[PATCH bpf-next v4 2/2] selftests/bpf: Add test to access const void pointer argument in tracing program

[KaFai Wan]

Adding verifier test for accessing const void pointer argument in
tracing programs.

The test program loads 1st argument of bpf_fentry_test10 function
which is const void pointer and checks that verifier allows that.

Signed-off-by: KaFai Wan <mannka...@gmail.com>
Acked-by: Jiri Olsa <jo...@kernel.org>
---
 net/bpf/test_run.c                                   |  8 +++++++-
 .../selftests/bpf/progs/verifier_btf_ctx_access.c    | 12 ++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 7cb192cbd65f..aaf13a7d58ed 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -569,6 +569,11 @@ __bpf_kfunc u32 bpf_fentry_test9(u32 *a)
        return *a;
 }
 
+int noinline bpf_fentry_test10(const void *a)
+{
+       return (long)a;
+}
+
 void noinline bpf_fentry_test_sinfo(struct skb_shared_info *sinfo)
 {
 }
@@ -699,7 +704,8 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog,
                    bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 
111 ||
                    bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 ||
                    bpf_fentry_test8(&arg) != 0 ||
-                   bpf_fentry_test9(&retval) != 0)
+                   bpf_fentry_test9(&retval) != 0 ||
+                   bpf_fentry_test10((void *)0) != 0)
                        goto out;
                break;
        case BPF_MODIFY_RETURN:
diff --git a/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c 
b/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
index 28b939572cda..03942cec07e5 100644
--- a/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
+++ b/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
@@ -65,4 +65,16 @@ __naked void ctx_access_u32_pointer_reject_8(void)
 "      ::: __clobber_all);
 }
 
+SEC("fentry/bpf_fentry_test10")
+__description("btf_ctx_access const void pointer accept")
+__success __retval(0)
+__naked void ctx_access_const_void_pointer_accept(void)
+{
+       asm volatile ("                                 \
+       r2 = *(u64 *)(r1 + 0);          /* load 1st argument value (const void 
pointer) */\
+       r0 = 0;                                         \
+       exit;                                           \
+"      ::: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.43.0