Subject: [PATCH bpf-next 21/29] libbpf: Add btf__find_by_glob_kind function

From: Jiri Olsa <[email-masked]>
Date: Thu, 18 Nov 2021 12:24:47 +0100

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 <[email-masked]>
Signed-off-by: Jiri Olsa <[email-masked]>
---
 tools/lib/bpf/btf.c | 77 +++++++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/btf.h |  3 ++
 2 files changed, 80 insertions(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index b6be579e0dc6..ebc02576390d 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -749,6 +749,83 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
 	return btf_find_by_name_kind(btf, 1, type_name, kind);
 }
 
+/* '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);
+		const char *name;
+		__u32 *p;
+
+		if (btf_kind(t) != kind)
+			continue;
+		name = btf__name_by_offset(btf, t->name_off);
+		if (!name)
+			continue;
+
+		if (deny_pattern && glob_matches(deny_pattern, name))
+			continue;
+		if (allow_pattern && !glob_matches(allow_pattern, name))
+			continue;
+
+		if (cnt == alloc) {
+			alloc = max(16, alloc * 3 / 2);
+			p = libbpf_reallocarray(ids, alloc, sizeof(__u32));
+			if (!p) {
+				free(ids);
+				return -ENOMEM;
+			}
+			ids = p;
+		}
+		ids[cnt] = i;
+		cnt++;
+	}
+
+	*__ids = ids;
+	return cnt;
+}
+
 static bool btf_is_modifiable(const struct btf *btf)
 {
 	return (void *)btf->hdr != btf->raw_data;
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 5c73a5b0a044..408b8e6d913b 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -572,6 +572,9 @@ static inline struct btf_decl_tag *btf_decl_tag(const struct btf_type *t)
 	return (struct btf_decl_tag *)(t + 1);
 }
 
+int btf__find_by_glob_kind(const struct btf *btf, __u32 kind,
+			   const char *allow_pattern, const char *deny_pattern,
+			   __u32 **__ids);
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
-- 
2.31.1