From 6ab7e5465a4d6188e29398fb43a30dbab1015b75 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Wed, 20 Feb 2013 15:21:09 +0000 Subject: [PATCH] Replace all setjmp()/longjmp() with sigsetjmp()/siglongjmp() The setjmp() function doesn't specify whether signal masks are saved and restored; on Linux they are not, but on BSD (including MacOSX) they are. We want to have consistent behaviour across platforms, so we should always use "don't save/restore signal mask" (this is also generally going to be faster). This also works around a bug in MacOSX where the signal-restoration on longjmp() affects the signal mask for a completely different thread, not just the mask for the thread which did the longjmp. The most visible effect of this was that ctrl-C was ignored on MacOSX because the CPU thread did a longjmp which resulted in its signal mask being applied to every thread, so that all threads had SIGINT and SIGTERM blocked. The POSIX-sanctioned portable way to do a jump without affecting signal masks is to siglongjmp() to a sigjmp_buf which was created by calling sigsetjmp() with a zero savemask parameter, so change all uses of setjmp()/longjmp() accordingly. [Technically POSIX allows sigsetjmp(buf, 0) to save the signal mask; however the following siglongjmp() must not restore the signal mask, so the pair can be effectively considered as "sigjmp/longjmp which don't touch the mask".] For Windows we provide a trivial sigsetjmp/siglongjmp in terms of setjmp/longjmp -- this is OK because no user will ever pass a non-zero savemask. The setjmp() uses in tests/tcg/test-i386.c and tests/tcg/linux-test.c are left untouched because these are self-contained singlethreaded test programs intended to be run under QEMU's Linux emulation, so they have neither the portability nor the multithreading issues to deal with. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Tested-by: Stefan Weil Reviewed-by: Laszlo Ersek Signed-off-by: Blue Swirl --- coroutine-sigaltstack.c | 26 +++++++++++++------------- coroutine-ucontext.c | 27 ++++++++++++++------------- cpu-exec.c | 6 +++--- disas/i386.c | 6 +++--- disas/m68k.c | 11 ++++++----- include/exec/cpu-defs.h | 2 +- include/sysemu/os-win32.h | 8 ++++++++ monitor.c | 6 +++--- user-exec.c | 2 +- 9 files changed, 52 insertions(+), 42 deletions(-) diff --git a/coroutine-sigaltstack.c b/coroutine-sigaltstack.c index e37ebac9c..1fb41c9f1 100644 --- a/coroutine-sigaltstack.c +++ b/coroutine-sigaltstack.c @@ -45,7 +45,7 @@ static unsigned int pool_size; typedef struct { Coroutine base; void *stack; - jmp_buf env; + sigjmp_buf env; } CoroutineUContext; /** @@ -59,7 +59,7 @@ typedef struct { CoroutineUContext leader; /** Information for the signal handler (trampoline) */ - jmp_buf tr_reenter; + sigjmp_buf tr_reenter; volatile sig_atomic_t tr_called; void *tr_handler; } CoroutineThreadState; @@ -115,8 +115,8 @@ static void __attribute__((constructor)) coroutine_init(void) static void coroutine_bootstrap(CoroutineUContext *self, Coroutine *co) { /* Initialize longjmp environment and switch back the caller */ - if (!setjmp(self->env)) { - longjmp(*(jmp_buf *)co->entry_arg, 1); + if (!sigsetjmp(self->env, 0)) { + siglongjmp(*(sigjmp_buf *)co->entry_arg, 1); } while (true) { @@ -145,14 +145,14 @@ static void coroutine_trampoline(int signal) /* * Here we have to do a bit of a ping pong between the caller, given that * this is a signal handler and we have to do a return "soon". Then the - * caller can reestablish everything and do a longjmp here again. + * caller can reestablish everything and do a siglongjmp here again. */ - if (!setjmp(coTS->tr_reenter)) { + if (!sigsetjmp(coTS->tr_reenter, 0)) { return; } /* - * Ok, the caller has longjmp'ed back to us, so now prepare + * Ok, the caller has siglongjmp'ed back to us, so now prepare * us for the real machine state switching. We have to jump * into another function here to get a new stack context for * the auto variables (which have to be auto-variables @@ -179,7 +179,7 @@ static Coroutine *coroutine_new(void) /* The way to manipulate stack is with the sigaltstack function. We * prepare a stack, with