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SubjectRe: [PATCH] perf callchain: separate eh/debug frame offset cache.
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@huawei.com>

Acked-by: Namhyung Kim <namhyung@kernel.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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