diff options
| -rw-r--r-- | include/linux/bpf.h | 2 | ||||
| -rw-r--r-- | kernel/bpf/trampoline.c | 77 |
2 files changed, 53 insertions, 26 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f615b56730d2..f6056bab6f23 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1353,8 +1353,6 @@ struct bpf_trampoline { /* hlist for trampoline_ip_table */ struct hlist_node hlist_ip; struct ftrace_ops *fops; - /* serializes access to fields of this trampoline */ - struct mutex mutex; refcount_t refcnt; u32 flags; u64 key; diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index a4298a25d4ba..c0b4732627be 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -30,6 +30,35 @@ static struct hlist_head trampoline_ip_table[TRAMPOLINE_TABLE_SIZE]; /* serializes access to trampoline tables */ static DEFINE_MUTEX(trampoline_mutex); +/* + * Keep 32 trampoline locks (5 bits) in the pool so trampoline_lock_all() + * stays below MAX_LOCK_DEPTH. Each pool slot has a distinct lockdep + * class because trampoline_lock_all() takes all pool mutexes at once; + * otherwise lockdep would report recursive locking on same-class mutexes. + */ +#define TRAMPOLINE_LOCKS_BITS 5 +#define TRAMPOLINE_LOCKS_TABLE_SIZE (1 << TRAMPOLINE_LOCKS_BITS) + +static struct { + struct mutex mutex; + struct lock_class_key key; +} trampoline_locks[TRAMPOLINE_LOCKS_TABLE_SIZE]; + +static struct mutex *select_trampoline_lock(struct bpf_trampoline *tr) +{ + return &trampoline_locks[hash_ptr(tr, TRAMPOLINE_LOCKS_BITS)].mutex; +} + +static void trampoline_lock(struct bpf_trampoline *tr) +{ + mutex_lock(select_trampoline_lock(tr)); +} + +static void trampoline_unlock(struct bpf_trampoline *tr) +{ + mutex_unlock(select_trampoline_lock(tr)); +} + #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex); @@ -69,9 +98,9 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip, if (cmd == FTRACE_OPS_CMD_ENABLE_SHARE_IPMODIFY_SELF) { /* This is called inside register_ftrace_direct_multi(), so - * tr->mutex is already locked. + * trampoline's mutex is already locked. */ - lockdep_assert_held_once(&tr->mutex); + lockdep_assert_held_once(select_trampoline_lock(tr)); /* Instead of updating the trampoline here, we propagate * -EAGAIN to register_ftrace_direct(). Then we can @@ -91,7 +120,7 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip, } /* The normal locking order is - * tr->mutex => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c) + * select_trampoline_lock(tr) => direct_mutex (ftrace.c) => ftrace_lock (ftrace.c) * * The following two commands are called from * @@ -99,12 +128,12 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip, * cleanup_direct_functions_after_ipmodify * * In both cases, direct_mutex is already locked. Use - * mutex_trylock(&tr->mutex) to avoid deadlock in race condition - * (something else is making changes to this same trampoline). + * mutex_trylock(select_trampoline_lock(tr)) to avoid deadlock in race condition + * (something else holds the same pool lock). */ - if (!mutex_trylock(&tr->mutex)) { - /* sleep 1 ms to make sure whatever holding tr->mutex makes - * some progress. + if (!mutex_trylock(select_trampoline_lock(tr))) { + /* sleep 1 ms to make sure whatever holding select_trampoline_lock(tr) + * makes some progress. */ msleep(1); return -EAGAIN; @@ -129,7 +158,7 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip, break; } - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); return ret; } #endif @@ -359,7 +388,6 @@ static struct bpf_trampoline *bpf_trampoline_lookup(u64 key, unsigned long ip) head = &trampoline_ip_table[hash_64(tr->ip, TRAMPOLINE_HASH_BITS)]; hlist_add_head(&tr->hlist_ip, head); refcount_set(&tr->refcnt, 1); - mutex_init(&tr->mutex); for (i = 0; i < BPF_TRAMP_MAX; i++) INIT_HLIST_HEAD(&tr->progs_hlist[i]); out: @@ -843,9 +871,9 @@ int bpf_trampoline_link_prog(struct bpf_tramp_link *link, { int err; - mutex_lock(&tr->mutex); + trampoline_lock(tr); err = __bpf_trampoline_link_prog(link, tr, tgt_prog); - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); return err; } @@ -886,9 +914,9 @@ int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, { int err; - mutex_lock(&tr->mutex); + trampoline_lock(tr); err = __bpf_trampoline_unlink_prog(link, tr, tgt_prog); - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); return err; } @@ -998,12 +1026,12 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog, if (!tr) return -ENOMEM; - mutex_lock(&tr->mutex); + trampoline_lock(tr); shim_link = cgroup_shim_find(tr, bpf_func); if (shim_link && !IS_ERR(bpf_link_inc_not_zero(&shim_link->link.link))) { /* Reusing existing shim attached by the other program. */ - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); bpf_trampoline_put(tr); /* bpf_trampoline_get above */ return 0; } @@ -1023,16 +1051,16 @@ int bpf_trampoline_link_cgroup_shim(struct bpf_prog *prog, shim_link->trampoline = tr; /* note, we're still holding tr refcnt from above */ - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); return 0; err: - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); if (shim_link) bpf_link_put(&shim_link->link.link); - /* have to release tr while _not_ holding its mutex */ + /* have to release tr while _not_ holding pool mutex for trampoline */ bpf_trampoline_put(tr); /* bpf_trampoline_get above */ return err; @@ -1053,9 +1081,9 @@ void bpf_trampoline_unlink_cgroup_shim(struct bpf_prog *prog) if (WARN_ON_ONCE(!tr)) return; - mutex_lock(&tr->mutex); + trampoline_lock(tr); shim_link = cgroup_shim_find(tr, bpf_func); - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); if (shim_link) bpf_link_put(&shim_link->link.link); @@ -1073,14 +1101,14 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key, if (!tr) return NULL; - mutex_lock(&tr->mutex); + trampoline_lock(tr); if (tr->func.addr) goto out; memcpy(&tr->func.model, &tgt_info->fmodel, sizeof(tgt_info->fmodel)); tr->func.addr = (void *)tgt_info->tgt_addr; out: - mutex_unlock(&tr->mutex); + trampoline_unlock(tr); return tr; } @@ -1093,7 +1121,6 @@ void bpf_trampoline_put(struct bpf_trampoline *tr) mutex_lock(&trampoline_mutex); if (!refcount_dec_and_test(&tr->refcnt)) goto out; - WARN_ON_ONCE(mutex_is_locked(&tr->mutex)); for (i = 0; i < BPF_TRAMP_MAX; i++) if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[i]))) @@ -1379,6 +1406,8 @@ static int __init init_trampolines(void) INIT_HLIST_HEAD(&trampoline_key_table[i]); for (i = 0; i < TRAMPOLINE_TABLE_SIZE; i++) INIT_HLIST_HEAD(&trampoline_ip_table[i]); + for (i = 0; i < TRAMPOLINE_LOCKS_TABLE_SIZE; i++) + __mutex_init(&trampoline_locks[i].mutex, "trampoline_lock", &trampoline_locks[i].key); return 0; } late_initcall(init_trampolines); |