it delivering a signal to ourselves and then - * put setjmp/longjmp where needed. + * put sigsetjmp/siglongjmp where needed. * This has been done keeping coroutine-ucontext as a model and with the * pth ideas (GNU Portable Threads). See coroutine-ucontext for the basics * of the coroutines and see pth_mctx.c (from the pth project) for the @@ -220,7 +220,7 @@ static Coroutine *coroutine_new(void) /* * Now transfer control onto the signal stack and set it up. - * It will return immediately via "return" after the setjmp() + * It will return immediately via "return" after the sigsetjmp() * was performed. Be careful here with race conditions. The * signal can be delivered the first time sigsuspend() is * called. @@ -261,8 +261,8 @@ static Coroutine *coroutine_new(void) * type-conversion warnings related to the `volatile' qualifier and * the fact that `jmp_buf' usually is an array type. */ - if (!setjmp(old_env)) { - longjmp(coTS->tr_reenter, 1); + if (!sigsetjmp(old_env, 0)) { + siglongjmp(coTS->tr_reenter, 1); } /* @@ -311,9 +311,9 @@ CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_, s->current = to_; - ret = setjmp(from->env); + ret = sigsetjmp(from->env, 0); if (ret == 0) { - longjmp(to->env, action); + siglongjmp(to->env, action); } return ret; } diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c index a9c30e9df..bd20e384b 100644 --- a/coroutine-ucontext.c +++ b/coroutine-ucontext.c @@ -46,7 +46,7 @@ static unsigned int pool_size; typedef struct { Coroutine base; void *stack; - jmp_buf env; + sigjmp_buf env; #ifdef CONFIG_VALGRIND_H unsigned int valgrind_stack_id; @@ -130,8 +130,8 @@ static void coroutine_trampoline(int i0, int i1) co = &self->base; /* Initialize longjmp environment and switch back the caller */ - if (!setjmp(self->env)) { - longjmp(*(jmp_buf *)co->entry_arg, 1); + if (!sigsetjmp(self->env, 0)) { + siglongjmp(*(sigjmp_buf *)co->entry_arg, 1); } while (true) { @@ -145,14 +145,15 @@ static Coroutine *coroutine_new(void) const size_t stack_size = 1 << 20; CoroutineUContext *co; ucontext_t old_uc, uc; - jmp_buf old_env; + sigjmp_buf old_env; union cc_arg arg = {0}; - /* The ucontext functions preserve signal masks which incurs a system call - * overhead. setjmp()/longjmp() does not preserve signal masks but only - * works on the current stack. Since we need a way to create and switch to - * a new stack, use the ucontext functions for that but setjmp()/longjmp() - * for everything else. + /* The ucontext functions preserve signal masks which incurs a + * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not + * preserve signal masks but only works on the current stack. + * Since we need a way to create and switch to a new stack, use + * the ucontext functions for that but sigsetjmp()/siglongjmp() for + * everything else. */ if (getcontext(&uc) == -1) { @@ -178,8 +179,8 @@ static Coroutine *coroutine_new(void) makecontext(&uc, (void (*)(void))coroutine_trampoline, 2, arg.i[0], arg.i[1]); - /* swapcontext() in, longjmp() back out */ - if (!setjmp(old_env)) { + /* swapcontext() in, siglongjmp() back out */ + if (!sigsetjmp(old_env, 0)) { swapcontext(&old_uc, &uc); } return &co->base; @@ -242,9 +243,9 @@ CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_, s->current = to_; - ret = setjmp(from->env); + ret = sigsetjmp(from->env, 0); if (ret == 0) { - longjmp(to->env, action); + siglongjmp(to->env, action); } return ret; } diff --git a/cpu-exec.c b/cpu-exec.c index 9fcfe9e0d..afbe4977a 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -35,7 +35,7 @@ void cpu_loop_exit(CPUArchState *env) CPUState *cpu = ENV_GET_CPU(env); cpu->current_tb = NULL; - longjmp(env->jmp_env, 1); + siglongjmp(env->jmp_env, 1); } /* exit the current TB from a signal handler. The host registers are @@ -47,7 +47,7 @@ void cpu_resume_from_signal(CPUArchState *env, void *puc) /* XXX: restore cpu registers saved in host registers */ env->exception_index = -1; - longjmp(env->jmp_env, 1); + siglongjmp(env->jmp_env, 1); } #endif @@ -234,7 +234,7 @@ int cpu_exec(CPUArchState *env) /* prepare setjmp context for exception handling */ for(;;) { - if (setjmp(env->jmp_env) == 