uml: dump registers on ptrace or wait failure

Provide a register dump if handle_trap fails.  Abstract out ptrace_dump_regs
since it now has two callers.
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/os-Linux/skas/process.c

@@ -44,6 +44,22 @@ int is_skas_winch(int pid, int fd, void *data)
 	return(1);
 }
 
+static int ptrace_dump_regs(int pid)
+{
+        unsigned long regs[MAX_REG_NR];
+        int i;
+
+        if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+                return -errno;
+        else {
+                printk("Stub registers -\n");
+                for(i = 0; i < ARRAY_SIZE(regs); i++)
+                        printk("\t%d - %lx\n", i, regs[i]);
+        }
+
+        return 0;
+}
+
 void wait_stub_done(int pid, int sig, char * fname)
 {
 	int n, status, err;
@@ -67,18 +83,10 @@ void wait_stub_done(int pid, int sig, char * fname)
 
 	if((n < 0) || !WIFSTOPPED(status) ||
 	   (WSTOPSIG(status) != SIGUSR1 && WSTOPSIG(status) != SIGTRAP)){
-		unsigned long regs[MAX_REG_NR];
-
-		if(ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
+		err = ptrace_dump_regs(pid);
+		if(err)
 			printk("Failed to get registers from stub, "
-			       "errno = %d\n", errno);
-		else {
-			int i;
-
-			printk("Stub registers -\n");
-			for(i = 0; i < ARRAY_SIZE(regs); i++)
-				printk("\t%d - %lx\n", i, regs[i]);
-		}
+			       "errno = %d\n", -err);
 		panic("%s : failed to wait for SIGUSR1/SIGTRAP, "
 		      "pid = %d, n = %d, errno = %d, status = 0x%x\n",
 		      fname, pid, n, errno, status);
@@ -142,10 +150,15 @@ static void handle_trap(int pid, union uml_pt_regs *regs, int local_using_sysemu
 
 		CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
 		if((err < 0) || !WIFSTOPPED(status) ||
-		   (WSTOPSIG(status) != SIGTRAP + 0x80))
+		   (WSTOPSIG(status) != SIGTRAP + 0x80)){
+                        err = ptrace_dump_regs(pid);
+                        if(err)
+                                printk("Failed to get registers from process, "
+                                       "errno = %d\n", -err);
 			panic("handle_trap - failed to wait at end of syscall, "
 			      "errno = %d, status = %d\n", errno, status);
                 }
+	}
 
 	handle_syscall(regs);
 }