v4.19.13 snapshot.
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
new file mode 100644
index 0000000..141710b
--- /dev/null
+++ b/kernel/bpf/devmap.c
@@ -0,0 +1,545 @@
+/* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+/* Devmaps primary use is as a backend map for XDP BPF helper call
+ * bpf_redirect_map(). Because XDP is mostly concerned with performance we
+ * spent some effort to ensure the datapath with redirect maps does not use
+ * any locking. This is a quick note on the details.
+ *
+ * We have three possible paths to get into the devmap control plane bpf
+ * syscalls, bpf programs, and driver side xmit/flush operations. A bpf syscall
+ * will invoke an update, delete, or lookup operation. To ensure updates and
+ * deletes appear atomic from the datapath side xchg() is used to modify the
+ * netdev_map array. Then because the datapath does a lookup into the netdev_map
+ * array (read-only) from an RCU critical section we use call_rcu() to wait for
+ * an rcu grace period before free'ing the old data structures. This ensures the
+ * datapath always has a valid copy. However, the datapath does a "flush"
+ * operation that pushes any pending packets in the driver outside the RCU
+ * critical section. Each bpf_dtab_netdev tracks these pending operations using
+ * an atomic per-cpu bitmap. The bpf_dtab_netdev object will not be destroyed
+ * until all bits are cleared indicating outstanding flush operations have
+ * completed.
+ *
+ * BPF syscalls may race with BPF program calls on any of the update, delete
+ * or lookup operations. As noted above the xchg() operation also keep the
+ * netdev_map consistent in this case. From the devmap side BPF programs
+ * calling into these operations are the same as multiple user space threads
+ * making system calls.
+ *
+ * Finally, any of the above may race with a netdev_unregister notifier. The
+ * unregister notifier must search for net devices in the map structure that
+ * contain a reference to the net device and remove them. This is a two step
+ * process (a) dereference the bpf_dtab_netdev object in netdev_map and (b)
+ * check to see if the ifindex is the same as the net_device being removed.
+ * When removing the dev a cmpxchg() is used to ensure the correct dev is
+ * removed, in the case of a concurrent update or delete operation it is
+ * possible that the initially referenced dev is no longer in the map. As the
+ * notifier hook walks the map we know that new dev references can not be
+ * added by the user because core infrastructure ensures dev_get_by_index()
+ * calls will fail at this point.
+ */
+#include <linux/bpf.h>
+#include <net/xdp.h>
+#include <linux/filter.h>
+#include <trace/events/xdp.h>
+
+#define DEV_CREATE_FLAG_MASK \
+ (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
+
+#define DEV_MAP_BULK_SIZE 16
+struct xdp_bulk_queue {
+ struct xdp_frame *q[DEV_MAP_BULK_SIZE];
+ struct net_device *dev_rx;
+ unsigned int count;
+};
+
+struct bpf_dtab_netdev {
+ struct net_device *dev; /* must be first member, due to tracepoint */
+ struct bpf_dtab *dtab;
+ unsigned int bit;
+ struct xdp_bulk_queue __percpu *bulkq;
+ struct rcu_head rcu;
+};
+
+struct bpf_dtab {
+ struct bpf_map map;
+ struct bpf_dtab_netdev **netdev_map;
+ unsigned long __percpu *flush_needed;
+ struct list_head list;
+};
+
+static DEFINE_SPINLOCK(dev_map_lock);
+static LIST_HEAD(dev_map_list);
+
+static u64 dev_map_bitmap_size(const union bpf_attr *attr)
+{
+ return BITS_TO_LONGS((u64) attr->max_entries) * sizeof(unsigned long);
+}
+
+static struct bpf_map *dev_map_alloc(union bpf_attr *attr)
+{
+ struct bpf_dtab *dtab;
+ int err = -EINVAL;
+ u64 cost;
+
+ if (!capable(CAP_NET_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ /* check sanity of attributes */
+ if (attr->max_entries == 0 || attr->key_size != 4 ||
+ attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
