On Tue, Aug 31, 2021 at 05:10:52PM -0700, Andrii Nakryiko wrote:
> On Thu, Aug 26, 2021 at 12:41 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> >
> > Adding btf__find_by_glob_kind function that returns array of
> > BTF ids that match given kind and allow/deny patterns.
> >
> > int btf__find_by_glob_kind(const struct btf *btf, __u32 kind,
> > const char *allow_pattern,
> > const char *deny_pattern,
> > __u32 **__ids);
> >
> > The __ids array is allocated and needs to be manually freed.
> >
> > At the moment the supported pattern is '*' at the beginning or
> > the end of the pattern.
> >
> > Kindly borrowed from retsnoop.
> >
> > Suggested-by: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > ---
> > tools/lib/bpf/btf.c | 80 +++++++++++++++++++++++++++++++++++++++++++++
> > tools/lib/bpf/btf.h | 3 ++
> > 2 files changed, 83 insertions(+)
> >
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index 77dc24d58302..5baaca6c3134 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
> > @@ -711,6 +711,86 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
> > return libbpf_err(-ENOENT);
> > }
> >
> > +/* 'borrowed' from retsnoop */
> > +static bool glob_matches(const char *glob, const char *s)
> > +{
> > + int n = strlen(glob);
> > +
> > + if (n == 1 && glob[0] == '*')
> > + return true;
> > +
> > + if (glob[0] == '*' && glob[n - 1] == '*') {
> > + const char *subs;
> > + /* substring match */
> > +
> > + /* this is hacky, but we don't want to allocate for no good reason */
> > + ((char *)glob)[n - 1] = '\0';
> > + subs = strstr(s, glob + 1);
> > + ((char *)glob)[n - 1] = '*';
> > +
> > + return subs != NULL;
> > + } else if (glob[0] == '*') {
> > + size_t nn = strlen(s);
> > + /* suffix match */
> > +
> > + /* too short for a given suffix */
> > + if (nn < n - 1)
> > + return false;
> > +
> > + return strcmp(s + nn - (n - 1), glob + 1) == 0;
> > + } else if (glob[n - 1] == '*') {
> > + /* prefix match */
> > + return strncmp(s, glob, n - 1) == 0;
> > + } else {
> > + /* exact match */
> > + return strcmp(glob, s) == 0;
> > + }
> > +}
> > +
> > +int btf__find_by_glob_kind(const struct btf *btf, __u32 kind,
> > + const char *allow_pattern, const char *deny_pattern,
> > + __u32 **__ids)
> > +{
> > + __u32 i, nr_types = btf__get_nr_types(btf);
> > + int cnt = 0, alloc = 0;
> > + __u32 *ids = NULL;
> > +
> > + for (i = 1; i <= nr_types; i++) {
> > + const struct btf_type *t = btf__type_by_id(btf, i);
> > + bool match = false;
> > + const char *name;
> > + __u32 *p;
> > +
> > + if (btf_kind(t) != kind)
> > + continue;
> > + name = btf__name_by_offset(btf, t->name_off);
> > + if (!name)
> > + continue;
> > +
> > + if (allow_pattern && glob_matches(allow_pattern, name))
> > + match = true;
> > + if (deny_pattern && !glob_matches(deny_pattern, name))
> > + match = true;
>
> this is wrong, if it matches both deny and allow patterns, you'll
> still pass it through. Drop the match flag, just check deny first and
> `continue` if matches.
true, ok
>
> > + if (!match)
> > + continue;
> > +
> > + if (cnt == alloc) {
> > + alloc = max(100, alloc * 3 / 2);
>
> nit: maybe start with something like 16?
ok
>
> > + p = realloc(ids, alloc * sizeof(__u32));
>
> we have libbpf_reallocarray, please use it
ok
>
> > + if (!p) {
> > + free(ids);
> > + return -ENOMEM;
> > + }
> > + ids = p;
> > + }
> > + ids[cnt] = i;
> > + cnt++;
> > + }
> > +
> > + *__ids = ids;
> > + return cnt ?: -ENOENT;
>
> cnt == 0 means -ENOENT, basically, no? It's up to the application to
> decide if that's an error, let's just return the number of matches,
> i.e., zero.
ok
thanks,
jirka
