From e6037d04c58284285726721d0d4741e1386594e9 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Thu, 16 Sep 2021 14:44:17 -0700 Subject: linux-user: Reorg handling for SIGSEGV MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add stub host-signal.h for all linux-user hosts. Add new code replacing cpu_signal_handler. Full migration will happen one host at a time. Reviewed-by: Warner Losh Reviewed-by: Philippe Mathieu-Daudé Acked-by: Alistair Francis Signed-off-by: Richard Henderson --- linux-user/signal.c | 105 +++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 91 insertions(+), 14 deletions(-) (limited to 'linux-user/signal.c') diff --git a/linux-user/signal.c b/linux-user/signal.c index 14d8fdfde1..6900acb122 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -19,6 +19,7 @@ #include "qemu/osdep.h" #include "qemu/bitops.h" #include "exec/gdbstub.h" +#include "hw/core/tcg-cpu-ops.h" #include #include @@ -29,6 +30,7 @@ #include "loader.h" #include "trace.h" #include "signal-common.h" +#include "host-signal.h" static struct target_sigaction sigact_table[TARGET_NSIG]; @@ -769,41 +771,116 @@ static inline void rewind_if_in_safe_syscall(void *puc) } #endif -static void host_signal_handler(int host_signum, siginfo_t *info, - void *puc) +static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) { CPUArchState *env = thread_cpu->env_ptr; CPUState *cpu = env_cpu(env); TaskState *ts = cpu->opaque; - - int sig; target_siginfo_t tinfo; ucontext_t *uc = puc; struct emulated_sigtable *k; + int guest_sig; +#ifdef HOST_SIGNAL_PLACEHOLDER /* the CPU emulator uses some host signals to detect exceptions, we forward to it some signals */ - if ((host_signum == SIGSEGV || host_signum == SIGBUS) + if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) { - if (cpu_signal_handler(host_signum, info, puc)) + if (cpu_signal_handler(host_sig, info, puc)) { return; + } + } +#else + uintptr_t pc = 0; + bool sync_sig = false; + + /* + * Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special + * handling wrt signal blocking and unwinding. + */ + if ((host_sig == SIGSEGV || host_sig == SIGBUS) && info->si_code > 0) { + MMUAccessType access_type; + uintptr_t host_addr; + abi_ptr guest_addr; + bool is_write; + + host_addr = (uintptr_t)info->si_addr; + + /* + * Convert forcefully to guest address space: addresses outside + * reserved_va are still valid to report via SEGV_MAPERR. + */ + guest_addr = h2g_nocheck(host_addr); + + pc = host_signal_pc(uc); + is_write = host_signal_write(info, uc); + access_type = adjust_signal_pc(&pc, is_write); + + if (host_sig == SIGSEGV) { + const struct TCGCPUOps *tcg_ops; + + if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) { + /* If this was a write to a TB protected page, restart. */ + if (is_write && + handle_sigsegv_accerr_write(cpu, &uc->uc_sigmask, + pc, guest_addr)) { + return; + } + + /* + * With reserved_va, the whole address space is PROT_NONE, + * which means that we may get ACCERR when we want MAPERR. + */ + if (page_get_flags(guest_addr) & PAGE_VALID) { + /* maperr = false; */ + } else { + info->si_code = SEGV_MAPERR; + } + } + + sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); + + tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; + tcg_ops->tlb_fill(cpu, guest_addr, 0, access_type, + MMU_USER_IDX, false, pc); + g_assert_not_reached(); + } else { + sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); + } + + sync_sig = true; } +#endif /* get target signal number */ - sig = host_to_target_signal(host_signum); - if (sig < 1 || sig > TARGET_NSIG) + guest_sig = host_to_target_signal(host_sig); + if (guest_sig < 1 || guest_sig > TARGET_NSIG) { return; - trace_user_host_signal(env, host_signum, sig); - - rewind_if_in_safe_syscall(puc); + } + trace_user_host_signal(env, host_sig, guest_sig); host_to_target_siginfo_noswap(&tinfo, info); - k = &ts->sigtab[sig - 1]; + k = &ts->sigtab[guest_sig - 1]; k->info = tinfo; - k->pending = sig; + k->pending = guest_sig; ts->signal_pending = 1; - /* Block host signals until target signal handler entered. We +#ifndef HOST_SIGNAL_PLACEHOLDER + /* + * For synchronous signals, unwind the cpu state to the faulting + * insn and then exit back to the main loop so that the signal + * is delivered immediately. + */ + if (sync_sig) { + cpu->exception_index = EXCP_INTERRUPT; + cpu_loop_exit_restore(cpu, pc); + } +#endif + + rewind_if_in_safe_syscall(puc); + + /* + * Block host signals until target