// 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 <linux/capability.h>

  #include "percpu_freelist.h"
  
  #define QUEUE_STACK_CREATE_FLAG_MASK \

  	(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)

  
  struct bpf_queue_stack {
  	struct bpf_map map;
  	raw_spinlock_t lock;
  	u32 head, tail;
  	u32 size; /* max_entries + 1 */

  	char elements[] __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)
  {

  	if (!bpf_capable())

  		return -EPERM;

  	/* check sanity of attributes */
  	if (attr->max_entries == 0 || attr->key_size != 0 ||

  	    attr->value_size == 0 ||

  	    attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK ||
  	    !bpf_map_flags_access_ok(attr->map_flags))

  		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_map_memory mem = {0};

  	struct bpf_queue_stack *qs;

  	u64 size, queue_size, cost;

  	size = (u64) attr->max_entries + 1;
  	cost = queue_size = sizeof(*qs) + size * attr->value_size;

  	ret = bpf_map_charge_init(&mem, cost);

  	if (ret < 0)
  		return ERR_PTR(ret);
  
  	qs = bpf_map_area_alloc(queue_size, numa_node);

  	if (!qs) {
  		bpf_map_charge_finish(&mem);

  		return ERR_PTR(-ENOMEM);

  	}

  
  	memset(qs, 0, sizeof(*qs));
  
  	bpf_map_init_from_attr(&qs->map, attr);

  	bpf_map_charge_move(&qs->map.memory, &mem);

  	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);

  	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)) {

  		memset(value, 0, qs->map.value_size);

  		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)) {

  		memset(value, 0, qs->map.value_size);

  		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;
  }

  static int queue_map_btf_id;

  const struct bpf_map_ops queue_map_ops = {

  	.map_meta_equal = bpf_map_meta_equal,

  	.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,

  	.map_btf_name = "bpf_queue_stack",
  	.map_btf_id = &queue_map_btf_id,

  };

  static int stack_map_btf_id;

  const struct bpf_map_ops stack_map_ops = {

  	.map_meta_equal = bpf_map_meta_equal,

  	.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,

  	.map_btf_name = "bpf_queue_stack",
  	.map_btf_id = &stack_map_btf_id,

  };