[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 <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index 90912aa..d1c5670 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -67,13 +67,32 @@
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 @@
}
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);