[RFC PATCH v11 bpf-next 12/14] selftests/bpf: Add verifier test for d_path helper

[Jiri Olsa]

Adding verifier test for attaching tracing program and
calling d_path helper from within and testing that it's
allowed for dentry_open function and denied for 'd_path'
function with appropriate error.

Acked-by: Andrii Nakryiko <andr...@fb.com>
Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
 tools/testing/selftests/bpf/test_verifier.c   | 19 +++++++++-
 tools/testing/selftests/bpf/verifier/d_path.c | 37 +++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/verifier/d_path.c

diff --git a/tools/testing/selftests/bpf/test_verifier.c 
b/tools/testing/selftests/bpf/test_verifier.c
index 78a6bae56ea6..9be395d9dc64 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -114,6 +114,7 @@ struct bpf_test {
                bpf_testdata_struct_t retvals[MAX_TEST_RUNS];
        };
        enum bpf_attach_type expected_attach_type;
+       const char *kfunc;
 };
 
 /* Note we want this to be 64 bit aligned so that the end of our array is
@@ -984,8 +985,24 @@ static void do_test_single(struct bpf_test *test, bool 
unpriv,
                attr.log_level = 4;
        attr.prog_flags = pflags;
 
+       if (prog_type == BPF_PROG_TYPE_TRACING && test->kfunc) {
+               attr.attach_btf_id = libbpf_find_vmlinux_btf_id(test->kfunc,
+                                               attr.expected_attach_type);
+               if (attr.attach_btf_id < 0) {
+                       printf("FAIL\nFailed to find BTF ID for '%s'!\n",
+                               test->kfunc);
+                       (*errors)++;
+                       return;
+               }
+       }
+
        fd_prog = bpf_load_program_xattr(&attr, bpf_vlog, sizeof(bpf_vlog));
-       if (fd_prog < 0 && !bpf_probe_prog_type(prog_type, 0)) {
+
+       /* BPF_PROG_TYPE_TRACING requires more setup and
+        * bpf_probe_prog_type won't give correct answer
+        */
+       if (fd_prog < 0 && prog_type != BPF_PROG_TYPE_TRACING &&
+           !bpf_probe_prog_type(prog_type, 0)) {
                printf("SKIP (unsupported program type %d)\n", prog_type);
                skips++;
                goto close_fds;
diff --git a/tools/testing/selftests/bpf/verifier/d_path.c 
b/tools/testing/selftests/bpf/verifier/d_path.c
new file mode 100644
index 000000000000..b988396379a7
--- /dev/null
+++ b/tools/testing/selftests/bpf/verifier/d_path.c
@@ -0,0 +1,37 @@
+{
+       "d_path accept",
+       .insns = {
+       BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_1, 0),
+       BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+       BPF_MOV64_IMM(BPF_REG_6, 0),
+       BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_6, 0),
+       BPF_LD_IMM64(BPF_REG_3, 8),
+       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_d_path),
+       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 = "dentry_open",
+},
+{
+       "d_path reject",
+       .insns = {
+       BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_1, 0),
+       BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+       BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+       BPF_MOV64_IMM(BPF_REG_6, 0),
+       BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_6, 0),
+       BPF_LD_IMM64(BPF_REG_3, 8),
+       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_d_path),
+       BPF_MOV64_IMM(BPF_REG_0, 0),
+       BPF_EXIT_INSN(),
+       },
+       .errstr = "helper call is not allowed in probe",
+       .result = REJECT,
+       .prog_type = BPF_PROG_TYPE_TRACING,
+       .expected_attach_type = BPF_TRACE_FENTRY,
+       .kfunc = "d_path",
+},
-- 
2.25.4