Rafael David Tinoco 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>
> ---
> tools/lib/bpf/libbpf.c | 10 ++++++++++
> tools/lib/bpf/libbpf.h | 1 +
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 12 insertions(+)
>
Hi Andrii and Rafael,
Did you consider making kernel version an attribute of the load
API, bpf_prog_load_xattr()? This feels slightly more natural
to me, to tell the API the kernel you need at load time.
Although, I don't use the skeleton pieces so maybe it would be
awkward for that usage.
Sorry, missed v1,v2 so didn't reply sooner.
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 058b643cbcb1..3ac3d8dced7f 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -8269,6 +8269,16 @@ 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, __u32 kern_version)
> +{
> + if (obj->loaded)
> + return -EINVAL;
> +
> + obj->kern_version = kern_version;
> +
> + return 0;
> +}
> +
Having a test to read uname and feed it into libbpf using
above to be sure we don't break this in the future would be
nice.
> int bpf_object__set_priv(struct bpf_object *obj, void *priv,
> bpf_object_clear_priv_t clear_priv)
> {
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index a1a424b9b8ff..cf9bc6f1f925 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/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, __u32 kern_version);
>
> struct btf;
> LIBBPF_API struct btf *bpf_object__btf(const struct bpf_object *obj);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 279ae861f568..f5990f7208ce 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -359,4 +359,5 @@ LIBBPF_0.4.0 {
> bpf_linker__finalize;
> bpf_linker__free;
> bpf_linker__new;
> + bpf_object__set_kversion;
> } LIBBPF_0.3.0;
> --
> 2.27.0
>
