// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/nospec.h>
#include <linux/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "io_uring.h"
#include "tctx.h"
#include "bpf_filter.h"

static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
                                        struct task_struct *task)
{
        struct io_wq_hash *hash;
        struct io_wq_data data;
        unsigned int concurrency;

        mutex_lock(&ctx->uring_lock);
        hash = ctx->hash_map;
        if (!hash) {
                hash = kzalloc_obj(*hash);
                if (!hash) {
                        mutex_unlock(&ctx->uring_lock);
                        return ERR_PTR(-ENOMEM);
                }
                refcount_set(&hash->refs, 1);
                init_waitqueue_head(&hash->wait);
                ctx->hash_map = hash;
        }
        mutex_unlock(&ctx->uring_lock);

        data.hash = hash;
        data.task = task;

        /* Do QD, or 4 * CPUS, whatever is smallest */
        concurrency = min(ctx->sq_entries, 4 * num_online_cpus());

        return io_wq_create(concurrency, &data);
}

void __io_uring_free(struct task_struct *tsk)
{
        struct io_uring_task *tctx = tsk->io_uring;
        struct io_tctx_node *node;
        unsigned long index;

        /*
         * Fault injection forcing allocation errors in the xa_store() path
         * can lead to xa_empty() returning false, even though no actual
         * node is stored in the xarray. Until that gets sorted out, attempt
         * an iteration here and warn if any entries are found.
         */
        if (tctx) {
                xa_for_each(&tctx->xa, index, node) {
                        WARN_ON_ONCE(1);
                        break;
                }
                WARN_ON_ONCE(tctx->io_wq);
                WARN_ON_ONCE(tctx->cached_refs);

                percpu_counter_destroy(&tctx->inflight);
                kfree(tctx);
                tsk->io_uring = NULL;
        }
        if (tsk->io_uring_restrict) {
                io_put_bpf_filters(tsk->io_uring_restrict);
                kfree(tsk->io_uring_restrict);
                tsk->io_uring_restrict = NULL;
        }
}

__cold int io_uring_alloc_task_context(struct task_struct *task,
                                       struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx;
        int ret;

        tctx = kzalloc_obj(*tctx);
        if (unlikely(!tctx))
                return -ENOMEM;

        ret = percpu_counter_init(&tctx->inflight, 0, GFP_KERNEL);
        if (unlikely(ret)) {
                kfree(tctx);
                return ret;
        }

        tctx->io_wq = io_init_wq_offload(ctx, task);
        if (IS_ERR(tctx->io_wq)) {
                ret = PTR_ERR(tctx->io_wq);
                percpu_counter_destroy(&tctx->inflight);
                kfree(tctx);
                return ret;
        }

        tctx->task = task;
        xa_init(&tctx->xa);
        init_waitqueue_head(&tctx->wait);
        atomic_set(&tctx->in_cancel, 0);
        atomic_set(&tctx->inflight_tracked, 0);
        task->io_uring = tctx;
        init_llist_head(&tctx->task_list);
        init_task_work(&tctx->task_work, tctx_task_work);
        return 0;
}

int __io_uring_add_tctx_node(struct io_ring_ctx *ctx)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_node *node;
        int ret;

        if (unlikely(!tctx)) {
                ret = io_uring_alloc_task_context(current, ctx);
                if (unlikely(ret))
                        return ret;

                tctx = current->io_uring;
                if (ctx->iowq_limits_set) {
                        unsigned int limits[2] = { ctx->iowq_limits[0],
                                                   ctx->iowq_limits[1], };

                        ret = io_wq_max_workers(tctx->io_wq, limits);
                        if (ret)
                                return ret;
                }
        }

        /*
         * Re-activate io-wq keepalive on any new io_uring usage. The wq may have
         * been marked for idle-exit when the task temporarily had no active
         * io_uring instances.
         */
        if (tctx->io_wq)
                io_wq_set_exit_on_idle(tctx->io_wq, false);
        if (!xa_load(&tctx->xa, (unsigned long)ctx)) {
                node = kmalloc_obj(*node);
                if (!node)
                        return -ENOMEM;
                node->ctx = ctx;
                node->task = current;

                ret = xa_err(xa_store(&tctx->xa, (unsigned long)ctx,
                                        node, GFP_KERNEL));
                if (ret) {
                        kfree(node);
                        return ret;
                }

                mutex_lock(&ctx->tctx_lock);
                list_add(&node->ctx_node, &ctx->tctx_list);
                mutex_unlock(&ctx->tctx_lock);
        }
        return 0;
}

int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx)
{
        int ret;

        if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
            && ctx->submitter_task != current)
                return -EEXIST;

        ret = __io_uring_add_tctx_node(ctx);
        if (ret)
                return ret;

        current->io_uring->last = ctx;
        return 0;
}

/*
 * Remove this io_uring_file -> task mapping.
 */
__cold void io_uring_del_tctx_node(unsigned long index)
{
        struct io_uring_task *tctx = current->io_uring;
        struct io_tctx_node *node;

        if (!tctx)
                return;
        node = xa_erase(&tctx->xa, index);
        if (!node)
                return;

        WARN_ON_ONCE(current != node->task);
        WARN_ON_ONCE(list_empty(&node->ctx_node));

        mutex_lock(&node->ctx->tctx_lock);
        list_del(&node->ctx_node);
        mutex_unlock(&node->ctx->tctx_lock);

        if (tctx->last == node->ctx)
                tctx->last = NULL;
        kfree(node);

        if (xa_empty(&tctx->xa) && tctx->io_wq)
                io_wq_set_exit_on_idle(tctx->io_wq, true);
}

