[PATCH v4 bpf-next 2/9] bpf: add generic support for lookup batch op

Brian Vazquez
2020-01-14T16:46:43Z

This commit introduces generic support for the bpf_map_lookup_batch.
This implementation can be used by almost all the bpf maps since its core
implementation is relying on the existing map_get_next_key and
map_lookup_elem. The bpf syscall subcommand introduced is:

BPF_MAP_LOOKUP_BATCH

The UAPI attribute is:

struct { /* struct used by BPF_MAP_*_BATCH commands */
__aligned_u64 in_batch; /* start batch,
* NULL to start from beginning
*/
__aligned_u64 out_batch; /* output: next start batch */
__aligned_u64 keys;
__aligned_u64 values;
__u32 count; /* input/output:
* input: # of key/value
* elements
* output: # of filled elements
*/
__u32 map_fd;
__u64 elem_flags;
__u64 flags;
} batch;

in_batch/out_batch are opaque values use to communicate between
user/kernel space, in_batch/out_batch must be of key_size length.

To start iterating from the beginning in_batch must be null,
count is the # of key/value elements to retrieve. Note that the 'keys'
buffer must be a buffer of key_size * count size and the 'values' buffer
must be value_size * count, where value_size must be aligned to 8 bytes
by userspace if it's dealing with percpu maps. 'count' will contain the
number of keys/values successfully retrieved. Note that 'count' is an
input/output variable and it can contain a lower value after a call.

If there's no more entries to retrieve, ENOENT will be returned. If error
is ENOENT, count might be > 0 in case it copied some values but there were
no more entries to retrieve.

Note that if the return code is an error and not -EFAULT,
count indicates the number of elements successfully processed.

Suggested-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Brian Vazquez <brianvv@google.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
include/linux/bpf.h | 5 ++
include/uapi/linux/bpf.h | 18 +++++
kernel/bpf/syscall.c | 154 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 173 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index aed2bc39d72b6..807744ecaa5a1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -44,6 +44,8 @@ struct bpf_map_ops {
int (*map_get_next_key)(struct bpf_map *map, void *key, void *next_key);
void (*map_release_uref)(struct bpf_map *map);
void *(*map_lookup_elem_sys_only)(struct bpf_map *map, void *key);
+ int (*map_lookup_batch)(struct bpf_map *map, const union bpf_attr *attr,
+ union bpf_attr __user *uattr);

/* funcs callable from userspace and from eBPF programs */
void *(*map_lookup_elem)(struct bpf_map *map, void *key);
@@ -982,6 +984,9 @@ void *bpf_map_area_alloc(u64 size, int numa_node);
void *bpf_map_area_mmapable_alloc(u64 size, int numa_node);
void bpf_map_area_free(void *base);
void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
+int generic_map_lookup_batch(struct bpf_map *map,
+ const union bpf_attr *attr,
+ union bpf_attr __user *uattr);

extern int sysctl_unprivileged_bpf_disabled;

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 52966e758fe59..8185f1542daa1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -107,6 +107,7 @@ enum bpf_cmd {
BPF_MAP_LOOKUP_AND_DELETE_ELEM,
BPF_MAP_FREEZE,
BPF_BTF_GET_NEXT_ID,
+ BPF_MAP_LOOKUP_BATCH,
};

enum bpf_map_type {
@@ -420,6 +421,23 @@ union bpf_attr {
__u64 flags;
};

+ struct { /* struct used by BPF_MAP_*_BATCH commands */
+ __aligned_u64 in_batch; /* start batch,
+ * NULL to start from beginning
+ */
+ __aligned_u64 out_batch; /* output: next start batch */
+ __aligned_u64 keys;
+ __aligned_u64 values;
+ __u32 count; /* input/output:
+ * input: # of key/value
+ * elements
+ * output: # of filled elements
+ */
+ __u32 map_fd;
+ __u64 elem_flags;
+ __u64 flags;
+ } batch;
+
struct { /* anonymous struct used by BPF_PROG_LOAD command */
__u32 prog_type; /* one of enum bpf_prog_type */
__u32 insn_cnt;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 08b0b6e40454b..d4acb6eb5ef9e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -219,10 +219,8 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
void *ptr;
int err;

- if (bpf_map_is_dev_bound(map)) {
- err = bpf_map_offload_lookup_elem(map, key, value);
- return err;
- }
+ if (bpf_map_is_dev_bound(map))
+ return bpf_map_offload_lookup_elem(map, key, value);

preempt_disable();
this_cpu_inc(bpf_prog_active);
@@ -1220,6 +1218,103 @@ static int map_get_next_key(union bpf_attr *attr)
return err;
}

