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Subject[RFC v3 13/22] bpf/cgroup: Replace struct bpf_prog with union bpf_object
Date
This allows CONFIG_CGROUP_BPF to manage different type of pointers
instead of only eBPF programs. This will be useful for the next commits
to support Landlock with cgroups.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Daniel Mack <daniel@zonque.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Tejun Heo <tj@kernel.org>
---
include/linux/bpf-cgroup.h | 8 ++++++--
kernel/bpf/cgroup.c | 44 +++++++++++++++++++++++---------------------
2 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index fc076de74ab9..2234042d7f61 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -14,14 +14,18 @@ struct sk_buff;
extern struct static_key_false cgroup_bpf_enabled_key;
#define cgroup_bpf_enabled static_branch_unlikely(&cgroup_bpf_enabled_key)

+union bpf_object {
+ struct bpf_prog *prog;
+};
+
struct cgroup_bpf {
/*
* Store two sets of bpf_prog pointers, one for programs that are
* pinned directly to this cgroup, and one for those that are effective
* when this cgroup is accessed.
*/
- struct bpf_prog *prog[MAX_BPF_ATTACH_TYPE];
- struct bpf_prog *effective[MAX_BPF_ATTACH_TYPE];
+ union bpf_object pinned[MAX_BPF_ATTACH_TYPE];
+ union bpf_object effective[MAX_BPF_ATTACH_TYPE];
};

void cgroup_bpf_put(struct cgroup *cgrp);
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 21d168c3ad35..782878ec4f2d 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -20,18 +20,18 @@ DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);
EXPORT_SYMBOL(cgroup_bpf_enabled_key);

/**
- * cgroup_bpf_put() - put references of all bpf programs
+ * cgroup_bpf_put() - put references of all bpf objects
* @cgrp: the cgroup to modify
*/
void cgroup_bpf_put(struct cgroup *cgrp)
{
unsigned int type;

- for (type = 0; type < ARRAY_SIZE(cgrp->bpf.prog); type++) {
- struct bpf_prog *prog = cgrp->bpf.prog[type];
+ for (type = 0; type < ARRAY_SIZE(cgrp->bpf.pinned); type++) {
+ union bpf_object pinned = cgrp->bpf.pinned[type];

- if (prog) {
- bpf_prog_put(prog);
+ if (pinned.prog) {
+ bpf_prog_put(pinned.prog);
static_branch_dec(&cgroup_bpf_enabled_key);
}
}
@@ -47,11 +47,12 @@ void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent)
unsigned int type;

for (type = 0; type < ARRAY_SIZE(cgrp->bpf.effective); type++) {
- struct bpf_prog *e;
+ union bpf_object e;

- e = rcu_dereference_protected(parent->bpf.effective[type],
- lockdep_is_held(&cgroup_mutex));
- rcu_assign_pointer(cgrp->bpf.effective[type], e);
+ e.prog = rcu_dereference_protected(
+ parent->bpf.effective[type].prog,
+ lockdep_is_held(&cgroup_mutex));
+ rcu_assign_pointer(cgrp->bpf.effective[type].prog, e.prog);
}
}

@@ -87,32 +88,33 @@ void __cgroup_bpf_update(struct cgroup *cgrp,
struct bpf_prog *prog,
enum bpf_attach_type type)
{
- struct bpf_prog *old_prog, *effective;
+ union bpf_object obj, old_pinned, effective;
struct cgroup_subsys_state *pos;

- old_prog = xchg(cgrp->bpf.prog + type, prog);
+ obj.prog = prog;
+ old_pinned = xchg(cgrp->bpf.pinned + type, obj);

- effective = (!prog && parent) ?
- rcu_dereference_protected(parent->bpf.effective[type],
+ effective.prog = (!obj.prog && parent) ?
+ rcu_dereference_protected(parent->bpf.effective[type].prog,
lockdep_is_held(&cgroup_mutex)) :
- prog;
+ obj.prog;

css_for_each_descendant_pre(pos, &cgrp->self) {
struct cgroup *desc = container_of(pos, struct cgroup, self);

/* skip the subtree if the descendant has its own program */
- if (desc->bpf.prog[type] && desc != cgrp)
+ if (desc->bpf.pinned[type].prog && desc != cgrp)
pos = css_rightmost_descendant(pos);
else
- rcu_assign_pointer(desc->bpf.effective[type],
- effective);
+ rcu_assign_pointer(desc->bpf.effective[type].prog,
+ effective.prog);
}

- if (prog)
+ if (obj.prog)
static_branch_inc(&cgroup_bpf_enabled_key);

- if (old_prog) {
- bpf_prog_put(old_prog);
+ if (old_pinned.prog) {
+ bpf_prog_put(old_pinned.prog);
static_branch_dec(&cgroup_bpf_enabled_key);
}
}
@@ -151,7 +153,7 @@ int __cgroup_bpf_run_filter(struct sock *sk,

rcu_read_lock();

- prog = rcu_dereference(cgrp->bpf.effective[type]);
+ prog = rcu_dereference(cgrp->bpf.effective[type].prog);
if (prog) {
unsigned int offset = skb->data - skb_mac_header(skb);

--
2.9.3
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