perf callchain: separate eh/debug frame offset cache.

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 <[email protected]>

---
 tools/perf/util/dso.h              | 3 ++-
 tools/perf/util/unwind-libunwind.c | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

tools/perf/util/dso.h +2 -1

index ced9284..408c65f 100644
@@ -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 */

tools/perf/util/unwind-libunwind.c +4 -5

index e3c40a5..7b09a44 100644
@@ -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

Hi Wang,

Quoted 16 lines · Wang Nan

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'.

Quoted 4 lines

This patch solves the problem by creating two cache fields for '.eh_frame_hdr' and '.debug_frame'.

Signed-off-by Wang Nan <[email protected]>

Acked-by Namhyung Kim <[email protected]>

Thanks,
Namhyung

Quoted 62 lines

---
 tools/perf/util/dso.h              | 3 ++-
 tools/perf/util/unwind-libunwind.c | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

tools/perf/util/dso.h +2 -1

index ced9284..408c65f 100644
@@ -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 */

tools/perf/util/unwind-libunwind.c +4 -5

index e3c40a5..7b09a44 100644
@@ -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

Hi Ingo,

Quoted 1 line

Could you please collect this patch? It fixes a bug which prevent unwind for ARM.

Quoted 92 lines

Hi Wang,

Quoted 16 lines · Wang Nan

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'.

Quoted 4 lines

This patch solves the problem by creating two cache fields for '.eh_frame_hdr' and '.debug_frame'.

Signed-off-by Wang Nan <[email protected]>

Acked-by Namhyung Kim <[email protected]>

Thanks,
Namhyung

Quoted 62 lines

---
 tools/perf/util/dso.h              | 3 ++-
 tools/perf/util/unwind-libunwind.c | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

tools/perf/util/dso.h +2 -1

index ced9284..408c65f 100644
@@ -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 */

tools/perf/util/unwind-libunwind.c +4 -5

index e3c40a5..7b09a44 100644
@@ -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

Em Thu, Mar 19, 2015 at 02:20:16PM +0800, Wang Nan escreveu:

Quoted 3 lines

Hi Ingo,

Quoted 1 line

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?