Date:   Thu, 4 Oct 2018 16:57:15 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Mauricio Vasquez B <mauricio.vasquez@...ito.it>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next v4 4/7] bpf: add bpf queue and stack maps

On Thu, Oct 04, 2018 at 07:12:44PM +0200, Mauricio Vasquez B wrote:
> Implement two new kind of maps that support the peek, push and pop
> operations.
> 
> A use case for this is to keep track of a pool of elements, like
> network ports in a SNAT.
> 
> Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@...ito.it>
> ---
>  include/linux/bpf.h           |    7 +
>  include/linux/bpf_types.h     |    2 
>  include/uapi/linux/bpf.h      |   35 ++++-
>  kernel/bpf/Makefile           |    2 
>  kernel/bpf/core.c             |    3 
>  kernel/bpf/helpers.c          |   43 ++++++
>  kernel/bpf/queue_stack_maps.c |  300 +++++++++++++++++++++++++++++++++++++++++
>  kernel/bpf/syscall.c          |   31 +++-
>  kernel/bpf/verifier.c         |   14 +-
>  net/core/filter.c             |    6 +
>  10 files changed, 424 insertions(+), 19 deletions(-)
>  create mode 100644 kernel/bpf/queue_stack_maps.c
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 98c7eeb6d138..cad3bc5cffd1 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -40,6 +40,9 @@ struct bpf_map_ops {
>  	int (*map_update_elem)(struct bpf_map *map, void *key, void *value, u64 flags);
>  	int (*map_delete_elem)(struct bpf_map *map, void *key);
>  	void *(*map_lookup_and_delete_elem)(struct bpf_map *map, void *key);
> +	int (*map_push_elem)(struct bpf_map *map, void *value, u64 flags);
> +	int (*map_pop_elem)(struct bpf_map *map, void *value);
> +	int (*map_peek_elem)(struct bpf_map *map, void *value);
>  
>  	/* funcs called by prog_array and perf_event_array map */
>  	void *(*map_fd_get_ptr)(struct bpf_map *map, struct file *map_file,
> @@ -139,6 +142,7 @@ enum bpf_arg_type {
>  	ARG_CONST_MAP_PTR,	/* const argument used as pointer to bpf_map */
>  	ARG_PTR_TO_MAP_KEY,	/* pointer to stack used as map key */
>  	ARG_PTR_TO_MAP_VALUE,	/* pointer to stack used as map value */
> +	ARG_PTR_TO_UNINIT_MAP_VALUE,	/* pointer to valid memory used to store a map value */
>  
>  	/* the following constraints used to prototype bpf_memcmp() and other
>  	 * functions that access data on eBPF program stack
> @@ -825,6 +829,9 @@ static inline int bpf_fd_reuseport_array_update_elem(struct bpf_map *map,
>  extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
>  extern const struct bpf_func_proto bpf_map_update_elem_proto;
>  extern const struct bpf_func_proto bpf_map_delete_elem_proto;
> +extern const struct bpf_func_proto bpf_map_push_elem_proto;
> +extern const struct bpf_func_proto bpf_map_pop_elem_proto;
> +extern const struct bpf_func_proto bpf_map_peek_elem_proto;
>  
>  extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
>  extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> index 658509daacd4..a2ec73aa1ec7 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -69,3 +69,5 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_XSKMAP, xsk_map_ops)
>  BPF_MAP_TYPE(BPF_MAP_TYPE_REUSEPORT_SOCKARRAY, reuseport_array_ops)
>  #endif
>  #endif
> +BPF_MAP_TYPE(BPF_MAP_TYPE_QUEUE, queue_map_ops)
> +BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 3bb94aa2d408..bfa042273fad 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -129,6 +129,8 @@ enum bpf_map_type {
>  	BPF_MAP_TYPE_CGROUP_STORAGE,
>  	BPF_MAP_TYPE_REUSEPORT_SOCKARRAY,
