netdev - [PATCH bpf-next] bpf: btf: Avoid variable length array

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Message-ID: <20180523174659.354660-1-kafai@fb.com>
Date:   Wed, 23 May 2018 10:46:59 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: [PATCH bpf-next] bpf: btf: Avoid variable length array

Sparse warning:
kernel/bpf/btf.c:1985:34: warning: Variable length array is used.

This patch moves the nr_secs from btf_check_sec_info() to a macro.

Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/btf.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 9cbeabb5aca3..517296712774 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1970,6 +1970,8 @@ static const size_t btf_sec_info_offset[] = {
 	offsetof(struct btf_header, str_off),
 };
 
+#define NR_SECS ARRAY_SIZE(btf_sec_info_offset)
+
 static int btf_sec_info_cmp(const void *a, const void *b)
 {
 	const struct btf_sec_info *x = a;
@@ -1981,8 +1983,7 @@ static int btf_sec_info_cmp(const void *a, const void *b)
 static int btf_check_sec_info(struct btf_verifier_env *env,
 			      u32 btf_data_size)
 {
-	const unsigned int nr_secs = ARRAY_SIZE(btf_sec_info_offset);
-	struct btf_sec_info secs[nr_secs];
+	struct btf_sec_info secs[NR_SECS];
 	u32 total, expected_total, i;
 	const struct btf_header *hdr;
 	const struct btf *btf;
@@ -1991,17 +1992,17 @@ static int btf_check_sec_info(struct btf_verifier_env *env,
 	hdr = &btf->hdr;
 
 	/* Populate the secs from hdr */
-	for (i = 0; i < nr_secs; i++)
+	for (i = 0; i < NR_SECS; i++)
 		secs[i] = *(struct btf_sec_info *)((void *)hdr +
 						   btf_sec_info_offset[i]);
 
-	sort(secs, nr_secs, sizeof(struct btf_sec_info),
+	sort(secs, NR_SECS, sizeof(struct btf_sec_info),
 	     btf_sec_info_cmp, NULL);
 
 	/* Check for gaps and overlap among sections */
 	total = 0;
 	expected_total = btf_data_size - hdr->hdr_len;
-	for (i = 0; i < nr_secs; i++) {
+	for (i = 0; i < NR_SECS; i++) {
 		if (expected_total < secs[i].off) {
 			btf_verifier_log(env, "Invalid section offset");
 			return -EINVAL;
-- 
2.9.5