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SubjectRe: [PATCH v8 3.2.0-rc5 9/9] perf: perf interface for uprobes
(2012/01/09 20:22), Srikar Dronamraju wrote:
>>> return true;
>>>
>>> for (i = 0; i < pev->nargs; i++)
>>> @@ -1344,11 +1389,17 @@ char *synthesize_probe_trace_command(struct
probe_trace_event *tev)
>>> if (buf == NULL)
>>> return NULL;
>>>
>>> - len = e_snprintf(buf, MAX_CMDLEN, "%c:%s/%s %s%s%s+%lu",
>>> - tp->retprobe ? 'r' : 'p',
>>> - tev->group, tev->event,
>>> - tp->module ?: "", tp->module ? ":" : "",
>>> - tp->symbol, tp->offset);
>>> + if (tev->uprobes)
>>> + len = e_snprintf(buf, MAX_CMDLEN, "%c:%s/%s %s",
>>> + tp->retprobe ? 'r' : 'p',
>>> + tev->group, tev->event, tp->symbol);
>>> + else
>>> + len = e_snprintf(buf, MAX_CMDLEN, "%c:%s/%s %s%s%s+%lu",
>>> + tp->retprobe ? 'r' : 'p',
>>> + tev->group, tev->event,
>>> + tp->module ?: "", tp->module ? ":" : "",
>>> + tp->symbol, tp->offset);
>>
>> I think tp->module should be the executable file even when
>> tp is a user space probe, because when parsing the uprobes list
>> in tracing/trace_uprobes, exec file will be stored in tp->module.
>
> can be done. What I used to do is overload the tp->symbol with the
> real-name as well as the offset. Now I will just keep the offset in the
> symbol and use the target that the user has requested.

I mean that tp->module always !NULL if uprobe, then, we don't need
to change the code. (thus we can reduce the patch size :))


>>> +int show_available_funcs(const char *target, struct strfilter *_filter,
>>> + bool user)
>>> +{
>>> + struct map *map;
>>> + int ret;
>>> +
>>> + setup_pager();
>>> available_func_filter = _filter;
>>> +
>>> + if (!user)
>>> + return available_kernel_funcs(target);
>>> +
>>> + symbol_conf.try_vmlinux_path = false;
>>> + symbol_conf.sort_by_name = true;
>>> + ret = symbol__init();
>>> + if (ret < 0) {
>>> + pr_err("Failed to init symbol map.\n");
>>> + return ret;
>>> + }
>>> + map = dso__new_map(target);
>>> + ret = __show_available_funcs(map);
>>> + dso__delete(map->dso);
>>> + map__delete(map);
>>> + return ret;
>>> +}
>>> +
>>> +#define DEFAULT_FUNC_FILTER "!_*"
>>
>> This is a hidden rule for users ... please remove it.
>> (or, is there any reason why we need to have it?)
>>
>
> This is to be in sync with your commit
> 3c42258c9a4db70133fa6946a275b62a16792bb5

I see, but that commit also provides filter option for changing
the function filter. Here, user can not change the filter rule.

I think, currently, we don't need to filter any function by name
here, since the user obviously intends to probe given function :)

>>> +
>>> +/*
>>> + * uprobe_events only accepts address:
>>> + * Convert function and any offset to address
>>> + */
>>> +static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>>> +{
>>
>> I'm not sure why wouldn't you convert function to "vaddr",
>> instead of "exec:vaddr"?
>>
>
> If the user provides a symbolic link, convert_name_to_addr would get the
> target executable for the given executable. This would handy if we were
> to compare existing probes registered on the same application using a
> different name (symbolic links). Since you seem to like that we register
> with the name the user has provided, I will just feed address here.

Hmm, why do we need to compare the probe points? Of course, event-name
conflict should be solved, but I think it is acceptable that user puts
several probes on the same exec:vaddr. Since different users may want
to use it concurrently bit different ways.

Thank you,


--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


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