[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>

1 files changed, 13 insertions, 18 deletions

diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 60e4faedf254..55b62e2b8f41 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)