[ARM] 5382/1: unwind: Reorganise the stacktrace support
This patch changes the walk_stacktrace and its callers for easier
integration of stack unwinding. The arch/arm/kernel/stacktrace.h file is
also moved to arch/arm/include/asm/stacktrace.h.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index fc650f6..9f444e5 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -2,34 +2,59 @@
#include <linux/sched.h>
#include <linux/stacktrace.h>
-#include "stacktrace.h"
+#include <asm/stacktrace.h>
-int walk_stackframe(unsigned long fp, unsigned long low, unsigned long high,
- int (*fn)(struct stackframe *, void *), void *data)
+#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
+/*
+ * Unwind the current stack frame and store the new register values in the
+ * structure passed as argument. Unwinding is equivalent to a function return,
+ * hence the new PC value rather than LR should be used for backtrace.
+ *
+ * With framepointer enabled, a simple function prologue looks like this:
+ * mov ip, sp
+ * stmdb sp!, {fp, ip, lr, pc}
+ * sub fp, ip, #4
+ *
+ * A simple function epilogue looks like this:
+ * ldm sp, {fp, sp, pc}
+ *
+ * Note that with framepointer enabled, even the leaf functions have the same
+ * prologue and epilogue, therefore we can ignore the LR value in this case.
+ */
+int unwind_frame(struct stackframe *frame)
{
- struct stackframe *frame;
+ unsigned long high, low;
+ unsigned long fp = frame->fp;
- do {
- /*
- * Check current frame pointer is within bounds
- */
- if (fp < (low + 12) || fp + 4 >= high)
- break;
+ /* only go to a higher address on the stack */
+ low = frame->sp;
+ high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
- frame = (struct stackframe *)(fp - 12);
+ /* check current frame pointer is within bounds */
+ if (fp < (low + 12) || fp + 4 >= high)
+ return -EINVAL;
+
+ /* restore the registers from the stack frame */
+ frame->fp = *(unsigned long *)(fp - 12);
+ frame->sp = *(unsigned long *)(fp - 8);
+ frame->pc = *(unsigned long *)(fp - 4);
+
+ return 0;
+}
+#endif
+
+void walk_stackframe(struct stackframe *frame,
+ int (*fn)(struct stackframe *, void *), void *data)
+{
+ while (1) {
+ int ret;
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;
+ ret = unwind_frame(frame);
+ if (ret < 0)
+ break;
+ }
}
EXPORT_SYMBOL(walk_stackframe);
@@ -44,7 +69,7 @@
{
struct stack_trace_data *data = d;
struct stack_trace *trace = data->trace;
- unsigned long addr = frame->lr;
+ unsigned long addr = frame->pc;
if (data->no_sched_functions && in_sched_functions(addr))
return 0;
@@ -61,11 +86,10 @@
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
struct stack_trace_data data;
- unsigned long fp, base;
+ struct stackframe frame;
data.trace = trace;
data.skip = trace->skip;
- base = (unsigned long)task_stack_page(tsk);
if (tsk != current) {
#ifdef CONFIG_SMP
@@ -76,14 +100,22 @@
BUG();
#else
data.no_sched_functions = 1;
- fp = thread_saved_fp(tsk);
+ frame.fp = thread_saved_fp(tsk);
+ frame.sp = thread_saved_sp(tsk);
+ frame.lr = 0; /* recovered from the stack */
+ frame.pc = thread_saved_pc(tsk);
#endif
} else {
+ register unsigned long current_sp asm ("sp");
+
data.no_sched_functions = 0;
- asm("mov %0, fp" : "=r" (fp));
+ frame.fp = (unsigned long)__builtin_frame_address(0);
+ frame.sp = current_sp;
+ frame.lr = (unsigned long)__builtin_return_address(0);
+ frame.pc = (unsigned long)save_stack_trace_tsk;
}
- walk_stackframe(fp, base, base + THREAD_SIZE, save_trace, &data);
+ walk_stackframe(&frame, save_trace, &data);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}