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>
[ Note: one hunk of this patch was applied by Mike in 57d8188 ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1265550376-12665-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
ee11b90b12