selftests/bpf: Fix kfunc_call/kfunc_call_test4 on 32-bit

This test currently fails on armhf:

verify_success:PASS:skel 0 nsec
verify_success:PASS:bpf_object__find_program_by_name 0 nsec
verify_success:PASS:kfunc_call_test4 0 nsec
verify_success:FAIL:retval unexpected retval: actual 4294966063 != expected -1234
torvalds#143/11  kfunc_call/kfunc_call_test4:FAIL

The problem can be traced to using 'long' as a 64-bit type in bpf_testmod
function bpf_kfunc_call_test4(), to force 64-bit signed arithmetic, which
breaks down on 32-bit systems.

Fix by explicitly using 's64' rather than long.

Signed-off-by: Tony Ambardar <[email protected]>

Author: guidosarducci

tools/testing/selftests/bpf/progs/kfunc_call_test.c

@@ -8,7 +8,7 @@ SEC("tc")
 int kfunc_call_test4(struct __sk_buff *skb)
 {
 	struct bpf_sock *sk = skb->sk;
-	long tmp;
+	s64 tmp;
 
 	if (!sk)
 		return -1;

tools/testing/selftests/bpf/test_kmods/bpf_testmod.c

@@ -703,12 +703,12 @@ __bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk)
 	return sk;
 }
 
-__bpf_kfunc long noinline bpf_kfunc_call_test4(signed char a, short b, int c, long d)
+__bpf_kfunc s64 noinline bpf_kfunc_call_test4(signed char a, short b, int c, s64 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;
+	return (s64)a + (s64)b + (s64)c + d;
 }
 
 static struct prog_test_ref_kfunc prog_test_struct = {

tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h

@@ -109,7 +109,7 @@ __u64 bpf_kfunc_call_test1(struct sock *sk, __u32 a, __u64 b,
 				__u32 c, __u64 d) __ksym;
 int bpf_kfunc_call_test2(struct sock *sk, __u32 a, __u32 b) __ksym;
 struct sock *bpf_kfunc_call_test3(struct sock *sk) __ksym;
-long bpf_kfunc_call_test4(signed char a, short b, int c, long d) __ksym;
+s64 bpf_kfunc_call_test4(signed char a, short b, int c, s64 d) __ksym;
 
 void bpf_kfunc_call_test_pass_ctx(struct __sk_buff *skb) __ksym;
 void bpf_kfunc_call_test_pass1(struct prog_test_pass1 *p) __ksym;