Allows to specify expected and unexpected instruction sequences in
test_verifier test cases. The instructions are requested from kernel
after BPF program loading, thus allowing to check some of the
transformations applied by BPF verifier.
- `expected_insn` field specifies a sequence of instructions expected
to be found in the program;
- `unexpected_insn` field specifies a sequence of instructions that
are not expected to be found in the program;
- `INSN_OFF_MASK` and `INSN_IMM_MASK` values could be used to mask
`off` and `imm` fields.
- `SKIP_INSNS` could be used to specify that some instructions in the
(un)expected pattern are not important (behavior similar to usage of
`\t` in `errstr` field).
The intended usage is as follows:
{
"inline simple bpf_loop call",
.insns = {
/* main */
BPF_ALU64_IMM(BPF_MOV, BPF_REG_1, 1),
BPF_RAW_INSN(BPF_LD | BPF_IMM | BPF_DW, BPF_REG_2,
BPF_PSEUDO_FUNC, 0, 6),
...
BPF_EXIT_INSN(),
/* callback */
BPF_ALU64_IMM(BPF_MOV, BPF_REG_0, 1),
BPF_EXIT_INSN(),
},
.expected_insns = {
BPF_ALU64_IMM(BPF_MOV, BPF_REG_1, 1),
SKIP_INSNS(),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_CALL, 8, 1)
},
.unexpected_insns = {
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0,
INSN_OFF_MASK, INSN_IMM_MASK),
},
.prog_type = BPF_PROG_TYPE_TRACEPOINT,
.result = ACCEPT,
.runs = 0,
},
Here it is expected that move of 1 to register 1 would remain in place
and helper function call instruction would be replaced by a relative
call instruction.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/testing/selftests/bpf/test_verifier.c | 222 ++++++++++++++++++++
1 file changed, 222 insertions(+)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 372579c9f45e..373f7661f4d0 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -51,6 +51,8 @@
#endif
#define MAX_INSNS BPF_MAXINSNS
+#define MAX_EXPECTED_INSNS 32
+#define MAX_UNEXPECTED_INSNS 32
#define MAX_TEST_INSNS 1000000
#define MAX_FIXUPS 8
#define MAX_NR_MAPS 23
@@ -58,6 +60,10 @@
#define POINTER_VALUE 0xcafe4all
#define TEST_DATA_LEN 64
+#define INSN_OFF_MASK ((s16)0xFFFF)
+#define INSN_IMM_MASK ((s32)0xFFFFFFFF)
+#define SKIP_INSNS() BPF_RAW_INSN(0xde, 0xa, 0xd, 0xbeef, 0xdeadbeef)
+
#define F_NEEDS_EFFICIENT_UNALIGNED_ACCESS (1 << 0)
#define F_LOAD_WITH_STRICT_ALIGNMENT (1 << 1)
@@ -79,6 +85,19 @@ struct bpf_test {
const char *descr;
struct bpf_insn insns[MAX_INSNS];
struct bpf_insn *fill_insns;
+ /* If specified, test engine looks for this sequence of
+ * instructions in the BPF program after loading. Allows to
+ * test rewrites applied by verifier. Use values
+ * INSN_OFF_MASK and INSN_IMM_MASK to mask `off` and `imm`
+ * fields if content does not matter. The test case fails if
+ * specified instructions are not found.
+ *
+ * The sequence could be split into sub-sequences by adding
+ * SKIP_INSNS instruction at the end of each sub-sequence. In
+ * such case sub-sequences are searched for one after another.
+ */
+ struct bpf_insn expected_insns[MAX_EXPECTED_INSNS];
+ struct bpf_insn unexpected_insns[MAX_UNEXPECTED_INSNS];
int fixup_map_hash_8b[MAX_FIXUPS];
int fixup_map_hash_48b[MAX_FIXUPS];
int fixup_map_hash_16b[MAX_FIXUPS];
@@ -1126,6 +1145,206 @@ static bool cmp_str_seq(const char *log, const char *exp)
return true;
}
+static int get_xlated_program(int fd_prog, struct bpf_insn **buf, int *cnt)
+{
+ struct bpf_prog_info info = {};
+ __u32 info_len = sizeof(info);
+ __u32 xlated_prog_len;
+ __u32 buf_elt_size = sizeof(**buf);
+
+ if (bpf_obj_get_info_by_fd(fd_prog, &info, &info_len)) {
+ perror("bpf_obj_get_info_by_fd failed");
+ return -1;
+ }
+
+ xlated_prog_len = info.xlated_prog_len;
+ if (xlated_prog_len % buf_elt_size) {
+ printf("Program length %d is not multiple of %d\n",
+ xlated_prog_len, buf_elt_size);
+ return -1;
+ }
+
+ *cnt = xlated_prog_len / buf_elt_size;
+ *buf = calloc(*cnt, buf_elt_size);
+ if (!buf) {
+ perror("can't allocate xlated program buffer");
+ return -ENOMEM;
+ }
+
+ bzero(&info, sizeof(info));
+ info.xlated_prog_len = xlated_prog_len;
+ info.xlated_prog_insns = (__u64)*buf;
+ if (bpf_obj_get_info_by_fd(fd_prog, &info, &info_len)) {
+ perror("second bpf_obj_get_info_by_fd failed");
+ goto out_free_buf;
+ }
+
+ return 0;
+
+out_free_buf:
+ free(*buf);
+ return -1;
+}
+
