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[PATCH] uml: Move signal handlers to arch code

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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>
This commit is contained in:
Jeff Dike 2006-09-25 23:33:04 -07:00 • committed by Linus Torvalds
parent 19bdf0409f
commit 4b84c69b5f
12 changed files with 102 additions and 89 deletions
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34
arch/um/os-Linux/main.c
View file

@ -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);