Hi Alan, On Wed, Mar 20, 2024 at 12:54:11PM +0000, Alan Maguire wrote: > On 15/03/2024 19:48, 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. > > > > Signed-off-by: Daniel Xu <dxu@xxxxxxxxx> > > This is great work; a lot of steps needed to collect this info, but it's > really valuable! > > Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx> > Tested-by: Alan Maguire <alan.maguire@xxxxxxxxxx> > > BTW we need something like the attached patch to switch to using > --btf_features for pahole 1.26 and later; will I send it officially or > do you have something that does the same that you want to roll into your > bpf-next series? Let me know what works from your side. Thanks! I was planning on sending that with the bpftool changes. IIRC there are a few conflicts with generated prototypes to fix. I think Andrii had const-ified some kfunc params from userspace side but not kernel. I probably need to go fixup the kernel side. Thanks, Daniel
