Re: [PATCH v4 2/3] media: rc: introduce BPF_PROG_LIRC_MODE2

[Y Song]

On Fri, May 18, 2018 at 7:07 AM, Sean Young <sean@xxxxxxxx> wrote:
> Add support for BPF_PROG_LIRC_MODE2. This type of BPF program can call
> rc_keydown() to reported decoded IR scancodes, or rc_repeat() to report
> that the last key should be repeated.
>
> The bpf program can be attached to using the bpf(BPF_PROG_ATTACH) syscall;
> the target_fd must be the /dev/lircN device.
>
> Signed-off-by: Sean Young <sean@xxxxxxxx>

Acked-by: Yonghong Song <yhs@xxxxxx>

> ---
>  drivers/media/rc/Kconfig        |  13 ++
>  drivers/media/rc/Makefile       |   1 +
>  drivers/media/rc/bpf-lirc.c     | 308 ++++++++++++++++++++++++++++++++
>  drivers/media/rc/lirc_dev.c     |  30 ++++
>  drivers/media/rc/rc-core-priv.h |  22 +++
>  drivers/media/rc/rc-ir-raw.c    |  12 +-
>  include/linux/bpf_rcdev.h       |  30 ++++
>  include/linux/bpf_types.h       |   3 +
>  include/uapi/linux/bpf.h        |  53 +++++-
>  kernel/bpf/syscall.c            |   7 +
>  10 files changed, 476 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/media/rc/bpf-lirc.c
>  create mode 100644 include/linux/bpf_rcdev.h
>
> diff --git a/drivers/media/rc/Kconfig b/drivers/media/rc/Kconfig
> index eb2c3b6eca7f..d5b35a6ba899 100644
> --- a/drivers/media/rc/Kconfig
> +++ b/drivers/media/rc/Kconfig
> @@ -25,6 +25,19 @@ config LIRC
>            passes raw IR to and from userspace, which is needed for
>            IR transmitting (aka "blasting") and for the lirc daemon.
>
> +config BPF_LIRC_MODE2
> +       bool "Support for eBPF programs attached to lirc devices"
> +       depends on BPF_SYSCALL
> +       depends on RC_CORE=y
> +       depends on LIRC
> +       help
> +          Allow attaching eBPF programs to a lirc device using the bpf(2)
> +          syscall command BPF_PROG_ATTACH. This is supported for raw IR
> +          receivers.
> +
> +          These eBPF programs can be used to decode IR into scancodes, for
> +          IR protocols not supported by the kernel decoders.
> +
>  menuconfig RC_DECODERS
>         bool "Remote controller decoders"
>         depends on RC_CORE
> diff --git a/drivers/media/rc/Makefile b/drivers/media/rc/Makefile
> index 2e1c87066f6c..e0340d043fe8 100644
> --- a/drivers/media/rc/Makefile
> +++ b/drivers/media/rc/Makefile
> @@ -5,6 +5,7 @@ obj-y += keymaps/
>  obj-$(CONFIG_RC_CORE) += rc-core.o
>  rc-core-y := rc-main.o rc-ir-raw.o
>  rc-core-$(CONFIG_LIRC) += lirc_dev.o
> +rc-core-$(CONFIG_BPF_LIRC_MODE2) += bpf-lirc.o
>  obj-$(CONFIG_IR_NEC_DECODER) += ir-nec-decoder.o
>  obj-$(CONFIG_IR_RC5_DECODER) += ir-rc5-decoder.o
>  obj-$(CONFIG_IR_RC6_DECODER) += ir-rc6-decoder.o
> diff --git a/drivers/media/rc/bpf-lirc.c b/drivers/media/rc/bpf-lirc.c
> new file mode 100644
> index 000000000000..c9673df2d9cd
> --- /dev/null
> +++ b/drivers/media/rc/bpf-lirc.c
> @@ -0,0 +1,308 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// bpf-lirc.c - handles bpf
> +//
> +// Copyright (C) 2018 Sean Young <sean@xxxxxxxx>
> +
> +#include <linux/bpf.h>
> +#include <linux/filter.h>
> +#include <linux/bpf_rcdev.h>
> +#include "rc-core-priv.h"
> +
> +/*
> + * 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,
> +};
> +
> +/*
> + * Currently rc-core does not support 64-bit scancodes, but there are many
> + * known protocols with more than 32 bits. So, define the interface as u64
> + * as a future-proof.
