s390/bpf: Fix indirect trampoline generation

The func_addr used to be NULL for indirect trampolines used by struct_ops.
Now func_addr is a valid function pointer.
Hence use BPF_TRAMP_F_INDIRECT flag to detect such condition.

Fixes: 2cd3e377 ("x86/cfi,bpf: Fix bpf_struct_ops CFI")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20231216004549.78355-1-alexei.starovoitov@gmail.com

arch/s390/net/bpf_jit_comp.c

@@ -2362,7 +2362,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 		return -ENOTSUPP;
 
 	/* Return to %r14, since func_addr and %r0 are not available. */
-	if (!func_addr && !(flags & BPF_TRAMP_F_ORIG_STACK))
+	if ((!func_addr && !(flags & BPF_TRAMP_F_ORIG_STACK)) ||
+	    (flags & BPF_TRAMP_F_INDIRECT))
 		flags |= BPF_TRAMP_F_SKIP_FRAME;
 
 	/*

tools/testing/selftests/bpf/DENYLIST.s390x

 # TEMPORARY
 # Alphabetical order
-dummy_st_ops/dummy_init_ret_value
-dummy_st_ops/dummy_init_ptr_arg
 exceptions				 # JIT does not support calling kfunc bpf_throw				       (exceptions)
 get_stack_raw_tp                         # user_stack corrupted user stack                                             (no backchain userspace)
 stacktrace_build_id                      # compare_map_keys stackid_hmap vs. stackmap err -2 errno 2                   (?)