Commit 7a2b6209 authored Feb 03, 2010 by Kirill Smelkov Committed by Ingo Molnar Feb 04, 2010

perf annotate: Fix it for non-prelinked *.so



The problem was we were incorrectly calculating objdump
addresses for sym->start and sym->end, look:

For simple ET_DYN type DSO (*.so) with one function, objdump -dS
output is something like this:

    000004ac <my_strlen>:
    int my_strlen(const char *s)
     4ac:   55                      push   %ebp
     4ad:   89 e5                   mov    %esp,%ebp
     4af:   83 ec 10                sub    $0x10,%esp
    {

i.e. we have relative-to-dso-mapping IPs (=RIP) there.

For ET_EXEC type and probably for prelinked libs as well (sorry
can't test - I don't use prelink) objdump outputs absolute IPs,
e.g.

    08048604 <zz_strlen>:
    extern "C"
    int zz_strlen(const char *s)
     8048604:       55                      push   %ebp
     8048605:       89 e5                   mov    %esp,%ebp
     8048607:       83 ec 10                sub    $0x10,%esp
    {

So, if sym->start is always relative to dso mapping(*), we'll
have to unmap it for ET_EXEC like cases, and leave as is for
ET_DYN cases.

(*) and it is - we've explicitely made it relative. Look for
    adjust_symbols handling in dso__load_sym()

Previously we were always unmapping sym->start and for ET_DYN
dsos resulting addresses were wrong, and so objdump output was
empty.

The end result was that perf annotate output for symbols from
non-prelinked *.so had always 0.00% percents only, which is
wrong.

To fix it, let's introduce a helper for converting rip to
objdump address, and also let's document what map_ip() and
unmap_ip() do -- I had to study sources for several hours to
understand it.

Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1265223128-11786-8-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 29a9f66d

tools/perf/builtin-annotate.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -189,7 +189,7 @@ static int parse_line(FILE file, struct hist_entry he, u64 len)
		line_ip = -1;
		}

		start = he->map->unmap_ip(he->map, sym->start);
		start = map__rip_2objdump(he->map, sym->start);

		if (line_ip != -1) {
		const char *path = NULL;
		@@ -397,7 +397,8 @@ static void annotate_sym(struct hist_entry *he)
		dso, dso->long_name, sym, sym->name);

		sprintf(command, "objdump --start-address=0x%016Lx --stop-address=0x%016Lx -dS %s\|grep -v %s",
		map->unmap_ip(map, sym->start), map->unmap_ip(map, sym->end),
		map__rip_2objdump(map, sym->start),
		map__rip_2objdump(map, sym->end),
		filename, filename);

		if (verbose >= 3)

tools/perf/util/map.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -210,3 +210,15 @@ size_t map__fprintf(struct map self, FILE fp)
		return fprintf(fp, " %Lx-%Lx %Lx %s\n",
		self->start, self->end, self->pgoff, self->dso->name);
		}

		/*
		* objdump wants/reports absolute IPs for ET_EXEC, and RIPs for ET_DYN.
		* map->dso->adjust_symbols==1 for ET_EXEC-like cases.
		*/
		u64 map__rip_2objdump(struct map *map, u64 rip)
		{
		u64 addr = map->dso->adjust_symbols ?
		map->unmap_ip(map, rip) : /* RIP -> IP */
		rip;
		return addr;
		}

tools/perf/util/map.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -26,8 +26,12 @@ struct map {
		u64 end;
		enum map_type type;
		u64 pgoff;

		/* ip -> dso rip */
		u64 (map_ip)(struct map , u64);
		/* dso rip -> ip */
		u64 (unmap_ip)(struct map , u64);

		struct dso *dso;
		};

		@@ -56,6 +60,11 @@ static inline u64 identity__map_ip(struct map *map __used, u64 ip)
		return ip;
		}


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


		struct symbol;
		struct mmap_event;

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