/* net/core/xdp.c
 *
 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
 * Released under terms in GPL version 2.  See COPYING.
 */
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/rhashtable.h>
#include <net/page_pool.h>

#include <net/xdp.h>

#define REG_STATE_NEW           0x0
#define REG_STATE_REGISTERED    0x1
#define REG_STATE_UNREGISTERED  0x2
#define REG_STATE_UNUSED        0x3

static DEFINE_IDA(mem_id_pool);
static DEFINE_MUTEX(mem_id_lock);
#define MEM_ID_MAX 0xFFFE
#define MEM_ID_MIN 1
static int mem_id_next = MEM_ID_MIN;

static bool mem_id_init; /* false */
static struct rhashtable *mem_id_ht;

struct xdp_mem_allocator {
        struct xdp_mem_info mem;
        union {
                void *allocator;
                struct page_pool *page_pool;
                struct zero_copy_allocator *zc_alloc;
        };
        struct rhash_head node;
        struct rcu_head rcu;
};

static u32 xdp_mem_id_hashfn(const void *data, u32 len, u32 seed)
{
        const u32 *k = data;
        const u32 key = *k;

        BUILD_BUG_ON(FIELD_SIZEOF(struct xdp_mem_allocator, mem.id)
                     != sizeof(u32));

        /* Use cyclic increasing ID as direct hash key */
        return key;
}

static int xdp_mem_id_cmp(struct rhashtable_compare_arg *arg,
                          const void *ptr)
{
        const struct xdp_mem_allocator *xa = ptr;
        u32 mem_id = *(u32 *)arg->key;

        return xa->mem.id != mem_id;
}

static const struct rhashtable_params mem_id_rht_params = {
        .nelem_hint = 64,
        .head_offset = offsetof(struct xdp_mem_allocator, node),
        .key_offset  = offsetof(struct xdp_mem_allocator, mem.id),
        .key_len = FIELD_SIZEOF(struct xdp_mem_allocator, mem.id),
        .max_size = MEM_ID_MAX,
        .min_size = 8,
        .automatic_shrinking = true,
        .hashfn    = xdp_mem_id_hashfn,
        .obj_cmpfn = xdp_mem_id_cmp,
};

static void __xdp_mem_allocator_rcu_free(struct rcu_head *rcu)
{
        struct xdp_mem_allocator *xa;

        xa = container_of(rcu, struct xdp_mem_allocator, rcu);

        /* Allow this ID to be reused */
        ida_simple_remove(&mem_id_pool, xa->mem.id);

        /* Notice, driver is expected to free the *allocator,
         * e.g. page_pool, and MUST also use RCU free.
         */

        /* Poison memory */
        xa->mem.id = 0xFFFF;
        xa->mem.type = 0xF0F0;
        xa->allocator = (void *)0xDEAD9001;

        kfree(xa);
}

void xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq)
{
        struct xdp_mem_allocator *xa;
        int id = xdp_rxq->mem.id;

        if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
                WARN(1, "Missing register, driver bug");
                return;
        }

        if (xdp_rxq->mem.type != MEM_TYPE_PAGE_POOL &&
            xdp_rxq->mem.type != MEM_TYPE_ZERO_COPY) {
                return;
        }

        if (id == 0)
                return;

        mutex_lock(&mem_id_lock);

        xa = rhashtable_lookup_fast(mem_id_ht, &id, mem_id_rht_params);
        if (xa && !rhashtable_remove_fast(mem_id_ht, &xa->node, mem_id_rht_params))
                call_rcu(&xa->rcu, __xdp_mem_allocator_rcu_free);

        mutex_unlock(&mem_id_lock);
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg_mem_model);

void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)
{
        /* Simplify driver cleanup code paths, allow unreg "unused" */
        if (xdp_rxq->reg_state == REG_STATE_UNUSED)
                return;

        WARN(!(xdp_rxq->reg_state == REG_STATE_REGISTERED), "Driver BUG");

        xdp_rxq_info_unreg_mem_model(xdp_rxq);

        xdp_rxq->reg_state = REG_STATE_UNREGISTERED;
        xdp_rxq->dev = NULL;

        /* Reset mem info to defaults */
        xdp_rxq->mem.id = 0;
        xdp_rxq->mem.type = 0;
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);

static void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq)
{
        memset(xdp_rxq, 0, sizeof(*xdp_rxq));
}

