From b3c09fdca1135167bd0682128cd51864c5aa5625 Mon Sep 17 00:00:00 2001 From: Rong Tao Date: Fri, 4 Nov 2022 09:27:54 +0800 Subject: selftests/bpf: cgroup_helpers.c: Fix strncpy() fortify warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Copy libbpf_strlcpy() from libbpf_internal.h to bpf_util.h, and rename it to bpf_strlcpy(), then replace selftests strncpy()/libbpf_strlcpy() with bpf_strlcpy(), fix compile warning. The libbpf_internal.h header cannot be used directly here, because references to cgroup_helpers.c in samples/bpf will generate compilation errors. We also can't add libbpf_strlcpy() directly to bpf_util.h, because the definition of libbpf_strlcpy() in libbpf_internal.h is duplicated. In order not to modify the libbpf code, add a new function bpf_strlcpy() to selftests bpf_util.h. How to reproduce this compilation warning: $ make -C samples/bpf cgroup_helpers.c: In function ‘__enable_controllers’: cgroup_helpers.c:80:17: warning: ‘strncpy’ specified bound 4097 equals destination size [-Wstringop-truncation] 80 | strncpy(enable, controllers, sizeof(enable)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Signed-off-by: Rong Tao Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/tencent_469D8AF32BD56816A29981BED06E96D22506@qq.com --- tools/testing/selftests/bpf/bpf_util.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'tools/testing/selftests/bpf/bpf_util.h') diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h index a3352a64c067..10587a29b967 100644 --- a/tools/testing/selftests/bpf/bpf_util.h +++ b/tools/testing/selftests/bpf/bpf_util.h @@ -20,6 +20,25 @@ static inline unsigned int bpf_num_possible_cpus(void) return possible_cpus; } +/* Copy up to sz - 1 bytes from zero-terminated src string and ensure that dst + * is zero-terminated string no matter what (unless sz == 0, in which case + * it's a no-op). It's conceptually close to FreeBSD's strlcpy(), but differs + * in what is returned. Given this is internal helper, it's trivial to extend + * this, when necessary. Use this instead of strncpy inside libbpf source code. + */ +static inline void bpf_strlcpy(char *dst, const char *src, size_t sz) +{ + size_t i; + + if (sz == 0) + return; + + sz--; + for (i = 0; i < sz && src[i]; i++) + dst[i] = src[i]; + dst[i] = '\0'; +} + #define __bpf_percpu_val_align __attribute__((__aligned__(8))) #define BPF_DECLARE_PERCPU(type, name) \ -- cgit v1.2.3