3 files changed, 84 insertions, 2 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index bb28087bf818..593b56509f4f 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -7,8 +7,8 @@ AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
 # Object file lists.
 
 obj-y           := compat.o entry-armv.o entry-common.o irq.o \
-                   process.o ptrace.o semaphore.o setup.o signal.o sys_arm.o \
-                   time.o traps.o
+                   process.o ptrace.o semaphore.o setup.o signal.o \
+                   sys_arm.o stacktrace.o time.o traps.o
 
 obj-$(CONFIG_ISA_DMA_API)       += dma.o
 obj-$(CONFIG_ARCH_ACORN)        += ecard.o 
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
new file mode 100644
index 000000000000..77ef35efaa8d
--- /dev/null
+++ b/arch/arm/kernel/stacktrace.c
@@ -0,0 +1,73 @@
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include "stacktrace.h"
+
+int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
+                    int (*fn)(struct stackframe *, void *), void *data)
+{
+        struct stackframe *frame;
+
+        do {
+                /*
+                 * Check current frame pointer is within bounds
+                 */
+                if ((fp - 12) < low || fp + 4 >= high)
+                        break;
+
+                frame = (struct stackframe *)(fp - 12);
+
+                if (fn(frame, data))
+                        break;
+
+                /*
+                 * Update the low bound - the next frame must always
+                 * be at a higher address than the current frame.
+                 */
+                low = fp + 4;
+                fp = frame->fp;
+        } while (fp);
+
+        return 0;
+}
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace_data {
+        struct stack_trace *trace;
+        unsigned int skip;
+};
+
+static int save_trace(struct stackframe *frame, void *d)
+{
+        struct stack_trace_data *data = d;
+        struct stack_trace *trace = data->trace;
+
+        if (data->skip) {
+                data->skip--;
+                return 0;
+        }
+
+        trace->entries[trace->nr_entries++] = frame->lr;
+
+        return trace->nr_entries >= trace->max_entries;
+}
+
+void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
+{
+        struct stack_trace_data data;
+        unsigned long fp, base;
+
+        data.trace = trace;
+        data.skip = trace->skip;
+
+        if (task) {
+                base = (unsigned long)task_stack_page(task);
+                fp = 0; /* FIXME */
+        } else {
+                base = (unsigned long)task_stack_page(current);
+                asm("mov %0, fp" : "=r" (fp));
+        }
+
+        walk_stackframe(fp, base, base + THREAD_SIZE, save_trace, &data);
+}
+#endif
diff --git a/arch/arm/kernel/stacktrace.h b/arch/arm/kernel/stacktrace.h
new file mode 100644
index 000000000000..e9fd20cb5662
--- /dev/null
+++ b/arch/arm/kernel/stacktrace.h
@@ -0,0 +1,9 @@
+struct stackframe {
+        unsigned long fp;
+        unsigned long sp;
+        unsigned long lr;
+        unsigned long pc;
+};
+
+int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
+                    int (*fn)(struct stackframe *, void *), void *data);