On Nov 6, 2015, at 3:44 PM, AKASHI Takahiro wrote: Hi Akashi,
> 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 <takahiro.aka...@linaro.org> > --- > arch/arm64/include/asm/ftrace.h | 2 ++ > arch/arm64/kernel/stacktrace.c | 21 +++++++++++++++++++++ > 2 files changed, 23 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index c5534fa..3c60f37 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -28,6 +28,8 @@ 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 ccb6078..5fd3477 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> > > @@ -73,6 +74,9 @@ 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) > @@ -81,6 +85,20 @@ 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) { not if (adds == (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 = addr = > + current->ret_stack[data->ret_stack_index--].ret > + - AARCH64_INSN_SIZE; Ditto. not without AARCH64_INSN_SIZE? I've observed many return_to_handler without the changes. Am I missing something? > + } > +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > + > if (data->no_sched_functions && in_sched_functions(addr)) > return 0; > if (data->skip) { > @@ -100,6 +118,9 @@ 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; Can I get an idea on why current->curr_ret_stack is used instead of tsk->curr_ret_stack? Best Regards Jungseok Lee-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/