The recent commit "bpf: Move BPF sysctls from kernel/sysctl.c to BPF core" triggered 0-day to issue an email for what seems to have been an old clang warning. So this issue should have existed before as well, from what I can tell. The issue is that clang expects a forward declaration for routines declared as weak while gcc does not. This can be reproduced with 0-day's x86_64-randconfig-c007 https://download.01.org/0day-ci/archive/20220424/202204240008.JDntM9cU-lkp@xxxxxxxxx/config And using: COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 SHELL=/bin/bash kernel/bpf/syscall.o Compiler will be installed in /home/mcgrof/0day make --keep-going HOSTCC=/home/mcgrof/0day/clang/bin/clang CC=/home/mcgrof/0day/clang/bin/clang LD=/home/mcgrof/0day/clang/bin/ld.lld HOSTLD=/home/mcgrof/0day/clang/bin/ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-size READELF=llvm-readelf HOSTCXX=clang++ HOSTAR=llvm-ar CROSS_COMPILE=x86_64-linux-gnu- --jobs=24 W=1 ARCH=x86_64 SHELL=/bin/bash kernel/bpf/syscall.o DESCEND objtool CALL scripts/atomic/check-atomics.sh CALL scripts/checksyscalls.sh CC kernel/bpf/syscall.o kernel/bpf/syscall.c:4944:13: warning: no previous prototype for function 'unpriv_ebpf_notify' [-Wmissing-prototypes] void __weak unpriv_ebpf_notify(int new_state) ^ kernel/bpf/syscall.c:4944:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __weak unpriv_ebpf_notify(int new_state) ^ static Fixes: 2900005ea287 ("bpf: Move BPF sysctls from kernel/sysctl.c to BPF core") Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx> --- Daniel, Given what we did fore 2900005ea287 ("bpf: Move BPF sysctls from kernel/sysctl.c to BPF core") where I had pulled pr/bpf-sysctl a while ago into sysctl-next and then merged the patch in question, should I just safely carry this patch onto sysctl-next? Let me know how you'd like to proceed. Also, it wasn't clear if putting this forward declaration on bpf.h was your ideal preference. Luis include/linux/bpf.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index bdb5298735ce..bd3e17a9f821 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1551,6 +1551,9 @@ bpf_map_alloc_percpu(const struct bpf_map *map, size_t size, size_t align, #endif extern int sysctl_unprivileged_bpf_disabled; +#ifdef CONFIG_SYSCTL +void unpriv_ebpf_notify(int new_state); +#endif static inline bool bpf_allow_ptr_leaks(void) { -- 2.35.1
