[PATCH] s390:ftrace: add save_stack_trace_regs()

[Pratyush Anand]

Implement save_stack_trace_regs, so that stacktrace of a kprobe events can
be obtained.

Without this we see following warning:
"save_stack_trace_regs() not implemented yet."
when we execute:
echo stacktrace > /sys/kernel/debug/tracing/trace_options
echo "p kfree" >> /sys/kernel/debug/tracing/kprobe_events
echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable

Reported-by: Chunyu Hu <chuhu@xxxxxxxxxx>
Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
---
 arch/s390/kernel/stacktrace.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/s390/kernel/stacktrace.c b/arch/s390/kernel/stacktrace.c
index 1785cd82253c..586da400f931 100644
--- a/arch/s390/kernel/stacktrace.c
+++ b/arch/s390/kernel/stacktrace.c
@@ -94,3 +94,16 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 		trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
+{
+	unsigned long sp, low, high;
+
+	sp = kernel_stack_pointer(regs);
+	low = (unsigned long) task_stack_page(current);
+	high = (unsigned long) task_pt_regs(current);
+	save_context_stack(trace, sp, low, high, 0);
+	if (trace->nr_entries < trace->max_entries)
+		trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_regs);
-- 
2.5.0