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Date: Sun, 1 Nov 2015 17:00:10 +0900 From: Jungseok Lee <jungseoklee85@...il.com> To: AKASHI Takahiro <takahiro.akashi@...aro.org> Cc: catalin.marinas@....com, will.deacon@....com, rostedt@...dmis.org, olof@...om.net, broonie@...nel.org, david.griego@...aro.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 3/6] arm64: ftrace: fix a stack tracer's output under function graph tracer 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 <takahiro.akashi@...aro.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 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 <linux/kernel.h> > #include <linux/export.h> > +#include <linux/ftrace.h> > #include <linux/sched.h> > #include <linux/stacktrace.h> > > @@ -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. Best Regards Jungseok Lee-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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