> + */
> +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,
> +};
> +
> +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_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_ktime_get_ns:
> +               return &bpf_ktime_get_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 (capable(CAP_SYS_ADMIN))
> +                       return bpf_get_trace_printk_proto();
> +               /* fall through */
> +       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 rc_dev_bpf_attach(struct rc_dev *rcdev, struct bpf_prog *prog)
> +{
> +       struct bpf_prog_array __rcu *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;
> +       }
> +
> +       if (raw->progs && bpf_prog_array_length(raw->progs) >= BPF_MAX_PROGS) {
> +               ret = -E2BIG;
> +               goto unlock;
> +       }
> +
> +       old_array = raw->progs;
> +       ret = bpf_prog_array_copy(old_array, NULL, prog, &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 rc_dev_bpf_detach(struct rc_dev *rcdev, struct bpf_prog *prog)
> +{
> +       struct bpf_prog_array __rcu *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 = raw->progs;
> +       ret = bpf_prog_array_copy(old_array, prog, NULL, &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 rc_dev_bpf_free()
> +        */
> +       if (ret == 0) {
> +               rcu_assign_pointer(raw->progs, new_array);
> +               bpf_prog_array_free(old_array);
> +       }
> +unlock:
> +       mutex_unlock(&ir_raw_handler_lock);
> +       return ret;
> +}
> +
> +void rc_dev_bpf_run(struct rc_dev *rcdev, u32 sample)
> +{
> +       struct ir_raw_event_ctrl *raw = rcdev->raw;
> +
> +       raw->bpf_sample = sample;
> +
> +       if (raw->progs)
> +               BPF_PROG_RUN_ARRAY(raw->progs, &raw->bpf_sample, BPF_PROG_RUN);
> +}
> +
> +/*
> + * This should be called once the rc thread has been stopped, so there can be
> + * no concurrent bpf execution.
> + */
> +void rc_dev_bpf_free(struct rc_dev *rcdev)
> +{
> +       struct bpf_prog **progs;
> +
> +       if (!rcdev->raw->progs)
> +               return;
> +
> +       progs = rcu_dereference(rcdev->raw->progs)->progs;
> +       while (*progs)
> +               bpf_prog_put(*progs++);
> +
> +       bpf_prog_array_free(rcdev->raw->progs);
> +}
> +
> +int rc_dev_prog_attach(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);
> +       if (IS_ERR(rcdev)) {
> +               bpf_prog_put(prog);
> +               return PTR_ERR(rcdev);
> +       }
> +
> +       ret = rc_dev_bpf_attach(rcdev, prog);
> +       if (ret)
> +               bpf_prog_put(prog);
> +
> +       put_device(&rcdev->dev);
> +
> +       return ret;
> +}
> +
> +int rc_dev_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);
> +       if (IS_ERR(rcdev)) {
> +               bpf_prog_put(prog);
> +               return PTR_ERR(rcdev);
> +       }
> +
> +       ret = rc_dev_bpf_detach(rcdev, prog);
> +
> +       bpf_prog_put(prog);
> +       put_device(&rcdev->dev);
> +
> +       return ret;
> +}
> +
> +int rc_dev_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 __rcu *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);
> +       if (IS_ERR(rcdev))
> +               return PTR_ERR(rcdev);
> +
> +       if (rcdev->driver_type != RC_DRIVER_IR_RAW)
> +               return -EINVAL;
> +
> +       ret = mutex_lock_interruptible(&ir_raw_handler_lock);
> +       if (ret)
> +               return ret;
> +
> +       progs = 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, cnt);
> +
