selftests/bpf: Test for map update access from within EXT programs

This adds further tests to ensure access permissions and restrictions
are applied properly for some map types such as sock-map.
It also adds another negative tests to assert static functions cannot be
replaced. In the 'unreliable' mode it still fails with error 'tracing progs
cannot use bpf_spin_lock yet' with the change in the verifier
Signed-off-by: Udip Pant <udippant@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200825232003.2877030-5-udippant@fb.com

tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c

@@ -142,7 +142,20 @@ static void test_func_replace_verify(void)
 				  prog_name, false);
 }
 
-static void test_func_replace_return_code(void)
+static void test_func_sockmap_update(void)
+{
+	const char *prog_name[] = {
+		"freplace/cls_redirect",
+	};
+	test_fexit_bpf2bpf_common("./freplace_cls_redirect.o",
+				  "./test_cls_redirect.o",
+				  ARRAY_SIZE(prog_name),
+				  prog_name, false);
+}
+
+static void test_obj_load_failure_common(const char *obj_file,
+					  const char *target_obj_file)
+
 {
 	/*
 	 * standalone test that asserts failure to load freplace prog
@@ -151,8 +164,6 @@ static void test_func_replace_return_code(void)
 	struct bpf_object *obj = NULL, *pkt_obj;
 	int err, pkt_fd;
 	__u32 duration = 0;
-	const char *target_obj_file = "./connect4_prog.o";
-	const char *obj_file = "./freplace_connect_v4_prog.o";
 
 	err = bpf_prog_load(target_obj_file, BPF_PROG_TYPE_UNSPEC,
 			    &pkt_obj, &pkt_fd);
@@ -181,11 +192,27 @@ static void test_func_replace_return_code(void)
 	bpf_object__close(pkt_obj);
 }
 
+static void test_func_replace_return_code(void)
+{
+	/* test invalid return code in the replaced program */
+	test_obj_load_failure_common("./freplace_connect_v4_prog.o",
+				     "./connect4_prog.o");
+}
+
+static void test_func_map_prog_compatibility(void)
+{
+	/* test with spin lock map value in the replaced program */
+	test_obj_load_failure_common("./freplace_attach_probe.o",
+				     "./test_attach_probe.o");
+}
+
 void test_fexit_bpf2bpf(void)
 {
 	test_target_no_callees();
 	test_target_yes_callees();
 	test_func_replace();
 	test_func_replace_verify();
+	test_func_sockmap_update();
 	test_func_replace_return_code();
+	test_func_map_prog_compatibility();
 }

tools/testing/selftests/bpf/progs/freplace_attach_probe.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define VAR_NUM 2
+
+struct hmap_elem {
+	struct bpf_spin_lock lock;
+	int var[VAR_NUM];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, struct hmap_elem);
+} hash_map SEC(".maps");
+
+SEC("freplace/handle_kprobe")
+int new_handle_kprobe(struct pt_regs *ctx)
+{
+	struct hmap_elem zero = {}, *val;
+	int key = 0;
+
+	val = bpf_map_lookup_elem(&hash_map, &key);
+	if (!val)
+		return 1;
+	/* spin_lock in hash map */
+	bpf_spin_lock(&val->lock);
+	val->var[0] = 99;
+	bpf_spin_unlock(&val->lock);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/freplace_cls_redirect.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+#include <bpf/bpf_endian.h>
+#include <bpf/bpf_helpers.h>
+
+struct bpf_map_def SEC("maps") sock_map = {
+	.type = BPF_MAP_TYPE_SOCKMAP,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = 2,
+};
+
+SEC("freplace/cls_redirect")
+int freplace_cls_redirect_test(struct __sk_buff *skb)
+{
+	int ret = 0;
+	const int zero = 0;
+	struct bpf_sock *sk;
+
+	sk = bpf_map_lookup_elem(&sock_map, &zero);
+	if (!sk)
+		return TC_ACT_SHOT;
+
+	ret = bpf_map_update_elem(&sock_map, &zero, sk, 0);
+	bpf_sk_release(sk);
+
+	return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT;
+}
+
+char _license[] SEC("license") = "GPL";