signal handler entered. We * can't block SIGSEGV or SIGBUS while we're executing guest * code in case the guest code provokes one in the window between * now and it getting out to the main loop. Signals will be -- cgit 1.4.1 From 04de121aaf0c896812792eb8489ae614c7f6dade Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 17 Sep 2021 12:00:31 -0700 Subject: linux-user/signal: Drop HOST_SIGNAL_PLACEHOLDER MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Now that all of the linux-user hosts have been converted to host-signal.h, drop the compatibility code. Reviewed by: Warner Losh Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- include/exec/exec-all.h | 12 ------------ linux-user/signal.c | 14 -------------- 2 files changed, 26 deletions(-) (limited to 'linux-user/signal.c') diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 5f94d799aa..5dd663c153 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -685,18 +685,6 @@ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write); 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 - * @pinfo: host siginfo_t - * @puc: host ucontext_t - * - * To be called from the SIGBUS and SIGSEGV signal handler to inform the - * virtual cpu of exceptions. Returns true if the signal was handled by - * the virtual CPU. - */ -int cpu_signal_handler(int signum, void *pinfo, void *puc); - #else static inline void mmap_lock(void) {} static inline void mmap_unlock(void) {} diff --git a/linux-user/signal.c b/linux-user/signal.c index 6900acb122..b816678ba5 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -780,17 +780,6 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) ucontext_t *uc = puc; struct emulated_sigtable *k; int guest_sig; - -#ifdef HOST_SIGNAL_PLACEHOLDER - /* the CPU emulator uses some host signals to detect exceptions, - we forward to it some signals */ - if ((host_sig == SIGSEGV || host_sig == SIGBUS) - && info->si_code > 0) { - if (cpu_signal_handler(host_sig, info, puc)) { - return; - } - } -#else uintptr_t pc = 0; bool sync_sig = false; @@ -850,7 +839,6 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) sync_sig = true; } -#endif /* get target signal number */ guest_sig = host_to_target_signal(host_sig); @@ -865,7 +853,6 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) k->pending = guest_sig; ts->signal_pending = 1; -#ifndef HOST_SIGNAL_PLACEHOLDER /* * For synchronous signals, unwind the cpu state to the faulting * insn and then exit back to the main loop so that the signal @@ -875,7 +862,6 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) cpu->exception_index = EXCP_INTERRUPT; cpu_loop_exit_restore(cpu, pc); } -#endif rewind_if_in_safe_syscall(puc); -- cgit 1.4.1 From 72d2bbf9ff3e1edf5d57b53149eeaa36f19fb891 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 17 Sep 2021 17:32:56 -0700 Subject: linux-user: Add cpu_loop_exit_sigsegv MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is a new interface to be provided by the os emulator for raising SIGSEGV on fault. Use the new record_sigsegv target hook. Reviewed by: Warner Losh Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- accel/tcg/user-exec.c | 33 ++++++++++++++++++--------------- include/exec/exec-all.h | 15 +++++++++++++++ linux-user/signal.c | 30 ++++++++++++++++++++++-------- 3 files changed, 55 insertions(+), 23 deletions(-) (limited to 'linux-user/signal.c') diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c index a0cba61e83..c4f69908e9 100644 --- a/accel/tcg/user-exec.c +++ b/accel/tcg/user-exec.c @@ -141,35 +141,38 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr, int fault_size, MMUAccessType access_type, bool nonfault, uintptr_t ra) { - int flags; + int acc_flag; + bool maperr; switch (access_type) { case MMU_DATA_STORE: - flags = PAGE_WRITE; + acc_flag = PAGE_WRITE_ORG; break; case MMU_DATA_LOAD: - flags = PAGE_READ; + acc_flag = PAGE_READ; break; case MMU_INST_FETCH: - flags = PAGE_EXEC; + acc_flag = PAGE_EXEC; break; default: g_assert_not_reached(); } - if (!guest_addr_valid_untagged(addr) || - page_check_range(addr, 1, flags) < 0) { - if (nonfault) { - return TLB_INVALID_MASK; - } else { - CPUState *cpu = env_cpu(env); - CPUClass *cc = CPU_GET_CLASS(cpu); - cc->tcg_ops->tlb_fill(cpu, addr, fault_size, access_type, - MMU_USER_IDX, false, ra); - g_assert_not_reached(); + if (guest_addr_valid_untagged(addr)) { + int page_flags = page_get_flags(addr); + if (page_flags & acc_flag) { + return 0; /* success */ } + maperr = !