> +unlock:
> +       mutex_unlock(&ir_raw_handler_lock);
> +       put_device(&rcdev->dev);
> +
> +       return ret;
> +}
> diff --git a/drivers/media/rc/lirc_dev.c b/drivers/media/rc/lirc_dev.c
> index 24e9fbb80e81..7e760bf11a51 100644
> --- a/drivers/media/rc/lirc_dev.c
> +++ b/drivers/media/rc/lirc_dev.c
> @@ -20,6 +20,7 @@
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/device.h>
> +#include <linux/file.h>
>  #include <linux/idr.h>
>  #include <linux/poll.h>
>  #include <linux/sched.h>
> @@ -104,6 +105,12 @@ void ir_lirc_raw_event(struct rc_dev *dev, struct ir_raw_event ev)
>                         TO_US(ev.duration), TO_STR(ev.pulse));
>         }
>
> +       /*
> +        * bpf does not care about the gap generated above; that exists
> +        * for backwards compatibility
> +        */
> +       rc_dev_bpf_run(dev, sample);
> +
>         spin_lock_irqsave(&dev->lirc_fh_lock, flags);
>         list_for_each_entry(fh, &dev->lirc_fh, list) {
>                 if (LIRC_IS_TIMEOUT(sample) && !fh->send_timeout_reports)
> @@ -816,4 +823,27 @@ void __exit lirc_dev_exit(void)
>         unregister_chrdev_region(lirc_base_dev, RC_DEV_MAX);
>  }
>
> +struct rc_dev *rc_dev_get_from_fd(int fd)
> +{
> +       struct fd f = fdget(fd);
> +       struct lirc_fh *fh;
> +       struct rc_dev *dev;
> +
> +       if (!f.file)
> +               return ERR_PTR(-EBADF);
> +
> +       if (f.file->f_op != &lirc_fops) {
> +               fdput(f);
> +               return ERR_PTR(-EINVAL);
> +       }
> +
> +       fh = f.file->private_data;
> +       dev = fh->rc;
> +
> +       get_device(&dev->dev);
> +       fdput(f);
> +
> +       return dev;
> +}
> +
>  MODULE_ALIAS("lirc_dev");
> diff --git a/drivers/media/rc/rc-core-priv.h b/drivers/media/rc/rc-core-priv.h
> index e0e6a17460f6..511e4a2dc2d5 100644
> --- a/drivers/media/rc/rc-core-priv.h
> +++ b/drivers/media/rc/rc-core-priv.h
> @@ -13,6 +13,7 @@
>  #define        MAX_IR_EVENT_SIZE       512
>
>  #include <linux/slab.h>
> +#include <uapi/linux/bpf.h>
>  #include <media/rc-core.h>
>
>  /**
> @@ -57,6 +58,11 @@ struct ir_raw_event_ctrl {
>         /* raw decoder state follows */
>         struct ir_raw_event prev_ev;
>         struct ir_raw_event this_ev;
> +
> +#ifdef CONFIG_BPF_LIRC_MODE2
> +       u32                             bpf_sample;
> +       struct bpf_prog_array __rcu     *progs;
> +#endif
>         struct nec_dec {
>                 int state;
>                 unsigned count;
> @@ -126,6 +132,9 @@ struct ir_raw_event_ctrl {
>         } imon;
>  };
>
> +/* Mutex for locking raw IR processing and handler change */
> +extern struct mutex ir_raw_handler_lock;
> +
>  /* macros for IR decoders */
>  static inline bool geq_margin(unsigned d1, unsigned d2, unsigned margin)
>  {
> @@ -288,6 +297,7 @@ void ir_lirc_raw_event(struct rc_dev *dev, struct ir_raw_event ev);
>  void ir_lirc_scancode_event(struct rc_dev *dev, struct lirc_scancode *lsc);
>  int ir_lirc_register(struct rc_dev *dev);
>  void ir_lirc_unregister(struct rc_dev *dev);
> +struct rc_dev *rc_dev_get_from_fd(int fd);
>  #else
>  static inline int lirc_dev_init(void) { return 0; }
>  static inline void lirc_dev_exit(void) {}
> @@ -299,4 +309,16 @@ static inline int ir_lirc_register(struct rc_dev *dev) { return 0; }
>  static inline void ir_lirc_unregister(struct rc_dev *dev) { }
>  #endif
>
> +/*
> + * bpf interface
> + */
> +#ifdef CONFIG_BPF_LIRC_MODE2
> +void rc_dev_bpf_free(struct rc_dev *dev);
> +void rc_dev_bpf_run(struct rc_dev *dev, u32 sample);
