[PATCH v3 bpf-next 06/13] selftests/bpf: test instructions arrays with blinding

Anton Protopopov
2025-09-18T09:32:46Z

Add a specific test for instructions arrays with blinding enabled.

Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
---
.../selftests/bpf/prog_tests/bpf_insn_array.c | 92 +++++++++++++++++++
1 file changed, 92 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c b/tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c
index f785132497d6..489badc17a2d 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c
@@ -287,6 +287,95 @@ static void check_with_functions(void)
close(map_fd);
}

+static int set_bpf_jit_harden(char *level)
+{
+ char old_level;
+ int err = -1;
+ int fd = -1;
+
+ fd = open("/proc/sys/net/core/bpf_jit_harden", O_RDWR | O_NONBLOCK);
+ if (fd < 0) {
+ ASSERT_FAIL("open .../bpf_jit_harden returned %d (errno=%d)", fd, errno);
+ return -1;
+ }
+
+ err = read(fd, &old_level, 1);
+ if (err != 1) {
+ ASSERT_FAIL("read from .../bpf_jit_harden returned %d (errno=%d)", err, errno);
+ err = -1;
+ goto end;
+ }
+
+ lseek(fd, 0, SEEK_SET);
+
+ err = write(fd, level, 1);
+ if (err != 1) {
+ ASSERT_FAIL("write to .../bpf_jit_harden returned %d (errno=%d)", err, errno);
+ err = -1;
+ goto end;
+ }
+
+ err = 0;
+ *level = old_level;
+end:
+ if (fd >= 0)
+ close(fd);
+ return err;
+}
+
+static void check_blindness(void)
+{
+ struct bpf_insn insns[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 4),
+ BPF_MOV64_IMM(BPF_REG_0, 3),
+ BPF_MOV64_IMM(BPF_REG_0, 2),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ };
+ int prog_fd = -1, map_fd;
+ struct bpf_insn_array_value val = {};
+ char bpf_jit_harden = '@'; /* non-exizsting value */
+ int i;
+
+ map_fd = map_create(BPF_MAP_TYPE_INSN_ARRAY, ARRAY_SIZE(insns));
+ if (!ASSERT_GE(map_fd, 0, "map_create"))
+ return;
+
+ for (i = 0; i < ARRAY_SIZE(insns); i++) {
+ val.xlated_off = i;
+ if (!ASSERT_EQ(bpf_map_update_elem(map_fd, &i, &val, 0), 0, "bpf_map_update_elem"))
+ goto cleanup;
+ }
+
+ bpf_jit_harden = '2';
+ if (set_bpf_jit_harden(&bpf_jit_harden)) {
+ bpf_jit_harden = '@'; /* open, read or write failed => no write was done */
+ goto cleanup;
+ }
+
+ prog_fd = prog_load(insns, ARRAY_SIZE(insns), &map_fd, 1);
+ if (!ASSERT_GE(prog_fd, 0, "bpf(BPF_PROG_LOAD)"))
+ goto cleanup;
+
+ for (i = 0; i < ARRAY_SIZE(insns); i++) {
+ char fmt[32];
+
+ if (!ASSERT_EQ(bpf_map_lookup_elem(map_fd, &i, &val), 0, "bpf_map_lookup_elem"))
+ goto cleanup;
+
+ snprintf(fmt, sizeof(fmt), "val should be equal 3*%d", i);
+ ASSERT_EQ(val.xlated_off, i * 3, fmt);
+ }
+
+cleanup:
+ /* restore the old one */
+ if (bpf_jit_harden != '@')
+ set_bpf_jit_harden(&bpf_jit_harden);
+
+ close(prog_fd);
+ close(map_fd);
+}
+
/* Map can be used only by one BPF program */
static void check_no_map_reuse(void)
{
@@ -392,6 +481,9 @@ void test_bpf_insn_array(void)
if (test__start_subtest("multiple-functions"))
check_with_functions();

+ if (test__start_subtest("blindness"))
+ check_blindness();
+
/* Check all kinds of operations and related restrictions */

if (test__start_subtest("incorrect-index"))
--
2.34.1