On Tue, Apr 30, 2024 at 04:57:26PM GMT, Arnaldo Carvalho de Melo wrote:
> On Mon, Apr 29, 2024 at 04:46:00PM -0600, Daniel Xu wrote:
> > This commit teaches pahole to parse symbols in .BTF_ids section in
> > vmlinux and discover exported kfuncs. Pahole then takes the list of
> > kfuncs and injects a BTF_KIND_DECL_TAG for each kfunc.
> >
> > Example of encoding:
> >
> > $ bpftool btf dump file .tmp_vmlinux.btf | rg "DECL_TAG 'bpf_kfunc'" | wc -l
> > 121
> >
> > $ bpftool btf dump file .tmp_vmlinux.btf | rg 56337
> > [56337] FUNC 'bpf_ct_change_timeout' type_id=56336 linkage=static
> > [127861] DECL_TAG 'bpf_kfunc' type_id=56337 component_idx=-1
> >
> > This enables downstream users and tools to dynamically discover which
> > kfuncs are available on a system by parsing vmlinux or module BTF, both
> > available in /sys/kernel/btf.
> >
> > This feature is enabled with --btf_features=decl_tag,decl_tag_kfuncs.
> >
> > Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Tested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> > Tested-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> > Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
>
> Here I needed this to avoid an strdup possibly followed by a free and
> then checking the strdup result, please Ack/revalidate tags. I'm
> dropping them as there are changes.
>
> - Arnaldo
>
> diff --git a/btf_encoder.c b/btf_encoder.c
> index e9d82e0af0e178fd..c2df2bc7a374447b 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -1434,11 +1434,13 @@ static char *get_func_name(const char *sym)
> return NULL;
>
> /* Strip prefix and handle malformed input such as __BTF_ID__func___ */
> - func = strdup(sym + sizeof(BTF_ID_FUNC_PFX) - 1);
> - if (!strstr(func, "__")) {
> - free(func);
> + const char *func_sans_prefix = sym + sizeof(BTF_ID_FUNC_PFX) - 1;
> + if (!strstr(func_sans_prefix, "__"))
> return NULL;
> - }
> +
> + func = strdup(func_sans_prefix);
> + if (!func)
> + return NULL;
>
> /* Strip suffix */
> end = strrchr(func, '_');
Thanks, that looks good to me. Please lemme know if I should re-spin.
Otherwise,
Acked-by: Daniel Xu <dxu@xxxxxxxxx>
