Message-ID: <4168d4f2-6f9e-45f1-78ca-befd3525c475@polito.it>
Date:   Tue, 9 Oct 2018 08:05:22 -0500
From:   Mauricio Vasquez <mauricio.vasquez@...ito.it>
To:     Song Liu <liu.song.a23@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 4/6] bpf: add queue and stack maps



On 10/08/2018 08:36 PM, Song Liu wrote:
> On Mon, Oct 8, 2018 at 12:12 PM Mauricio Vasquez B
> <mauricio.vasquez@...ito.it> wrote:
>> Queue/stack maps implement a FIFO/LIFO data storage for ebpf programs.
>> These maps support peek, pop and push operations that are exposed to eBPF
>> programs through the new bpf_map[peek/pop/push] helpers.  Those operations
>> are exposed to userspace applications through the already existing
>> syscalls in the following way:
>>
>> BPF_MAP_LOOKUP_ELEM            -> peek
>> BPF_MAP_LOOKUP_AND_DELETE_ELEM -> pop
>> BPF_MAP_UPDATE_ELEM            -> push
>>
>> Queue/stack maps are implemented using a buffer, tail and head indexes,
>> hence BPF_F_NO_PREALLOC is not supported.
>>
>> As opposite to other maps, queue and stack do not use RCU for protecting
>> maps values, the bpf_map[peek/pop] have a ARG_PTR_TO_UNINIT_MAP_VALUE
>> argument that is a pointer to a memory zone where to save the value of a
>> map.  Basically the same as ARG_PTR_TO_UNINIT_MEM, but the size has not
>> be passed as an extra argument.
>>
>> Our main motivation for implementing queue/stack maps was to keep track
>> of a pool of elements, like network ports in a SNAT, however we forsee
>> other use cases, like for exampling saving last N kernel events in a map
>> and then analysing from userspace.
>>
>> 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 |  288 +++++++++++++++++++++++++++++++++++++++++
>>   kernel/bpf/syscall.c          |   30 +++-
>>   kernel/bpf/verifier.c         |   28 +++-
>>   net/core/filter.c             |    6 +
>>   10 files changed, 426 insertions(+), 18 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 */
> How about we put ARG_PTR_TO_UNINIT_MAP_VALUE and related logic to a
> separate patch?

I thought it too, but this is a really small change (6 additions, 3 
deletions). Does it worth a separated patch?
>
>>          /* 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..12a93fb37449
>> --- /dev/null
>> +++ b/kernel/bpf/queue_stack_maps.c
>> @@ -0,0 +1,288 @@
>> +// 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 size; /* max_entries + 1 */
>> +
>> +       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->head == qs->tail;
>> +}
>> +
>> +static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
>> +{
>> +       u32 head = qs->head + 1;
>> +
>> +       if (unlikely(head >= qs->size))
>> +               head = 0;
>> +
>> +       return head == qs->tail;
>> +}
>> +
>> +/* 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);
>> +       struct bpf_queue_stack *qs;
>> +       u32 size, value_size;
>> +       u64 queue_size, cost;
>> +
>> +       size = attr->max_entries + 1;
>> +       value_size = attr->value_size;
>> +
>> +       queue_size = sizeof(*qs) + (u64) value_size * size;
>> +
>> +       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->size = size;
>> +
>> +       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) {
>> +               if (unlikely(++qs->tail >= qs->size))
>> +                       qs->tail = 0;
>> +       }
>> +
>> +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;
>> +       if (unlikely(index >= qs->size))
>> +               index = qs->size - 1;
>> +
>> +       ptr = &qs->elements[index * qs->map.value_size];
>> +       memcpy(value, ptr, qs->map.value_size);
>> +
>> +       if (delete)
>> +               qs->head = index;
>> +
>> +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;
>> +                       goto out;
>> +               }
>> +               /* advance tail pointer to overwrite oldest element */
>> +               if (unlikely(++qs->tail >= qs->size))
>> +                       qs->tail = 0;
>> +       }
>> +
>> +       dst = &qs->elements[qs->head * qs->map.value_size];
>> +       memcpy(dst, value, qs->map.value_size);
>> +
>> +       if (unlikely(++qs->head >= qs->size))
>> +               qs->head = 0;
>> +
>> +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 c33d9303f72f..c135d205fd09 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);
>> @@ -1023,16 +1029,22 @@ static int map_lookup_and_delete_elem(union bpf_attr *attr)
>>           */
>>          preempt_disable();
>>          __this_cpu_inc(bpf_prog_active);
>> -       if (!map->ops->map_lookup_and_delete_elem) {
>> -               err = -ENOTSUPP;
>> -               goto free_value;
>> +       if (map->map_type == BPF_MAP_TYPE_QUEUE ||
>> +           map->map_type == BPF_MAP_TYPE_STACK) {
>> +               err = map->ops->map_pop_elem(map, value);
>> +       } else {
>> +               if (!map->ops->map_lookup_and_delete_elem) {
>> +                       err = -ENOTSUPP;
>> +                       goto free_value;
> similar to previous patch: either we move this check, or we add
> __this_cpu_dec() and preempt_enable().

In this case the check cannot be moved, I'll change it to fix the 
problem and make it more readable.

>
> Thanks,
> Song
>

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