(page_flags & PAGE_VALID); + } else { + maperr = true; + } + + if (nonfault) { + return TLB_INVALID_MASK; } - return 0; + + cpu_loop_exit_sigsegv(env_cpu(env), addr, access_type, maperr, ra); } int probe_access_flags(CPUArchState *env, target_ulong addr, diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 5dd663c153..f74578500c 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -685,6 +685,21 @@ MMUAccessType adjust_signal_pc(uintptr_t *pc, bool is_write); bool handle_sigsegv_accerr_write(CPUState *cpu, sigset_t *old_set, uintptr_t host_pc, abi_ptr guest_addr); +/** + * cpu_loop_exit_sigsegv: + * @cpu: the cpu context + * @addr: the guest address of the fault + * @access_type: access was read/write/execute + * @maperr: true for invalid page, false for permission fault + * @ra: host pc for unwinding + * + * Use the TCGCPUOps hook to record cpu state, do guest operating system + * specific things to raise SIGSEGV, and jump to the main cpu loop. + */ +void QEMU_NORETURN cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, + bool maperr, uintptr_t ra); + #else static inline void mmap_lock(void) {} static inline void mmap_unlock(void) {} diff --git a/linux-user/signal.c b/linux-user/signal.c index b816678ba5..135983747d 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -688,9 +688,27 @@ void force_sigsegv(int oldsig) } force_sig(TARGET_SIGSEGV); } - #endif +void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, bool maperr, uintptr_t ra) +{ + const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; + + if (tcg_ops->record_sigsegv) { + tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra); + } else if (tcg_ops->tlb_fill) { + tcg_ops->tlb_fill(cpu, addr, 0, access_type, MMU_USER_IDX, false, ra); + g_assert_not_reached(); + } + + force_sig_fault(TARGET_SIGSEGV, + maperr ? TARGET_SEGV_MAPERR : TARGET_SEGV_ACCERR, + addr); + cpu->exception_index = EXCP_INTERRUPT; + cpu_loop_exit_restore(cpu, ra); +} + /* abort execution with signal */ static void QEMU_NORETURN dump_core_and_abort(int target_sig) { @@ -806,7 +824,7 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) access_type = adjust_signal_pc(&pc, is_write); if (host_sig == SIGSEGV) { - const struct TCGCPUOps *tcg_ops; + bool maperr = true; if (info->si_code == SEGV_ACCERR && h2g_valid(host_addr)) { /* If this was a write to a TB protected page, restart. */ @@ -821,18 +839,14 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) * which means that we may get ACCERR when we want MAPERR. */ if (page_get_flags(guest_addr) & PAGE_VALID) { - /* maperr = false; */ + maperr = false; } else { info->si_code = SEGV_MAPERR; } } sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); - - tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; - tcg_ops->tlb_fill(cpu, guest_addr, 0, access_type, - MMU_USER_IDX, false, pc); - g_assert_not_reached(); + cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc); } else { sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); } -- cgit 1.4.1 From eeca7dc566076d6130d986e17508372bc7916281 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Wed, 15 Sep 2021 08:13:38 -0700 Subject: accel/tcg: Restrict TCGCPUOps::tlb_fill() to sysemu MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We have replaced tlb_fill with record_sigsegv for user mode. Move the declaration to restrict it to system emulation. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- include/hw/core/tcg-cpu-ops.h | 22 ++++++++++------------ linux-user/signal.c | 3 --- 2 files changed, 10 insertions(+), 15 deletions(-) (limited to 'linux-user/signal.c') diff --git a/include/hw/core/tcg-cpu-ops.h b/include/hw/core/tcg-cpu-ops.h index 41718b695b..8eadd404c8 100644 --- a/include/hw/core/tcg-cpu-ops.h +++ b/include/hw/core/tcg-cpu-ops.h @@ -35,18 +35,6 @@ struct TCGCPUOps { void (*cpu_exec_enter)(CPUState *cpu); /** @cpu_exec_exit: Callback for cpu_exec cleanup */ void (*cpu_exec_exit)(CPUState *cpu); - /** - * @tlb_fill: Handle a softmmu tlb miss or user-only address fault - * - * For system mode, if the access is valid, call tlb_set_page - * and return true; if the access is invalid, and probe is - * true, return false; otherwise raise an exception and do - * not return. For user-only mode, always raise an exception - * and do not return. - */ - bool (*tlb_fill)(CPUState *cpu, vaddr address, int size, - MMUAccessType access_type, int mmu_idx, - bool probe, uintptr_t retaddr); /** @debug_excp_handler: