On Tue, Oct 5, 2021 at 5:29 PM Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> wrote:
>
> This patch adds typeless and weak ksym support to BTF_KIND_VAR
> relocation code in gen_loader. For typeless ksym, we use the newly added
> bpf_kallsyms_lookup_name helper.
>
> For weak ksym, we simply skip error check, and fix up the srg_reg for
> the insn, as keeping it as BPF_PSEUDO_BTF_ID for weak ksym with its
> insn[0].imm and insn[1].imm set as 0 will cause a failure. This is
> consistent with how libbpf relocates these two cases of BTF_KIND_VAR.
>
> We also modify cleanup_relos to check for typeless ksyms in fd closing
> loop, since those have no fd associated with the ksym. For this we can
> reuse the unused 'off' member of ksym_desc.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
[...]
Everything above (trimmed) makes sense to me.
> +/* Expects:
> + * BPF_REG_8 - pointer to instruction
> + */
> +static void emit_relo_ksym_btf(struct bpf_gen *gen, struct ksym_relo_desc *relo, int insn)
> +{
But I don't quite follow why we need these changes to emit_relo_ksym_btf.
Maybe we should have these changes in a separate patch and add some
more explanations?
Thanks,
Song
[...]