>  	BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE,
> +	BPF_MAP_TYPE_QUEUE,
> +	BPF_MAP_TYPE_STACK,
>  };
>  
>  enum bpf_prog_type {
> @@ -463,6 +465,28 @@ union bpf_attr {
>   * 	Return
>   * 		0 on success, or a negative error in case of failure.
>   *
> + * int bpf_map_push_elem(struct bpf_map *map, const void *value, u64 flags)
> + * 	Description
> + * 		Push an element *value* in *map*. *flags* is one of:
> + *
> + * 		**BPF_EXIST**
> + * 		If the queue/stack is full, the oldest element is removed to
> + * 		make room for this.
> + * 	Return
> + * 		0 on success, or a negative error in case of failure.
> + *
> + * int bpf_map_pop_elem(struct bpf_map *map, void *value)
> + * 	Description
> + * 		Pop an element from *map*.
> + * Return
> + * 		0 on success, or a negative error in case of failure.
> + *
> + * int bpf_map_peek_elem(struct bpf_map *map, void *value)
> + * 	Description
> + * 		Get an element from *map* without removing it.
> + * Return
> + * 		0 on success, or a negative error in case of failure.
> + *
>   * int bpf_probe_read(void *dst, u32 size, const void *src)
>   * 	Description
>   * 		For tracing programs, safely attempt to read *size* bytes from
> @@ -790,14 +814,14 @@ union bpf_attr {
>   *
>   * 			int ret;
>   * 			struct bpf_tunnel_key key = {};
> - * 			
> + *
>   * 			ret = bpf_skb_get_tunnel_key(skb, &key, sizeof(key), 0);
>   * 			if (ret < 0)
>   * 				return TC_ACT_SHOT;	// drop packet
> - * 			
> + *
>   * 			if (key.remote_ipv4 != 0x0a000001)
>   * 				return TC_ACT_SHOT;	// drop packet
> - * 			
> + *
>   * 			return TC_ACT_OK;		// accept packet
>   *
>   * 		This interface can also be used with all encapsulation devices
> @@ -2304,7 +2328,10 @@ union bpf_attr {
>  	FN(skb_ancestor_cgroup_id),	\
>  	FN(sk_lookup_tcp),		\
>  	FN(sk_lookup_udp),		\
> -	FN(sk_release),
> +	FN(sk_release),			\
> +	FN(map_push_elem),		\
> +	FN(map_pop_elem),		\
> +	FN(map_peek_elem),
>  
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> index 0488b8258321..17afae9e65f3 100644
> --- a/kernel/bpf/Makefile
> +++ b/kernel/bpf/Makefile
> @@ -3,7 +3,7 @@ obj-y := core.o
>  
>  obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o
>  obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
> -obj-$(CONFIG_BPF_SYSCALL) += local_storage.o
> +obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
>  obj-$(CONFIG_BPF_SYSCALL) += disasm.o
>  obj-$(CONFIG_BPF_SYSCALL) += btf.o
>  ifeq ($(CONFIG_NET),y)
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 3f5bf1af0826..8d2db076d123 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1783,6 +1783,9 @@ BPF_CALL_0(bpf_user_rnd_u32)
>  const struct bpf_func_proto bpf_map_lookup_elem_proto __weak;
>  const struct bpf_func_proto bpf_map_update_elem_proto __weak;
>  const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
> +const struct bpf_func_proto bpf_map_push_elem_proto __weak;
> +const struct bpf_func_proto bpf_map_pop_elem_proto __weak;
> +const struct bpf_func_proto bpf_map_peek_elem_proto __weak;
>  
>  const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
>  const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 6502115e8f55..ab0d5e3f9892 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -76,6 +76,49 @@ const struct bpf_func_proto bpf_map_delete_elem_proto = {
>  	.arg2_type	= ARG_PTR_TO_MAP_KEY,
>  };
>  
> +BPF_CALL_3(bpf_map_push_elem, struct bpf_map *, map, void *, value, u64, flags)
> +{
> +	return map->ops->map_push_elem(map, value, flags);
> +}
> +
