On Fri, Mar 17, 2023 at 1:19 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> Introduce bpf_ksym_exists() macro that can be used by BPF programs
> to detect at load time whether particular ksym (either variable or kfunc)
> is present in the kernel.
>
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> ---
> tools/lib/bpf/bpf_helpers.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 7d12d3e620cc..b49823117dae 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -177,6 +177,9 @@ enum libbpf_tristate {
> #define __kptr_untrusted __attribute__((btf_type_tag("kptr_untrusted")))
> #define __kptr __attribute__((btf_type_tag("kptr")))
>
> +#define bpf_ksym_exists(sym) \
> + ({ _Static_assert(!__builtin_constant_p(!!sym), #sym " should be marked as __weak"); !!sym; })
> +
I reformatted this to fit under 100 characters.
-#define bpf_ksym_exists(sym) \
- ({ _Static_assert(!__builtin_constant_p(!!sym), #sym " should
be marked as __weak"); !!sym; })
+#define bpf_ksym_exists(sym) ({
\
+ _Static_assert(!__builtin_constant_p(!!sym), #sym " should be
marked as __weak"); \
+ !!sym;
\
+})
Other than that, it looks great! Applied to bpf-next, thanks.
> #ifndef ___bpf_concat
> #define ___bpf_concat(a, b) a ## b
> #endif
> --
> 2.34.1
>