0) { + if (sigsetjmp(env->jmp_env, 0) == 0) { /* if an exception is pending, we execute it here */ if (env->exception_index >= 0) { if (env->exception_index >= EXCP_INTERRUPT) { diff --git a/disas/i386.c b/disas/i386.c index dbecf1ffb..73cc06f1c 100644 --- a/disas/i386.c +++ b/disas/i386.c @@ -226,7 +226,7 @@ struct dis_private { bfd_byte the_buffer[MAX_MNEM_SIZE]; bfd_vma insn_start; int orig_sizeflag; - jmp_buf bailout; + sigjmp_buf bailout; }; enum address_mode @@ -303,7 +303,7 @@ fetch_data2(struct disassemble_info *info, bfd_byte *addr) STATUS. */ if (priv->max_fetched == priv->the_buffer) (*info->memory_error_func) (status, start, info); - longjmp (priv->bailout, 1); + siglongjmp(priv->bailout, 1); } else priv->max_fetched = addr; @@ -3661,7 +3661,7 @@ print_insn (bfd_vma pc, disassemble_info *info) start_codep = priv.the_buffer; codep = priv.the_buffer; - if (setjmp (priv.bailout) != 0) + if (sigsetjmp(priv.bailout, 0) != 0) { const char *name; diff --git a/disas/m68k.c b/disas/m68k.c index c950241f7..cc0db96ca 100644 --- a/disas/m68k.c +++ b/disas/m68k.c @@ -624,7 +624,7 @@ struct private bfd_byte *max_fetched; bfd_byte the_buffer[MAXLEN]; bfd_vma insn_start; - jmp_buf bailout; + sigjmp_buf bailout; }; /* Make sure that bytes from INFO->PRIVATE_DATA->BUFFER (inclusive) @@ -644,7 +644,7 @@ fetch_data2(struct disassemble_info *info, bfd_byte *addr) if (status != 0) { (*info->memory_error_func) (status, start, info); - longjmp (priv->bailout, 1); + siglongjmp(priv->bailout, 1); } else priv->max_fetched = addr; @@ -1912,9 +1912,10 @@ print_insn_m68k (bfd_vma memaddr, disassemble_info *info) priv.max_fetched = priv.the_buffer; priv.insn_start = memaddr; - if (setjmp (priv.bailout) != 0) - /* Error return. */ - return -1; + if (sigsetjmp(priv.bailout, 0) != 0) { + /* Error return. */ + return -1; + } switch (info->mach) { diff --git a/include/exec/cpu-defs.h b/include/exec/cpu-defs.h index ae64590cd..3dc96568a 100644 --- a/include/exec/cpu-defs.h +++ b/include/exec/cpu-defs.h @@ -184,7 +184,7 @@ typedef struct CPUWatchpoint { struct GDBRegisterState *gdb_regs; \ \ /* Core interrupt code */ \ - jmp_buf jmp_env; \ + sigjmp_buf jmp_env; \ int exception_index; \ \ CPUArchState *next_cpu; /* next CPU sharing TB cache */ \ diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h index bf9edeb9a..71f5fa0a9 100644 --- a/include/sysemu/os-win32.h +++ b/include/sysemu/os-win32.h @@ -63,6 +63,14 @@ # undef setjmp # define setjmp(env) _setjmp(env, NULL) #endif +/* QEMU uses sigsetjmp()/siglongjmp() as the portable way to specify + * "longjmp and don't touch the signal masks". Since we know that the + * savemask parameter will always be zero we can safely define these + * in terms of setjmp/longjmp on Win32. + */ +#define sigjmp_buf jmp_buf +#define sigsetjmp(env, savemask) setjmp(env) +#define siglongjmp(env, val) longjmp(env, val) /* Declaration of ffs() is missing in MinGW's strings.h. */ int ffs(int i); diff --git a/monitor.c b/monitor.c index 6a0f2573f..32a6e74fd 100644 --- a/monitor.c +++ b/monitor.c @@ -2740,7 +2740,7 @@ static const mon_cmd_t qmp_cmds[] = { /*******************************************************************/ static const char *pch; -static jmp_buf expr_env; +static sigjmp_buf expr_env; #define MD_TLONG 0 #define MD_I32 1 @@ -3135,7 +3135,7 @@ static const MonitorDef monitor_defs[] = { static void expr_error(Monitor *mon, const char *msg) { monitor_printf(mon, "%s\n", msg); - longjmp(expr_env, 1); + siglongjmp(expr_env, 1); } /* return 0 if OK, -1 if not found */ @@ -3345,7 +3345,7 @@ static int64_t expr_sum(Monitor *mon) static int get_expr(Monitor *mon, int64_t *pval, const char **pp) { pch = *pp; - if (setjmp(expr_env)) { + if (sigsetjmp(expr_env, 0)) { *pp = pch; return -1; } diff --git a/user-exec.c b/user-exec.c index c71acbc50..71bd6c531 100644 --- a/user-exec.c +++ b/user-exec.c @@ -70,7 +70,7 @@ void cpu_resume_from_signal(CPUArchState *env1, void *puc) #endif } env1->exception_index = -1; - longjmp(env1->jmp_env, 1); + siglongjmp(env1->jmp_env, 1); } /* 'pc' is the host PC at which the exception was raised. 'address' is -- 2.39.2