[POWERPC] print backtrace when entering xmon

xmon does not print a backtrace per default. This is bad on systems with
USB keyboard, the most needed info about the crash is lost.
print a backtrace during the very first xmon entry.

Booting with xmon=nobt disables the autobacktrace functionality.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 179b10ced8c7..8adad1444a51 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -137,10 +137,14 @@ static void bootcmds(void);
 static void proccall(void);
 void dump_segments(void);
 static void symbol_lookup(void);
+static void xmon_show_stack(unsigned long sp, unsigned long lr,
+                            unsigned long pc);
 static void xmon_print_symbol(unsigned long address, const char *mid,
                               const char *after);
 static const char *getvecname(unsigned long vec);
 
+int xmon_no_auto_backtrace;
+
 extern int print_insn_powerpc(unsigned long, unsigned long, int);
 
 extern void xmon_enter(void);
@@ -736,6 +740,12 @@ cmds(struct pt_regs *excp)
 
         last_cmd = NULL;
         xmon_regs = excp;
+
+        if (!xmon_no_auto_backtrace) {
+                xmon_no_auto_backtrace = 1;
+                xmon_show_stack(excp->gpr[1], excp->link, excp->nip);
+        }
+
         for(;;) {
 #ifdef CONFIG_SMP
                 printf("%x:", smp_processor_id());