[PATCH v3 3/7] arm64: ftrace: fix a stack tracer's output under function graph tracer
From: AKASHI Takahiro <hidden>
Date: 2015-10-08 10:03:30
Also in:
lkml
Subsystem:
arm64 port (aarch64 architecture), function hooks (ftrace), the rest · Maintainers:
Catalin Marinas, Will Deacon, Steven Rostedt, Masami Hiramatsu, Linus Torvalds
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 stack tracer's output. This patch replaces such entries with originals values preserved in current->ret_stack[]. Signed-off-by: AKASHI Takahiro <redacted> --- arch/arm64/include/asm/ftrace.h | 2 ++ arch/arm64/kernel/stacktrace.c | 20 ++++++++++++++++++++ 2 files changed, 22 insertions(+)
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 2b43e20..b7d597c 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h@@ -29,6 +29,8 @@ struct dyn_arch_ftrace { extern unsigned long ftrace_graph_call; +extern void return_to_handler(void); + static inline unsigned long ftrace_call_adjust(unsigned long addr) { /*
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index bc0689a..1555a8b 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c@@ -78,6 +78,9 @@ struct stack_trace_data { struct stack_trace *trace; unsigned int no_sched_functions; unsigned int skip; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + unsigned int ret_stack_index; +#endif }; static int save_trace(struct stackframe *frame, void *d)
@@ -86,6 +89,20 @@ static int save_trace(struct stackframe *frame, void *d) struct stack_trace *trace = data->trace; unsigned long addr = frame->pc; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + if (addr == (unsigned long)return_to_handler - AARCH64_INSN_SIZE) { + /* + * 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 = addr = + current->ret_stack[data->ret_stack_index--].ret + - AARCH64_INSN_SIZE; + } +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ + if (data->no_sched_functions && in_sched_functions(addr)) return 0; if (data->skip) {
@@ -105,6 +122,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) data.trace = trace; data.skip = trace->skip; +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + data.ret_stack_index = current->curr_ret_stack; +#endif if (tsk != current) { data.no_sched_functions = 1;
--
1.7.9.5