uml: dump core on panic

Dump core after a panic.  This will provide better debugging information than
is currently available.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/include/os.h

@@ -279,6 +279,7 @@ extern int raw(int fd);
 extern void setup_machinename(char *machine_out);
 extern void setup_hostinfo(char *buf, int len);
 extern int setjmp_wrapper(void (*proc)(void *, void *), ...);
+extern void os_dump_core(void);
 
 /* time.c */
 #define BILLION (1000 * 1000 * 1000)

arch/um/kernel/um_arch.c

@@ -474,7 +474,7 @@ static int panic_exit(struct notifier_block *self, unsigned long unused1,
 	show_regs(&(current->thread.regs));
 	bust_spinlocks(0);
 	uml_exitcode = 1;
-	machine_halt();
+	os_dump_core();
 	return 0;
 }
 

arch/um/os-Linux/util.c

@@ -119,3 +119,9 @@ int setjmp_wrapper(void (*proc)(void *, void *), ...)
 	va_end(args);
 	return n;
 }
+
+void os_dump_core(void)
+{
+	signal(SIGSEGV, SIG_DFL);
+	abort();
+}