+#define MAP_LOOKUP_RETRIES 3
+
+int generic_map_lookup_batch(struct bpf_map *map,
+ const union bpf_attr *attr,
+ union bpf_attr __user *uattr)
+{
+ void __user *uobatch = u64_to_user_ptr(attr->batch.out_batch);
+ void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
+ void __user *values = u64_to_user_ptr(attr->batch.values);
+ void __user *keys = u64_to_user_ptr(attr->batch.keys);
+ void *buf, *buf_prevkey, *prev_key, *key, *value;
+ int err, retry = MAP_LOOKUP_RETRIES;
+ u32 value_size, cp, max_count;
+ bool first_key = false;
+
+ if (attr->batch.elem_flags & ~BPF_F_LOCK)
+ return -EINVAL;
+
+ if ((attr->batch.elem_flags & BPF_F_LOCK) &&
+ !map_value_has_spin_lock(map))
+ return -EINVAL;
+
+ value_size = bpf_map_value_size(map);
+
+ max_count = attr->batch.count;
+ if (!max_count)
+ return 0;
+
+ buf_prevkey = kmalloc(map->key_size, GFP_USER | __GFP_NOWARN);
+ if (!buf_prevkey)
+ return -ENOMEM;
+
+ buf = kmalloc(map->key_size + value_size, GFP_USER | __GFP_NOWARN);
+ if (!buf) {
+ kvfree(buf_prevkey);
+ return -ENOMEM;
+ }
+
+ err = -EFAULT;
+ first_key = false;
+ prev_key = NULL;
+ if (ubatch && copy_from_user(buf_prevkey, ubatch, map->key_size))
+ goto free_buf;
+ key = buf;
+ value = key + map->key_size;
+ if (ubatch)
+ prev_key = buf_prevkey;
+
+ for (cp = 0; cp < max_count;) {
+ rcu_read_lock();
+ err = map->ops->map_get_next_key(map, prev_key, key);
+ rcu_read_unlock();
+ if (err)
+ break;
+ err = bpf_map_copy_value(map, key, value,
+ attr->batch.elem_flags);
+
+ if (err == -ENOENT) {
+ if (retry) {
+ retry--;
+ continue;
+ }
+ err = -EINTR;
+ break;
+ }
+
+ if (err)
+ goto free_buf;
+
+ if (copy_to_user(keys + cp * map->key_size, key,
+ map->key_size)) {
+ err = -EFAULT;
+ goto free_buf;
+ }
+ if (copy_to_user(values + cp * value_size, value, value_size)) {
+ err = -EFAULT;
+ goto free_buf;
+ }
+
+ if (!prev_key)
+ prev_key = buf_prevkey;
+
+ swap(prev_key, key);
+ retry = MAP_LOOKUP_RETRIES;
+ cp++;
+ }
+
+ if ((copy_to_user(&uattr->batch.count, &cp, sizeof(cp)) ||
+ (cp && copy_to_user(uobatch, prev_key, map->key_size))))
+ err = -EFAULT;
+
+free_buf:
+ kfree(buf_prevkey);
+ kfree(buf);
+ return err;
+}
+
#define BPF_MAP_LOOKUP_AND_DELETE_ELEM_LAST_FIELD value

static int map_lookup_and_delete_elem(union bpf_attr *attr)
@@ -3076,6 +3171,54 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
return err;
}

+#define BPF_MAP_BATCH_LAST_FIELD batch.flags
+
+#define BPF_DO_BATCH(fn) \
+ do { \
+ if (!fn) { \
+ err = -ENOTSUPP; \
+ goto err_put; \
+ } \
+ err = fn(map, attr, uattr); \
+ } while (0)
+
+static int bpf_map_do_batch(const union bpf_attr *attr,
+ union bpf_attr __user *uattr,
+ int cmd)
+{
+ struct bpf_map *map;
+ int err, ufd;
+ struct fd f;
+
+ if (CHECK_ATTR(BPF_MAP_BATCH))
+ return -EINVAL;
+
+ ufd = attr->batch.map_fd;
+ f = fdget(ufd);
+ map = __bpf_map_get(f);
+ if (IS_ERR(map))
+ return PTR_ERR(map);
+
+ if (cmd == BPF_MAP_LOOKUP_BATCH &&
+ !(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
+ if (cmd != BPF_MAP_LOOKUP_BATCH &&
+ !(map_get_sys_perms(map, f) & FMODE_CAN_WRITE)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
+ if (cmd == BPF_MAP_LOOKUP_BATCH)
+ BPF_DO_BATCH(map->ops->map_lookup_batch);
+
+err_put:
+ fdput(f);
+ return err;
+}
+
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr = {};
@@ -3173,6 +3316,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_MAP_LOOKUP_AND_DELETE_ELEM:
err = map_lookup_and_delete_elem(&attr);
break;
+ case BPF_MAP_LOOKUP_BATCH:
+ err = bpf_map_do_batch(&attr, uattr, BPF_MAP_LOOKUP_BATCH);
+ break;
default:
err = -EINVAL;
break;
--
2.25.0.rc1.283.g88dfdc4193-goog