__cold void io_uring_clean_tctx(struct io_uring_task *tctx)
{
        struct io_wq *wq = tctx->io_wq;
        struct io_tctx_node *node;
        unsigned long index;

        xa_for_each(&tctx->xa, index, node) {
                io_uring_del_tctx_node(index);
                cond_resched();
        }
        if (wq) {
                /*
                 * Must be after io_uring_del_tctx_node() (removes nodes under
                 * uring_lock) to avoid race with io_uring_try_cancel_iowq().
                 */
                io_wq_put_and_exit(wq);
                tctx->io_wq = NULL;
        }
}

void io_uring_unreg_ringfd(void)
{
        struct io_uring_task *tctx = current->io_uring;
        int i;

        for (i = 0; i < IO_RINGFD_REG_MAX; i++) {
                if (tctx->registered_rings[i]) {
                        fput(tctx->registered_rings[i]);
                        tctx->registered_rings[i] = NULL;
                }
        }
}

int io_ring_add_registered_file(struct io_uring_task *tctx, struct file *file,
                                     int start, int end)
{
        int offset, idx;
        for (offset = start; offset < end; offset++) {
                idx = array_index_nospec(offset, IO_RINGFD_REG_MAX);
                if (tctx->registered_rings[idx])
                        continue;

                tctx->registered_rings[idx] = file;
                return idx;
        }
        return -EBUSY;
}

static int io_ring_add_registered_fd(struct io_uring_task *tctx, int fd,
                                     int start, int end)
{
        struct file *file;
        int offset;

        file = fget(fd);
        if (!file) {
                return -EBADF;
        } else if (!io_is_uring_fops(file)) {
                fput(file);
                return -EOPNOTSUPP;
        }
        offset = io_ring_add_registered_file(tctx, file, start, end);
        if (offset < 0)
                fput(file);
        return offset;
}

/*
 * Register a ring fd to avoid fdget/fdput for each io_uring_enter()
 * invocation. User passes in an array of struct io_uring_rsrc_update
 * with ->data set to the ring_fd, and ->offset given for the desired
 * index. If no index is desired, application may set ->offset == -1U
 * and we'll find an available index. Returns number of entries
 * successfully processed, or < 0 on error if none were processed.
 */
int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,
                       unsigned nr_args)
{
        struct io_uring_rsrc_update __user *arg = __arg;
        struct io_uring_rsrc_update reg;
        struct io_uring_task *tctx;
        int ret, i;

        if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
                return -EINVAL;

        mutex_unlock(&ctx->uring_lock);
        ret = __io_uring_add_tctx_node(ctx);
        mutex_lock(&ctx->uring_lock);
        if (ret)
                return ret;

        tctx = current->io_uring;
        for (i = 0; i < nr_args; i++) {
                int start, end;

                if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
                        ret = -EFAULT;
                        break;
                }

                if (reg.resv) {
                        ret = -EINVAL;
                        break;
                }

                if (reg.offset == -1U) {
                        start = 0;
                        end = IO_RINGFD_REG_MAX;
                } else {
                        if (reg.offset >= IO_RINGFD_REG_MAX) {
                                ret = -EINVAL;
                                break;
                        }
                        start = reg.offset;
                        end = start + 1;
                }

                ret = io_ring_add_registered_fd(tctx, reg.data, start, end);
                if (ret < 0)
                        break;

                reg.offset = ret;
                if (copy_to_user(&arg[i], &reg, sizeof(reg))) {
                        fput(tctx->registered_rings[reg.offset]);
                        tctx->registered_rings[reg.offset] = NULL;
                        ret = -EFAULT;
                        break;
                }
        }

        return i ? i : ret;
}

int io_ringfd_unregister(struct io_ring_ctx *ctx, void __user *__arg,
                         unsigned nr_args)
{
        struct io_uring_rsrc_update __user *arg = __arg;
        struct io_uring_task *tctx = current->io_uring;
        struct io_uring_rsrc_update reg;
        int ret = 0, i;

        if (!nr_args || nr_args > IO_RINGFD_REG_MAX)
                return -EINVAL;
        if (!tctx)
                return 0;

        for (i = 0; i < nr_args; i++) {
                if (copy_from_user(&reg, &arg[i], sizeof(reg))) {
                        ret = -EFAULT;
                        break;
                }
                if (reg.resv || reg.data || reg.offset >= IO_RINGFD_REG_MAX) {
                        ret = -EINVAL;
                        break;
                }

                reg.offset = array_index_nospec(reg.offset, IO_RINGFD_REG_MAX);
                if (tctx->registered_rings[reg.offset]) {
                        fput(tctx->registered_rings[reg.offset]);
                        tctx->registered_rings[reg.offset] = NULL;
                }
        }

        return i ? i : ret;
}

int __io_uring_fork(struct task_struct *tsk)
{
        struct io_restriction *res, *src = tsk->io_uring_restrict;

        /* Don't leave it dangling on error */
        tsk->io_uring_restrict = NULL;

        res = kzalloc_obj(*res, GFP_KERNEL_ACCOUNT);
        if (!res)
                return -ENOMEM;

        tsk->io_uring_restrict = res;
        io_restriction_clone(res, src);
        return 0;
}