bpf: Pass the same orig_call value to trampoline functions

There is currently some confusion in the s390x JIT regarding whether
orig_call can be NULL and what that means. Originally the NULL value
was used to distinguish the struct_ops case, but this was superseded by
BPF_TRAMP_F_INDIRECT (see commit 0c970ed2f87c ("s390/bpf: Fix indirect
trampoline generation").

The remaining reason to have this check is that NULL can actually be
passed to the arch_bpf_trampoline_size() call - but not to the
respective arch_prepare_bpf_trampoline()! call - by
bpf_struct_ops_prepare_trampoline().

Remove this asymmetry by passing stub_func to both functions, so that
JITs may rely on orig_call never being NULL.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250512221911.61314-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index db13ee7..9611363 100644 (file)
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -601,7 +601,7 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
        if (model->ret_size > 0)
                flags |= BPF_TRAMP_F_RET_FENTRY_RET;
 
-       size = arch_bpf_trampoline_size(model, flags, tlinks, NULL);
+       size = arch_bpf_trampoline_size(model, flags, tlinks, stub_func);
        if (size <= 0)
                return size ? : -EFAULT;