bpf: Change bpf_session_cookie return value to __u64 *

This reverts [1] and changes return value for bpf_session_cookie
in bpf selftests. Having long * might lead to problems on 32-bit
architectures.

Fixes: 2b8dd873

 ("bpf: Make bpf_session_cookie() kfunc return long *")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240619081624.1620152-1-jolsa@kernel.org

kernel/trace/bpf_trace.c

@@ -3530,7 +3530,7 @@ __bpf_kfunc bool bpf_session_is_return(void)
 	return session_ctx->is_return;
 }
 
-__bpf_kfunc long *bpf_session_cookie(void)
+__bpf_kfunc __u64 *bpf_session_cookie(void)
 {
 	struct bpf_session_run_ctx *session_ctx;
 

tools/testing/selftests/bpf/bpf_kfuncs.h

@@ -77,5 +77,5 @@ extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
 				      struct bpf_key *trusted_keyring) __ksym;
 
 extern bool bpf_session_is_return(void) __ksym __weak;
-extern long *bpf_session_cookie(void) __ksym __weak;
+extern __u64 *bpf_session_cookie(void) __ksym __weak;
 #endif

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

@@ -25,7 +25,7 @@ int BPF_PROG(trigger)
 
 static int check_cookie(__u64 val, __u64 *result)
 {
-	long *cookie;
+	__u64 *cookie;
 
 	if (bpf_get_current_pid_tgid() >> 32 != pid)
 		return 1;