Re: [PATCH] perf inject: Add a command line option to specify build ids.

[Raul Silvera]

Thank you. Will apply these suggestions and send an updated version shortly.

Raúl E. Silvera
Software Engineer
waymo.com

Raúl E. Silvera
Software Engineer
waymo.com


On Wed, Jul 6, 2022 at 2:27 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> Hi Raul,
>
> On Wed, Jun 29, 2022 at 5:18 PM Raul Silvera <rsilvera@xxxxxxxxxx> wrote:
> >
> > This commit adds the option --known-build-ids to perf inject.
> > It allows the user to explicitly specify the build id for a given
> > path, instead of retrieving it from the current system. This is
> > useful in cases where a perf.data file is processed on a different
> > system from where it was collected, or if some of the binaries are
> > no longer available.
> >
> > The build ids and paths are specified in pairs in the command line.
> > Using the file:// specifier, build ids can be loaded from a file
> > directly generated by perf buildid-list. This is convenient to copy
> > build ids from one perf.data file to another.
> >
> > ** Example: In this example we use perf record to create two
> > perf.data files, one with build ids and another without, and use
> > perf buildid-list and perf inject to copy the build ids from the
> > first file to the second.
> >
> > $ perf record ls /tmp                  # Create perf.data file
> > $ perf record --no-buildid ls /tmp -o perf.data.no-buildid
> > $ perf buildid-list > /tmp/build-ids.txt
> > $ perf inject -b --known-build-ids='file:///tmp/build-ids.txt' \
> > $  -i perf.data.no-buildid -o perf.data.buildid
>
> You'd better indent the block for the readability and to prevent
> possible interference from the shell (for comments usually).
>
> The last line is a continuation from the above line and it used
> to print other prompts like ">".
>
> >
> > Signed-off-by: Raul Silvera <rsilvera@xxxxxxxxxx>
> > ---
> >  tools/perf/builtin-inject.c | 57 +++++++++++++++++++++++++++++++++++++
> >  1 file changed, 57 insertions(+)
> >
> > diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> > index a75bf11585b5..667b942f870e 100644
> > --- a/tools/perf/builtin-inject.c
> > +++ b/tools/perf/builtin-inject.c
> > @@ -21,6 +21,7 @@
> >  #include "util/data.h"
> >  #include "util/auxtrace.h"
> >  #include "util/jit.h"
> > +#include "util/string2.h"
> >  #include "util/symbol.h"
> >  #include "util/synthetic-events.h"
> >  #include "util/thread.h"
> > @@ -35,6 +36,7 @@
> >
> >  #include <linux/list.h>
> >  #include <linux/string.h>
> > +#include <ctype.h>
> >  #include <errno.h>
> >  #include <signal.h>
> >
> > @@ -59,6 +61,8 @@ struct perf_inject {
> >         struct itrace_synth_opts itrace_synth_opts;
> >         char                    event_copy[PERF_SAMPLE_MAX_SIZE];
> >         struct perf_file_section secs[HEADER_FEAT_BITS];
> > +       const char              *known_build_ids_source;
> > +       struct strlist          *known_build_ids;
> >  };
> >
> >  struct event_entry {
> > @@ -570,9 +574,43 @@ static int dso__read_build_id(struct dso *dso)
> >         return dso->has_build_id ? 0 : -1;
> >  }
> >
> > +static bool perf_inject__lookup_known_build_id(struct perf_inject *inject,
> > +                                              struct dso *dso)
> > +{
> > +       struct str_node *pos;
> > +       int bid_len;
> > +
> > +       strlist__for_each_entry(pos, inject->known_build_ids) {
> > +               const char *space;
> > +
> > +               pos->s = skip_spaces(pos->s);
> > +               space = strstr(pos->s, " ");
> > +               if (space == NULL ||
> > +                   !strcmp(dso->long_name, skip_spaces(space)))
> > +                       continue;
> > +               bid_len = space - pos->s;
> > +               if (bid_len == 0 || bid_len / 2 > BUILD_ID_SIZE)
>
> I'm not sure how bid_len can be 0.  And you can compare to
> SBUILD_ID_SIZE (without dividing by 2) - but it'd be ">=".
> Also it could be worthwhile to check if bid_len is even.
>
>
> > +                       return false;
> > +               for (int ix = 0; 2 * ix + 1 < bid_len; ++ix) {
> > +                       if (!isxdigit(pos->s[2 * ix]) ||
> > +                           !isxdigit(pos->s[2 * ix + 1]))
> > +                               return false;
> > +
> > +                       dso->bid.data[ix] = (hex(pos->s[2 * ix]) << 4 |
> > +                                            hex(pos->s[2 * ix + 1]));
> > +               }
> > +               dso->bid.size = bid_len / 2;
> > +               dso->has_build_id = 1;
> > +               return true;
> > +       }
> > +       return false;
> > +}
> > +
> >  static int dso__inject_build_id(struct dso *dso, struct perf_tool *tool,
> >                                 struct machine *machine, u8 cpumode, u32 flags)
> >  {
> > +       struct perf_inject *inject = container_of(tool, struct perf_inject,
> > +                                                 tool);
> >         int err;
> >
> >         if (is_anon_memory(dso->long_name) || flags & MAP_HUGETLB)
> > @@ -580,6 +618,10 @@ static int dso__inject_build_id(struct dso *dso, struct perf_tool *tool,
> >         if (is_no_dso_memory(dso->long_name))
> >                 return 0;
> >
> > +       if (inject->known_build_ids != NULL &&
> > +           perf_inject__lookup_known_build_id(inject, dso))
> > +               return 1;
> > +
> >         if (dso__read_build_id(dso) < 0) {
> >                 pr_debug("no build_id found for %s\n", dso->long_name);
> >                 return -1;
> > @@ -1082,6 +1124,9 @@ int cmd_inject(int argc, const char **argv)
> >                             "Inject build-ids into the output stream"),
> >                 OPT_BOOLEAN(0, "buildid-all", &inject.build_id_all,
> >                             "Inject build-ids of all DSOs into the output stream"),
> > +               OPT_STRING(0, "known-build-ids", &inject.known_build_ids_source,
> > +                          "buildid path [buildid path...]",
> > +                          "build-ids to use for specific files"),
> >                 OPT_STRING('i', "input", &inject.input_name, "file",
> >                            "input file name"),
> >                 OPT_STRING('o', "output", &inject.output.path, "file",
> > @@ -1215,6 +1260,18 @@ int cmd_inject(int argc, const char **argv)
> >                  */
> >                 inject.tool.ordered_events = true;
> >                 inject.tool.ordering_requires_timestamps = true;
> > +               if (inject.known_build_ids_source != NULL) {
> > +                       struct strlist *known_build_ids;
> > +
> > +                       known_build_ids = strlist__new(
> > +                           inject.known_build_ids_source, NULL);
> > +
> > +                       if (known_build_ids == NULL) {
> > +                               pr_err("Couldn't parse known build ids.\n");
> > +                               goto out_delete;
> > +                       }
> > +                       inject.known_build_ids = known_build_ids;
>
> You need to release it after use.  Note that strlist__delete()
> accepts a NULL pointer.
>
> Thanks,
> Namhyung
>
>
> > +               }
> >         }
> >
> >         if (inject.sched_stat) {
> > --
> > 2.37.0.rc0.161.g10f37bed90-goog
> >