Re: [PATCH bpf-next v1 4/4] selftests/bpf: Add kfunc set test to resolve_btfids

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Jun 17, 2026 at 02:06:19PM -0700, Ihor Solodrai wrote:
> Extend the resolve_btfids selftest to cover kfunc sets defined with
> BTF_KFUNCS_START/BTF_KFUNCS_END.
> 
> The test verifies that resolve_btfids correctly processes BTF_ID_FLAGS,
> resolves function IDs, and checks the kfunc set is sorted.
> 
> Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---
>  .../selftests/bpf/prog_tests/resolve_btfids.c | 63 ++++++++++++++++---
>  tools/testing/selftests/bpf/progs/btf_data.c  | 10 +++
>  2 files changed, 66 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
> index 6bcadee50bb8..65ede3ac5845 100644
> --- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
> +++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
> @@ -12,6 +12,10 @@
>  
>  #define BTF_DATA_FILE "resolve_btfids.test.o.BTF"
>  
> +#ifndef KF_FASTCALL
> +#define KF_FASTCALL (1 << 12)
> +#endif
> +
>  struct symbol {
>  	const char	*name;
>  	int		 type;
> @@ -28,6 +32,17 @@ struct symbol test_symbols[] = {
>  	{ "func",    BTF_KIND_FUNC,    -1 },
>  };
>  
> +struct kfunc_symbol {
> +	const char	*name;
> +	s32		 id;
> +	u32		 flags;
> +};
> +
> +static struct kfunc_symbol kfunc_symbols[] = {
> +	{ "kfunc_a", -1, 0 },
> +	{ "kfunc_b", -1, KF_FASTCALL },
> +};
> +
>  /* Align the .BTF_ids section to 4 bytes */
>  asm (
>  ".pushsection " BTF_IDS_SECTION " ,\"a\"; \n"
> @@ -35,9 +50,9 @@ asm (
>  ".popsection;                             \n");
>  
>  /*
> - * test_list_local and test_set are .local symbols placed in .BTF_ids by
> - * inline asm, and are read here directly by C name. To the compiler they
> - * are plain, default-visibility extern objects.
> + * test_list_local, test_set and test_kfunc_set are .local symbols placed
> + * in .BTF_ids by inline asm, and are read here directly by C name. To the
> + * compiler they are plain, default-visibility extern objects.
>   *
>   * When test_progs is linked as a position-independent executable (PIE),
>   * taking the address of such an extern is routed through the GOT. The
> @@ -69,6 +84,11 @@ BTF_ID(struct,  S)
>  BTF_ID(union,   U)
>  BTF_ID(func,    func)
>  BTF_SET_END(test_set)
> +
> +BTF_KFUNCS_START(test_kfunc_set)
> +BTF_ID_FLAGS(func, kfunc_a)
> +BTF_ID_FLAGS(func, kfunc_b, KF_FASTCALL)
> +BTF_KFUNCS_END(test_kfunc_set)
>  #pragma GCC visibility pop
>  
>  extern __u32 test_list_global[];
> @@ -92,6 +112,8 @@ __resolve_symbol(struct btf *btf, int type_id)
>  	if (!ASSERT_OK_PTR(type, "btf__type_by_id"))
>  		return -1;
>  
> +	str = btf__name_by_offset(btf, type->name_off);

should we assert str != NULL like below?

jirka

> +
>  	for (i = 0; i < ARRAY_SIZE(test_symbols); i++) {
>  		if (test_symbols[i].id >= 0)
>  			continue;
> @@ -99,14 +121,20 @@ __resolve_symbol(struct btf *btf, int type_id)
>  		if (BTF_INFO_KIND(type->info) != test_symbols[i].type)
>  			continue;
>  
> -		str = btf__name_by_offset(btf, type->name_off);
> -		if (!ASSERT_OK_PTR(str, "btf__name_by_offset"))
> -			return -1;
> -
>  		if (!strcmp(str, test_symbols[i].name))
>  			test_symbols[i].id = type_id;
>  	}
>  

SNIP