+ return ERR_PTR(-EINVAL);
+
+ dtab = kzalloc(sizeof(*dtab), GFP_USER);
+ if (!dtab)
+ return ERR_PTR(-ENOMEM);
+
+ bpf_map_init_from_attr(&dtab->map, attr);
+
+ /* make sure page count doesn't overflow */
+ cost = (u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *);
+ cost += dev_map_bitmap_size(attr) * num_possible_cpus();
+ if (cost >= U32_MAX - PAGE_SIZE)
+ goto free_dtab;
+
+ dtab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
+
+ /* if map size is larger than memlock limit, reject it early */
+ err = bpf_map_precharge_memlock(dtab->map.pages);
+ if (err)
+ goto free_dtab;
+
+ err = -ENOMEM;
+
+ /* A per cpu bitfield with a bit per possible net device */
+ dtab->flush_needed = __alloc_percpu_gfp(dev_map_bitmap_size(attr),
+ __alignof__(unsigned long),
+ GFP_KERNEL | __GFP_NOWARN);
+ if (!dtab->flush_needed)
+ goto free_dtab;
+
+ dtab->netdev_map = bpf_map_area_alloc(dtab->map.max_entries *
+ sizeof(struct bpf_dtab_netdev *),
+ dtab->map.numa_node);
+ if (!dtab->netdev_map)
+ goto free_dtab;
+
+ spin_lock(&dev_map_lock);
+ list_add_tail_rcu(&dtab->list, &dev_map_list);
+ spin_unlock(&dev_map_lock);
+
+ return &dtab->map;
+free_dtab:
+ free_percpu(dtab->flush_needed);
+ kfree(dtab);
+ return ERR_PTR(err);
+}
+
+static void dev_map_free(struct bpf_map *map)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ int i, cpu;
+
+ /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
+ * so the programs (can be more than one that used this map) were
+ * disconnected from events. Wait for outstanding critical sections in
+ * these programs to complete. The rcu critical section only guarantees
+ * no further reads against netdev_map. It does __not__ ensure pending
+ * flush operations (if any) are complete.
+ */
+
+ spin_lock(&dev_map_lock);
+ list_del_rcu(&dtab->list);
+ spin_unlock(&dev_map_lock);
+
+ bpf_clear_redirect_map(map);
+ synchronize_rcu();
+
+ /* To ensure all pending flush operations have completed wait for flush
+ * bitmap to indicate all flush_needed bits to be zero on _all_ cpus.
+ * Because the above synchronize_rcu() ensures the map is disconnected
+ * from the program we can assume no new bits will be set.
+ */
+ for_each_online_cpu(cpu) {
+ unsigned long *bitmap = per_cpu_ptr(dtab->flush_needed, cpu);
+
+ while (!bitmap_empty(bitmap, dtab->map.max_entries))
+ cond_resched();
+ }
+
+ for (i = 0; i < dtab->map.max_entries; i++) {
+ struct bpf_dtab_netdev *dev;
+
+ dev = dtab->netdev_map[i];
+ if (!dev)
+ continue;
+
+ dev_put(dev->dev);
+ kfree(dev);
+ }
+
+ free_percpu(dtab->flush_needed);
+ bpf_map_area_free(dtab->netdev_map);
+ kfree(dtab);
+}
+
+static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ u32 index = key ? *(u32 *)key : U32_MAX;
+ u32 *next = next_key;
+
+ if (index >= dtab->map.max_entries) {
+ *next = 0;
+ return 0;
+ }
+
+ if (index == dtab->map.max_entries - 1)
+ return -ENOENT;
+ *next = index + 1;
+ return 0;
+}
+
+void __dev_map_insert_ctx(struct bpf_map *map, u32 bit)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ unsigned long *bitmap = this_cpu_ptr(dtab->flush_needed);
+
+ __set_bit(bit, bitmap);
+}
+
+static int bq_xmit_all(struct bpf_dtab_netdev *obj,
+ struct xdp_bulk_queue *bq, u32 flags,
+ bool in_napi_ctx)
+{
+ struct net_device *dev = obj->dev;
+ int sent = 0, drops = 0, err = 0;
+ int i;
+
+ if (unlikely(!bq->count))
+ return 0;
+
+ for (i = 0; i < bq->count; i++) {
+ struct xdp_frame *xdpf = bq->q[i];
+
+ prefetch(xdpf);
+ }
+
+ sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
+ if (sent < 0) {
+ err = sent;
+ sent = 0;
+ goto error;
+ }
+ drops = bq->count - sent;
+out:
+ bq->count = 0;
+
+ trace_xdp_devmap_xmit(&obj->dtab->map, obj->bit,
+ sent, drops, bq->dev_rx, dev, err);
+ bq->dev_rx = NULL;
+ return 0;
+error:
+ /* If ndo_xdp_xmit fails with an errno, no frames have been
+ * xmit'ed and it's our responsibility to them free all.
