Re: [PATCH 05/12] perf tools: Read also the end of the kernel

Arnaldo Carvalho de Melo
2019-05-24T18:17:25Z

Em Fri, May 24, 2019 at 03:15:06PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, May 08, 2019 at 03:20:03PM +0200, Jiri Olsa escreveu:
> > We mark the end of kernel based on the first module,
> > but that could cover some bpf program maps. Reading
> > _etext symbol if it's present to get precise kernel
> > map end.
>
> Investigating... Have you run 'perf test' before hitting the send
> button? :-)

<SNIP>

> [root@quaco c]# perf test -v 1
> 1: vmlinux symtab matches kallsyms :
<SNIP>
> --- start ---
> ERR : 0xffffffff8cc00e41: __indirect_thunk_end not on kallsyms
<SNIP>
> test child finished with -1
> ---- end ----
> vmlinux symtab matches kallsyms: FAILED!
> [root@quaco c]#

So...

[root@quaco c]# grep __indirect_thunk_end /proc/kallsyms
ffffffff8cc00e41 T __indirect_thunk_end
[root@quaco c]# grep -w _etext /proc/kallsyms
ffffffff8cc00e41 T _etext
[root@quaco c]#

[root@quaco c]# grep -w ffffffff8cc00e41 /proc/kallsyms
ffffffff8cc00e41 T _etext
ffffffff8cc00e41 T __indirect_thunk_end
[root@quaco c]#

Lemme try to fix this.

- Arnaldo

> [acme@quaco perf]$ git bisect good
> 7d98e1a73bd7dae6cb321ec8b0b97b9fed7c0e1b is the first bad commit
> commit 7d98e1a73bd7dae6cb321ec8b0b97b9fed7c0e1b
> Author: Jiri Olsa <jolsa@kernel.org>
> Date: Wed May 8 15:20:03 2019 +0200
>
> perf machine: Read also the end of the kernel
>
> We mark the end of kernel based on the first module, but that could
> cover some bpf program maps. Reading _etext symbol if it's present to
> get precise kernel map end.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> Acked-by: Song Liu <songliubraving@fb.com>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Stanislav Fomichev <sdf@google.com>
> Cc: Thomas Richter <tmricht@linux.ibm.com>
> Link: http://lkml.kernel.org/r/20190508132010.14512-6-jolsa@kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
>
> :040000 040000 4ca5fa4c6f15fd8cf9a0eee870efbd01e9fe309d 8311b30f94e9cf9a863dc9619b0499863f64960e M tools
> [acme@quaco perf]$
>
> > Link: http://lkml.kernel.org/n/tip-ynut991ttyyhvo1sbhlm4c42@git.kernel.org
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> > tools/perf/util/machine.c | 27 ++++++++++++++++++---------
> > 1 file changed, 18 insertions(+), 9 deletions(-)
> >
> > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > index 3c520baa198c..ad0205fbb506 100644
> > --- a/tools/perf/util/machine.c
> > +++ b/tools/perf/util/machine.c
> > @@ -924,7 +924,8 @@ const char *ref_reloc_sym_names[] = {"_text", "_stext", NULL};
> > * symbol_name if it's not that important.
> > */
> > static int machine__get_running_kernel_start(struct machine *machine,
> > - const char **symbol_name, u64 *start)
> > + const char **symbol_name,
> > + u64 *start, u64 *end)
> > {
> > char filename[PATH_MAX];
> > int i, err = -1;
> > @@ -949,6 +950,11 @@ static int machine__get_running_kernel_start(struct machine *machine,
> > *symbol_name = name;
> >
> > *start = addr;
> > +
> > + err = kallsyms__get_function_start(filename, "_etext", &addr);
> > + if (!err)
> > + *end = addr;
> > +
> > return 0;
> > }
> >
> > @@ -1440,7 +1446,7 @@ int machine__create_kernel_maps(struct machine *machine)
> > struct dso *kernel = machine__get_kernel(machine);
> > const char *name = NULL;
> > struct map *map;
> > - u64 addr = 0;
> > + u64 start = 0, end = ~0ULL;
> > int ret;
> >
> > if (kernel == NULL)
> > @@ -1459,9 +1465,9 @@ int machine__create_kernel_maps(struct machine *machine)
> > "continuing anyway...\n", machine->pid);
> > }
> >
> > - if (!machine__get_running_kernel_start(machine, &name, &addr)) {
> > + if (!machine__get_running_kernel_start(machine, &name, &start, &end)) {
> > if (name &&
> > - map__set_kallsyms_ref_reloc_sym(machine->vmlinux_map, name, addr)) {
> > + map__set_kallsyms_ref_reloc_sym(machine->vmlinux_map, name, start)) {
> > machine__destroy_kernel_maps(machine);
> > ret = -1;
> > goto out_put;
> > @@ -1471,16 +1477,19 @@ int machine__create_kernel_maps(struct machine *machine)
> > * we have a real start address now, so re-order the kmaps
> > * assume it's the last in the kmaps
> > */
> > - machine__update_kernel_mmap(machine, addr, ~0ULL);
> > + machine__update_kernel_mmap(machine, start, end);
> > }
> >
> > if (machine__create_extra_kernel_maps(machine, kernel))
> > pr_debug("Problems creating extra kernel maps, continuing anyway...\n");
> >
> > - /* update end address of the kernel map using adjacent module address */
> > - map = map__next(machine__kernel_map(machine));
> > - if (map)
> > - machine__set_kernel_mmap(machine, addr, map->start);
> > + if (end == ~0ULL) {
> > + /* update end address of the kernel map using adjacent module address */
> > + map = map__next(machine__kernel_map(machine));
> > + if (map)
> > + machine__set_kernel_mmap(machine, start, map->start);
> > + }
> > +
> > out_put:
> > dso__put(kernel);
> > return ret;
> > --
> > 2.20.1
>
> --
>
> - Arnaldo

--

- Arnaldo