From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Wed, 4 Nov 2015 16:49:53 +0900 Subject: [PATCH v4 3/6] arm64: ftrace: fix a stack tracer's output under function graph tracer In-Reply-To: References: <1446182741-31019-1-git-send-email-takahiro.akashi@linaro.org> <1446182741-31019-4-git-send-email-takahiro.akashi@linaro.org> Message-ID: <5639B8A1.90701@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/01/2015 05:00 PM, Jungseok Lee wrote: > On Oct 30, 2015, at 2:25 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 >> --- >> 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 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..631c49d 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -17,6 +17,7 @@ >> */ >> #include >> #include >> +#include >> #include >> #include >> >> @@ -78,6 +79,9 @@ 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 +90,20 @@ 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 */ >> + > > This hunk would be affected as the commit, "ARM64: unwind: Fix PC calculation", > e306dfd0, has been reverted. Yeah, we don't need apply this patch any more. The other patches in the series will not be affected. Thanks, -Takahiro AKASHI > Best Regards > Jungseok Lee >