[PATCH 9/9] selftests/bpf: Add verifier test for d_path helper

Jiri Olsa
2020-05-06T13:30:38Z

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.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/testing/selftests/bpf/test_verifier.c | 13 ++++++-
tools/testing/selftests/bpf/verifier/d_path.c | 37 +++++++++++++++++++
2 files changed, 49 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 21a1ce219c1c..1e38179f0dbf 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
@@ -961,8 +962,18 @@ 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);
+ }
+
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