> +const struct bpf_func_proto bpf_map_push_elem_proto = {
> +	.func		= bpf_map_push_elem,
> +	.gpl_only	= false,
> +	.pkt_access	= true,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_CONST_MAP_PTR,
> +	.arg2_type	= ARG_PTR_TO_MAP_VALUE,
> +	.arg3_type	= ARG_ANYTHING,
> +};
> +
> +BPF_CALL_2(bpf_map_pop_elem, struct bpf_map *, map, void *, value)
> +{
> +	return map->ops->map_pop_elem(map, value);
> +}
> +
> +const struct bpf_func_proto bpf_map_pop_elem_proto = {
> +	.func		= bpf_map_pop_elem,
> +	.gpl_only	= false,
> +	.pkt_access	= true,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_CONST_MAP_PTR,
> +	.arg2_type	= ARG_PTR_TO_UNINIT_MAP_VALUE,
> +};
> +
> +BPF_CALL_2(bpf_map_peek_elem, struct bpf_map *, map, void *, value)
> +{
> +	return map->ops->map_peek_elem(map, value);
> +}
> +
> +const struct bpf_func_proto bpf_map_peek_elem_proto = {
> +	.func		= bpf_map_pop_elem,
> +	.gpl_only	= false,
> +	.pkt_access	= true,
> +	.ret_type	= RET_INTEGER,
> +	.arg1_type	= ARG_CONST_MAP_PTR,
> +	.arg2_type	= ARG_PTR_TO_UNINIT_MAP_VALUE,
> +};
> +
>  const struct bpf_func_proto bpf_get_prandom_u32_proto = {
>  	.func		= bpf_user_rnd_u32,
>  	.gpl_only	= false,
> diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
> new file mode 100644
> index 000000000000..a597c5ba68f6
> --- /dev/null
> +++ b/kernel/bpf/queue_stack_maps.c
> @@ -0,0 +1,300 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * queue_stack_maps.c: BPF queue and stack maps
> + *
> + * Copyright (c) 2018 Politecnico di Torino
> + */
> +#include <linux/bpf.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include "percpu_freelist.h"
> +
> +#define QUEUE_STACK_CREATE_FLAG_MASK \
> +	(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
> +
> +
> +struct bpf_queue_stack {
> +	struct bpf_map map;
> +	raw_spinlock_t lock;
> +	u32 head, tail;
> +	u32 index_mask;
> +	u32 count;
> +
> +	char elements[0] __aligned(8);
> +};
> +
> +static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
> +{
> +	return container_of(map, struct bpf_queue_stack, map);
> +}
> +
> +static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
> +{
> +	return qs->count == 0;
> +}
> +
> +static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
> +{
> +	return qs->count == qs->map.max_entries;
> +}
> +
> +/* Called from syscall */
> +static int queue_stack_map_alloc_check(union bpf_attr *attr)
> +{
> +	/* check sanity of attributes */
> +	if (attr->max_entries == 0 || attr->key_size != 0 ||
> +	    attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
> +		return -EINVAL;
> +
> +	if (attr->value_size > KMALLOC_MAX_SIZE)
> +		/* if value_size is bigger, the user space won't be able to
> +		 * access the elements.
> +		 */
> +		return -E2BIG;
> +
> +	return 0;
> +}
> +
> +static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
> +{
> +	int ret, numa_node = bpf_map_attr_numa_node(attr);
> +	u32 max_entries, value_size, index_mask;
> +	u64 queue_size, cost, mask64;
> +	struct bpf_queue_stack *qs;
> +
> +	max_entries = attr->max_entries;
> +	value_size = attr->value_size;
> +
> +	/* From arraymap.c:
> +	 * On 32 bit archs roundup_pow_of_two() with max_entries that has
> +	 * upper most bit set in u32 space is undefined behavior due to
> +	 * resulting 1U << 32, so do it manually here in u64 space.
> +	 */
> +	mask64 = fls_long(max_entries - 1);
> +	mask64 = 1ULL << mask64;
> +	mask64 -= 1;
> +
> +	index_mask = mask64;
> +
> +	/* Round up queue size to nearest power of 2 */
> +	max_entries = index_mask + 1;

