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authorYonghong Song <yhs@fb.com>2021-04-13 18:34:35 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-04-16 02:50:22 +0300
commit8af50142763c6e70d426e45278b23d7103e5b7a7 (patch)
treeec2efa9094e3d90a3988a08c8cac9f0c670fcf62 /tools
parentef9985893caf905b769fae8984780847e8527065 (diff)
downloadlinux-8af50142763c6e70d426e45278b23d7103e5b7a7.tar.xz
bpftool: Fix a clang compilation warning
With clang compiler: make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel # build selftests/bpf or bpftool make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1 make -j60 -C tools/bpf/bpftool LLVM=1 LLVM_IAS=1 the following compilation warning showed up, net.c:160:37: warning: comparison of integers of different signs: '__u32' (aka 'unsigned int') and 'int' [-Wsign-compare] for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len); ^~~~~~~~~~~~~~~~~ .../tools/include/uapi/linux/netlink.h:99:24: note: expanded from macro 'NLMSG_OK' (nlh)->nlmsg_len <= (len)) ~~~~~~~~~~~~~~~~ ^ ~~~ In this particular case, "len" is defined as "int" and (nlh)->nlmsg_len is "unsigned int". The macro NLMSG_OK is defined as below in uapi/linux/netlink.h. #define NLMSG_OK(nlh,len) ((len) >= (int)sizeof(struct nlmsghdr) && \ (nlh)->nlmsg_len >= sizeof(struct nlmsghdr) && \ (nlh)->nlmsg_len <= (len)) The clang compiler complains the comparision "(nlh)->nlmsg_len <= (len))", but in bpftool/net.c, it is already ensured that "len > 0" must be true. So theoretically the compiler could deduce that comparison of "(nlh)->nlmsg_len" and "len" is okay, but this really depends on compiler internals. Let us add an explicit type conversion (from "int" to "unsigned int") for "len" in NLMSG_OK to silence this warning right now. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20210413153435.3029635-1-yhs@fb.com
Diffstat (limited to 'tools')
-rw-r--r--tools/bpf/bpftool/net.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index ff3aa0cf3997..f836d115d7d6 100644
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -157,7 +157,7 @@ static int netlink_recv(int sock, __u32 nl_pid, __u32 seq,
if (len == 0)
break;
- for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
+ for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, (unsigned int)len);
nh = NLMSG_NEXT(nh, len)) {
if (nh->nlmsg_pid != nl_pid) {
ret = -LIBBPF_ERRNO__WRNGPID;