From 4b84c69b5f6c08a540e3683f1360a6cdef2806c7 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Mon, 25 Sep 2006 23:33:04 -0700 Subject: [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/os-Linux/main.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) (limited to 'arch/um/os-Linux/main.c') diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c index 90912aaca7aa..d1c5670787dc 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); -- cgit v1.2.2