// SPDX-License-Identifier: GPL-2.0
  /* XDP user-space packet buffer
   * Copyright(c) 2018 Intel Corporation.

   */
  
  #include <linux/init.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/signal.h>
  #include <linux/sched/task.h>
  #include <linux/uaccess.h>
  #include <linux/slab.h>
  #include <linux/bpf.h>
  #include <linux/mm.h>

  #include <linux/netdevice.h>
  #include <linux/rtnetlink.h>

  #include <linux/idr.h>

  #include <linux/vmalloc.h>

  
  #include "xdp_umem.h"

  #include "xsk_queue.h"

  #define XDP_UMEM_MIN_CHUNK_SIZE 2048

  static DEFINE_IDA(umem_ida);

  static void xdp_umem_unpin_pages(struct xdp_umem *umem)

  {

  	unpin_user_pages_dirty_lock(umem->pgs, umem->npgs, true);

  	kfree(umem->pgs);
  	umem->pgs = NULL;

  }

  static void xdp_umem_unaccount_pages(struct xdp_umem *umem)

  {

  	if (umem->user) {
  		atomic_long_sub(umem->npgs, &umem->user->locked_vm);
  		free_uid(umem->user);
  	}

  }

  static void xdp_umem_addr_unmap(struct xdp_umem *umem)
  {
  	vunmap(umem->addrs);
  	umem->addrs = NULL;
  }
  
  static int xdp_umem_addr_map(struct xdp_umem *umem, struct page **pages,
  			     u32 nr_pages)
  {
  	umem->addrs = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
  	if (!umem->addrs)
  		return -ENOMEM;
  	return 0;
  }

  static void xdp_umem_release(struct xdp_umem *umem)
  {

  	umem->zc = false;

  	ida_simple_remove(&umem_ida, umem->id);

  	xdp_umem_addr_unmap(umem);

  	xdp_umem_unpin_pages(umem);

  	xdp_umem_unaccount_pages(umem);

  	kfree(umem);
  }

  static void xdp_umem_release_deferred(struct work_struct *work)
  {
  	struct xdp_umem *umem = container_of(work, struct xdp_umem, work);
  
  	xdp_umem_release(umem);
  }

  void xdp_get_umem(struct xdp_umem *umem)
  {

  	refcount_inc(&umem->users);

  }

  void xdp_put_umem(struct xdp_umem *umem, bool defer_cleanup)

  {
  	if (!umem)
  		return;

  	if (refcount_dec_and_test(&umem->users)) {
  		if (defer_cleanup) {
  			INIT_WORK(&umem->work, xdp_umem_release_deferred);
  			schedule_work(&umem->work);
  		} else {
  			xdp_umem_release(umem);
  		}
  	}

  }

  static int xdp_umem_pin_pages(struct xdp_umem *umem, unsigned long address)

  {
  	unsigned int gup_flags = FOLL_WRITE;
  	long npgs;
  	int err;

  	umem->pgs = kcalloc(umem->npgs, sizeof(*umem->pgs),
  			    GFP_KERNEL | __GFP_NOWARN);

  	if (!umem->pgs)
  		return -ENOMEM;

  	mmap_read_lock(current->mm);

  	npgs = pin_user_pages(address, umem->npgs,

  			      gup_flags | FOLL_LONGTERM, &umem->pgs[0], NULL);

  	mmap_read_unlock(current->mm);

  
  	if (npgs != umem->npgs) {
  		if (npgs >= 0) {
  			umem->npgs = npgs;
  			err = -ENOMEM;
  			goto out_pin;
  		}
  		err = npgs;
  		goto out_pgs;
  	}
  	return 0;
  
  out_pin:
  	xdp_umem_unpin_pages(umem);
  out_pgs:
  	kfree(umem->pgs);
  	umem->pgs = NULL;
  	return err;
  }
  
  static int xdp_umem_account_pages(struct xdp_umem *umem)
  {
  	unsigned long lock_limit, new_npgs, old_npgs;
  
  	if (capable(CAP_IPC_LOCK))
  		return 0;
  
