> From: Francis Moreau <[email protected]>
> Date: Mon, May 2, 2011 at 3:02 AM
> Subject: Re: vmlinux buildid doesn't match the running one (/sys/kernel/notes)
> To: [email protected]
>
>
> Hi,
>
> Sorry for asking again but I would be really greatfull is someone can
> tell me what's wrong when using a kernel that I compiled by my own.
>
> I do not have that issue is I use the kernel shipped by my distro (FC14).
>
> Thanks
>
> On Thu, Apr 28, 2011 at 7:04 PM, Francis Moreau <[email protected]>
> wrote:
> > Hello,
> >
> > I'm trying to use perf-probe, but it fails.
> >
> > Basically it's due to the buildid of the running kernel (the one which
> > can be read from /sys/kernel/notes) and the one in vmlinx (which I
> > compiled my self).
> >
> > I did this:
> >
> > $ make
> > $ make modules_install install
> > $ ls vmlinux
> > vmlinux
> >
> > reboot
Could you make sure you indeed reboot with the new kernel running?
Use below patch to dump the 2 build_ids.
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 516876d..4b66c1c 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1036,6 +1036,15 @@ static size_t elf_addr_to_index(Elf *elf, GElf_Addr addr)
return -1;
}
+static void dump_build_id(u8 *build_id)
+{
+ int i;
+
+ for (i = 0; i < BUILD_ID_SIZE; i++)
+ printf("%02x ", build_id[i]);
+ printf("\n");
+}
+
static int dso__load_sym(struct dso *dso, struct map *map, const char *name,
int fd, symbol_filter_t filter, int kmodule,
int want_symtab)
@@ -1075,8 +1084,11 @@ static int dso__load_sym(struct dso *dso, struct map
*map, const char *name,
BUILD_ID_SIZE) != BUILD_ID_SIZE)
goto out_elf_end;
- if (!dso__build_id_equal(dso, build_id))
+ if (!dso__build_id_equal(dso, build_id)) {
+ dump_build_id(build_id);
+ dump_build_id(dso->build_id);
goto out_elf_end;
+ }
}
sec = elf_section_by_name(elf, &ehdr, &shdr, ".symtab", NULL);
> >
> > $ perf probe -k vmlinux -L schedule
> > Failed to find path of kernel module.
> > Failed to open debuginfo file.
> > Error: Failed to show lines. (-2)
> >
> > So my question is why the buildids doesn't match ?
> >
> > I guess I did something wrong since it's pretty a standard use case
> > but I don't see why...
> >
> > Thanks
> > --
> > Francis
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