what's the point of roundup ?
The memory waste becomes quite large when max_entries are high.

If queue/stack is sized to exact max_entries,
then 'count' can be removed too, right?

> +	/* Check for overflows. */
> +	if (max_entries < attr->max_entries)
> +		return ERR_PTR(-E2BIG);
> +
> +	queue_size = sizeof(*qs) + (u64) value_size * max_entries;
> +
> +	cost = queue_size;
> +	if (cost >= U32_MAX - PAGE_SIZE)
> +		return ERR_PTR(-E2BIG);
> +
> +	cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
> +
> +	ret = bpf_map_precharge_memlock(cost);
> +	if (ret < 0)
> +		return ERR_PTR(ret);
> +
> +	qs = bpf_map_area_alloc(queue_size, numa_node);
> +	if (!qs)
> +		return ERR_PTR(-ENOMEM);
> +
> +	memset(qs, 0, sizeof(*qs));
> +
> +	bpf_map_init_from_attr(&qs->map, attr);
> +
> +	qs->map.pages = cost;
> +	qs->index_mask = index_mask;
> +
> +	raw_spin_lock_init(&qs->lock);
> +
> +	return &qs->map;
> +}
> +
> +/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
> +static void queue_stack_map_free(struct bpf_map *map)
> +{
> +	struct bpf_queue_stack *qs = bpf_queue_stack(map);
> +
> +	/* 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
> +	 */
> +	synchronize_rcu();
> +
> +	bpf_map_area_free(qs);
> +}
> +
> +static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
> +{
> +	struct bpf_queue_stack *qs = bpf_queue_stack(map);
> +	unsigned long flags;
> +	int err = 0;
> +	void *ptr;
> +
> +	raw_spin_lock_irqsave(&qs->lock, flags);
> +
> +	if (queue_stack_map_is_empty(qs)) {
> +		err = -ENOENT;
> +		goto out;
> +	}
> +
> +	ptr = &qs->elements[qs->tail * qs->map.value_size];
> +	memcpy(value, ptr, qs->map.value_size);
> +
> +	if (delete) {
> +		qs->tail = (qs->tail + 1) & qs->index_mask;
> +		qs->count--;
> +	}
> +
> +out:
> +	raw_spin_unlock_irqrestore(&qs->lock, flags);
> +	return err;
> +}
> +
> +
> +static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
> +{
> +	struct bpf_queue_stack *qs = bpf_queue_stack(map);
> +	unsigned long flags;
> +	int err = 0;
> +	void *ptr;
> +	u32 index;
> +
> +	raw_spin_lock_irqsave(&qs->lock, flags);
> +
> +	if (queue_stack_map_is_empty(qs)) {
> +		err = -ENOENT;
> +		goto out;
> +	}
> +
> +	index = (qs->head - 1) & qs->index_mask;
> +	ptr = &qs->elements[index * qs->map.value_size];
> +	memcpy(value, ptr, qs->map.value_size);
> +
> +	if (delete) {
> +		qs->head = (qs->head - 1) & qs->index_mask;
> +		qs->count--;
> +	}
> +
> +out:
> +	raw_spin_unlock_irqrestore(&qs->lock, flags);
> +	return err;
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int queue_map_peek_elem(struct bpf_map *map, void *value)
> +{
> +	return __queue_map_get(map, value, false);
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int stack_map_peek_elem(struct bpf_map *map, void *value)
> +{
> +	return __stack_map_get(map, value, false);
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int queue_map_pop_elem(struct bpf_map *map, void *value)
> +{
> +	return __queue_map_get(map, value, true);
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int stack_map_pop_elem(struct bpf_map *map, void *value)
> +{
> +	return __stack_map_get(map, value, true);
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
> +				     u64 flags)
> +{
> +	struct bpf_queue_stack *qs = bpf_queue_stack(map);
> +	unsigned long irq_flags;
> +	int err = 0;
> +	void *dst;
> +
> +	/* BPF_EXIST is used to force making room for a new element in case the
> +	 * map is full
> +	 */
> +	bool replace = (flags & BPF_EXIST);
> +
> +	/* Check supported flags for queue and stack maps */
> +	if (flags & BPF_NOEXIST || flags > BPF_EXIST)
> +		return -EINVAL;
> +
> +	raw_spin_lock_irqsave(&qs->lock, irq_flags);
> +
> +	if (queue_stack_map_is_full(qs)) {
> +		if (!replace) {
> +			err = -E2BIG;

ENOSPC is probably more accurate ?

