > + * for user trying to use the stack as intended. > + */ A decent short-term solution. I'll draw your attention to my vdso patch set for linux-user: https://patchew.org/QEMU/20210706234932.356913-1-richard.henderson@linaro.org/ Modulo randomness, Reviewed-by: Richard Henderson r~