From 4b84c69b5f6c08a540e3683f1360a6cdef2806c7 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Mon, 25 Sep 2006 23:33:04 -0700 Subject: [PATCH] [PATCH] uml: Move signal handlers to arch code Have most signals go through an arch-provided handler which recovers the sigcontext and then calls a generic handler. This replaces the ARCH_GET_SIGCONTEXT macro, which was somewhat fragile. On x86_64, recovering %rdx (which holds the sigcontext pointer) must be the first thing that happens. sig_handler duly invokes that first, but there is no guarantee that I can see that instructions won't be reordered such that %rdx is used before that. Having the arch provide the handler seems much more robust. Some signals in some parts of UML require their own handlers - these places don't call set_handler any more. They call sigaction or signal themselves. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/include/sysdep-i386/signal.h | 27 -------------------- arch/um/include/sysdep-x86_64/signal.h | 29 ---------------------- arch/um/os-Linux/irq.c | 2 +- arch/um/os-Linux/main.c | 34 +++++++++++++++++++++----- arch/um/os-Linux/process.c | 12 ++++++++- arch/um/os-Linux/signal.c | 31 ++++++++++------------- arch/um/os-Linux/skas/process.c | 17 ++++++++++--- arch/um/os-Linux/sys-i386/Makefile | 2 +- arch/um/os-Linux/sys-i386/signal.c | 15 ++++++++++++ arch/um/os-Linux/sys-x86_64/Makefile | 2 +- arch/um/os-Linux/sys-x86_64/signal.c | 16 ++++++++++++ arch/um/os-Linux/time.c | 4 +-- 12 files changed, 102 insertions(+), 89 deletions(-) delete mode 100644 arch/um/include/sysdep-i386/signal.h delete mode 100644 arch/um/include/sysdep-x86_64/signal.h create mode 100644 arch/um/os-Linux/sys-i386/signal.c create mode 100644 arch/um/os-Linux/sys-x86_64/signal.c diff --git a/arch/um/include/sysdep-i386/signal.h b/arch/um/include/sysdep-i386/signal.h deleted file mode 100644 index 07518b16213..00000000000 --- a/arch/um/include/sysdep-i386/signal.h +++ /dev/null @@ -1,27 +0,0 @@ -/* - * Copyright (C) 2004 PathScale, Inc - * Licensed under the GPL - */ - -#ifndef __I386_SIGNAL_H_ -#define __I386_SIGNAL_H_ - -#include - -#define ARCH_SIGHDLR_PARAM int sig - -#define ARCH_GET_SIGCONTEXT(sc, sig) \ - do sc = (struct sigcontext *) (&sig + 1); while(0) - -#endif - -/* - * Overrides for Emacs so that we follow Linus's tabbing style. - * Emacs will notice this stuff at the end of the file and automatically - * adjust the settings for this buffer only. This must remain at the end - * of the file. - * --------------------------------------------------------------------------- - * Local variables: - * c-file-style: "linux" - * End: - */ diff --git a/arch/um/include/sysdep-x86_64/signal.h b/arch/um/include/sysdep-x86_64/signal.h deleted file mode 100644 index 6142897af3d..00000000000 --- a/arch/um/include/sysdep-x86_64/signal.h +++ /dev/null @@ -1,29 +0,0 @@ -/* - * Copyright (C) 2004 PathScale, Inc - * Licensed under the GPL - */ - -#ifndef __X86_64_SIGNAL_H_ -#define __X86_64_SIGNAL_H_ - -#define ARCH_SIGHDLR_PARAM int sig - -#define ARCH_GET_SIGCONTEXT(sc, sig_addr) \ - do { \ - struct ucontext *__uc; \ - asm("movq %%rdx, %0" : "=r" (__uc)); \ - sc = (struct sigcontext *) &__uc->uc_mcontext; \ - } while(0) - -#endif - -/* - * Overrides for Emacs so that we follow Linus's tabbing style. - * Emacs will notice this stuff at the end of the file and automatically - * adjust the settings for this buffer only. This must remain at the end - * of the file. - * --------------------------------------------------------------------------- - * Local variables: - * c-file-style: "linux" - * End: - */ diff --git a/arch/um/os-Linux/irq.c b/arch/um/os-Linux/irq.c index 7555bf9c33d..a97206df5b5 100644 --- a/arch/um/os-Linux/irq.c +++ b/arch/um/os-Linux/irq.c @@ -132,7 +132,7 @@ void os_set_pollfd(int i, int fd) void os_set_ioignore(void) { - set_handler(SIGIO, SIG_IGN, 