On Wed, May 10, 2023 at 9:03 PM Alan Maguire <alan.maguire@xxxxxxxxxx> wrote:
>
> v1.25 of pahole supports filtering out functions with multiple inconsistent
> function prototypes or optimized-out parameters from the BTF representation.
> These present problems because there is no additional info in BTF saying which
> inconsistent prototype matches which function instance to help guide attachment,
> and functions with optimized-out parameters can lead to incorrect assumptions
> about register contents.
>
> So for now, filter out such functions while adding BTF representations for
> functions that have "."-suffixes (foo.isra.0) but not optimized-out parameters.
> This patch assumes that below linked changes land in pahole for v1.25.
>
> Issues with pahole filtering being too aggressive in removing functions
> appear to be resolved now, but CI and further testing will confirm.
>
> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> ---
> scripts/pahole-flags.sh | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
> index 1f1f1d397c39..728d55190d97 100755
> --- a/scripts/pahole-flags.sh
> +++ b/scripts/pahole-flags.sh
> @@ -23,5 +23,8 @@ if [ "${pahole_ver}" -ge "124" ]; then
> # see PAHOLE_HAS_LANG_EXCLUDE
> extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
> fi
> +if [ "${pahole_ver}" -ge "125" ]; then
> + extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_inconsistent_proto --btf_gen_optimized"
> +fi
>
> echo ${extra_paholeopt}
> --
> 2.31.1
>
That change looks like a workaround to me.
There may be multiple functions that have the same proto, e.g.:
$ grep -r "bpf_iter_detach_map(struct bpf_iter_aux_info \*aux)"
kernel/bpf/ net/core/
kernel/bpf/map_iter.c:static void bpf_iter_detach_map(struct
bpf_iter_aux_info *aux)
net/core/bpf_sk_storage.c:static void bpf_iter_detach_map(struct
bpf_iter_aux_info *aux)
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep -B 2
bpf_iter_detach_map
[34691] FUNC_PROTO '(anon)' ret_type_id=0 vlen=1
'aux' type_id=2638
[34692] FUNC 'bpf_iter_detach_map' type_id=34691 linkage=static
We don't know which one it is in the BTF.
However, I'm not against this change, as it can avoid some issues.
--
Regards
Yafang
