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perf symbols: Fix vsyscall symbol lookup

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Perf can't currently trace into the vsyscall page.  It looks like it was
meant to work.

Tested on 2.6.38 and today's -git.

The bug is easy to reproduce.  Compile this:

int main()
{
	int i;
	struct timespec t;
	for(i = 0; i < 10000000; i++)
		clock_gettime(CLOCK_MONOTONIC, &t);
	return 0;
}

and run it through perf record; perf report.  The top entry shows
"[unknown]" and you can't zoom in.

It looks like there are two issues.  The first is a that a test for user
mode executing in kernel space is backwards.  (That's the first hunk
below).  The second (I think) is that something's wrong with the code
that generates lots of little struct dso objects for different sections
-- when it runs on vmlinux it results in bogus long_name values which
cause objdump to fail.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LPU-Reference: <AANLkTikxSw5+wJZUWNz++nL7mgivCh_Zf=2Kq6=f9Ce_@mail.gmail.com>
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Andrew Lutomirski 2011-03-24 00:36:56 -04:00 committed by Arnaldo Carvalho de Melo
parent 18bcd0c8cb
commit 6c6804fb2c
2 changed files with 4 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
tools/perf/util/event.c
View file

@ -710,7 +710,7 @@ try_again:
* in the whole kernel symbol list.
*/
if ((long long)al->addr < 0 &&
cpumode == PERF_RECORD_MISC_KERNEL &&
cpumode == PERF_RECORD_MISC_USER &&
machine && mg != &machine->kmaps) {
mg = &machine->kmaps;
goto try_again;

3
tools/perf/util/symbol.c
View file

@ -1196,6 +1196,8 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
if (curr_dso == NULL)
goto out_elf_end;
curr_dso->kernel = self->kernel;
curr_dso->long_name = self->long_name;
curr_dso->long_name_len = self->long_name_len;
curr_map = map__new2(start, curr_dso,
map->type);
if (curr_map == NULL) {
@ -1842,6 +1844,7 @@ int dso__load_vmlinux(struct dso *self, struct map *map,
if (fd < 0)
return -1;
dso__set_long_name(self, (char *)vmlinux);
dso__set_loaded(self, map->type);
err = dso__load_sym(self, map, symfs_vmlinux, fd, filter, 0, 0);
close(fd);