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SubjectRe: [PATCH] trace-cmd: Leave out absolute addresses to fix bogus symbol resolutions
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On 2015-09-15 19:00, Steven Rostedt wrote:
> On Tue, 15 Sep 2015 18:30:22 +0200
> Jan Kiszka <jan.kiszka@siemens.com> wrote:
>
>> On 2015-07-31 16:04, Jan Kiszka wrote:
>>> On x86, page_fault_* tracepoints report userspace address via kernel
>>> symbols because all the per-cpu variable offsets are in kallsyms,
>>> occupying the lower address space. Fix this by skipping over absolute
>>> addresses while processing kallsyms.
>>>
>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>> ---
>>> trace-util.c | 8 ++++++--
>>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/trace-util.c b/trace-util.c
>>> index 8a81dd0..da20e4c 100644
>>> --- a/trace-util.c
>>> +++ b/trace-util.c
>>> @@ -434,8 +434,12 @@ void parse_proc_kallsyms(struct pevent *pevent,
>>> if (mod)
>>> mod[strlen(mod) - 1] = 0;
>>>
>>> - /* Hack for arm arch that adds a lot of bogus '$a' functions */
>>> - if (func[0] != '$')
>>> + /*
>>> + * Hacks for
>>> + * - arm arch that adds a lot of bogus '$a' functions
>>> + * - x86-64 that reports per-cpu variable offsets as absolute
>>> + */
>>> + if (func[0] != '$' && ch != 'A')
>>> pevent_register_function(pevent, func, addr, mod);
>>> free(func);
>>> free(mod);
>>>
>>
>> Ping.
>
> Thanks for the reminder ping.
>
> Hmm, I don't see anything marked 'A' in my kallsyms. Have a config I
> can test to see what you are seeing?

Huh? Your /proc/kallsyms doesn't start like this?

0000000000000000 A irq_stack_union
0000000000000000 A __per_cpu_start
...

That's from a stock distro SUSE kernel I'm running (config attached).

Jan

--
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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