// SPDX-License-Identifier: GPL-2.0
// bpf-lirc.c - handles bpf
//
// Copyright (C) 2018 Sean Young <sean@mess.org>

#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/bpf_lirc.h>
#include "rc-core-priv.h"

#define lirc_rcu_dereference(p)                                         \
        rcu_dereference_protected(p, lockdep_is_held(&ir_raw_handler_lock))

/*
 * BPF interface for raw IR
 */
const struct bpf_prog_ops lirc_mode2_prog_ops = {
};

BPF_CALL_1(bpf_rc_repeat, u32*, sample)
{
        struct ir_raw_event_ctrl *ctrl;

        ctrl = container_of(sample, struct ir_raw_event_ctrl, bpf_sample);

        rc_repeat(ctrl->dev);

        return 0;
}

static const struct bpf_func_proto rc_repeat_proto = {
        .func      = bpf_rc_repeat,
        .gpl_only  = true, /* rc_repeat is EXPORT_SYMBOL_GPL */
        .ret_type  = RET_INTEGER,
        .arg1_type = ARG_PTR_TO_CTX,
};

BPF_CALL_4(bpf_rc_keydown, u32*, sample, u32, protocol, u64, scancode,
           u32, toggle)
{
        struct ir_raw_event_ctrl *ctrl;

        ctrl = container_of(sample, struct ir_raw_event_ctrl, bpf_sample);

        rc_keydown(ctrl->dev, protocol, scancode, toggle != 0);

        return 0;
}

static const struct bpf_func_proto rc_keydown_proto = {
        .func      = bpf_rc_keydown,
        .gpl_only  = true, /* rc_keydown is EXPORT_SYMBOL_GPL */
        .ret_type  = RET_INTEGER,
        .arg1_type = ARG_PTR_TO_CTX,
        .arg2_type = ARG_ANYTHING,
        .arg3_type = ARG_ANYTHING,
        .arg4_type = ARG_ANYTHING,
};

BPF_CALL_3(bpf_rc_pointer_rel, u32*, sample, s32, rel_x, s32, rel_y)
{
        struct ir_raw_event_ctrl *ctrl;

        ctrl = container_of(sample, struct ir_raw_event_ctrl, bpf_sample);

        input_report_rel(ctrl->dev->input_dev, REL_X, rel_x);
        input_report_rel(ctrl->dev->input_dev, REL_Y, rel_y);
        input_sync(ctrl->dev->input_dev);

        return 0;
}

static const struct bpf_func_proto rc_pointer_rel_proto = {
        .func      = bpf_rc_pointer_rel,
        .gpl_only  = true,
        .ret_type  = RET_INTEGER,
        .arg1_type = ARG_PTR_TO_CTX,
        .arg2_type = ARG_ANYTHING,
        .arg3_type = ARG_ANYTHING,
};

static const struct bpf_func_proto *
lirc_mode2_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
        switch (func_id) {
        case BPF_FUNC_rc_repeat:
                return &rc_repeat_proto;
        case BPF_FUNC_rc_keydown:
                return &rc_keydown_proto;
        case BPF_FUNC_rc_pointer_rel:
                return &rc_pointer_rel_proto;
        case BPF_FUNC_map_lookup_elem:
                return &bpf_map_lookup_elem_proto;
        case BPF_FUNC_map_update_elem:
                return &bpf_map_update_elem_proto;
        case BPF_FUNC_map_delete_elem:
                return &bpf_map_delete_elem_proto;
        case BPF_FUNC_map_push_elem:
                return &bpf_map_push_elem_proto;
        case BPF_FUNC_map_pop_elem:
                return &bpf_map_pop_elem_proto;
        case BPF_FUNC_map_peek_elem:
                return &bpf_map_peek_elem_proto;
        case BPF_FUNC_ktime_get_ns:
                return &bpf_ktime_get_ns_proto;
        case BPF_FUNC_ktime_get_boot_ns:
                return &bpf_ktime_get_boot_ns_proto;
        case BPF_FUNC_tail_call:
                return &bpf_tail_call_proto;
        case BPF_FUNC_get_prandom_u32:
                return &bpf_get_prandom_u32_proto;
        case BPF_FUNC_trace_printk:
                if (bpf_token_capable(prog->aux->token, CAP_PERFMON))
                        return bpf_get_trace_printk_proto();
                fallthrough;
        default:
                return NULL;
        }
}

static bool lirc_mode2_is_valid_access(int off, int size,
                                       enum bpf_access_type type,
                                       const struct bpf_prog *prog,
                                       struct bpf_insn_access_aux *info)
{
        /* We have one field of u32 */
        return type == BPF_READ && off == 0 && size == sizeof(u32);
}

const struct bpf_verifier_ops lirc_mode2_verifier_ops = {
        .get_func_proto  = lirc_mode2_func_proto,
        .is_valid_access = lirc_mode2_is_valid_access
};