+ */
+ for (i = 0; i < bq->count; i++) {
+ struct xdp_frame *xdpf = bq->q[i];
+
+ /* RX path under NAPI protection, can return frames faster */
+ if (likely(in_napi_ctx))
+ xdp_return_frame_rx_napi(xdpf);
+ else
+ xdp_return_frame(xdpf);
+ drops++;
+ }
+ goto out;
+}
+
+/* __dev_map_flush is called from xdp_do_flush_map() which _must_ be signaled
+ * from the driver before returning from its napi->poll() routine. The poll()
+ * routine is called either from busy_poll context or net_rx_action signaled
+ * from NET_RX_SOFTIRQ. Either way the poll routine must complete before the
+ * net device can be torn down. On devmap tear down we ensure the ctx bitmap
+ * is zeroed before completing to ensure all flush operations have completed.
+ */
+void __dev_map_flush(struct bpf_map *map)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ unsigned long *bitmap = this_cpu_ptr(dtab->flush_needed);
+ u32 bit;
+
+ for_each_set_bit(bit, bitmap, map->max_entries) {
+ struct bpf_dtab_netdev *dev = READ_ONCE(dtab->netdev_map[bit]);
+ struct xdp_bulk_queue *bq;
+
+ /* This is possible if the dev entry is removed by user space
+ * between xdp redirect and flush op.
+ */
+ if (unlikely(!dev))
+ continue;
+
+ __clear_bit(bit, bitmap);
+
+ bq = this_cpu_ptr(dev->bulkq);
+ bq_xmit_all(dev, bq, XDP_XMIT_FLUSH, true);
+ }
+}
+
+/* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or
+ * update happens in parallel here a dev_put wont happen until after reading the
+ * ifindex.
+ */
+struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ struct bpf_dtab_netdev *obj;
+
+ if (key >= map->max_entries)
+ return NULL;
+
+ obj = READ_ONCE(dtab->netdev_map[key]);
+ return obj;
+}
+
+/* Runs under RCU-read-side, plus in softirq under NAPI protection.
+ * Thus, safe percpu variable access.
+ */
+static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
+ struct net_device *dev_rx)
+
+{
+ struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
+
+ if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
+ bq_xmit_all(obj, bq, 0, true);
+
+ /* Ingress dev_rx will be the same for all xdp_frame's in
+ * bulk_queue, because bq stored per-CPU and must be flushed
+ * from net_device drivers NAPI func end.
+ */
+ if (!bq->dev_rx)
+ bq->dev_rx = dev_rx;
+
+ bq->q[bq->count++] = xdpf;
+ return 0;
+}
+
+int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
+ struct net_device *dev_rx)
+{
+ struct net_device *dev = dst->dev;
+ struct xdp_frame *xdpf;
+ int err;
+
+ if (!dev->netdev_ops->ndo_xdp_xmit)
+ return -EOPNOTSUPP;
+
+ err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
+ if (unlikely(err))
+ return err;
+
+ xdpf = convert_to_xdp_frame(xdp);
+ if (unlikely(!xdpf))
+ return -EOVERFLOW;
+
+ return bq_enqueue(dst, xdpf, dev_rx);
+}
+
+int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
+ struct bpf_prog *xdp_prog)
+{
+ int err;
+
+ err = xdp_ok_fwd_dev(dst->dev, skb->len);
+ if (unlikely(err))
+ return err;
+ skb->dev = dst->dev;
+ generic_xdp_tx(skb, xdp_prog);
+
+ return 0;
+}
+
+static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
+{
+ struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
+ struct net_device *dev = obj ? obj->dev : NULL;
+
+ return dev ? &dev->ifindex : NULL;
+}
+
+static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
+{
+ if (dev->dev->netdev_ops->ndo_xdp_xmit) {
+ struct xdp_bulk_queue *bq;
+ unsigned long *bitmap;
+
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ bitmap = per_cpu_ptr(dev->dtab->flush_needed, cpu);
+ __clear_bit(dev->bit, bitmap);
+
+ bq = per_cpu_ptr(dev->bulkq, cpu);
+ bq_xmit_all(dev, bq, XDP_XMIT_FLUSH, false);
+ }
+ }
+}
+
+static void __dev_map_entry_free(struct rcu_head *rcu)
+{
+ struct bpf_dtab_netdev *dev;
+
+ dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
+ dev_map_flush_old(dev);
+ free_percpu(dev->bulkq);
+ dev_put(dev->dev);
+ kfree(dev);
+}
+
+static int dev_map_delete_elem(struct bpf_map *map, void *key)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ struct bpf_dtab_netdev *old_dev;
+ int k = *(u32 *)key;
+
+ if (k >= map->max_entries)
+ return -EINVAL;
+
+ /* Use call_rcu() here to ensure any rcu critical sections have
+ * completed, but this does not guarantee a flush has happened
+ * yet. Because driver side rcu_read_lock/unlock only protects the
+ * running XDP program. However, for pending flush operations the
+ * dev and ctx are stored in another per cpu map. And additionally,
+ * the driver tear down ensures all soft irqs are complete before
+ * removing the net device in the case of dev_put equals zero.
