selftests/bpf: Add test to access int ptr argument in tracing program

Adding verifier test for accessing int pointer argument in
tracing programs.

The test program loads 2nd argument of bpf_modify_return_test
function which is int pointer and checks that verifier allows
that.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211208193245.172141-3-jolsa@kernel.org

diff --git a/tools/testing/selftests/bpf/verifier/btf_ctx_access.c b/tools/testing/selftests/bpf/verifier/btf_ctx_access.c
new file mode 100644 (file)
index 0000000..6340db6
--- /dev/null
+++ b/tools/testing/selftests/bpf/verifier/btf_ctx_access.c
@@ -0,0 +1,12 @@
+{
+       "btf_ctx_access accept",
+       .insns = {
+       BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 8),    /* load 2nd argument value (int pointer) */
+       BPF_MOV64_IMM(BPF_REG_0, 0),
+       BPF_EXIT_INSN(),
+       },
+       .result = ACCEPT,
+       .prog_type = BPF_PROG_TYPE_TRACING,
+       .expected_attach_type = BPF_TRACE_FENTRY,
+       .kfunc = "bpf_modify_return_test",
+},