Callback for handling debug exceptions */ void (*debug_excp_handler)(CPUState *cpu); @@ -68,6 +56,16 @@ struct TCGCPUOps { #ifdef CONFIG_SOFTMMU /** @cpu_exec_interrupt: Callback for processing interrupts in cpu_exec */ bool (*cpu_exec_interrupt)(CPUState *cpu, int interrupt_request); + /** + * @tlb_fill: Handle a softmmu tlb miss + * + * If the access is valid, call tlb_set_page and return true; + * if the access is invalid and probe is true, return false; + * otherwise raise an exception and do not return. + */ + bool (*tlb_fill)(CPUState *cpu, vaddr address, int size, + MMUAccessType access_type, int mmu_idx, + bool probe, uintptr_t retaddr); /** * @do_transaction_failed: Callback for handling failed memory transactions * (ie bus faults or external aborts; not MMU faults) diff --git a/linux-user/signal.c b/linux-user/signal.c index 135983747d..9d60abc038 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -697,9 +697,6 @@ void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr, if (tcg_ops->record_sigsegv) { tcg_ops->record_sigsegv(cpu, addr, access_type, maperr, ra); - } else if (tcg_ops->tlb_fill) { - tcg_ops->tlb_fill(cpu, addr, 0, access_type, MMU_USER_IDX, false, ra); - g_assert_not_reached(); } force_sig_fault(TARGET_SIGSEGV, -- cgit 1.4.1 From 12ed56407e60371d45ffa3b7f2fd00c4d7efa580 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 4 Oct 2021 10:06:10 -0700 Subject: linux-user: Add cpu_loop_exit_sigbus MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This is a new interface to be provided by the os emulator for raising SIGBUS on fault. Use the new record_sigbus target hook. Reviewed-by: Warner Losh Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- include/exec/exec-all.h | 14 ++++++++++++++ linux-user/signal.c | 14 ++++++++++++++ 2 files changed, 28 insertions(+) (limited to 'linux-user/signal.c') diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index f74578500c..6bb2a0f7ec 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -700,6 +700,20 @@ void QEMU_NORETURN cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr, MMUAccessType access_type, bool maperr, uintptr_t ra); +/** + * cpu_loop_exit_sigbus: + * @cpu: the cpu context + * @addr: the guest address of the alignment fault + * @access_type: access was read/write/execute + * @ra: host pc for unwinding + * + * Use the TCGCPUOps hook to record cpu state, do guest operating system + * specific things to raise SIGBUS, and jump to the main cpu loop. + */ +void QEMU_NORETURN cpu_loop_exit_sigbus(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, + uintptr_t ra); + #else static inline void mmap_lock(void) {} static inline void mmap_unlock(void) {} diff --git a/linux-user/signal.c b/linux-user/signal.c index 9d60abc038..df2c8678d0 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -706,6 +706,20 @@ void cpu_loop_exit_sigsegv(CPUState *cpu, target_ulong addr, cpu_loop_exit_restore(cpu, ra); } +void cpu_loop_exit_sigbus(CPUState *cpu, target_ulong addr, + MMUAccessType access_type, uintptr_t ra) +{ + const struct TCGCPUOps *tcg_ops = CPU_GET_CLASS(cpu)->tcg_ops; + + if (tcg_ops->record_sigbus) { + tcg_ops->record_sigbus(cpu, addr, access_type, ra); + } + + force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, addr); + cpu->exception_index = EXCP_INTERRUPT; + cpu_loop_exit_restore(cpu, ra); +} + /* abort execution with signal */ static void QEMU_NORETURN dump_core_and_abort(int target_sig) { -- cgit 1.4.1 From 742f07628c0a0bd847b47ee0a0b20c44531e0ba5 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 4 Oct 2021 19:39:29 -0700 Subject: linux-user: Handle BUS_ADRALN in host_signal_handler MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Handle BUS_ADRALN via cpu_loop_exit_sigbus, but allow other SIGBUS si_codes to continue into the host-to-guest signal conversion code. Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Richard Henderson --- linux-user/signal.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'linux-user/signal.c') diff --git a/linux-user/signal.c b/linux-user/signal.c index df2c8678d0..81c45bfce9 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -860,6 +860,9 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) cpu_loop_exit_sigsegv(cpu, guest_addr, access_type, maperr, pc); } else { sigprocmask(SIG_SETMASK, &uc->uc_sigmask, NULL); + if (info->si_code == BUS_ADRALN) { + cpu_loop_exit_sigbus(cpu, guest_addr, access_type, pc); + } } sync_sig = true; -- cgit 1.4.1