  	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
  	umem->user = get_uid(current_user());
  
  	do {
  		old_npgs = atomic_long_read(&umem->user->locked_vm);
  		new_npgs = old_npgs + umem->npgs;
  		if (new_npgs > lock_limit) {
  			free_uid(umem->user);
  			umem->user = NULL;
  			return -ENOBUFS;
  		}
  	} while (atomic_long_cmpxchg(&umem->user->locked_vm, old_npgs,
  				     new_npgs) != old_npgs);
  	return 0;
  }

  static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)

  {

  	u32 npgs_rem, chunk_size = mr->chunk_size, headroom = mr->headroom;

  	bool unaligned_chunks = mr->flags & XDP_UMEM_UNALIGNED_CHUNK_FLAG;

  	u64 npgs, addr = mr->addr, size = mr->len;

  	unsigned int chunks, chunks_rem;

  	int err;

  	if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {

  		/* Strictly speaking we could support this, if:
  		 * - huge pages, or*
  		 * - using an IOMMU, or
  		 * - making sure the memory area is consecutive
  		 * but for now, we simply say "computer says no".
  		 */
  		return -EINVAL;
  	}

  	if (mr->flags & ~XDP_UMEM_UNALIGNED_CHUNK_FLAG)

  		return -EINVAL;
  
  	if (!unaligned_chunks && !is_power_of_2(chunk_size))

  		return -EINVAL;
  
  	if (!PAGE_ALIGNED(addr)) {
  		/* Memory area has to be page size aligned. For
  		 * simplicity, this might change.
  		 */
  		return -EINVAL;
  	}
  
  	if ((addr + size) < addr)
  		return -EINVAL;

  	npgs = div_u64_rem(size, PAGE_SIZE, &npgs_rem);
  	if (npgs_rem)
  		npgs++;

  	if (npgs > U32_MAX)
  		return -EINVAL;

  	chunks = (unsigned int)div_u64_rem(size, chunk_size, &chunks_rem);

  	if (chunks == 0)

  		return -EINVAL;

  	if (!unaligned_chunks && chunks_rem)
  		return -EINVAL;

  	if (headroom >= chunk_size - XDP_PACKET_HEADROOM)

  		return -EINVAL;

  	umem->size = size;

  	umem->headroom = headroom;

  	umem->chunk_size = chunk_size;

  	umem->chunks = chunks;

  	umem->npgs = (u32)npgs;

  	umem->pgs = NULL;
  	umem->user = NULL;

  	umem->flags = mr->flags;

  	INIT_LIST_HEAD(&umem->xsk_dma_list);

  	refcount_set(&umem->users, 1);

  
  	err = xdp_umem_account_pages(umem);
  	if (err)

  		return err;

  	err = xdp_umem_pin_pages(umem, (unsigned long)addr);

  	if (err)
  		goto out_account;

  	err = xdp_umem_addr_map(umem, umem->pgs, umem->npgs);
  	if (err)
  		goto out_unpin;

  	return 0;

  out_unpin:
  	xdp_umem_unpin_pages(umem);

  out_account:
  	xdp_umem_unaccount_pages(umem);

  	return err;
  }

  struct xdp_umem *xdp_umem_create(struct xdp_umem_reg *mr)
  {
  	struct xdp_umem *umem;
  	int err;
  
  	umem = kzalloc(sizeof(*umem), GFP_KERNEL);
  	if (!umem)
  		return ERR_PTR(-ENOMEM);

  	err = ida_simple_get(&umem_ida, 0, 0, GFP_KERNEL);
  	if (err < 0) {
  		kfree(umem);
  		return ERR_PTR(err);
  	}
  	umem->id = err;

  	err = xdp_umem_reg(umem, mr);
  	if (err) {

  		ida_simple_remove(&umem_ida, umem->id);

  		kfree(umem);
  		return ERR_PTR(err);
  	}
  
  	return umem;
  }