[PATCH 14/19] libbpf: Add btf__find_by_pattern_kind function

Jiri Olsa
2021-06-05T11:11:32Z

Adding btf__find_by_pattern_kind function that returns
array of BTF ids for given function name pattern.

Using libc's regex.h support for that.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/lib/bpf/btf.c | 68 +++++++++++++++++++++++++++++++++++++++++++++
tools/lib/bpf/btf.h | 3 ++
2 files changed, 71 insertions(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index b46760b93bb4..421dd6c1e44a 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2018 Facebook */

+#define _GNU_SOURCE
#include <byteswap.h>
#include <endian.h>
#include <stdio.h>
@@ -16,6 +17,7 @@
#include <linux/err.h>
#include <linux/btf.h>
#include <gelf.h>
+#include <regex.h>
#include "btf.h"
#include "bpf.h"
#include "libbpf.h"
@@ -711,6 +713,72 @@ __s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
return libbpf_err(-ENOENT);
}

+static bool is_wildcard(char c)
+{
+ static const char *wildchars = "*?[|";
+
+ return strchr(wildchars, c);
+}
+
+int btf__find_by_pattern_kind(const struct btf *btf,
+ const char *type_pattern, __u32 kind,
+ __s32 **__ids)
+{
+ __u32 i, nr_types = btf__get_nr_types(btf);
+ __s32 *ids = NULL;
+ int cnt = 0, alloc = 0, ret;
+ regex_t regex;
+ char *pattern;
+
+ if (kind == BTF_KIND_UNKN || !strcmp(type_pattern, "void"))
+ return 0;
+
+ /* When the pattern does not start with wildcard, treat it as
+ * if we'd want to match it from the beginning of the string.
+ */
+ asprintf(&pattern, "%s%s",
+ is_wildcard(type_pattern[0]) ? "^" : "",
+ type_pattern);
+
+ ret = regcomp(&regex, pattern, REG_EXTENDED);
+ if (ret) {
+ pr_warn("failed to compile regex\n");
+ free(pattern);
+ return -EINVAL;
+ }
+
+ free(pattern);
+
+ for (i = 1; i <= nr_types; i++) {
+ const struct btf_type *t = btf__type_by_id(btf, i);
+ const char *name;
+ __s32 *p;
+
+ if (btf_kind(t) != kind)
+ continue;
+ name = btf__name_by_offset(btf, t->name_off);
+ if (name && regexec(&regex, name, 0, NULL, 0))
+ continue;
+ if (cnt == alloc) {
+ alloc = max(100, alloc * 3 / 2);
+ p = realloc(ids, alloc * sizeof(__u32));
+ if (!p) {
+ free(ids);
+ regfree(&regex);
+ return -ENOMEM;
+ }
+ ids = p;
+ }
+
+ ids[cnt] = i;
+ cnt++;
+ }
+
+ regfree(&regex);
+ *__ids = ids;
+ return cnt ?: -ENOENT;
+}
+
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 b54f1c3ebd57..036857aded94 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -371,6 +371,9 @@ btf_var_secinfos(const struct btf_type *t)
return (struct btf_var_secinfo *)(t + 1);
}

+int btf__find_by_pattern_kind(const struct btf *btf,
+ const char *type_pattern, __u32 kind,
+ __s32 **__ids);
#ifdef __cplusplus
} /* extern "C" */
#endif
--
2.31.1