selftests/bpf: Test linking with duplicate extern functions

Previously when multiple BPF object files referencing the same extern
function (usually kfunc) are statically linked using `bpftool gen
object`, libbpf tries to get the nonexistent size of BTF_KIND_FUNC_PROTO
and fails. This test ensures it is fixed.

Signed-off-by: Eric Long <i@hack3r.moe>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241002-libbpf-dup-extern-funcs-v4-2-560eb460ff90@hack3r.moe

diff --git a/tools/testing/selftests/bpf/progs/linked_funcs1.c b/tools/testing/selftests/bpf/progs/linked_funcs1.c
index cc79dddac182c20da69a1a57fa39bc81004184f1..049a1f78de3f835e7658dde6f2d03161b6a5a07f 100644 (file)
--- a/tools/testing/selftests/bpf/progs/linked_funcs1.c
+++ b/tools/testing/selftests/bpf/progs/linked_funcs1.c
@@ -63,6 +63,8 @@ extern int set_output_val2(int x);
 /* here we'll force set_output_ctx2() to be __hidden in the final obj file */
 __hidden extern void set_output_ctx2(__u64 *ctx);
 
+void *bpf_cast_to_kern_ctx(void *obj) __ksym;
+
 SEC("?raw_tp/sys_enter")
 int BPF_PROG(handler1, struct pt_regs *regs, long id)
 {
@@ -86,4 +88,10 @@ int BPF_PROG(handler1, struct pt_regs *regs, long id)
        return 0;
 }
 
+/* Generate BTF FUNC record and test linking with duplicate extern functions */
+void kfunc_gen1(void)
+{
+       bpf_cast_to_kern_ctx(0);
+}
+
 char LICENSE[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/linked_funcs2.c b/tools/testing/selftests/bpf/progs/linked_funcs2.c
index 942cc5526ddf02004bf82d1f72c74cfba6eaf486..96850759fd8d0074249bbf1f743aab08e20de0fc 100644 (file)
--- a/tools/testing/selftests/bpf/progs/linked_funcs2.c
+++ b/tools/testing/selftests/bpf/progs/linked_funcs2.c
@@ -63,6 +63,8 @@ extern int set_output_val1(int x);
 /* here we'll force set_output_ctx1() to be __hidden in the final obj file */
 __hidden extern void set_output_ctx1(__u64 *ctx);
 
+void *bpf_cast_to_kern_ctx(void *obj) __ksym;
+
 SEC("?raw_tp/sys_enter")
 int BPF_PROG(handler2, struct pt_regs *regs, long id)
 {
@@ -86,4 +88,10 @@ int BPF_PROG(handler2, struct pt_regs *regs, long id)
        return 0;
 }
 
+/* Generate BTF FUNC record and test linking with duplicate extern functions */
+void kfunc_gen2(void)
+{
+       bpf_cast_to_kern_ctx(0);
+}
+
 char LICENSE[] SEC("license") = "GPL";