Hi,
On Fri, Feb 28, 2025 at 7:56 PM Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
>
> Hi,
>
> On 2/28/2025 8:33 AM, Emil Tsalapatis wrote:
> > Add a helper kfunc that sets the bitmap of a bpf_cpumask from BPF
> > memory.
> >
> > Signed-off-by: Emil Tsalapatis (Meta) <emil@xxxxxxxxxxxxxxx>
> > ---
> > kernel/bpf/cpumask.c | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> >
> > diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
> > index cfa1c18e3a48..a13839b3595f 100644
> > --- a/kernel/bpf/cpumask.c
> > +++ b/kernel/bpf/cpumask.c
> > @@ -420,6 +420,26 @@ __bpf_kfunc u32 bpf_cpumask_weight(const struct cpumask *cpumask)
> > return cpumask_weight(cpumask);
> > }
> >
> > +/**
> > + * bpf_cpumask_fill() - Populate the CPU mask from the contents of
> > + * a BPF memory region.
> > + *
> > + * @cpumask: The cpumask being populated.
> > + * @src: The BPF memory holding the bit pattern.
> > + * @src__sz: Length of the BPF memory region in bytes.
> > + *
> > + */
> > +__bpf_kfunc int bpf_cpumask_fill(struct cpumask *cpumask, void *src, size_t src__sz)
> > +{
> > + /* The memory region must be large enough to populate the entire CPU mask. */
> > + if (src__sz < BITS_TO_BYTES(nr_cpu_ids))
> > + return -EACCES;
> > +
> > + bitmap_copy(cpumask_bits(cpumask), src, nr_cpu_ids);
>
> Should we use src__sz < bitmap_size(nr_cpu_ids) instead ? Because in
> bitmap_copy(), it assumes the size of src should be bitmap_size(nr_cpu_ids).
This is a great catch, thank you. Comparing with
BITS_TO_BYTES(nr_cpu_ids) allows byte-aligned
masks through, even though bitmap_copy assumes all masks are long-aligned.
> > +
> > + return 0;
> > +}
> > +
> > __bpf_kfunc_end_defs();
> >
> > BTF_KFUNCS_START(cpumask_kfunc_btf_ids)
> > @@ -448,6 +468,7 @@ BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_RCU)
> > BTF_ID_FLAGS(func, bpf_cpumask_any_distribute, KF_RCU)
> > BTF_ID_FLAGS(func, bpf_cpumask_any_and_distribute, KF_RCU)
> > BTF_ID_FLAGS(func, bpf_cpumask_weight, KF_RCU)
> > +BTF_ID_FLAGS(func, bpf_cpumask_fill, KF_RCU)
> > BTF_KFUNCS_END(cpumask_kfunc_btf_ids)
> >
> > static const struct btf_kfunc_id_set cpumask_kfunc_set = {
>
