[PATCH bpf v2 1/4] bpf: btf: implement btf_name_valid_identifier()

[Yonghong Song]

Function btf_name_valid_identifier() have been implemented in
bpf-next commit 2667a2626f4d ("bpf: btf: Add BTF_KIND_FUNC and
BTF_KIND_FUNC_PROTO"). Backport this function so later patch
can use it.

Fixes: 69b693f0aefa ("bpf: btf: Introduce BPF Type Format (BTF)")
Signed-off-by: Yonghong Song <y...@fb.com>
---
 kernel/bpf/btf.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ee4c82667d65..93c233ab2db6 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5,6 +5,7 @@
 #include <uapi/linux/types.h>
 #include <linux/seq_file.h>
 #include <linux/compiler.h>
+#include <linux/ctype.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/anon_inodes.h>
@@ -426,6 +427,30 @@ static bool btf_name_offset_valid(const struct btf *btf, 
u32 offset)
                offset < btf->hdr.str_len;
 }
 
+/* Only C-style identifier is permitted. This can be relaxed if
+ * necessary.
+ */
+static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
+{
+       /* offset must be valid */
+       const char *src = &btf->strings[offset];
+       const char *src_limit;
+
+       if (!isalpha(*src) && *src != '_')
+               return false;
+
+       /* set a limit on identifier length */
+       src_limit = src + KSYM_NAME_LEN;
+       src++;
+       while (*src && src < src_limit) {
+               if (!isalnum(*src) && *src != '_')
+                       return false;
+               src++;
+       }
+
+       return !*src;
+}
+
 static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
 {
        if (!offset)
-- 
2.17.1