linux-kernel - Re: [PATCH] perf callchain: separate eh/debug frame offset cache.

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Message-ID: <20150319140352.GJ2983@kernel.org>
Date:	Thu, 19 Mar 2015 11:03:52 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Wang Nan <wangnan0@...wei.com>, Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Li Zefan <lizefan@...wei.com>
Subject: Re: [PATCH] perf callchain: separate eh/debug frame offset cache.

Em Thu, Mar 19, 2015 at 02:20:16PM +0800, Wang Nan escreveu:
> Hi Ingo,
> 
>> Could you please collect this patch? It fixes a bug which prevent unwind for ARM.

Hi Jiri, can I have your Acked-by for this change, since you worked on
this unwind code the most?

- Arnaldo
 
> 
> On 2015/3/13 17:44, Namhyung Kim wrote:
> > Hi Wang,
> > 
> > On Fri, Mar 13, 2015 at 03:02:56PM +0800, Wang Nan wrote:
> >> Commit f1f13af99a90 ("perf callchain: Cache eh/debug frame offset for
> >> dwarf unwind") introduces a cache for .debug_frame and .eh_frame_hdr.
> >> Unfortunately, it makes them share a same cache (dso->frame_offset).
> >> Which causes unwind failure on ARM:
> >>
> >>    $ perf test unwind
> >>   Test dwarf unwind: FAILED!
> >>
> >> The reason is that, if a dso has '.debug_frame' but doesn't have
> >> '.eh_frame_hdr' (like ARM), dso->frame_offset will be filled by offset
> >> of '.debug_frame' during the first time calling of find_proc_info() ->
> >> read_unwind_spec_debug_frame(), and be regarded to '.eh_frame_hdr' when
> >> the second time calling of find_proc_info() ->
> >> read_unwind_spec_eh_frame(), since '.eh_frame_hdr' is checked prior to
> >> '.debug_frame'.
> >>
> >> This patch solves the problem by creating two cache fields for
> >> '.eh_frame_hdr' and '.debug_frame'.
> >>
> >> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> > 
> > Acked-by: Namhyung Kim <namhyung@...nel.org>
> > 
> > Thanks,
> > Namhyung
> > 
> > 
> >> ---
> >>  tools/perf/util/dso.h              | 3 ++-
> >>  tools/perf/util/unwind-libunwind.c | 8 ++++----
> >>  2 files changed, 6 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
> >> index ced9284..408c65f 100644
> >> --- a/tools/perf/util/dso.h
> >> +++ b/tools/perf/util/dso.h
> >> @@ -139,7 +139,8 @@ struct dso {
> >>  		u32		 status_seen;
> >>  		size_t		 file_size;
> >>  		struct list_head open_entry;
> >> -		u64		 frame_offset;
> >> +		u64		 debug_frame_offset;
> >> +		u64		 eh_frame_hdr_offset;
> >>  	} data;
> >>
> >>  	union { /* Tool specific area */
> >> diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
> >> index e3c40a5..7b09a44 100644
> >> --- a/tools/perf/util/unwind-libunwind.c
> >> +++ b/tools/perf/util/unwind-libunwind.c
> >> @@ -266,7 +266,7 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
> >>  				     u64 *fde_count)
> >>  {
> >>  	int ret = -EINVAL, fd;
> >> -	u64 offset = dso->data.frame_offset;
> >> +	u64 offset = dso->data.eh_frame_hdr_offset;
> >>
> >>  	if (offset == 0) {
> >>  		fd = dso__data_fd(dso, machine);
> >> @@ -275,7 +275,7 @@ static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
> >>
> >>  		/* Check the .eh_frame section for unwinding info */
> >>  		offset = elf_section_offset(fd, ".eh_frame_hdr");
> >> -		dso->data.frame_offset = offset;
> >> +		dso->data.eh_frame_hdr_offset = offset;
> >>  	}
> >>
> >>  	if (offset)
> >> @@ -291,7 +291,7 @@ static int read_unwind_spec_debug_frame(struct dso *dso,
> >>  					struct machine *machine, u64 *offset)
> >>  {
> >>  	int fd;
> >> -	u64 ofs = dso->data.frame_offset;
> >> +	u64 ofs = dso->data.debug_frame_offset;
> >>
> >>  	if (ofs == 0) {
> >>  		fd = dso__data_fd(dso, machine);
> >> @@ -300,7 +300,7 @@ static int read_unwind_spec_debug_frame(struct dso *dso,
> >>
> >>  		/* Check the .debug_frame section for unwinding info */
> >>  		ofs = elf_section_offset(fd, ".debug_frame");
> >> -		dso->data.frame_offset = ofs;
> >> +		dso->data.debug_frame_offset = ofs;
> >>  	}
> >>
> >>  	*offset = ofs;
> >> --
> >> 1.8.3.4
> >>
> 
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