+static bool is_null_insn(struct bpf_insn *insn)
+{
+ struct bpf_insn null_insn = {};
+
+ return memcmp(insn, &null_insn, sizeof(null_insn)) == 0;
+}
+
+static bool is_skip_insn(struct bpf_insn *insn)
+{
+ struct bpf_insn skip_insn = SKIP_INSNS();
+
+ return memcmp(insn, &skip_insn, sizeof(skip_insn)) == 0;
+}
+
+static int null_terminated_insn_len(struct bpf_insn *seq, int max_len)
+{
+ for (int i = 0; i < max_len; ++i) {
+ if (is_null_insn(&seq[i]))
+ return i;
+ }
+ return max_len;
+}
+
+static bool compare_masked_insn(struct bpf_insn *orig, struct bpf_insn *masked)
+{
+ struct bpf_insn orig_masked;
+
+ memcpy(&orig_masked, orig, sizeof(orig_masked));
+ if (masked->imm == INSN_IMM_MASK)
+ orig_masked.imm = INSN_IMM_MASK;
+ if (masked->off == INSN_OFF_MASK)
+ orig_masked.off = INSN_OFF_MASK;
+
+ return memcmp(&orig_masked, masked, sizeof(orig_masked)) == 0;
+}
+
+static int find_insn_subseq(struct bpf_insn *seq, struct bpf_insn *subseq,
+ int seq_len, int subseq_len)
+{
+ if (subseq_len > seq_len)
+ return -1;
+
+ for (int i = 0; i < seq_len - subseq_len + 1; ++i) {
+ bool found = true;
+
+ for (int j = 0; j < subseq_len; ++j) {
+ if (!compare_masked_insn(&seq[i + j], &subseq[j])) {
+ found = false;
+ break;
+ }
+ }
+ if (found)
+ return i;
+ }
+
+ return -1;
+}
+
+static int find_skip_insn_marker(struct bpf_insn *seq, int len)
+{
+ for (int i = 0; i < len; ++i)
+ if (is_skip_insn(&seq[i]))
+ return i;
+
+ return -1;
+}
+
+/* Return true if all sub-sequences in `subseqs` could be found in
+ * `seq` one after another. Sub-sequences are separated by a single
+ * nil instruction.
+ */
+static bool find_all_insn_subseqs(struct bpf_insn *seq, struct bpf_insn *subseqs,
+ int seq_len, int max_subseqs_len)
+{
+ int subseqs_len = null_terminated_insn_len(subseqs, max_subseqs_len);
+
+ while (subseqs_len > 0) {
+ int skip_idx = find_skip_insn_marker(subseqs, subseqs_len);
+ int cur_subseq_len = skip_idx < 0 ? subseqs_len : skip_idx;
+ int subseq_idx = find_insn_subseq(seq, subseqs,
+ seq_len, cur_subseq_len);
+
+ if (subseq_idx < 0)
+ return false;
+ seq += subseq_idx + cur_subseq_len;
+ seq_len -= subseq_idx + cur_subseq_len;
+ subseqs += cur_subseq_len + 1;
+ subseqs_len -= cur_subseq_len + 1;
+ }
+
+ return true;
+}
+
+static void print_insn(struct bpf_insn *buf, int cnt)
+{
+ printf(" addr op d s off imm\n");
+ for (int i = 0; i < cnt; ++i) {
+ struct bpf_insn *insn = &buf[i];
+
+ if (is_null_insn(insn))
+ break;
+
+ if (is_skip_insn(insn))
+ printf(" ...\n");
+ else
+ printf(" %04x: %02x %1x %x %04hx %08x\n",
+ i, insn->code, insn->dst_reg,
+ insn->src_reg, insn->off, insn->imm);
+ }
+}
+
+static bool check_xlated_program(struct bpf_test *test, int fd_prog)
+{
+ struct bpf_insn *buf;
+ int cnt;
+ bool result = true;
+ bool check_expected = !is_null_insn(test->expected_insns);
+ bool check_unexpected = !is_null_insn(test->unexpected_insns);
+
+ if (!check_expected && !check_unexpected)
+ goto out;
+
+ if (get_xlated_program(fd_prog, &buf, &cnt)) {
+ printf("FAIL: can't get xlated program\n");
+ result = false;
+ goto out;
+ }
+
+ if (check_expected &&
+ !find_all_insn_subseqs(buf, test->expected_insns,
+ cnt, MAX_EXPECTED_INSNS)) {
+ printf("FAIL: can't find expected subsequence of instructions\n");
+ result = false;
+ if (verbose) {
+ printf("Program:\n");
+ print_insn(buf, cnt);
+ printf("Expected subsequence:\n");
+ print_insn(test->expected_insns, MAX_EXPECTED_INSNS);
+ }
+ }
+
+ if (check_unexpected &&
+ find_all_insn_subseqs(buf, test->unexpected_insns,
+ cnt, MAX_UNEXPECTED_INSNS)) {
+ printf("FAIL: found unexpected subsequence of instructions\n");
+ result = false;
+ if (verbose) {
+ printf("Program:\n");
+ print_insn(buf, cnt);
+ printf("Un-expected subsequence:\n");
+ print_insn(test->unexpected_insns, MAX_UNEXPECTED_INSNS);
+ }
+ }
+
+ free(buf);
+ out:
+ return result;
+}
+
static void do_test_single(struct bpf_test *test, bool unpriv,
int *passes, int *errors)
{
@@ -1262,6 +1481,9 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
if (verbose)
printf(", verifier log:\n%s", bpf_vlog);
+ if (!check_xlated_program(test, fd_prog))
+ goto fail_log;
+
run_errs = 0;
run_successes = 0;
if (!alignment_prevented_execution && fd_prog >= 0 && test->runs >= 0) {
--
2.25.1
