On 8/15/24 3:07 PM, Eduard Zingerman wrote:
On Thu, 2024-08-15 at 14:24 -0700, Andrii Nakryiko wrote:
[...]
@@ -16140,6 +16140,28 @@ static bool verifier_inlines_helper_call(struct bpf_verifier_env *env, s32 imm)
}
}
+/* Same as helper_nocsr_clobber_mask() but for kfuncs, see comment above */
+static u32 kfunc_nocsr_clobber_mask(struct bpf_kfunc_call_arg_meta *meta)
+{
+ const struct btf_param *params;
+ u32 vlen, i, mask;
+
+ params = btf_params(meta->func_proto);
+ vlen = btf_type_vlen(meta->func_proto);
+ mask = 0;
+ if (!btf_type_is_void(btf_type_by_id(meta->btf, meta->func_proto->type)))
+ mask |= BIT(BPF_REG_0);
+ for (i = 0; i < vlen; ++i)
+ mask |= BIT(BPF_REG_1 + i);
Somewhere deep in btf_dump implementation of libbpf, there is a
special handling of `<whatever> func(void)` (no args) function as
having vlen == 1 and type being VOID (i.e., zero). I don't know if
that still can happen, but I believe at some point we could get this
vlen==1 and type=VOID for no-args functions. So I wonder if we should
handle that here as well, or is it some compiler atavism we can forget
about?
I just checked BTF generated for 'int filelock_init(void)',
for gcc compiled kernel using latest pahole and func proto looks as follows:
FUNC_PROTO '(anon)' ret_type_id=12 vlen=0
So I assume this is an atavism.
Agree, for kernel vmlinux BTF, we should be fine.
[...]
