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Sat, 18 Sep 2021 11:45:31 -0700 (PDT) Received: from localhost.localdomain ([71.212.134.125]) by smtp.gmail.com with ESMTPSA id y26sm9555858pfe.69.2021.09.18.11.45.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 18 Sep 2021 11:45:31 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v2 03/41] accel/tcg: Split out handle_sigsegv_accerr_write Date: Sat, 18 Sep 2021 11:44:49 -0700 Message-Id: <20210918184527.408540-4-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210918184527.408540-1-richard.henderson@linaro.org> References: <20210918184527.408540-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::62f; envelope-from=richard.henderson@linaro.org; helo=mail-pl1-x62f.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, 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: laurent@vivier.eu, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is the major portion of handle_cpu_signal which is specific to tcg, handling the page protections for the translations. Most of the rest will migrate to linux-user/ shortly. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- v2: Pass guest address to handle_sigsegv_accerr_write. --- include/exec/exec-all.h | 12 +++++ accel/tcg/user-exec.c | 103 ++++++++++++++++++++++++---------------- 2 files changed, 74 insertions(+), 41 deletions(-) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index e54f8e5d65..5f94d799aa 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -673,6 +673,18 @@ static inline tb_page_addr_t get_page_addr_code_hostp(CPUArchState *env, */ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write); +/** + * handle_sigsegv_accerr_write: + * @cpu: the cpu context + * @old_set: the sigset_t from the signal ucontext_t + * @host_pc: the host pc, adjusted for the signal + * @host_addr: the host address of the fault + * + * Return true if the write fault has been handled, and should be re-tried. + */ +bool handle_sigsegv_accerr_write(CPUState *cpu, sigset_t *old_set, + uintptr_t host_pc, abi_ptr guest_addr); + /** * cpu_signal_handler * @signum: host signal number diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index e94f1fed00..6f4fc01b60 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -114,6 +114,54 @@ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write) return is_write ? MMU_DATA_STORE : MMU_DATA_LOAD; } +/** + * handle_sigsegv_accerr_write: + * @cpu: the cpu context + * @old_set: the sigset_t from the signal ucontext_t + * @host_pc: the host pc, adjusted for the signal + * @guest_addr: the guest address of the fault + * + * Return true if the write fault has been handled, and should be re-tried. + * + * Note that it is important that we don't call page_unprotect() unless + * this is really a "write to nonwriteable page" fault, because + * page_unprotect() assumes that if it is called for an access to + * a page that's writeable this means we had two threads racing and + * another thread got there first and already made the page writeable; + * so we will retry the access. If we were to call page_unprotect() + * for some other kind of fault that should really be passed to the + * guest, we'd end up in an infinite loop of retrying the faulting access. + */ +bool handle_sigsegv_accerr_write(CPUState *cpu, sigset_t *old_set, + uintptr_t host_pc, abi_ptr guest_addr) +{ + switch (page_unprotect(guest_addr, host_pc)) { + case 0: + /* + * Fault not caused by a page marked unwritable to protect + * cached translations, must be the guest binary's problem. + */ + return false; + case 1: + /* + * Fault caused by protection of cached translation; TBs + * invalidated, so resume execution. Retain helper_retaddr + * for a possible second fault. + */ + return true; + case 2: + /* + * Fault caused by protection of cached translation, and the + * currently executing TB was modified and must be exited + * immediately. Clear helper_retaddr for next execution. + */ + cpu_exit_tb_from_sighandler(cpu, old_set); + /* NORETURN */ + default: + g_assert_not_reached(); + } +} + /* * 'pc' is the host PC at which the exception was raised. * 'address' is the effective address of the memory exception. @@ -125,8 +173,9 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info, { CPUState *cpu = current_cpu; CPUClass *cc; - unsigned long address = (unsigned long)info->si_addr; + unsigned long host_addr = (unsigned long)info->si_addr; MMUAccessType access_type = adjust_signal_pc(&pc, is_write); + abi_ptr guest_addr; /* For synchronous signals we expect to be coming from the vCPU * thread (so current_cpu should be valid) and either from running @@ -143,49 +192,21 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info, #if defined(DEBUG_SIGNAL) printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n", - pc, address, is_write, *(unsigned long *)old_set); + pc, host_addr, is_write, *(unsigned long *)old_set); #endif - /* XXX: locking issue */ - /* Note that it is important that we don't call page_unprotect() unless - * this is really a "write to nonwriteable page" fault, because - * page_unprotect() assumes that if it is called for an access to - * a page that's writeable this means we had two threads racing and - * another thread got there first and already made the page writeable; - * so we will retry the access. If we were to call page_unprotect() - * for some other kind of fault that should really be passed to the - * guest, we'd end up in an infinite loop of retrying the faulting - * access. - */ - if (is_write && info->si_signo == SIGSEGV && info->si_code == SEGV_ACCERR && - h2g_valid(address)) { - switch (page_unprotect(h2g(address), pc)) { - case 0: - /* Fault not caused by a page marked unwritable to protect - * cached translations, must be the guest binary's problem. - */ - break; - case 1: - /* Fault caused by protection of cached translation; TBs - * invalidated, so resume execution. Retain helper_retaddr - * for a possible second fault. - */ - return 1; - case 2: - /* Fault caused by protection of cached translation, and the - * currently executing TB was modified and must be exited - * immediately. Clear helper_retaddr for next execution. - */ - cpu_exit_tb_from_sighandler(cpu, old_set); - /* NORETURN */ - - default: - g_assert_not_reached(); - } - } /* Convert forcefully to guest address space, invalid addresses are still valid segv ones */ - address = h2g_nocheck(address); + guest_addr = h2g_nocheck(host_addr); + + /* XXX: locking issue */ + if (is_write && + info->si_signo == SIGSEGV && + info->si_code == SEGV_ACCERR && + h2g_valid(host_addr) && + handle_sigsegv_accerr_write(cpu, old_set, pc, guest_addr)) { + return 1; + } /* * There is no way the target can handle this other than raising @@ -194,7 +215,7 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info, sigprocmask(SIG_SETMASK, old_set, NULL); cc = CPU_GET_CLASS(cpu); - cc->tcg_ops->tlb_fill(cpu, address, 0, access_type, + cc->tcg_ops->tlb_fill(cpu, guest_addr, 0, access_type, MMU_USER_IDX, false, pc); g_assert_not_reached(); } -- 2.25.1