// 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;
}