With CONFIG_CFI_CLANG enabled, the kernel strictly enforces that
indirect function calls use a function pointer type that matches the
target function. As bpf_testmod_ctx_release() signature differs from
the btf_dtor_kfunc_t pointer type used for the destructor calls in
bpf_obj_free_fields(), add a stub function with the correct type to
fix the type mismatch.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 tools/testing/selftests/bpf/test_kmods/bpf_testmod.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index e9e918cdf31f..7f8cd8637a7b 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -249,6 +249,12 @@ __bpf_kfunc void bpf_testmod_ctx_release(struct bpf_testmod_ctx *ctx)
 		call_rcu(&ctx->rcu, testmod_free_cb);
 }
 
+__bpf_kfunc void bpf_testmod_ctx_release_dtor(void *ctx)
+{
+	bpf_testmod_ctx_release(ctx);
+}
+CFI_NOSEAL(bpf_testmod_ctx_release_dtor);
+
 static struct bpf_testmod_ops3 *st_ops3;
 
 static int bpf_testmod_test_3(void)
@@ -631,7 +637,7 @@ BTF_KFUNCS_END(bpf_testmod_common_kfunc_ids)
 
 BTF_ID_LIST(bpf_testmod_dtor_ids)
 BTF_ID(struct, bpf_testmod_ctx)
-BTF_ID(func, bpf_testmod_ctx_release)
+BTF_ID(func, bpf_testmod_ctx_release_dtor)
 
 static const struct btf_kfunc_id_set bpf_testmod_common_kfunc_set = {
 	.owner = THIS_MODULE,
-- 
2.50.1.552.g942d659e1b-goog

On 7/28/25 1:27 PM, Sami Tolvanen wrote:
> With CONFIG_CFI_CLANG enabled, the kernel strictly enforces that
> indirect function calls use a function pointer type that matches the
> target function. As bpf_testmod_ctx_release() signature differs from
> the btf_dtor_kfunc_t pointer type used for the destructor calls in
> bpf_obj_free_fields(), add a stub function with the correct type to
> fix the type mismatch.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Acked-by: Yonghong Song <yonghong.song@linux.dev>