[PATCH bpf-next 1/8] s390/bpf: Let arch_prepare_bpf_trampoline return program size

Song Liu
2023-09-20T05:32:22Z

arch_prepare_bpf_trampoline() for s390 currently returns 0 on success. This
is not a problem for regular trampoline. However, struct_ops relies on the
return value to advance "image" pointer:

bpf_struct_ops_map_update_elem() {
...
for_each_member(i, t, member) {
...
err = bpf_struct_ops_prepare_trampoline();
...
image += err;
}
}

When arch_prepare_bpf_trampoline returns 0 on success, all members of the
struct_ops will point to the same trampoline (the last one).

Fix this by returning the program size in arch_prepare_bpf_trampoline (on
success). This is the same behavior as other architectures.

Signed-off-by: Song Liu <song@kernel.org>
Fixes: 528eb2cb87bc ("s390/bpf: Implement arch_prepare_bpf_trampoline()")
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230919060258.3237176-2-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
arch/s390/net/bpf_jit_comp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index eeb42e5cd7d6..e6a643f63ebf 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -2513,7 +2513,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
return -E2BIG;
}

- return ret;
+ return tjit.common.prg;
}

bool bpf_jit_supports_subprog_tailcalls(void)
--
2.34.1