> +#else
> +static inline void rc_dev_bpf_free(struct rc_dev *dev) { }
> +static inline void rc_dev_bpf_run(struct rc_dev *dev, u32 sample)
> +{ }
> +#endif
> +
>  #endif /* _RC_CORE_PRIV */
> diff --git a/drivers/media/rc/rc-ir-raw.c b/drivers/media/rc/rc-ir-raw.c
> index 374f83105a23..a3131d4236b3 100644
> --- a/drivers/media/rc/rc-ir-raw.c
> +++ b/drivers/media/rc/rc-ir-raw.c
> @@ -14,7 +14,7 @@
>  static LIST_HEAD(ir_raw_client_list);
>
>  /* Used to handle IR raw handler extensions */
> -static DEFINE_MUTEX(ir_raw_handler_lock);
> +DEFINE_MUTEX(ir_raw_handler_lock);
>  static LIST_HEAD(ir_raw_handler_list);
>  static atomic64_t available_protocols = ATOMIC64_INIT(0);
>
> @@ -621,9 +621,17 @@ void ir_raw_event_unregister(struct rc_dev *dev)
>         list_for_each_entry(handler, &ir_raw_handler_list, list)
>                 if (handler->raw_unregister)
>                         handler->raw_unregister(dev);
> -       mutex_unlock(&ir_raw_handler_lock);
> +
> +       rc_dev_bpf_free(dev);
>
>         ir_raw_event_free(dev);
> +
> +       /*
> +        * A user can be calling bpf(BPF_PROG_{QUERY|ATTACH|DETACH}), so
> +        * ensure that the raw member is null on unlock; this is how
> +        * "device gone" is checked.
> +        */
> +       mutex_unlock(&ir_raw_handler_lock);
>  }
>
>  /*
> diff --git a/include/linux/bpf_rcdev.h b/include/linux/bpf_rcdev.h
> new file mode 100644
> index 000000000000..570ca0036cf5
> --- /dev/null
> +++ b/include/linux/bpf_rcdev.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _BPF_RCDEV_H
> +#define _BPF_RCDEV_H
> +
> +#include <linux/bpf.h>
> +#include <uapi/linux/bpf.h>
> +
> +#ifdef CONFIG_BPF_LIRC_MODE2
> +int rc_dev_prog_attach(const union bpf_attr *attr);
> +int rc_dev_prog_detach(const union bpf_attr *attr);
> +int rc_dev_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr);
> +#else
> +static inline int rc_dev_prog_attach(const union bpf_attr *attr)
> +{
> +       return -EINVAL;
> +}
> +
> +static inline int rc_dev_prog_detach(const union bpf_attr *attr)
> +{
> +       return -EINVAL;
> +}
> +
> +static inline int rc_dev_prog_query(const union bpf_attr *attr,
> +                                   union bpf_attr __user *uattr)
> +{
> +       return -EINVAL;
> +}
> +#endif
> +
> +#endif /* _BPF_RCDEV_H */
> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> index b67f8793de0d..47b771421d40 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -25,6 +25,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint)
>  #ifdef CONFIG_CGROUP_BPF
>  BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
>  #endif
> +#ifdef CONFIG_BPF_LIRC_MODE2
> +BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
> +#endif
>
>  BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
>  BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index d94d333a8225..8227832b713e 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -141,6 +141,7 @@ enum bpf_prog_type {
>         BPF_PROG_TYPE_SK_MSG,
>         BPF_PROG_TYPE_RAW_TRACEPOINT,
>         BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
> +       BPF_PROG_TYPE_LIRC_MODE2,
>  };
>
>  enum bpf_attach_type {
> @@ -158,6 +159,7 @@ enum bpf_attach_type {
>         BPF_CGROUP_INET6_CONNECT,
>         BPF_CGROUP_INET4_POST_BIND,
>         BPF_CGROUP_INET6_POST_BIND,
> +       BPF_LIRC_MODE2,
>         __MAX_BPF_ATTACH_TYPE
>  };
>
> @@ -1902,6 +1904,53 @@ union bpf_attr {
>   *             egress otherwise). This is the only flag supported for now.