> +			goto out;
> +		}
> +		/* advance tail pointer to overwrite oldest element */

'oldest' is ambiguous here.
For queue it's true, but for stack it's the last element.
Since stack is poping from the head, push w/exist flag will keep
overwriting the last element.
Pls explain it more clearly in helper description in bpf.h

> +		qs->tail = (qs->tail + 1) & qs->index_mask;
> +		qs->count--;
> +	}
> +
> +	dst = &qs->elements[qs->head * qs->map.value_size];
> +	memcpy(dst, value, qs->map.value_size);
> +
> +	qs->head = (qs->head + 1) & qs->index_mask;
> +	qs->count++;
> +
> +out:
> +	raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
> +	return err;
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
> +{
> +	return NULL;
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
> +				       void *value, u64 flags)
> +{
> +	return -EINVAL;
> +}
> +
> +/* Called from syscall or from eBPF program */
> +static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
> +{
> +	return -EINVAL;
> +}
> +
> +/* Called from syscall */
> +static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
> +					void *next_key)
> +{
> +	return -EINVAL;
> +}
> +
> +const struct bpf_map_ops queue_map_ops = {
> +	.map_alloc_check = queue_stack_map_alloc_check,
> +	.map_alloc = queue_stack_map_alloc,
> +	.map_free = queue_stack_map_free,
> +	.map_lookup_elem = queue_stack_map_lookup_elem,
> +	.map_update_elem = queue_stack_map_update_elem,
> +	.map_delete_elem = queue_stack_map_delete_elem,
> +	.map_push_elem = queue_stack_map_push_elem,
> +	.map_pop_elem = queue_map_pop_elem,
> +	.map_peek_elem = queue_map_peek_elem,
> +	.map_get_next_key = queue_stack_map_get_next_key,
> +};
> +
> +const struct bpf_map_ops stack_map_ops = {
> +	.map_alloc_check = queue_stack_map_alloc_check,
> +	.map_alloc = queue_stack_map_alloc,
> +	.map_free = queue_stack_map_free,
> +	.map_lookup_elem = queue_stack_map_lookup_elem,
> +	.map_update_elem = queue_stack_map_update_elem,
> +	.map_delete_elem = queue_stack_map_delete_elem,
> +	.map_push_elem = queue_stack_map_push_elem,
> +	.map_pop_elem = stack_map_pop_elem,
> +	.map_peek_elem = stack_map_peek_elem,
> +	.map_get_next_key = queue_stack_map_get_next_key,
> +};
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 50957e243bfb..c46bf2d38be3 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -727,6 +727,9 @@ static int map_lookup_elem(union bpf_attr *attr)
>  		err = bpf_fd_htab_map_lookup_elem(map, key, value);
>  	} else if (map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) {
>  		err = bpf_fd_reuseport_array_lookup_elem(map, key, value);
> +	} else if (map->map_type == BPF_MAP_TYPE_QUEUE ||
> +		   map->map_type == BPF_MAP_TYPE_STACK) {
> +		err = map->ops->map_peek_elem(map, value);
>  	} else {
>  		rcu_read_lock();
>  		ptr = map->ops->map_lookup_elem(map, key);
> @@ -841,6 +844,9 @@ static int map_update_elem(union bpf_attr *attr)
>  		/* rcu_read_lock() is not needed */
>  		err = bpf_fd_reuseport_array_update_elem(map, key, value,
>  							 attr->flags);
> +	} else if (map->map_type == BPF_MAP_TYPE_QUEUE ||
> +		   map->map_type == BPF_MAP_TYPE_STACK) {
> +		err = map->ops->map_push_elem(map, value, attr->flags);
>  	} else {
>  		rcu_read_lock();
>  		err = map->ops->map_update_elem(map, key, value, attr->flags);
> @@ -1001,11 +1007,6 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
>  		goto err_put;
>  	}
>  
> -	if (!map->ops->map_lookup_and_delete_elem) {
> -		err = -ENOTSUPP;
> -		goto err_put;
> -	}
> -
>  	key = __bpf_copy_key(ukey, map->key_size);
>  	if (IS_ERR(key)) {
>  		err = PTR_ERR(key);
> @@ -1028,12 +1029,22 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
>  	 */
>  	preempt_disable();
>  	__this_cpu_inc(bpf_prog_active);
> -	rcu_read_lock();
> -	ptr = map->ops->map_lookup_and_delete_elem(map, key);
> -	if (ptr)
> -		memcpy(value, ptr, value_size);
> -	rcu_read_unlock();
> +	if (map->map_type == BPF_MAP_TYPE_QUEUE ||
> +	    map->map_type == BPF_MAP_TYPE_STACK) {
> +		err = map->ops->map_pop_elem(map, value);

