selftests/bpf: test instructions arrays with blinding

Add a specific test for instructions arrays with blinding enabled.

Signed-off-by: Anton Protopopov <[e-mail]>
Acked-by: Eduard Zingerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/prog_tests/bpf_insn_array.c

···
 	check_mid_insn_index();
 }
 
+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.orig_off = i;
+		if (!ASSERT_EQ(bpf_map_update_elem(map_fd, &i, &val, 0), 0, "bpf_map_update_elem"))
+			goto cleanup;
+	}
+
+	if (!ASSERT_EQ(bpf_map_freeze(map_fd), 0, "bpf_map_freeze"))
+		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);
+}
+
 /* Once map was initialized, it should be frozen */
 static void check_load_unfrozen_map(void)
 {
···
 
 	if (test__start_subtest("deletions-with-functions"))
 		check_deletions_with_functions();
+
+	if (test__start_subtest("blindness"))
+		check_blindness();
 
 	/* Check all kinds of operations and related restrictions */