+ */
+ old_dev = xchg(&dtab->netdev_map[k], NULL);
+ if (old_dev)
+ call_rcu(&old_dev->rcu, __dev_map_entry_free);
+ return 0;
+}
+
+static int dev_map_update_elem(struct bpf_map *map, void *key, void *value,
+ u64 map_flags)
+{
+ struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+ struct net *net = current->nsproxy->net_ns;
+ gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN;
+ struct bpf_dtab_netdev *dev, *old_dev;
+ u32 i = *(u32 *)key;
+ u32 ifindex = *(u32 *)value;
+
+ if (unlikely(map_flags > BPF_EXIST))
+ return -EINVAL;
+ if (unlikely(i >= dtab->map.max_entries))
+ return -E2BIG;
+ if (unlikely(map_flags == BPF_NOEXIST))
+ return -EEXIST;
+
+ if (!ifindex) {
+ dev = NULL;
+ } else {
+ dev = kmalloc_node(sizeof(*dev), gfp, map->numa_node);
+ if (!dev)
+ return -ENOMEM;
+
+ dev->bulkq = __alloc_percpu_gfp(sizeof(*dev->bulkq),
+ sizeof(void *), gfp);
+ if (!dev->bulkq) {
+ kfree(dev);
+ return -ENOMEM;
+ }
+
+ dev->dev = dev_get_by_index(net, ifindex);
+ if (!dev->dev) {
+ free_percpu(dev->bulkq);
+ kfree(dev);
+ return -EINVAL;
+ }
+
+ dev->bit = i;
+ dev->dtab = dtab;
+ }
+
+ /* Use call_rcu() here to ensure rcu critical sections have completed
+ * Remembering the driver side flush operation will happen before the
+ * net device is removed.
+ */
+ old_dev = xchg(&dtab->netdev_map[i], dev);
+ if (old_dev)
+ call_rcu(&old_dev->rcu, __dev_map_entry_free);
+
+ return 0;
+}
+
+const struct bpf_map_ops dev_map_ops = {
+ .map_alloc = dev_map_alloc,
+ .map_free = dev_map_free,
+ .map_get_next_key = dev_map_get_next_key,
+ .map_lookup_elem = dev_map_lookup_elem,
+ .map_update_elem = dev_map_update_elem,
+ .map_delete_elem = dev_map_delete_elem,
+ .map_check_btf = map_check_no_btf,
+};
+
+static int dev_map_notification(struct notifier_block *notifier,
+ ulong event, void *ptr)
+{
+ struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
+ struct bpf_dtab *dtab;
+ int i;
+
+ switch (event) {
+ case NETDEV_UNREGISTER:
+ /* This rcu_read_lock/unlock pair is needed because
+ * dev_map_list is an RCU list AND to ensure a delete
+ * operation does not free a netdev_map entry while we
+ * are comparing it against the netdev being unregistered.
+ */
+ rcu_read_lock();
+ list_for_each_entry_rcu(dtab, &dev_map_list, list) {
+ for (i = 0; i < dtab->map.max_entries; i++) {
+ struct bpf_dtab_netdev *dev, *odev;
+
+ dev = READ_ONCE(dtab->netdev_map[i]);
+ if (!dev ||
+ dev->dev->ifindex != netdev->ifindex)
+ continue;
+ odev = cmpxchg(&dtab->netdev_map[i], dev, NULL);
+ if (dev == odev)
+ call_rcu(&dev->rcu,
+ __dev_map_entry_free);
+ }
+ }
+ rcu_read_unlock();
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block dev_map_notifier = {
+ .notifier_call = dev_map_notification,
+};
+
+static int __init dev_map_init(void)
+{
+ /* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
+ BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
+ offsetof(struct _bpf_dtab_netdev, dev));
+ register_netdevice_notifier(&dev_map_notifier);
+ return 0;
+}
+
+subsys_initcall(dev_map_init);