Commit f9d04127 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

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: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-2-andriin@fb.com
parent 9b329d0d

include/linux/bpf-cgroup.h

+0 −12
Original line number Diff line number Diff line
@@ -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)

{

include/linux/bpf.h

+2 −1
Original line number Diff line number Diff line
@@ -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,

kernel/bpf/cgroup.c

+28 −2
Original line number Diff line number Diff line
@@ -557,7 +557,8 @@ found: 
 *

 * 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)

kernel/bpf/syscall.c

+4 −7
Original line number Diff line number Diff line
@@ -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)

kernel/cgroup/cgroup.c

+0 −27
Original line number Diff line number Diff line
@@ -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)

{

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