[bpf,v3,6/6] selftests/bpf: Test outer map update operations in syscall program

Commit Message

Hou Tao Nov. 24, 2023, 11:30 a.m. UTC

From: Hou Tao <[e-mail]>

Syscall program is running with rcu_read_lock_trace being held, so if
bpf_map_update_elem() or bpf_map_delete_elem() invokes
synchronize_rcu_tasks_trace() when operating on an outer map, there will
be dead-lock, so add a test to guarantee that it is dead-lock free.

Signed-off-by: Hou Tao <[e-mail]>
---
 .../selftests/bpf/prog_tests/syscall.c        | 30 +++++-
 tools/testing/selftests/bpf/progs/syscall.c   | 91 ++++++++++++++++++-
 2 files changed, 114 insertions(+), 7 deletions(-)

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/syscall.c b/tools/testing/selftests/bpf/prog_tests/syscall.c
index f4d40001155a..0be8301c0ffd 100644
--- a/tools/testing/selftests/bpf/prog_tests/syscall.c
+++ b/tools/testing/selftests/bpf/prog_tests/syscall.c
@@ -12,7 +12,7 @@  struct args {
 	int btf_fd;
 };
 
-void test_syscall(void)
+static void test_syscall_load_prog(void)
 {
 	static char verifier_log[8192];
 	struct args ctx = {
@@ -32,7 +32,7 @@  void test_syscall(void)
 	if (!ASSERT_OK_PTR(skel, "skel_load"))
 		goto cleanup;
 
-	prog_fd = bpf_program__fd(skel->progs.bpf_prog);
+	prog_fd = bpf_program__fd(skel->progs.load_prog);
 	err = bpf_prog_test_run_opts(prog_fd, &tattr);
 	ASSERT_EQ(err, 0, "err");
 	ASSERT_EQ(tattr.retval, 1, "retval");
@@ -53,3 +53,29 @@  void test_syscall(void)
 	if (ctx.btf_fd > 0)
 		close(ctx.btf_fd);
 }
+
+static void test_syscall_update_outer_map(void)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+	struct syscall *skel;
+	int err, prog_fd;
+
+	skel = syscall__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_load"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.update_outer_map);
+	err = bpf_prog_test_run_opts(prog_fd, &opts);
+	ASSERT_EQ(err, 0, "err");
+	ASSERT_EQ(opts.retval, 1, "retval");
+cleanup:
+	syscall__destroy(skel);
+}
+
+void test_syscall(void)
+{
+	if (test__start_subtest("load_prog"))
+		test_syscall_load_prog();
+	if (test__start_subtest("update_outer_map"))
+		test_syscall_update_outer_map();
+}
diff --git a/tools/testing/selftests/bpf/progs/syscall.c b/tools/testing/selftests/bpf/progs/syscall.c
index e550f728962d..23058abbaabd 100644
--- a/tools/testing/selftests/bpf/progs/syscall.c
+++ b/tools/testing/selftests/bpf/progs/syscall.c
@@ -6,9 +6,15 @@ 
 #include <bpf/bpf_tracing.h>
 #include <../../../tools/include/linux/filter.h>
 #include <linux/btf.h>
+#include <string.h>
+#include <errno.h>
 
 char _license[] SEC("license") = "GPL";
 
+struct bpf_map {
+	int id;
+}  __attribute__((preserve_access_index));
+
 struct args {
 	__u64 log_buf;
 	__u32 log_size;
@@ -27,6 +33,32 @@  struct args {
 	BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_INT, 0, 0), sz), \
 	BTF_INT_ENC(encoding, bits_offset, bits)
 
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, union bpf_attr);
+	__uint(max_entries, 1);
+} bpf_attr_array SEC(".maps");
+
+struct inner_map_type {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(key_size, 4);
+	__uint(value_size, 4);
+	__uint(max_entries, 1);
+} inner_map SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+	__type(key, int);
+	__type(value, int);
+	__uint(max_entries, 1);
+	__array(values, struct inner_map_type);
+} outer_array_map SEC(".maps") = {
+	.values = {
+		[0] = &inner_map,
+	},
+};
+
 static int btf_load(void)
 {
 	struct btf_blob {
@@ -58,7 +90,7 @@  static int btf_load(void)
 }
 
 SEC("syscall")
-int bpf_prog(struct args *ctx)
+int load_prog(struct args *ctx)
 {
 	static char license[] = "GPL";
 	static struct bpf_insn insns[] = {
@@ -94,8 +126,8 @@  int bpf_prog(struct args *ctx)
 	map_create_attr.max_entries = ctx->max_entries;
 	map_create_attr.btf_fd = ret;
 
-	prog_load_attr.license = (long) license;
-	prog_load_attr.insns = (long) insns;
+	prog_load_attr.license = (unsigned long)license;
+	prog_load_attr.insns = (unsigned long)insns;
 	prog_load_attr.log_buf = ctx->log_buf;
 	prog_load_attr.log_size = ctx->log_size;
 	prog_load_attr.log_level = 1;
@@ -107,8 +139,8 @@  int bpf_prog(struct args *ctx)
 	insns[3].imm = ret;
 
 	map_update_attr.map_fd = ret;
-	map_update_attr.key = (long) &key;
-	map_update_attr.value = (long) &value;
+	map_update_attr.key = (unsigned long)&key;
+	map_update_attr.value = (unsigned long)&value;
 	ret = bpf_sys_bpf(BPF_MAP_UPDATE_ELEM, &map_update_attr, sizeof(map_update_attr));
 	if (ret < 0)
 		return ret;
@@ -119,3 +151,52 @@  int bpf_prog(struct args *ctx)
 	ctx->prog_fd = ret;
 	return 1;
 }
+
+SEC("syscall")
+int update_outer_map(void *ctx)
+{
+	int zero = 0, ret = 0, outer_fd = -1, inner_fd = -1, err;
+	const int attr_sz = sizeof(union bpf_attr);
+	union bpf_attr *attr;
+
+	attr = bpf_map_lookup_elem((struct bpf_map *)&bpf_attr_array, &zero);
+	if (!attr)
+		goto out;
+
+	memset(attr, 0, attr_sz);
+	attr->map_id = ((struct bpf_map *)&outer_array_map)->id;
+	outer_fd = bpf_sys_bpf(BPF_MAP_GET_FD_BY_ID, attr, attr_sz);
+	if (outer_fd < 0)
+		goto out;
+
+	memset(attr, 0, attr_sz);
+	attr->map_type = BPF_MAP_TYPE_ARRAY;
+	attr->key_size = 4;
+	attr->value_size = 4;
+	attr->max_entries = 1;
+	inner_fd = bpf_sys_bpf(BPF_MAP_CREATE, attr, attr_sz);
+	if (inner_fd < 0)
+		goto out;
+
+	memset(attr, 0, attr_sz);
+	attr->map_fd = outer_fd;
+	attr->key = (unsigned long)&zero;
+	attr->value = (unsigned long)&inner_fd;
+	err = bpf_sys_bpf(BPF_MAP_UPDATE_ELEM, attr, attr_sz);
+	if (err)
+		goto out;
+
+	memset(attr, 0, attr_sz);
+	attr->map_fd = outer_fd;
+	attr->key = (unsigned long)&zero;
+	err = bpf_sys_bpf(BPF_MAP_DELETE_ELEM, attr, attr_sz);
+	if (err)
+		goto out;
+	ret = 1;
+out:
+	if (inner_fd >= 0)
+		bpf_sys_close(inner_fd);
+	if (outer_fd >= 0)
+		bpf_sys_close(outer_fd);
+	return ret;
+}