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 <[email protected]>
Reported-by: "kernelci.org bot" <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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 <[email protected]> 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 <[email protected]>
> Reported-by: "kernelci.org bot" <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
Acked-by: Björn Töpel <[email protected]>
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 <[email protected]>
> Reported-by: "kernelci.org bot" <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Hello:
This patch was applied to bpf/bpf.git (master)
by Martin KaFai Lau <[email protected]>:
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