[PATCH bpf-next v1 2/2] selftests/bpf: Add test for static subprog call in lock cs

[Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>]

Add selftests for static subprog calls within bpf_spin_lock critical
section, and ensure we still reject global subprog calls. Also test the
case where a subprog call will unlock the caller's held lock, or the
caller will unlock a lock taken by a subprog call, ensuring correct
transfer of lock state across frames on exit.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
 .../selftests/bpf/prog_tests/spin_lock.c      |  2 +
 .../selftests/bpf/progs/test_spin_lock.c      | 65 +++++++++++++++++++
 .../selftests/bpf/progs/test_spin_lock_fail.c | 44 +++++++++++++
 3 files changed, 111 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/spin_lock.c b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
index 18d451be57c8..6a4962ca0e5e 100644
--- a/tools/testing/selftests/bpf/prog_tests/spin_lock.c
+++ b/tools/testing/selftests/bpf/prog_tests/spin_lock.c
@@ -48,6 +48,8 @@ static struct {
 	{ "lock_id_mismatch_innermapval_kptr", "bpf_spin_unlock of different lock" },
 	{ "lock_id_mismatch_innermapval_global", "bpf_spin_unlock of different lock" },
 	{ "lock_id_mismatch_innermapval_mapval", "bpf_spin_unlock of different lock" },
+	{ "lock_global_subprog_call1", "function calls are not allowed while holding a lock" },
+	{ "lock_global_subprog_call2", "function calls are not allowed while holding a lock" },
 };
 
 static int match_regex(const char *pattern, const char *string)
diff --git a/tools/testing/selftests/bpf/progs/test_spin_lock.c b/tools/testing/selftests/bpf/progs/test_spin_lock.c
index b2440a0ff422..d8d77bdffd3d 100644
--- a/tools/testing/selftests/bpf/progs/test_spin_lock.c
+++ b/tools/testing/selftests/bpf/progs/test_spin_lock.c
@@ -101,4 +101,69 @@ int bpf_spin_lock_test(struct __sk_buff *skb)
 err:
 	return err;
 }
+
+struct bpf_spin_lock lockA __hidden SEC(".data.A");
+
+__noinline
+static int static_subprog(struct __sk_buff *ctx)
+{
+	volatile int ret = 0;
+
+	if (ctx->protocol)
+		return ret;
+	return ret + ctx->len;
+}
+
+__noinline
+static int static_subprog_lock(struct __sk_buff *ctx)
+{
+	volatile int ret = 0;
+
+	ret = static_subprog(ctx);
+	bpf_spin_lock(&lockA);
+	return ret + ctx->len;
+}
+
+__noinline
+static int static_subprog_unlock(struct __sk_buff *ctx)
+{
+	volatile int ret = 0;
+
+	ret = static_subprog(ctx);
+	bpf_spin_unlock(&lockA);
+	return ret + ctx->len;
+}
+
+SEC("tc")
+int lock_static_subprog_call(struct __sk_buff *ctx)
+{
+	int ret = 0;
+
+	bpf_spin_lock(&lockA);
+	if (ctx->mark == 42)
+		ret = static_subprog(ctx);
+	bpf_spin_unlock(&lockA);
+	return ret;
+}
+
+SEC("tc")
+int lock_static_subprog_lock(struct __sk_buff *ctx)
+{
+	int ret = 0;
+
+	ret = static_subprog_lock(ctx);
+	bpf_spin_unlock(&lockA);
+	return ret;
+}
+
+SEC("tc")
+int lock_static_subprog_unlock(struct __sk_buff *ctx)
+{
+	int ret = 0;
+
+	bpf_spin_lock(&lockA);
+	ret = static_subprog_unlock(ctx);
+	return ret;
+}
+
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
index 86cd183ef6dc..43f40c4fe241 100644
--- a/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
+++ b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
@@ -201,4 +201,48 @@ CHECK(innermapval_mapval, &iv->lock, &v->lock);
 
 #undef CHECK
 
+__noinline
+int global_subprog(struct __sk_buff *ctx)
+{
+	volatile int ret = 0;
+
+	if (ctx->protocol)
+		ret += ctx->protocol;
+	return ret + ctx->mark;
+}
+
+__noinline
+static int static_subprog_call_global(struct __sk_buff *ctx)
+{
+	volatile int ret = 0;
+
+	if (ctx->protocol)
+		return ret;
+	return ret + ctx->len + global_subprog(ctx);
+}
+
+SEC("?tc")
+int lock_global_subprog_call1(struct __sk_buff *ctx)
+{
+	int ret = 0;
+
+	bpf_spin_lock(&lockA);
+	if (ctx->mark == 42)
+		ret = global_subprog(ctx);
+	bpf_spin_unlock(&lockA);
+	return ret;
+}
+
+SEC("?tc")
+int lock_global_subprog_call2(struct __sk_buff *ctx)
+{
+	int ret = 0;
+
+	bpf_spin_lock(&lockA);
+	if (ctx->mark == 42)
+		ret = static_subprog_call_global(ctx);
+	bpf_spin_unlock(&lockA);
+	return ret;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.40.1