[PATCH] uml: improve stub debugging

Add some more debugging information when a stub does something unexpected,
usually segfaulting.  Now, it dumps out the stub's registers as well as the
signal.
Signed-off-by: NJeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/um/kernel/skas/process.c

@@ -69,6 +69,17 @@ void wait_stub_done(int pid, int sig, char * fname)
 
         if((n < 0) || !WIFSTOPPED(status) ||
            (WSTOPSIG(status) != SIGUSR1 && WSTOPSIG(status) != SIGTRAP)){
+		unsigned long regs[FRAME_SIZE];
+		if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+			printk("Failed to get registers from stub, "
+			       "errno = %d\n", errno);
+		else {
+			int i;
+
+			printk("Stub registers -\n");
+			for(i = 0; i < FRAME_SIZE; i++)
+				printk("\t%d - %lx\n", i, regs[i]);
+		}
                 panic("%s : failed to wait for SIGUSR1/SIGTRAP, "
                       "pid = %d, n = %d, errno = %d, status = 0x%x\n",
                       fname, pid, n, errno, status);