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Subject[PATCH 5/6] perf top: fix annotate for userspace
Date
First, for programs and prelinked libraries, annotate code was fooled by
objdump output IPs (src->eip in the code) being wrongly converted to
absolute IPs. In such case there were no conversion needed, but in

src->eip = strtoull(src->line, NULL, 16);
src->eip = map->unmap_ip(map, src->eip); // = eip + map->start - map->pgoff
we were reading absolute address from objdump (e.g. 8048604) and then
almost doubling it, because eip & map->start are approximately close for
small programs.

Needless to say, that later, in record_precise_ip() there was no
matching with real runtime IPs.

And second, like with `perf annotate` the problem with non-prelinked
*.so was that we were doing rip -> objdump address conversion wrong.

Also, because unlike `perf annotate`, `perf top` code does annotation based on
absolute IPs for performance reasons(*), new helper for mapping objdump
addresse to IP is introduced.

(*) we get samples info in absolute IPs, and since we do lots of
hit-testing on absolute IPs at runtime in record_precise_ip(), it's
better to convert objdump addresses to IPs once and do no conversion
at runtime.

I also had to fix how objdump output is parsed (with hardcoded 8/16
characters format, which was inappropriate for ET_DYN dsos with small
addresses like '4ac')

Also note, that not all objdump output lines has associtated IPs, e.g.
look at source lines here:

000004ac <my_strlen>:
extern "C"
int my_strlen(const char *s)
4ac: 55 push %ebp
4ad: 89 e5 mov %esp,%ebp
4af: 83 ec 10 sub $0x10,%esp
{
int len = 0;
4b2: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%ebp)
4b9: eb 08 jmp 4c3 <my_strlen+0x17>
while (*s) {
++len;
4bb: 83 45 fc 01 addl $0x1,-0x4(%ebp)
++s;
4bf: 83 45 08 01 addl $0x1,0x8(%ebp)
So we mark them with eip=0, and ignore such lines in annotate lookup
code.

Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
---
tools/perf/builtin-top.c | 24 ++++++++++++++----------
tools/perf/util/map.c | 8 ++++++++
tools/perf/util/map.h | 3 ++-
3 files changed, 24 insertions(+), 11 deletions(-)
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 4067e4d..6aa9b02 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -176,6 +176,7 @@ static void parse_source(struct sym_entry *syme)
FILE *file;
char command[PATH_MAX*2];
const char *path;
+ char *tmp;
u64 len;

if (!syme)
@@ -204,8 +205,8 @@ static void parse_source(struct sym_entry *syme)
sprintf(command,
"objdump --start-address=0x%016Lx "
"--stop-address=0x%016Lx -dS %s",
- map->unmap_ip(map, sym->start),
- map->unmap_ip(map, sym->end), path);
+ map__rip_2objdump(map, sym->start),
+ map__rip_2objdump(map, sym->end), path);

file = popen(command, "r");
if (!file)
@@ -235,14 +236,13 @@ static void parse_source(struct sym_entry *syme)
*source->lines_tail = src;
source->lines_tail = &src->next;

- if (strlen(src->line)>8 && src->line[8] == ':') {
- src->eip = strtoull(src->line, NULL, 16);
- src->eip = map->unmap_ip(map, src->eip);
- }
- if (strlen(src->line)>8 && src->line[16] == ':') {
- src->eip = strtoull(src->line, NULL, 16);
- src->eip = map->unmap_ip(map, src->eip);
- }
+
+ src->eip = strtoull(src->line, &tmp, 16);
+ if (*tmp == ':')
+ src->eip = map__objdump_2ip(map, src->eip);
+ else
+ /* this line has no ip info (e.g. source line) */
+ src->eip = 0;
}
pclose(file);
out_assign:
@@ -277,6 +277,10 @@ static void record_precise_ip(struct sym_entry *syme, int counter, u64 ip)
goto out_unlock;

for (line = syme->src->lines; line; line = line->next) {
+ /* skip lines without IP info */
+ if (line->eip == 0)
+ continue;
+
if (line->eip == ip) {
line->count[counter]++;
break;
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index d6da969..37bfcc5 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -215,3 +215,11 @@ u64 map__rip_2objdump(struct map *map, u64 rip)
rip;
return addr;
}
+
+u64 map__objdump_2ip(struct map *map, u64 addr)
+{
+ u64 ip = map->dso->adjust_symbols ?
+ addr :
+ map->unmap_ip(map, addr); /* RIP -> IP */
+ return ip;
+}
diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 39fa478..2bcd9d4 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -49,8 +49,9 @@ static inline u64 identity__map_ip(struct map *map __used, u64 ip)
}


-/* rip -> addr suitable for passing to `objdump --start-address=` */
+/* rip/ip <-> addr suitable for passing to `objdump --start-address=` */
u64 map__rip_2objdump(struct map *map, u64 rip);
+u64 map__objdump_2ip(struct map *map, u64 addr);


struct symbol;
--
1.6.6.79.gd514e.dirty

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