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

    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)
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