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authorAKASHI Takahiro <takahiro.akashi@linaro.org>2015-12-15 11:33:41 +0300
committerWill Deacon <will.deacon@arm.com>2015-12-21 20:26:02 +0300
commit20380bb390a443b2c5c8800cec59743faf8151b4 (patch)
tree3f9d14ec8f265c8969f322a8cd239f3e946e18bb /arch/arm64/kernel/stacktrace.c
parentfe13f95b720075327a761fe6ddb45b0c90cab504 (diff)
downloadlinux-20380bb390a443b2c5c8800cec59743faf8151b4.tar.xz
arm64: ftrace: fix a stack tracer's output under function graph tracer
Function graph tracer modifies a return address (LR) in a stack frame to hook a function return. This will result in many useless entries (return_to_handler) showing up in a) a stack tracer's output b) perf call graph (with perf record -g) c) dump_backtrace (at panic et al.) For example, in case of a), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo 1 > /proc/sys/kernel/stack_trace_enabled $ cat /sys/kernel/debug/tracing/stack_trace Depth Size Location (54 entries) ----- ---- -------- 0) 4504 16 gic_raise_softirq+0x28/0x150 1) 4488 80 smp_cross_call+0x38/0xb8 2) 4408 48 return_to_handler+0x0/0x40 3) 4360 32 return_to_handler+0x0/0x40 ... In case of b), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ perf record -e mem:XXX:x -ag -- sleep 10 $ perf report ... | | |--0.22%-- 0x550f8 | | | 0x10888 | | | el0_svc_naked | | | sys_openat | | | return_to_handler | | | return_to_handler ... In case of c), $ echo function_graph > /sys/kernel/debug/tracing/current_tracer $ echo c > /proc/sysrq-trigger ... Call trace: [<ffffffc00044d3ac>] sysrq_handle_crash+0x24/0x30 [<ffffffc000092250>] return_to_handler+0x0/0x40 [<ffffffc000092250>] return_to_handler+0x0/0x40 ... This patch replaces such entries with real addresses preserved in current->ret_stack[] at unwind_frame(). This way, we can cover all the cases. Reviewed-by: Jungseok Lee <jungseoklee85@gmail.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> [will: fixed minor context changes conflicting with irq stack bits] Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/stacktrace.c')
-rw-r--r--arch/arm64/kernel/stacktrace.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index f7ee597ec883..4fad9787ab46 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -17,6 +17,7 @@
*/
#include <linux/kernel.h>
#include <linux/export.h>
+#include <linux/ftrace.h>
#include <linux/sched.h>
#include <linux/stacktrace.h>
@@ -66,6 +67,19 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
frame->fp = *(unsigned long *)(fp);
frame->pc = *(unsigned long *)(fp + 8);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ if (tsk && tsk->ret_stack &&
+ (frame->pc == (unsigned long)return_to_handler)) {
+ /*
+ * This is a case where function graph tracer has
+ * modified a return address (LR) in a stack frame
+ * to hook a function return.
+ * So replace it to an original value.
+ */
+ frame->pc = tsk->ret_stack[frame->graph--].ret;
+ }
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
/*
* Check whether we are going to walk through from interrupt stack
* to task stack.
@@ -158,6 +172,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
frame.sp = current_stack_pointer;
frame.pc = (unsigned long)save_stack_trace_tsk;
}
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ frame.graph = tsk->curr_ret_stack;
+#endif
walk_stackframe(tsk, &frame, save_trace, &data);
if (trace->nr_entries < trace->max_entries)