| Message ID | 20230811172541.618284-1-void@manifault.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next,v2] bpf: Support default .validate() and .update() behavior for struct_ops links | expand |
LGTM! Acked-by: Kui-Feng Lee <thinker.li@gmail.com> On 8/11/23 10:25, David Vernet wrote: > Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also > define the .validate() and .update() callbacks in its corresponding > struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful > in its own right to ensure that the map is unloaded if an application > crashes. For example, with sched_ext, we want to automatically unload > the host-wide scheduler if the application crashes. We would likely > never support updating elements of a sched_ext struct_ops map, so we'd > have to implement these callbacks showing that they _can't_ support > element updates just to benefit from the basic lifetime management of > struct_ops links. > > Let's enable struct_ops maps to work with BPF_F_LINK even if they > haven't defined these callbacks, by assuming that a struct_ops map > element cannot be updated by default. > > Signed-off-by: David Vernet <void@manifault.com> > --- > kernel/bpf/bpf_struct_ops.c | 15 +++++++++------ > 1 file changed, 9 insertions(+), 6 deletions(-) > > diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c > index eaff04eefb31..fdc3e8705a3c 100644 > --- a/kernel/bpf/bpf_struct_ops.c > +++ b/kernel/bpf/bpf_struct_ops.c > @@ -509,9 +509,12 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, > } > > if (st_map->map.map_flags & BPF_F_LINK) { > - err = st_ops->validate(kdata); > - if (err) > - goto reset_unlock; > + err = 0; > + if (st_ops->validate) { > + err = st_ops->validate(kdata); > + if (err) > + goto reset_unlock; > + } > set_memory_rox((long)st_map->image, 1); > /* Let bpf_link handle registration & unregistration. > * > @@ -663,9 +666,6 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) > if (attr->value_size != vt->size) > return ERR_PTR(-EINVAL); > > - if (attr->map_flags & BPF_F_LINK && (!st_ops->validate || !st_ops->update)) > - return ERR_PTR(-EOPNOTSUPP); > - > t = st_ops->type; > > st_map_size = sizeof(*st_map) + > @@ -823,6 +823,9 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map > if (!bpf_struct_ops_valid_to_reg(new_map)) > return -EINVAL; > > + if (!st_map->st_ops->update) > + return -EOPNOTSUPP; > + > mutex_lock(&update_mutex); > > old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c index eaff04eefb31..fdc3e8705a3c 100644 --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -509,9 +509,12 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, } if (st_map->map.map_flags & BPF_F_LINK) { - err = st_ops->validate(kdata); - if (err) - goto reset_unlock; + err = 0; + if (st_ops->validate) { + err = st_ops->validate(kdata); + if (err) + goto reset_unlock; + } set_memory_rox((long)st_map->image, 1); /* Let bpf_link handle registration & unregistration. * @@ -663,9 +666,6 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) if (attr->value_size != vt->size) return ERR_PTR(-EINVAL); - if (attr->map_flags & BPF_F_LINK && (!st_ops->validate || !st_ops->update)) - return ERR_PTR(-EOPNOTSUPP); - t = st_ops->type; st_map_size = sizeof(*st_map) + @@ -823,6 +823,9 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map if (!bpf_struct_ops_valid_to_reg(new_map)) return -EINVAL; + if (!st_map->st_ops->update) + return -EOPNOTSUPP; + mutex_lock(&update_mutex); old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also define the .validate() and .update() callbacks in its corresponding struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful in its own right to ensure that the map is unloaded if an application crashes. For example, with sched_ext, we want to automatically unload the host-wide scheduler if the application crashes. We would likely never support updating elements of a sched_ext struct_ops map, so we'd have to implement these callbacks showing that they _can't_ support element updates just to benefit from the basic lifetime management of struct_ops links. Let's enable struct_ops maps to work with BPF_F_LINK even if they haven't defined these callbacks, by assuming that a struct_ops map element cannot be updated by default. Signed-off-by: David Vernet <void@manifault.com> --- kernel/bpf/bpf_struct_ops.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)