/* Returns 0 on success, negative on failure */
int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
                     struct net_device *dev, u32 queue_index)
{
        if (xdp_rxq->reg_state == REG_STATE_UNUSED) {
                WARN(1, "Driver promised not to register this");
                return -EINVAL;
        }

        if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {
                WARN(1, "Missing unregister, handled but fix driver");
                xdp_rxq_info_unreg(xdp_rxq);
        }

        if (!dev) {
                WARN(1, "Missing net_device from driver");
                return -ENODEV;
        }

        /* State either UNREGISTERED or NEW */
        xdp_rxq_info_init(xdp_rxq);
        xdp_rxq->dev = dev;
        xdp_rxq->queue_index = queue_index;

        xdp_rxq->reg_state = REG_STATE_REGISTERED;
        return 0;
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);

void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)
{
        xdp_rxq->reg_state = REG_STATE_UNUSED;
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);

bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq)
{
        return (xdp_rxq->reg_state == REG_STATE_REGISTERED);
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_is_reg);

static int __mem_id_init_hash_table(void)
{
        struct rhashtable *rht;
        int ret;

        if (unlikely(mem_id_init))
                return 0;

        rht = kzalloc(sizeof(*rht), GFP_KERNEL);
        if (!rht)
                return -ENOMEM;

        ret = rhashtable_init(rht, &mem_id_rht_params);
        if (ret < 0) {
                kfree(rht);
                return ret;
        }
        mem_id_ht = rht;
        smp_mb(); /* mutex lock should provide enough pairing */
        mem_id_init = true;

        return 0;
}

/* Allocate a cyclic ID that maps to allocator pointer.
 * See: https://www.kernel.org/doc/html/latest/core-api/idr.html
 *
 * Caller must lock mem_id_lock.
 */
static int __mem_id_cyclic_get(gfp_t gfp)
{
        int retries = 1;
        int id;

again:
        id = ida_simple_get(&mem_id_pool, mem_id_next, MEM_ID_MAX, gfp);
        if (id < 0) {
                if (id == -ENOSPC) {
                        /* Cyclic allocator, reset next id */
                        if (retries--) {
                                mem_id_next = MEM_ID_MIN;
                                goto again;
                        }
                }
                return id; /* errno */
        }
        mem_id_next = id + 1;

        return id;
}

static bool __is_supported_mem_type(enum xdp_mem_type type)
{
        if (type == MEM_TYPE_PAGE_POOL)
                return is_page_pool_compiled_in();

        if (type >= MEM_TYPE_MAX)
                return false;

        return true;
}

int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
                               enum xdp_mem_type type, void *allocator)
{
        struct xdp_mem_allocator *xdp_alloc;
        gfp_t gfp = GFP_KERNEL;
        int id, errno, ret;
        void *ptr;

        if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
                WARN(1, "Missing register, driver bug");
                return -EFAULT;
        }

        if (!__is_supported_mem_type(type))
                return -EOPNOTSUPP;

        xdp_rxq->mem.type = type;

        if (!allocator) {
                if (type == MEM_TYPE_PAGE_POOL || type == MEM_TYPE_ZERO_COPY)
                        return -EINVAL; /* Setup time check page_pool req */
                return 0;
        }

        /* Delay init of rhashtable to save memory if feature isn't used */
        if (!mem_id_init) {
                mutex_lock(&mem_id_lock);
                ret = __mem_id_init_hash_table();
                mutex_unlock(&mem_id_lock);
                if (ret < 0) {
                        WARN_ON(1);
                        return ret;
                }
        }

        xdp_alloc = kzalloc(sizeof(*xdp_alloc), gfp);
        if (!xdp_alloc)
                return -ENOMEM;

        mutex_lock(&mem_id_lock);
        id = __mem_id_cyclic_get(gfp);
        if (id < 0) {
                errno = id;
                goto err;
        }
        xdp_rxq->mem.id = id;
        xdp_alloc->mem  = xdp_rxq->mem;
        xdp_alloc->allocator = allocator;

        /* Insert allocator into ID lookup table */
        ptr = rhashtable_insert_slow(mem_id_ht, &id, &xdp_alloc->node);
        if (IS_ERR(ptr)) {
                errno = PTR_ERR(ptr);
                goto err;
        }

        mutex_unlock(&mem_id_lock);

        return 0;
err:
        mutex_unlock(&mem_id_lock);
        kfree(xdp_alloc);
        return errno;
}
EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);

