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 <redacted>

---

no changes in v9

no changes in v8

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 25d8ecf105aa..f16baf977a21 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c

@@ -1634,6 +1634,7 @@ static int __init bpf_prog_test_run_init(void)

        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_TRACING, &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 eede7c304f86..1edad012fe01 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c

@@ -9,10 +9,22 @@

 #include "cap_helpers.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),

@@ -38,6 +50,22 @@ 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);
+