0, -1); + signal(SIGIO, SIG_IGN); } void init_irq_signals(int on_sigstack) diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c index 90912aaca7a..d1c5670787d 100644 --- a/arch/um/os-Linux/main.c +++ b/arch/um/os-Linux/main.c @@ -67,13 +67,32 @@ static __init void do_uml_initcalls(void) static void last_ditch_exit(int sig) { - signal(SIGINT, SIG_DFL); - signal(SIGTERM, SIG_DFL); - signal(SIGHUP, SIG_DFL); uml_cleanup(); exit(1); } +static void install_fatal_handler(int sig) +{ + struct sigaction action; + + /* All signals are enabled in this handler ... */ + sigemptyset(&action.sa_mask); + + /* ... including the signal being handled, plus we want the + * handler reset to the default behavior, so that if an exit + * handler is hanging for some reason, the UML will just die + * after this signal is sent a second time. + */ + action.sa_flags = SA_RESETHAND | SA_NODEFER; + action.sa_restorer = NULL; + action.sa_handler = last_ditch_exit; + if(sigaction(sig, &action, NULL) < 0){ + printf("failed to install handler for signal %d - errno = %d\n", + errno); + exit(1); + } +} + #define UML_LIB_PATH ":/usr/lib/uml" static void setup_env_path(void) @@ -158,9 +177,12 @@ int main(int argc, char **argv, char **envp) } new_argv[argc] = NULL; - set_handler(SIGINT, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1); - set_handler(SIGTERM, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1); - set_handler(SIGHUP, last_ditch_exit, SA_ONESHOT | SA_NODEFER, -1); + /* Allow these signals to bring down a UML if all other + * methods of control fail. + */ + install_fatal_handler(SIGINT); + install_fatal_handler(SIGTERM); + install_fatal_handler(SIGHUP); scan_elf_aux( envp); diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c index 3afde92ad2c..ff203625a4b 100644 --- a/arch/um/os-Linux/process.c +++ b/arch/um/os-Linux/process.c @@ -246,7 +246,17 @@ void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int)) set_sigstack(sig_stack, pages * page_size()); flags = SA_ONSTACK; } - if(usr1_handler) set_handler(SIGUSR1, usr1_handler, flags, -1); + if(usr1_handler){ + struct sigaction sa; + + sa.sa_handler = usr1_handler; + sigemptyset(&sa.sa_mask); + sa.sa_flags = flags; + sa.sa_restorer = NULL; + if(sigaction(SIGUSR1, &sa, NULL) < 0) + panic("init_new_thread_stack - sigaction failed - " + "errno = %d\n", errno); + } } void init_new_thread_signals(void) diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c index 60e4faedf25..55b62e2b8f4 100644 --- a/arch/um/os-Linux/signal.c +++ b/arch/um/os-Linux/signal.c @@ -15,7 +15,6 @@ #include "user.h" #include "signal_kern.h" #include "sysdep/sigcontext.h" -#include "sysdep/signal.h" #include "sigcontext.h" #include "mode.h" #include "os.h" @@ -38,18 +37,10 @@ static int signals_enabled = 1; static int pending = 0; -void sig_handler(ARCH_SIGHDLR_PARAM) +void sig_handler(int sig, struct sigcontext *sc) { - struct sigcontext *sc; int enabled; - /* Must be the first thing that this handler does - x86_64 stores - * the sigcontext in %rdx, and we need to save it before it has a - * chance to get trashed. - */ - - ARCH_GET_SIGCONTEXT(sc, sig); - enabled = signals_enabled; if(!enabled && (sig == SIGIO)){ pending |= SIGIO_MASK; @@ -84,13 +75,10 @@ static void real_alarm_handler(int sig, struct sigcontext *sc) } -void alarm_handler(ARCH_SIGHDLR_PARAM) +void alarm_handler(int sig, struct sigcontext *sc) { - struct sigcontext *sc; int enabled; - ARCH_GET_SIGCONTEXT(sc, sig); - enabled = signals_enabled; if(!signals_enabled){ if(sig == SIGVTALRM) @@ -126,6 +114,10 @@ void remove_sigstack(void) panic("disabling signal stack failed, errno = %d\n", errno); } +void (*handlers[_NSIG])(int sig, struct sigcontext *sc); + +extern void hard_handler(int sig); + void set_handler(int sig, void (*handler)(int), int flags, ...) { struct sigaction action; @@ -133,13 +125,16 @@ void set_handler(int sig, void (*handler)(int), int flags, ...) sigset_t sig_mask; int mask; - va_start(ap, flags); - action.sa_handler = handler; + handlers[sig] = (void (*)(int, struct sigcontext *)) handler; + action.sa_handler = hard_handler; + sigemptyset(&action.sa_mask); - while((mask = va_arg(ap, int)) != -1){ + + va_start(ap, flags); + while((mask = va_arg(ap, int)) != -1) sigaddset(&action.sa_mask, mask); - } va_end(ap); + action.sa_flags = flags; action.sa_restorer = NULL; if(sigaction(sig, &action, NULL) < 0) diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index 50418a5e713..88ff0de95cd 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -189,14 +189,25 @@ static int userspace_tramp(void *stack) } } if(!ptrace_faultinfo && (stack != NULL)){ + struct sigaction sa; + unsigned long v = UML_CONFIG_STUB_CODE + (unsigned long) stub_segv_handler - (unsigned long) &__syscall_stub_start; set_sigstack((void *) UML_CONFIG_STUB_DATA, page_size()); - set_handler(SIGSEGV, (void *) v, SA_ONSTACK, - SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, - SIGUSR1, -1); + sigemptyset(&sa.sa_mask); + sigaddset(&sa.sa_mask, SIGIO); + sigaddset(&sa.sa_mask, SIGWINCH); + sigaddset(&sa.sa_mask, SIGALRM); + sigaddset(&sa.sa_mask, SIGVTALRM); + sigaddset(&sa.sa_mask, SIGUSR1); + sa.sa_flags = SA_ONSTACK; + sa.sa_handler = (void *) v; + sa.sa_restorer = NULL; + if(sigaction(SIGSEGV, &sa, NULL) < 0) + panic("userspace_tramp - setting SIGSEGV handler " + "failed - errno = %d\n", errno); } os_stop_process(os_getpid()); diff --git a/arch/um/os-Linux/sys-i386/Makefile b/arch/um/os-Linux/sys-i386/Makefile index b3213613c41..37806621b25 100644 --- a/arch/um/os-Linux/sys-i386/Makefile +++ b/arch/um/os-Linux/sys-i386/Makefile @@ -3,7 +3,7 @@ # Licensed under the GPL # -obj-$(CONFIG_MODE_SKAS) = registers.o tls.o +obj-$(CONFIG_MODE_SKAS) = registers.o signal.o tls.o USER_OBJS := $(obj-y) diff --git a/arch/um/os-Linux/sys-i386/signal.c b/arch/um/os-Linux/sys-i386/signal.c new file mode 100644 index 00000000000..0d3eae51835 --- /dev/null +++ b/arch/um/os-Linux/sys-i386/signal.c @@ -0,0 +1,15 @@ +/* + * Copyright (C) 2006 Jeff Dike (jdike@addtoit.com) + * Licensed under the GPL + */ + +#include + +extern void (*handlers[])(int sig, struct sigcontext *sc); + +void hard_handler(int sig) +{ + struct sigcontext *sc = (struct sigcontext *) (&sig + 1); + + (*handlers[sig])(sig, sc); +} diff --git a/arch/um/os-Linux/sys-x86_64/Makefile b/arch/um/os-Linux/sys-x86_64/Makefile index 340ef26f594..f67842a7735 100644 --- a/arch/um/os-Linux/sys-x86_64/Makefile +++ b/arch/um/os-Linux/sys-x86_64/Makefile @@ -3,7 +3,7 @@ # Licensed under the GPL # -obj-$(CONFIG_MODE_SKAS) = registers.o +obj-$(CONFIG_MODE_SKAS) = registers.o signal.o USER_OBJS := $(obj-y) diff --git a/arch/um/os-Linux/sys-x86_64/signal.c b/arch/um/os-Linux/sys-x86_64/signal.c new file mode 100644 index 00000000000..3f369e5f976 --- /dev/null +++ b/arch/um/os-Linux/sys-x86_64/signal.c @@ -0,0 +1,16 @@ +/* + * Copyright (C) 2006 Jeff Dike (jdike@addtoit.com) + * Licensed under the GPL + */ + +#include + +extern void (*handlers[])(int sig, struct sigcontext *sc); + +void hard_handler(int sig) +{ + struct ucontext *uc; + asm("movq %%rdx, %0" : "=r" (uc)); + + (*handlers[sig])(sig, (struct sigcontext *) &uc->uc_mcontext); +} diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c index 4ae73c0e548..7f5ebbadca6 100644 --- a/arch/um/os-Linux/time.c +++ b/arch/um/os-Linux/time.c @@ -40,8 +40,8 @@ void disable_timer(void) printk("disnable_timer - setitimer failed, errno = %d\n", errno); /* If there are signals already queued, after unblocking ignore them */ - set_handler(SIGALRM, SIG_IGN, 0, -1); - set_handler(SIGVTALRM, SIG_IGN, 0, -1); + signal(SIGALRM, SIG_IGN); + signal(SIGVTALRM, SIG_IGN); } void switch_timers(int to_real) -- 2.41.1