On Sat, Mar 20, 2021 at 10:23 AM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Fri, Mar 19, 2021 at 9:16 PM Rafael David Tinoco
> <rafaeldtinoco@xxxxxxxxxx> wrote:
> >
> > Unfortunately some distros don't have their kernel version defined
> > accurately in <linux/version.h> due to different long term support
> > reasons.
> >
> > It is important to have a way to override the bpf kern_version
> > attribute during runtime: some old kernels might still check for
> > kern_version attribute during bpf_prog_load().
> >
> > Signed-off-by: Rafael David Tinoco <rafaeldtinoco@xxxxxxxxxx>
> > ---
> > src/libbpf.c | 15 +++++++++++++++
> > src/libbpf.h | 1 +
> > 2 files changed, 16 insertions(+)
> >
> > diff --git a/src/libbpf.c b/src/libbpf.c
> > index 0c4a386..7b52cd6 100644
> > --- a/src/libbpf.c
> > +++ b/src/libbpf.c
> > @@ -8278,6 +8278,21 @@ int bpf_object__btf_fd(const struct bpf_object *obj)
> > return obj->btf ? btf__fd(obj->btf) : -1;
> > }
> >
> > +int bpf_object__set_kversion(struct bpf_object *obj, char *kern_version)
> > +{
> > + __u32 major, minor, patch;
> > +
> > + if (!kern_version) {
> > + obj->kern_version = 0;
> > + return 0;
> > + }
> > + if (sscanf(kern_version, "%u.%u.%u", &major, &minor, &patch) != 3)
>
> given SEC("version") expects `int` and bpf_object__kversion() returns
> int, I think it's appropriate for bpf_object__set_kversion() to accept
> just opaque int as well. Please also check that obj is not loaded and
> return error if it is. Thanks!
>
Oh, and please use [PATCH bpf-next] subject prefix to specify that
this is destined to the bpf-next tree. You'll also add v2 in between
PATCH and bpf-next for the next version, of course.
> > + return -1;
> > + obj->kern_version = KERNEL_VERSION(major, minor, patch);
> > +
> > + return 0;
> > +}
> > +
> > int bpf_object__set_priv(struct bpf_object *obj, void *priv,
> > bpf_object_clear_priv_t clear_priv)
> > {
> > diff --git a/src/libbpf.h b/src/libbpf.h
> > index 3c35eb4..3e14ae7 100644
> > --- a/src/libbpf.h
> > +++ b/src/libbpf.h
> > @@ -143,6 +143,7 @@ LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
> >
> > LIBBPF_API const char *bpf_object__name(const struct bpf_object *obj);
> > LIBBPF_API unsigned int bpf_object__kversion(const struct bpf_object *obj);
> > +LIBBPF_API int bpf_object__set_kversion(struct bpf_object *obj, char *kern_version);
> >
> > struct btf;
> > LIBBPF_API struct btf *bpf_object__btf(const struct bpf_object *obj);
> > --
> > 2.27.0
> >