/* XDP RX runs under NAPI protection, and in different delivery error
 * scenarios (e.g. queue full), it is possible to return the xdp_frame
 * while still leveraging this protection.  The @napi_direct boolian
 * is used for those calls sites.  Thus, allowing for faster recycling
 * of xdp_frames/pages in those cases.
 */
static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
                         unsigned long handle)
{
        struct xdp_mem_allocator *xa;
        struct page *page;

        switch (mem->type) {
        case MEM_TYPE_PAGE_POOL:
                rcu_read_lock();
                /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
                xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
                page = virt_to_head_page(data);
                if (xa) {
                        napi_direct &= !xdp_return_frame_no_direct();
                        page_pool_put_page(xa->page_pool, page, napi_direct);
                } else {
                        put_page(page);
                }
                rcu_read_unlock();
                break;
        case MEM_TYPE_PAGE_SHARED:
                page_frag_free(data);
                break;
        case MEM_TYPE_PAGE_ORDER0:
                page = virt_to_page(data); /* Assumes order0 page*/
                put_page(page);
                break;
        case MEM_TYPE_ZERO_COPY:
                /* NB! Only valid from an xdp_buff! */
                rcu_read_lock();
                /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
                xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
                xa->zc_alloc->free(xa->zc_alloc, handle);
                rcu_read_unlock();
        default:
                /* Not possible, checked in xdp_rxq_info_reg_mem_model() */
                break;
        }
}

void xdp_return_frame(struct xdp_frame *xdpf)
{
        __xdp_return(xdpf->data, &xdpf->mem, false, 0);
}
EXPORT_SYMBOL_GPL(xdp_return_frame);

void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
{
        __xdp_return(xdpf->data, &xdpf->mem, true, 0);
}
EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);

void xdp_return_buff(struct xdp_buff *xdp)
{
        __xdp_return(xdp->data, &xdp->rxq->mem, true, xdp->handle);
}
EXPORT_SYMBOL_GPL(xdp_return_buff);

int xdp_attachment_query(struct xdp_attachment_info *info,
                         struct netdev_bpf *bpf)
{
        bpf->prog_id = info->prog ? info->prog->aux->id : 0;
        bpf->prog_flags = info->prog ? info->flags : 0;
        return 0;
}
EXPORT_SYMBOL_GPL(xdp_attachment_query);

bool xdp_attachment_flags_ok(struct xdp_attachment_info *info,
                             struct netdev_bpf *bpf)
{
        if (info->prog && (bpf->flags ^ info->flags) & XDP_FLAGS_MODES) {
                NL_SET_ERR_MSG(bpf->extack,
                               "program loaded with different flags");
                return false;
        }
        return true;
}
EXPORT_SYMBOL_GPL(xdp_attachment_flags_ok);

void xdp_attachment_setup(struct xdp_attachment_info *info,
                          struct netdev_bpf *bpf)
{
        if (info->prog)
                bpf_prog_put(info->prog);
        info->prog = bpf->prog;
        info->flags = bpf->flags;
}
EXPORT_SYMBOL_GPL(xdp_attachment_setup);

struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp)
{
        unsigned int metasize, totsize;
        void *addr, *data_to_copy;
        struct xdp_frame *xdpf;
        struct page *page;

        /* Clone into a MEM_TYPE_PAGE_ORDER0 xdp_frame. */
        metasize = xdp_data_meta_unsupported(xdp) ? 0 :
                   xdp->data - xdp->data_meta;
        totsize = xdp->data_end - xdp->data + metasize;

        if (sizeof(*xdpf) + totsize > PAGE_SIZE)
                return NULL;

        page = dev_alloc_page();
        if (!page)
                return NULL;

        addr = page_to_virt(page);
        xdpf = addr;
        memset(xdpf, 0, sizeof(*xdpf));

        addr += sizeof(*xdpf);
        data_to_copy = metasize ? xdp->data_meta : xdp->data;
        memcpy(addr, data_to_copy, totsize);

        xdpf->data = addr + metasize;
        xdpf->len = totsize - metasize;
        xdpf->headroom = 0;
        xdpf->metasize = metasize;
        xdpf->mem.type = MEM_TYPE_PAGE_ORDER0;

        xdp_return_buff(xdp);
        return xdpf;
}
EXPORT_SYMBOL_GPL(xdp_convert_zc_to_xdp_frame);