>   *     Return
>   *             **SK_PASS** on success, or **SK_DROP** on error.
> + *
> + * int bpf_rc_keydown(void *ctx, u32 protocol, u64 scancode, u32 toggle)
> + *     Description
> + *             This helper is used in programs implementing IR decoding, to
> + *             report a successfully decoded key press with *scancode*,
> + *             *toggle* value in the given *protocol*. The scancode will be
> + *             translated to a keycode using the rc keymap, and reported as
> + *             an input key down event. After a period a key up event is
> + *             generated. This period can be extended by calling either
> + *             **bpf_rc_keydown** () with the same values, or calling
> + *             **bpf_rc_repeat** ().
> + *
> + *             Some protocols include a toggle bit, in case the button
> + *             was released and pressed again between consecutive scancodes
> + *
> + *             The *ctx* should point to the lirc sample as passed into
> + *             the program.
> + *
> + *             The *protocol* is the decoded protocol number (see
> + *             **enum rc_proto** for some predefined values).
> + *
> + *             This helper is only available is the kernel was compiled with
> + *             the **CONFIG_BPF_LIRC_MODE2** configuration option set to
> + *             "**y**".
> + *
> + *     Return
> + *             0
> + *
> + * int bpf_rc_repeat(void *ctx)
> + *     Description
> + *             This helper is used in programs implementing IR decoding, to
> + *             report a successfully decoded repeat key message. This delays
> + *             the generation of a key up event for previously generated
> + *             key down event.
> + *
> + *             Some IR protocols like NEC have a special IR message for
> + *             repeating last button, for when a button is held down.
> + *
> + *             The *ctx* should point to the lirc sample as passed into
> + *             the program.
> + *
> + *             This helper is only available is the kernel was compiled with
> + *             the **CONFIG_BPF_LIRC_MODE2** configuration option set to
> + *             "**y**".
> + *
> + *     Return
> + *             0
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -1976,7 +2025,9 @@ union bpf_attr {
>         FN(fib_lookup),                 \
>         FN(sock_hash_update),           \
>         FN(msg_redirect_hash),          \
> -       FN(sk_redirect_hash),
> +       FN(sk_redirect_hash),           \
> +       FN(rc_repeat),                  \
> +       FN(rc_keydown),
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index bfcde949c7f8..6e9a4cbc14b9 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -11,6 +11,7 @@
>   */
>  #include <linux/bpf.h>
>  #include <linux/bpf_trace.h>
> +#include <linux/bpf_rcdev.h>
>  #include <linux/btf.h>
>  #include <linux/syscalls.h>
>  #include <linux/slab.h>
> @@ -1576,6 +1577,8 @@ static int bpf_prog_attach(const union bpf_attr *attr)
>         case BPF_SK_SKB_STREAM_PARSER:
>         case BPF_SK_SKB_STREAM_VERDICT:
>                 return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, true);
> +       case BPF_LIRC_MODE2:
> +               return rc_dev_prog_attach(attr);
>         default:
>                 return -EINVAL;
>         }
> @@ -1646,6 +1649,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
>         case BPF_SK_SKB_STREAM_PARSER:
>         case BPF_SK_SKB_STREAM_VERDICT:
>                 return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, false);
> +       case BPF_LIRC_MODE2:
> +               return rc_dev_prog_detach(attr);
>         default:
>                 return -EINVAL;
>         }
> @@ -1693,6 +1698,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
>         case BPF_CGROUP_SOCK_OPS:
>         case BPF_CGROUP_DEVICE:
>                 break;
> +       case BPF_LIRC_MODE2:
> +               return rc_dev_prog_query(attr, uattr);
>         default:
>                 return -EINVAL;
>         }
> --
> 2.17.0
>