please clean up the paches, so that patch 4 doesn't immediately
deletes the lines that were introduced in patch 3.
Otherwise what was the point of them in patch 3?

> +	} else {
> +		if (!map->ops->map_lookup_and_delete_elem) {
> +			err = -ENOTSUPP;
> +			goto free_value;
> +		}
> +		rcu_read_lock();
> +		ptr = map->ops->map_lookup_and_delete_elem(map, key);
> +		if (ptr)
> +			memcpy(value, ptr, value_size);
> +		rcu_read_unlock();
>  		err = ptr ? 0 : -ENOENT;
> +	}
> +
>  	__this_cpu_dec(bpf_prog_active);
>  	preempt_enable();
>  
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 73c81bef6ae8..489667f93061 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2121,7 +2121,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>  	}
>  
>  	if (arg_type == ARG_PTR_TO_MAP_KEY ||
> -	    arg_type == ARG_PTR_TO_MAP_VALUE) {
> +	    arg_type == ARG_PTR_TO_MAP_VALUE ||
> +	    arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
>  		expected_type = PTR_TO_STACK;
>  		if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE &&
>  		    type != expected_type)
> @@ -2191,7 +2192,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>  		err = check_helper_mem_access(env, regno,
>  					      meta->map_ptr->key_size, false,
>  					      NULL);
> -	} else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
> +	} else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
> +		   arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
>  		/* bpf_map_xxx(..., map_ptr, ..., value) call:
>  		 * check [value, value + map->value_size) validity
>  		 */
> @@ -2200,9 +2202,10 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>  			verbose(env, "invalid map_ptr to access map->value\n");
>  			return -EACCES;
>  		}
> +		meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
>  		err = check_helper_mem_access(env, regno,
>  					      meta->map_ptr->value_size, false,
> -					      NULL);
> +					      meta);
>  	} else if (arg_type_is_mem_size(arg_type)) {
>  		bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
>  
> @@ -2676,7 +2679,10 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
>  	if (func_id != BPF_FUNC_tail_call &&
>  	    func_id != BPF_FUNC_map_lookup_elem &&
>  	    func_id != BPF_FUNC_map_update_elem &&
> -	    func_id != BPF_FUNC_map_delete_elem)
> +	    func_id != BPF_FUNC_map_delete_elem &&
> +	    func_id != BPF_FUNC_map_push_elem &&
> +	    func_id != BPF_FUNC_map_pop_elem &&
> +	    func_id != BPF_FUNC_map_peek_elem)
>  		return 0;
>  
>  	if (meta->map_ptr == NULL) {
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 591c698bc517..40736e0d9cff 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4993,6 +4993,12 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>  		return &bpf_map_update_elem_proto;
>  	case BPF_FUNC_map_delete_elem:
>  		return &bpf_map_delete_elem_proto;
> +	case BPF_FUNC_map_push_elem:
> +		return &bpf_map_push_elem_proto;
> +	case BPF_FUNC_map_pop_elem:
> +		return &bpf_map_pop_elem_proto;
> +	case BPF_FUNC_map_peek_elem:
> +		return &bpf_map_peek_elem_proto;
>  	case BPF_FUNC_get_prandom_u32:
>  		return &bpf_get_prandom_u32_proto;
>  	case BPF_FUNC_get_smp_processor_id:
> 

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