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| author | Yonghong Song <yhs@fb.com> | 2021-04-13 18:34:35 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-04-16 02:50:22 +0300 |
| commit | 8af50142763c6e70d426e45278b23d7103e5b7a7 (patch) | |
| tree | ec2efa9094e3d90a3988a08c8cac9f0c670fcf62 /tools/bpf | |
| parent | ef9985893caf905b769fae8984780847e8527065 (diff) | |
| download | linux-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/bpf')
| -rw-r--r-- | tools/bpf/bpftool/net.c | 2 |
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; |