[PATCH bpf-next v2 14/31] selftests/bpf: Add a sign-extension test for kfuncs

Ilya Leoshkevich
2023-01-28T00:07:47Z

s390x ABI requires the caller to zero- or sign-extend the arguments.
eBPF already deals with zero-extension (by definition of its ABI), but
not with sign-extension.

Add a test to cover that potentially problematic area.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
net/bpf/test_run.c | 9 +++++++++
.../selftests/bpf/prog_tests/kfunc_call.c | 1 +
.../selftests/bpf/progs/kfunc_call_test.c | 18 ++++++++++++++++++
3 files changed, 28 insertions(+)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 8da0d73b368e..7dbefa4fd2eb 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -550,6 +550,14 @@ struct sock * noinline bpf_kfunc_call_test3(struct sock *sk)
return sk;
}

+long noinline bpf_kfunc_call_test4(signed char a, short b, int c, long d)
+{
+ /* Provoke the compiler to assume that the caller has sign-extended a,
+ * b and c on platforms where this is required (e.g. s390x).
+ */
+ return (long)a + (long)b + (long)c + d;
+}
+
struct prog_test_member1 {
int a;
};
@@ -746,6 +754,7 @@ BTF_SET8_START(test_sk_check_kfunc_ids)
BTF_ID_FLAGS(func, bpf_kfunc_call_test1)
BTF_ID_FLAGS(func, bpf_kfunc_call_test2)
BTF_ID_FLAGS(func, bpf_kfunc_call_test3)
+BTF_ID_FLAGS(func, bpf_kfunc_call_test4)
BTF_ID_FLAGS(func, bpf_kfunc_call_test_acquire, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_kfunc_call_memb_acquire, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_kfunc_call_test_release, KF_RELEASE)
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
index 5af1ee8f0e6e..bb4cd82a788a 100644
--- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c
@@ -72,6 +72,7 @@ static struct kfunc_test_params kfunc_tests[] = {
/* success cases */
TC_TEST(kfunc_call_test1, 12),
TC_TEST(kfunc_call_test2, 3),
+ TC_TEST(kfunc_call_test4, -1234),
TC_TEST(kfunc_call_test_ref_btf_id, 0),
TC_TEST(kfunc_call_test_get_mem, 42),
SYSCALL_TEST(kfunc_syscall_test, 0),
diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
index f636e50be259..d91c58d06d38 100644
--- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c
+++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c
@@ -3,6 +3,7 @@
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>

+extern long bpf_kfunc_call_test4(signed char a, short b, int c, long d) __ksym;
extern int bpf_kfunc_call_test2(struct sock *sk, __u32 a, __u32 b) __ksym;
extern __u64 bpf_kfunc_call_test1(struct sock *sk, __u32 a, __u64 b,
__u32 c, __u64 d) __ksym;
@@ -17,6 +18,23 @@ extern void bpf_kfunc_call_test_mem_len_fail2(__u64 *mem, int len) __ksym;
extern int *bpf_kfunc_call_test_get_rdwr_mem(struct prog_test_ref_kfunc *p, const int rdwr_buf_size) __ksym;
extern int *bpf_kfunc_call_test_get_rdonly_mem(struct prog_test_ref_kfunc *p, const int rdonly_buf_size) __ksym;

+SEC("tc")
+int kfunc_call_test4(struct __sk_buff *skb)
+{
+ struct bpf_sock *sk = skb->sk;
+ long tmp;
+
+ if (!sk)
+ return -1;
+
+ sk = bpf_sk_fullsock(sk);
+ if (!sk)
+ return -1;
+
+ tmp = bpf_kfunc_call_test4(-3, -30, -200, -1000);
+ return (tmp >> 32) + tmp;
+}
+
SEC("tc")
int kfunc_call_test2(struct __sk_buff *skb)
{
--
2.39.1