[PATCH bpf-next v7 04/24] selftests/bpf: add test for accessing ctx from syscall program type

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

We need to also export the kfunc set to the syscall program type,
and then add a couple of eBPF programs that are testing those calls.

The first one checks for valid access, and the second one is OK
from a static analysis point of view but fails at run time because
we are trying to access outside of the allocated memory.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

---

changes in v7:
- add 1 more case to ensure we can read the entire sizeof(ctx)
- add a test case for when the context is NULL

new in v6
---
 net/bpf/test_run.c                            |  1 +
 .../selftests/bpf/prog_tests/kfunc_call.c     | 28 +++++++++++++++
 .../selftests/bpf/progs/kfunc_call_test.c     | 36 +++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dc9dc0bedca0..8ada09ab1b15 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1649,6 +1649,7 @@ static int __init bpf_prog_test_run_init(void)
 	int ret;
 
 	ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_prog_test_kfunc_set);
+	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_prog_test_kfunc_set);
 	return ret ?: register_btf_id_dtor_kfuncs(bpf_prog_test_dtor_kfunc,
 						  ARRAY_SIZE(bpf_prog_test_dtor_kfunc),
 						  THIS_MODULE);
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
index c00eb974eb85..7e4804cce6b9 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
@@ -6,10 +6,22 @@
 #include "kfunc_call_test_subprog.skel.h"
 #include "kfunc_call_test_subprog.lskel.h"
 
+struct syscall_test_args {
+	__u8 data[16];
+	size_t size;
+};
+
 static void test_main(void)
 {
 	struct kfunc_call_test_lskel *skel;
 	int prog_fd, err;
+	struct syscall_test_args args = {
+		.size = 10,
+	};
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, syscall_topts,
+		.ctx_in = &args,
+		.ctx_size_in = sizeof(args),
+	);
 	LIBBPF_OPTS(bpf_test_run_opts, topts,
 		.data_in = &pkt_v4,
 		.data_size_in = sizeof(pkt_v4),
@@ -35,6 +47,22 @@ static void test_main(void)
 	ASSERT_OK(err, "bpf_prog_test_run(test_ref_btf_id)");
 	ASSERT_EQ(topts.retval, 0, "test_ref_btf_id-retval");
 
+	prog_fd = skel->progs.kfunc_syscall_test.prog_fd;
+	err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+	ASSERT_OK(err, "bpf_prog_test_run(syscall_test)");
+
+	prog_fd = skel->progs.kfunc_syscall_test_fail.prog_fd;
+	err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+	ASSERT_ERR(err, "bpf_prog_test_run(syscall_test_fail)");
+
+	syscall_topts.ctx_in = NULL;
+	syscall_topts.ctx_size_in = 0;
+
+	prog_fd = skel->progs.kfunc_syscall_test_null.prog_fd;
+	err = bpf_prog_test_run_opts(prog_fd, &syscall_topts);
+	ASSERT_OK(err, "bpf_prog_test_run(syscall_test_null)");
+	ASSERT_EQ(syscall_topts.retval, 0, "syscall_test_null-retval");
+
 	kfunc_call_test_lskel__destroy(skel);
 }
 
diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
index 5aecbb9fdc68..da7ae0ef9100 100644
--- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c
+++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
@@ -92,4 +92,40 @@ int kfunc_call_test_pass(struct __sk_buff *skb)
 	return 0;
 }
 
+struct syscall_test_args {
+	__u8 data[16];
+	size_t size;
+};
+
+SEC("syscall")
+int kfunc_syscall_test(struct syscall_test_args *args)
+{
+	const int size = args->size;
+
+	if (size > sizeof(args->data))
+		return -7; /* -E2BIG */
+
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(args->data));
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args));
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, size);
+
+	return 0;
+}
+
+SEC("syscall")
+int kfunc_syscall_test_null(struct syscall_test_args *args)
+{
+	bpf_kfunc_call_test_mem_len_pass1(args, 0);
+
+	return 0;
+}
+
+SEC("syscall")
+int kfunc_syscall_test_fail(struct syscall_test_args *args)
+{
+	bpf_kfunc_call_test_mem_len_pass1(&args->data, sizeof(*args) + 1);
+
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.36.1