[POWERPC] Stacktrace support for lockdep

This adds stacktrace support for powerpc, which will be needed for
lockdep.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 48 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index c1baf9d5903f..5183a9012a08 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_BOOTX_TEXT)	+= btext.o
 obj-$(CONFIG_SMP)               += smp.o
 obj-$(CONFIG_KPROBES)           += kprobes.o
 obj-$(CONFIG_PPC_UDBG_16550)    += legacy_serial.o udbg_16550.o
+obj-$(CONFIG_STACKTRACE)        += stacktrace.o
 
 pci64-$(CONFIG_PPC64)           += pci_dn.o isa-bridge.o
 obj-$(CONFIG_PCI)               += pci_$(CONFIG_WORD_SIZE).o $(pci64-y) \
diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
new file mode 100644
index 000000000000..e3638eeaaae7
--- /dev/null
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -0,0 +1,47 @@
+/*
+ * Stack trace utility
+ *
+ * Copyright 2008 Christoph Hellwig, IBM Corp.
+ *
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+#include <asm/ptrace.h>
+#include <asm/asm-offsets.h>
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+void save_stack_trace(struct stack_trace *trace)
+{
+        unsigned long sp;
+
+        asm("mr %0,1" : "=r" (sp));
+
+        for (;;) {
+                unsigned long *stack = (unsigned long *) sp;
+                unsigned long newsp, ip;
+
+                if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
+                        return;
+
+                newsp = stack[0];
+                ip = stack[STACK_FRAME_LR_SAVE];
+
+                if (!trace->skip)
+                        trace->entries[trace->nr_entries++] = ip;
+                else
+                        trace->skip--;
+
+                if (trace->nr_entries >= trace->max_entries)
+                        return;
+
+                sp = newsp;
+        }
+}