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bpf: Refactor bpf_link update handling 

Make bpf_link update support more generic by making it into another
bpf_link_ops methods. This allows generic syscall handling code to be agnostic
to various conditionally compiled features (e.g., the case of
CONFIG_CGROUP_BPF). This also allows to keep link type-specific code to remain
static within respective code base. Refactor existing bpf_cgroup_link code and
take advantage of this.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-04-28 17:16:05 -07:00 committed by Alexei Starovoitov
parent 9b329d0dbe
commit f9d041271c
5 changed files with 34 additions and 49 deletions
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12
include/linux/bpf-cgroup.h
View File

@ -100,8 +100,6 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
struct bpf_cgroup_link *link,
enum bpf_attach_type type);
int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
struct bpf_prog *new_prog);
int __cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
union bpf_attr __user *uattr);
@ -112,8 +110,6 @@ int cgroup_bpf_attach(struct cgroup *cgrp,
u32 flags);
int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
enum bpf_attach_type type);
int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *old_prog,
struct bpf_prog *new_prog);
int cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
union bpf_attr __user *uattr);
@ -353,7 +349,6 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr,
#else
struct bpf_prog;
struct bpf_link;
struct cgroup_bpf {};
static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
static inline void cgroup_bpf_offline(struct cgroup *cgrp) {}
@ -377,13 +372,6 @@ static inline int cgroup_bpf_link_attach(const union bpf_attr *attr,
return -EINVAL;
}
static inline int cgroup_bpf_replace(struct bpf_link *link,
struct bpf_prog *old_prog,
struct bpf_prog *new_prog)
{
return -EINVAL;
}
static inline int cgroup_bpf_prog_query(const union bpf_attr *attr,
union bpf_attr __user *uattr)
{

3
include/linux/bpf.h
View File

@ -1093,7 +1093,8 @@ struct bpf_link {
struct bpf_link_ops {
void (*release)(struct bpf_link *link);
void (*dealloc)(struct bpf_link *link);
int (*update_prog)(struct bpf_link *link, struct bpf_prog *new_prog,
struct bpf_prog *old_prog);
};
void bpf_link_init(struct bpf_link *link, const struct bpf_link_ops *ops,

28
kernel/bpf/cgroup.c
View File

@ -557,7 +557,8 @@ static void replace_effective_prog(struct cgroup *cgrp,
*
* Must be called with cgroup_mutex held.
*/
int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
static int __cgroup_bpf_replace(struct cgroup *cgrp,
struct bpf_cgroup_link *link,
struct bpf_prog *new_prog)
{
struct list_head *progs = &cgrp->bpf.progs[link->type];
@ -583,6 +584,30 @@ int __cgroup_bpf_replace(struct cgroup *cgrp, struct bpf_cgroup_link *link,
return 0;
}
static int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *new_prog,
struct bpf_prog *old_prog)
{
struct bpf_cgroup_link *cg_link;
int ret;
cg_link = container_of(link, struct bpf_cgroup_link, link);
mutex_lock(&cgroup_mutex);
/* link might have been auto-released by dying cgroup, so fail */
if (!cg_link->cgroup) {
ret = -EINVAL;
goto out_unlock;
}
if (old_prog && link->prog != old_prog) {
ret = -EPERM;
goto out_unlock;
}
ret = __cgroup_bpf_replace(cg_link->cgroup, cg_link, new_prog);
out_unlock:
mutex_unlock(&cgroup_mutex);
return ret;
}
static struct bpf_prog_list *find_detach_entry(struct list_head *progs,
struct bpf_prog *prog,
struct bpf_cgroup_link *link,
@ -811,6 +836,7 @@ static void bpf_cgroup_link_dealloc(struct bpf_link *link)
const struct bpf_link_ops bpf_cgroup_link_lops = {
.release = bpf_cgroup_link_release,
.dealloc = bpf_cgroup_link_dealloc,
.update_prog = cgroup_bpf_replace,
};
int cgroup_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)

11
kernel/bpf/syscall.c
View File

@ -3645,13 +3645,10 @@ static int link_update(union bpf_attr *attr)
goto out_put_progs;
}
#ifdef CONFIG_CGROUP_BPF
if (link->ops == &bpf_cgroup_link_lops) {
ret = cgroup_bpf_replace(link, old_prog, new_prog);
goto out_put_progs;
}
#endif
ret = -EINVAL;
if (link->ops->update_prog)
ret = link->ops->update_prog(link, new_prog, old_prog);
else
ret = EINVAL;
out_put_progs:
if (old_prog)

27
kernel/cgroup/cgroup.c
View File

@ -6508,33 +6508,6 @@ int cgroup_bpf_attach(struct cgroup *cgrp,
return ret;
}
int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *old_prog,
struct bpf_prog *new_prog)
{
struct bpf_cgroup_link *cg_link;
int ret;
if (link->ops != &bpf_cgroup_link_lops)
return -EINVAL;
cg_link = container_of(link, struct bpf_cgroup_link, link);
mutex_lock(&cgroup_mutex);
/* link might have been auto-released by dying cgroup, so fail */
if (!cg_link->cgroup) {
ret = -EINVAL;
goto out_unlock;
}
if (old_prog && link->prog != old_prog) {
ret = -EPERM;
goto out_unlock;
}
ret = __cgroup_bpf_replace(cg_link->cgroup, cg_link, new_prog);
out_unlock:
mutex_unlock(&cgroup_mutex);
return ret;
}
int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
enum bpf_attach_type type)
{