When building with clang: kernel/bpf/dispatcher.c:126:33: error: pointer type mismatch ('void *' and 'unsigned int (*)(const void *, const struct bpf_insn *, bpf_func_t)' (aka 'unsigned int (*)(const void *, const struct bpf_insn *, unsigned int (*)(const void *, const struct bpf_insn *))')) [-Werror,-Wpointer-type-mismatch] __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/bpf.h:1045:54: note: expanded from macro '__BPF_DISPATCHER_UPDATE' __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new)) ^~~~ 1 error generated. The warning is pointing out that the type of new ('void *') and &bpf_dispatcher_nop_func are not compatible, which could have side effects coming out of a conditional operator due to promotion rules. Add the explicit cast to 'void *' to make it clear that this is expected, as __BPF_DISPATCHER_UPDATE() expands to a call to __static_call_update(), which expects a 'void *' as its final argument. Fixes: c86df29d11df ("bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace)") Link: https://github.com/ClangBuiltLinux/linux/issues/1755 Reported-by: kernel test robot <lkp@intel.com> Reported-by: "kernelci.org bot" <bot@kernelci.org> Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- kernel/bpf/dispatcher.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 7dfb8d0d5202..c19719f48ce0 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -123,7 +123,7 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) return; } - __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); + __BPF_DISPATCHER_UPDATE(d, new ?: (void *)&bpf_dispatcher_nop_func); if (new) d->image_off = noff; base-commit: c86df29d11dfba27c0a1f5039cd6fe387fbf4239 -- 2.38.1
Nathan Chancellor <nathan@kernel.org> writes:
> When building with clang:
>
> kernel/bpf/dispatcher.c:126:33: error: pointer type mismatch ('void *' and 'unsigned int (*)(const void *, const struct bpf_insn *, bpf_func_t)' (aka 'unsigned int (*)(const void *, const struct bpf_insn *, unsigned int (*)(const void *, const struct bpf_insn *))')) [-Werror,-Wpointer-type-mismatch]
> __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func);
> ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/bpf.h:1045:54: note: expanded from macro '__BPF_DISPATCHER_UPDATE'
> __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new))
> ^~~~
> 1 error generated.
>
> The warning is pointing out that the type of new ('void *') and
> &bpf_dispatcher_nop_func are not compatible, which could have side
> effects coming out of a conditional operator due to promotion rules.
>
> Add the explicit cast to 'void *' to make it clear that this is
> expected, as __BPF_DISPATCHER_UPDATE() expands to a call to
> __static_call_update(), which expects a 'void *' as its final argument.
>
> Fixes: c86df29d11df ("bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1755
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: "kernelci.org bot" <bot@kernelci.org>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
On 11/7/22 9:07 AM, Nathan Chancellor wrote:
> When building with clang:
>
> kernel/bpf/dispatcher.c:126:33: error: pointer type mismatch ('void *' and 'unsigned int (*)(const void *, const struct bpf_insn *, bpf_func_t)' (aka 'unsigned int (*)(const void *, const struct bpf_insn *, unsigned int (*)(const void *, const struct bpf_insn *))')) [-Werror,-Wpointer-type-mismatch]
> __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func);
> ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~
> ./include/linux/bpf.h:1045:54: note: expanded from macro '__BPF_DISPATCHER_UPDATE'
> __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new))
> ^~~~
> 1 error generated.
>
> The warning is pointing out that the type of new ('void *') and
> &bpf_dispatcher_nop_func are not compatible, which could have side
> effects coming out of a conditional operator due to promotion rules.
>
> Add the explicit cast to 'void *' to make it clear that this is
> expected, as __BPF_DISPATCHER_UPDATE() expands to a call to
> __static_call_update(), which expects a 'void *' as its final argument.
>
> Fixes: c86df29d11df ("bpf: Convert BPF_DISPATCHER to use static_call() (not ftrace)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1755
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: "kernelci.org bot" <bot@kernelci.org>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Hello: This patch was applied to bpf/bpf.git (master) by Martin KaFai Lau <martin.lau@kernel.org>: On Mon, 7 Nov 2022 10:07:11 -0700 you wrote: > When building with clang: > > kernel/bpf/dispatcher.c:126:33: error: pointer type mismatch ('void *' and 'unsigned int (*)(const void *, const struct bpf_insn *, bpf_func_t)' (aka 'unsigned int (*)(const void *, const struct bpf_insn *, unsigned int (*)(const void *, const struct bpf_insn *))')) [-Werror,-Wpointer-type-mismatch] > __BPF_DISPATCHER_UPDATE(d, new ?: &bpf_dispatcher_nop_func); > ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~ > ./include/linux/bpf.h:1045:54: note: expanded from macro '__BPF_DISPATCHER_UPDATE' > __static_call_update((_d)->sc_key, (_d)->sc_tramp, (_new)) > ^~~~ > 1 error generated. > > [...] Here is the summary with links: - [bpf] bpf: Add explicit cast to 'void *' for __BPF_DISPATCHER_UPDATE() https://git.kernel.org/bpf/bpf/c/a679120edfcf You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html