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Date: Thu, 21 Nov 2019 17:36:09 +0000
From: Yonghong Song <yhs@...com>
To: Brian Vazquez <brianvv@...gle.com>,
Brian Vazquez <brianvv.kernel@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
"Daniel Borkmann" <daniel@...earbox.net>,
"David S . Miller" <davem@...emloft.net>
CC: Stanislav Fomichev <sdf@...gle.com>,
Petar Penkov <ppenkov@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 bpf-next 2/9] bpf: add generic support for lookup and
lookup_and_delete batch ops
On 11/19/19 11:30 AM, Brian Vazquez wrote:
> This commit introduces generic support for the bpf_map_lookup_batch and
> bpf_map_lookup_and_delete_batch ops. This implementation can be used by
> almost all the bpf maps since its core implementation is relying on the
> existing map_get_next_key, map_lookup_elem and map_delete_elem
> functions. The bpf syscall subcommands introduced are:
>
> BPF_MAP_LOOKUP_BATCH
> BPF_MAP_LOOKUP_AND_DELETE_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@...gle.com>
> Signed-off-by: Brian Vazquez <brianvv@...gle.com>
> Signed-off-by: Yonghong Song <yhs@...com>
> ---
> include/linux/bpf.h | 11 +++
> include/uapi/linux/bpf.h | 19 +++++
> kernel/bpf/syscall.c | 176 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 206 insertions(+)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 5b81cde47314e..767a823dbac74 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -41,6 +41,11 @@ 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);
> + int (*map_lookup_and_delete_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);
> @@ -797,6 +802,12 @@ void bpf_map_charge_move(struct bpf_map_memory *dst,
> void *bpf_map_area_alloc(size_t 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);
> +int generic_map_lookup_and_delete_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 4842a134b202a..e60b7b7cda61a 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -107,6 +107,8 @@ enum bpf_cmd {
> BPF_MAP_LOOKUP_AND_DELETE_ELEM,
> BPF_MAP_FREEZE,
> BPF_BTF_GET_NEXT_ID,
> + BPF_MAP_LOOKUP_BATCH,
> + BPF_MAP_LOOKUP_AND_DELETE_BATCH,
> };
>
> enum bpf_map_type {
> @@ -400,6 +402,23 @@ 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 cc714c9d5b4cc..d0d3d0e0eaca4 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1127,6 +1127,124 @@ static int map_get_next_key(union bpf_attr *attr)
> return err;
> }
>
> +static int __generic_map_lookup_batch(struct bpf_map *map,
> + const union bpf_attr *attr,
> + union bpf_attr __user *uattr,
> + bool do_delete)
> +{
> + void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
> + void __user *uobatch = u64_to_user_ptr(attr->batch.out_batch);
> + void __user *values = u64_to_user_ptr(attr->batch.values);
> + void __user *keys = u64_to_user_ptr(attr->batch.keys);
> + void *buf, *prev_key, *key, *value;
> + u32 value_size, cp, max_count;
> + bool first_key = false;
> + int err, retry = 3;
> +
> + if (attr->batch.elem_flags & ~BPF_F_LOCK)
> + return -EINVAL;
> +
> + if ((attr->batch.elem_flags & BPF_F_LOCK) &&
> + !map_value_has_spin_lock(map)) {
> + err = -EINVAL;
> + goto err_put;
> + }
Direct return -EINVAL?
> +
> + if (map->map_type == BPF_MAP_TYPE_QUEUE ||
> + map->map_type == BPF_MAP_TYPE_STACK) {
> + err = -ENOTSUPP;
> + goto err_put;
> + }
Direct return -ENOTSUPP?
> +
> + value_size = bpf_map_value_size(map);
> +
> + max_count = attr->batch.count;
> + if (!max_count)
> + return 0;
> +
> + err = -ENOMEM;
> + buf = kmalloc(map->key_size + value_size, GFP_USER | __GFP_NOWARN);
> + if (!buf)
> + goto err_put;
Direct return -ENOMEM?
> +
> + err = -EFAULT;
> + first_key = false;
> + if (ubatch && copy_from_user(buf, ubatch, map->key_size))
> + goto free_buf;
> + key = buf;
> + value = key + map->key_size;
> + if (!ubatch) {
> + prev_key = NULL;
> + first_key = true;
> + }
> +
> +
One extra line.
> + for (cp = 0; cp < max_count; cp++) {
> + if (cp || first_key) {
> + 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, do_delete);
> +
> + if (err == -ENOENT) {
> + if (retry) {
> + retry--;
What is the 'retry' semantics here? After 'continue', cp++ is executed.
> + continue;
> + }
> + err = -EINTR;
Why returning -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;
> + }
> +
> + prev_key = key;
> + retry = 3;
> + }
> + if (!err) {
> + rcu_read_lock();
> + err = map->ops->map_get_next_key(map, prev_key, key);
if err != 0, the 'key' will be invalid and it cannot be used by below
copy_to_user.
> + rcu_read_unlock();
> + } > +
> + if ((copy_to_user(&uattr->batch.count, &cp, sizeof(cp)) ||
The 'cp' may not be accurate if 'retry' is triggered in the above.
> + (copy_to_user(uobatch, key, map->key_size))))
> + err = -EFAULT;
> +
> +free_buf:
> + kfree(buf);
> +err_put:
err_put can be removed.
> + return err;
> +}
> +
> +int generic_map_lookup_batch(struct bpf_map *map,
> + const union bpf_attr *attr,
> + union bpf_attr __user *uattr)
> +{
> + return __generic_map_lookup_batch(map, attr, uattr, false);
> +}
> +
> +int generic_map_lookup_and_delete_batch(struct bpf_map *map,
> + const union bpf_attr *attr,
> + union bpf_attr __user *uattr)
> +{
> + return __generic_map_lookup_batch(map, attr, uattr, true);
> +}
> +
> #define BPF_MAP_LOOKUP_AND_DELETE_ELEM_LAST_FIELD value
>
> static int map_lookup_and_delete_elem(union bpf_attr *attr)
> @@ -2956,6 +3074,57 @@ 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 ||
> + cmd == BPF_MAP_LOOKUP_AND_DELETE_BATCH) &&
> + !(map_get_sys_perms(map, f) & FMODE_CAN_READ)) {
> + err = -EPERM;
> + goto err_put;
> + }
> +
> + if (cmd != BPF_MAP_LOOKUP_BATCH &&
Here should be BPF_MAP_LOOKUP_AND_DELETE_BATCH.
BPF_MAP_LOOKUP_BATCH does not need FMODE_CAN_WRITE.
> + !(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);
> + else
> + BPF_DO_BATCH(map->ops->map_lookup_and_delete_batch);
> +
> +err_put:
> + fdput(f);
> + return err;
> +}
> +
> SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
> {
> union bpf_attr attr = {};
> @@ -3053,6 +3222,13 @@ 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;
> + case BPF_MAP_LOOKUP_AND_DELETE_BATCH:
> + err = bpf_map_do_batch(&attr, uattr,
> + BPF_MAP_LOOKUP_AND_DELETE_BATCH);
> + break;
> default:
> err = -EINVAL;
> break;
>
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