On Thu, Nov 19, 2020 at 4:55 PM Maciej Fijalkowski
<maciej.fijalkowski@xxxxxxxxx> wrote:
>
> On Thu, Nov 19, 2020 at 03:22:42PM -0800, Andrii Nakryiko wrote:
> > Teach libbpf to search for candidate types for CO-RE relocations across kernel
> > modules BTFs, in addition to vmlinux BTF. If at least one candidate type is
> > found in vmlinux BTF, kernel module BTFs are not iterated. If vmlinux BTF has
> > no matching candidates, then find all kernel module BTFs and search for all
> > matching candidates across all of them.
> >
> > Kernel's support for module BTFs are inferred from the support for BTF name
> > pointer in BPF UAPI.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > ---
> > tools/lib/bpf/libbpf.c | 185 ++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 172 insertions(+), 13 deletions(-)
> >
>
> [...]
>
> > +static int probe_module_btf(void)
> > +{
> > + static const char strs[] = "\0int";
> > + __u32 types[] = {
> > + /* int */
> > + BTF_TYPE_INT_ENC(1, BTF_INT_SIGNED, 0, 32, 4),
> > + };
> > + struct bpf_btf_info info;
> > + __u32 len = sizeof(info);
> > + char name[16];
> > + int fd, err;
> > +
> > + fd = libbpf__load_raw_btf((char *)types, sizeof(types), strs, sizeof(strs));
> > + if (fd < 0)
> > + return 0; /* BTF not supported at all */
> > +
> > + len = sizeof(info);
>
> nit: reinit of len
>
oops, right, I'll remove it
> > + memset(&info, 0, sizeof(info));
>
> use len in memset
why?
>
> > + info.name = ptr_to_u64(name);
> > + info.name_len = sizeof(name);
> > +
> > + /* check that BPF_OBJ_GET_INFO_BY_FD supports specifying name pointer;
> > + * kernel's module BTF support coincides with support for
> > + * name/name_len fields in struct bpf_btf_info.
> > + */
> > + err = bpf_obj_get_info_by_fd(fd, &info, &len);
> > + close(fd);
> > + return !err;
> > +}
>
> [...]