#define BPF_MAX_PROGS 64

static int lirc_bpf_attach(struct rc_dev *rcdev, struct bpf_prog *prog)
{
        struct bpf_prog_array *old_array;
        struct bpf_prog_array *new_array;
        struct ir_raw_event_ctrl *raw;
        int ret;

        if (rcdev->driver_type != RC_DRIVER_IR_RAW)
                return -EINVAL;

        ret = mutex_lock_interruptible(&ir_raw_handler_lock);
        if (ret)
                return ret;

        raw = rcdev->raw;
        if (!raw) {
                ret = -ENODEV;
                goto unlock;
        }

        old_array = lirc_rcu_dereference(raw->progs);
        if (old_array && bpf_prog_array_length(old_array) >= BPF_MAX_PROGS) {
                ret = -E2BIG;
                goto unlock;
        }

        ret = bpf_prog_array_copy(old_array, NULL, prog, 0, &new_array);
        if (ret < 0)
                goto unlock;

        rcu_assign_pointer(raw->progs, new_array);
        bpf_prog_array_free(old_array);

unlock:
        mutex_unlock(&ir_raw_handler_lock);
        return ret;
}

static int lirc_bpf_detach(struct rc_dev *rcdev, struct bpf_prog *prog)
{
        struct bpf_prog_array *old_array;
        struct bpf_prog_array *new_array;
        struct ir_raw_event_ctrl *raw;
        int ret;

        if (rcdev->driver_type != RC_DRIVER_IR_RAW)
                return -EINVAL;

        ret = mutex_lock_interruptible(&ir_raw_handler_lock);
        if (ret)
                return ret;

        raw = rcdev->raw;
        if (!raw) {
                ret = -ENODEV;
                goto unlock;
        }

        old_array = lirc_rcu_dereference(raw->progs);
        ret = bpf_prog_array_copy(old_array, prog, NULL, 0, &new_array);
        /*
         * Do not use bpf_prog_array_delete_safe() as we would end up
         * with a dummy entry in the array, and the we would free the
         * dummy in lirc_bpf_free()
         */
        if (ret)
                goto unlock;

        rcu_assign_pointer(raw->progs, new_array);
        bpf_prog_array_free(old_array);
        bpf_prog_put(prog);
unlock:
        mutex_unlock(&ir_raw_handler_lock);
        return ret;
}

void lirc_bpf_run(struct rc_dev *rcdev, u32 sample)
{
        struct ir_raw_event_ctrl *raw = rcdev->raw;

        raw->bpf_sample = sample;

        if (raw->progs) {
                rcu_read_lock();
                bpf_prog_run_array(rcu_dereference(raw->progs),
                                   &raw->bpf_sample, bpf_prog_run);
                rcu_read_unlock();
        }
}

/*
 * This should be called once the rc thread has been stopped, so there can be
 * no concurrent bpf execution.
 *
 * Should be called with the ir_raw_handler_lock held.
 */
void lirc_bpf_free(struct rc_dev *rcdev)
{
        struct bpf_prog_array_item *item;
        struct bpf_prog_array *array;

        array = lirc_rcu_dereference(rcdev->raw->progs);
        if (!array)
                return;

        for (item = array->items; item->prog; item++)
                bpf_prog_put(item->prog);

        bpf_prog_array_free(array);
}

int lirc_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
        struct rc_dev *rcdev;
        int ret;

        if (attr->attach_flags)
                return -EINVAL;

        rcdev = rc_dev_get_from_fd(attr->target_fd, true);
        if (IS_ERR(rcdev))
                return PTR_ERR(rcdev);

        ret = lirc_bpf_attach(rcdev, prog);

        put_device(&rcdev->dev);

        return ret;
}

int lirc_prog_detach(const union bpf_attr *attr)
{
        struct bpf_prog *prog;
        struct rc_dev *rcdev;
        int ret;

        if (attr->attach_flags)
                return -EINVAL;

        prog = bpf_prog_get_type(attr->attach_bpf_fd,
                                 BPF_PROG_TYPE_LIRC_MODE2);
        if (IS_ERR(prog))
                return PTR_ERR(prog);

        rcdev = rc_dev_get_from_fd(attr->target_fd, true);
        if (IS_ERR(rcdev)) {
                bpf_prog_put(prog);
                return PTR_ERR(rcdev);
        }

        ret = lirc_bpf_detach(rcdev, prog);

        bpf_prog_put(prog);
        put_device(&rcdev->dev);

        return ret;
}

int lirc_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
{
        __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
        struct bpf_prog_array *progs;
        struct rc_dev *rcdev;
        u32 cnt, flags = 0;
        int ret;

        if (attr->query.query_flags)
                return -EINVAL;

        rcdev = rc_dev_get_from_fd(attr->query.target_fd, false);
        if (IS_ERR(rcdev))
                return PTR_ERR(rcdev);

        if (rcdev->driver_type != RC_DRIVER_IR_RAW) {
                ret = -EINVAL;
                goto put;
        }

        ret = mutex_lock_interruptible(&ir_raw_handler_lock);
        if (ret)
                goto put;

        progs = lirc_rcu_dereference(rcdev->raw->progs);
        cnt = progs ? bpf_prog_array_length(progs) : 0;

        if (copy_to_user(&uattr->query.prog_cnt, &cnt, sizeof(cnt))) {
                ret = -EFAULT;
                goto unlock;
        }

        if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) {
                ret = -EFAULT;
                goto unlock;
        }

        if (attr->query.prog_cnt != 0 && prog_ids && cnt)
                ret = bpf_prog_array_copy_to_user(progs, prog_ids,
                                                  attr->query.prog_cnt);

unlock:
        mutex_unlock(&ir_raw_handler_lock);
put:
        put_device(&rcdev->dev);

        return ret;
}