Commit 6c6804fb authored Mar 24, 2011 by Andrew Lutomirski Committed by Arnaldo Carvalho de Melo Mar 28, 2011

perf symbols: Fix vsyscall symbol lookup



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>

parent 18bcd0c8

tools/perf/util/event.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;

tools/perf/util/symbol.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);

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