Re: [PATCH perf/core v2 4/4] perf-probe: Find probe events without target module

Arnaldo Carvalho de Melo
2017-01-16T18:45:19Z

Em Wed, Jan 11, 2017 at 03:03:06PM +0900, Masami Hiramatsu escreveu:
> Find probe events without -m "module" option. If perf-probe
> failed to find given function in kernel image, it tries to
> find same symbol and module in kallsyms, and retry search
> in the found module. E.g.
>
> # perf probe -D i915_capabilities
> p:probe/i915_capabilities i915:i915_capabilities+0
>
> Note: without -m option, perf probe can not find inlined
> function since there is no symbol information in kallsyms.

As this is a new feature, I'll postpone merging it till we get
perf/urgent, with the first three patches in this series, merged into
perf/core, ok?

- Arnaldo

> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
> Changes in v2:
> - Fix to remove unneeded zero-return.
> - Remove unneeded debug message.
> ---
> tools/perf/util/probe-event.c | 69 ++++++++++++++++++++++++++++++-----------
> 1 file changed, 51 insertions(+), 18 deletions(-)
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 6a6f44d..715f330 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -858,11 +858,7 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
>
> debuginfo__delete(dinfo);
>
> - if (ntevs == 0) { /* No error but failed to find probe point. */
> - pr_warning("Probe point '%s' not found.\n",
> - synthesize_perf_probe_point(&pev->point));
> - return -ENOENT;
> - } else if (ntevs < 0) {
> + if (ntevs < 0) {
> /* Error path : ntevs < 0 */
> pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
> if (ntevs == -EBADF)
> @@ -2829,9 +2825,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
> */
> num_matched_functions = find_probe_functions(map, pp->function, syms);
> if (num_matched_functions == 0) {
> - pr_err("Failed to find symbol %s in %s\n", pp->function,
> - pev->target ? : "kernel");
> - ret = -ENOENT;
> + ret = 0;
> goto out;
> } else if (num_matched_functions > probe_conf.max_probes) {
> pr_err("Too many functions matched in %s\n",
> @@ -3233,6 +3227,42 @@ static int find_probe_trace_events_from_cache(struct perf_probe_event *pev,
> return ret;
> }
>
> +static int __convert_to_probe_trace_events(struct perf_probe_event *pev,
> + struct probe_trace_event **tevs)
> +{
> + int ret;
> +
> + /* At first, we need to lookup cache entry */
> + ret = find_probe_trace_events_from_cache(pev, tevs);
> + if (ret > 0 || pev->sdt) /* SDT can be found only in the cache */
> + return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
> +
> + /* Convert perf_probe_event with debuginfo */
> + ret = try_to_find_probe_trace_events(pev, tevs);
> + if (ret != 0)
> + return ret; /* Found in debuginfo or got an error */
> +
> + return find_probe_trace_events_from_map(pev, tevs);
> +}
> +
> +static char *find_module_from_kallsyms(const char *symbol_name)
> +{
> + struct machine *machine = machine__new_kallsyms();
> + struct symbol *sym;
> + struct map *map;
> + char *module;
> +
> + sym = machine__find_kernel_function_by_name(machine, symbol_name, &map);
> + if (!sym || map->dso->short_name[0] != '[')
> + return NULL;
> + pr_debug("Found %s in %s\n", sym->name, map->dso->short_name);
> + module = strdup(map->dso->short_name + 1);
> + if (module)
> + module[strlen(module) - 1] = '\0';
> +
> + return module;
> +}
> +
> static int convert_to_probe_trace_events(struct perf_probe_event *pev,
> struct probe_trace_event **tevs)
> {
> @@ -3255,17 +3285,20 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
> if (ret > 0)
> return ret;
>
> - /* At first, we need to lookup cache entry */
> - ret = find_probe_trace_events_from_cache(pev, tevs);
> - if (ret > 0 || pev->sdt) /* SDT can be found only in the cache */
> - return ret == 0 ? -ENOENT : ret; /* Found in probe cache */
> -
> - /* Convert perf_probe_event with debuginfo */
> - ret = try_to_find_probe_trace_events(pev, tevs);
> - if (ret != 0)
> - return ret; /* Found in debuginfo or got an error */
> + ret = __convert_to_probe_trace_events(pev, tevs);
> + /* Not found. will retry to check kmodule if possible */
> + if (ret == 0 && !pev->uprobes && !pev->target) {
> + pev->target = find_module_from_kallsyms(pev->point.function);
> + if (pev->target)
> + ret = __convert_to_probe_trace_events(pev, tevs);
> + }
>
> - return find_probe_trace_events_from_map(pev, tevs);
> + if (ret == 0) {
> + pr_warning("Probe point '%s' not found.\n",
> + synthesize_perf_probe_point(&pev->point));
> + ret = -ENOENT;
> + }
> + return ret;
> }
>
> int convert_perf_probe_events(struct perf_probe_event *pevs, int npevs)