[PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

[PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

[Yannick Brosseau]

When using a map file from a JIT, due to memory reuse, we can
obtain multiple symbols with the same start address but a different
length.
The symbols__find does check for the end so not doing it in sort__sym_cmp
was causing the hist_entry in the annotate part of a report to match to the
wrong entry, causing a fatal error.

Signed-off-by: Yannick Brosseau <scientist@fb.com>
---
 tools/perf/util/sort.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 4593f36..e226118 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -182,18 +182,16 @@ static int64_t _sort__addr_cmp(u64 left_ip, u64 right_ip)
 
 static int64_t _sort__sym_cmp(struct symbol *sym_l, struct symbol *sym_r)
 {
-	u64 ip_l, ip_r;
-
 	if (!sym_l || !sym_r)
 		return cmp_null(sym_l, sym_r);
 
 	if (sym_l == sym_r)
 		return 0;
 
-	ip_l = sym_l->start;
-	ip_r = sym_r->start;
+	if (sym_l->start != sym_r->start)
+		return (int64_t)(sym_r->start - sym_l->start);
 
-	return (int64_t)(ip_r - ip_l);
+	return (int64_t)(sym_r->end - sym_l->end);
 }
 
 static int64_t
-- 
2.1.4

Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

[Jeff Epler]

On Wed, Jun 17, 2015 at 04:41:10PM -0700, Yannick Brosseau wrote:
> When using a map file from a JIT, due to memory reuse, we can
> obtain multiple symbols with the same start address but a different
> length.

Is there some reason it's impossible for the reused memory to have the
same length / end address?

Jeff

Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

[Yannick Brosseau]

On 06/17/2015 04:53 PM, Jeff Epler wrote:
> On Wed, Jun 17, 2015 at 04:41:10PM -0700, Yannick Brosseau wrote:
>> When using a map file from a JIT, due to memory reuse, we can
>> obtain multiple symbols with the same start address but a different
>> length.
> Is there some reason it's impossible for the reused memory to have the
> same length / end address?
>
It's possible that they are the same, and in that case the function
returns 0.
The patch is adding the handling of the case where they are different.

Re: [PATCH] perf report: Fix sort__sym_cmp to also compare end of symbol

[Arnaldo Carvalho de Melo]

Em Wed, Jun 17, 2015 at 04:55:58PM -0700, Yannick Brosseau escreveu:
> On 06/17/2015 04:53 PM, Jeff Epler wrote:
> > On Wed, Jun 17, 2015 at 04:41:10PM -0700, Yannick Brosseau wrote:
> >> When using a map file from a JIT, due to memory reuse, we can
> >> obtain multiple symbols with the same start address but a different
> >> length.
> > Is there some reason it's impossible for the reused memory to have the
> > same length / end address?
> >
> It's possible that they are the same, and in that case the function
> returns 0.
> The patch is adding the handling of the case where they are different.

Looks sensible, applied.

- Arnaldo
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[tip:perf/core] perf report: Fix sort__sym_cmp to also compare end of symbol

[tip-bot for Yannick Brosseau]

Commit-ID:  c05676c06232e6459a6106ddf0d4e154ce6cd859
Gitweb:     http://git.kernel.org/tip/c05676c06232e6459a6106ddf0d4e154ce6cd859
Author:     Yannick Brosseau <scientist@fb.com>
AuthorDate: Wed, 17 Jun 2015 16:41:10 -0700
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 19 Jun 2015 18:14:05 -0300

perf report: Fix sort__sym_cmp to also compare end of symbol

When using a map file from a JIT, due to memory reuse, we can obtain
multiple symbols with the same start address but a different length.

The symbols__find does check for the end so not doing it in
sort__sym_cmp was causing the hist_entry in the annotate part of a
report to match to the wrong entry, causing a fatal error.

Signed-off-by: Yannick Brosseau <scientist@fb.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/1434584470-17771-1-git-send-email-scientist@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/sort.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 09d4696..4c65a14 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -182,18 +182,16 @@ static int64_t _sort__addr_cmp(u64 left_ip, u64 right_ip)
 
 static int64_t _sort__sym_cmp(struct symbol *sym_l, struct symbol *sym_r)
 {
-	u64 ip_l, ip_r;
-
 	if (!sym_l || !sym_r)
 		return cmp_null(sym_l, sym_r);
 
 	if (sym_l == sym_r)
 		return 0;
 
-	ip_l = sym_l->start;
-	ip_r = sym_r->start;
+	if (sym_l->start != sym_r->start)
+		return (int64_t)(sym_r->start - sym_l->start);
 
-	return (int64_t)(ip_r - ip_l);
+	return (int64_t)(sym_r->end - sym_l->end);
 }
 
 static int64_t
--
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