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    SubjectRe: [PATCH bpf-next v7 13/24] HID: initial BPF implementation
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    On 7/28/22 16:19, Greg KH wrote:
    > On Thu, Jul 21, 2022 at 05:36:14PM +0200, Benjamin Tissoires wrote:
    >> --- /dev/null
    >> +++ b/include/linux/hid_bpf.h
    >> @@ -0,0 +1,102 @@
    >> +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
    >
    > This is not a uapi .h file, so the "WITH Linux-syscall-note" should not
    > be here, right?

    thanks, dropping this syscall note from the series.

    >
    >
    >> +
    >> +#ifndef __HID_BPF_H
    >> +#define __HID_BPF_H
    >> +
    >> +#include <linux/spinlock.h>
    >> +#include <uapi/linux/hid.h>
    >> +#include <uapi/linux/hid_bpf.h>
    >> +
    >> +struct hid_device;
    >> +
    >> +/*
    >> + * The following is the HID BPF API.
    >> + *
    >> + * It should be treated as UAPI, so extra care is required
    >> + * when making change to this file.
    >
    > So is this uapi? If so, shouldn't it go into a uapi include directory
    > so we know this and properly track it and maintain it that way?

    IMO it's a grey area. It is not "uapi" because it doesn't export
    anything that userspace can use. A userspace program can not include
    that and use it in other words.

    So strictly speaking, it's a normal part of a kernel header file,
    because it's a description of what other kernel users (though here, eBPF
    programs) can use.

    But I really want that part of the API to be considered as "stable" and
    give some guarantees to the users that I won't change it at every
    release. Thus the "uapi-like".

    >
    >> + */
    >> +
    >> +/**
    >> + * struct hid_bpf_ctx - User accessible data for all HID programs
    >> + *
    >> + * ``data`` is not directly accessible from the context. We need to issue
    >> + * a call to ``hid_bpf_get_data()`` in order to get a pointer to that field.
    >> + *
    >> + * All of these fields are currently read-only.
    >> + *
    >> + * @index: program index in the jump table. No special meaning (a smaller index
    >> + * doesn't mean the program will be executed before another program with
    >> + * a bigger index).
    >> + * @hid: the ``struct hid_device`` representing the device itself
    >> + * @report_type: used for ``hid_bpf_device_event()``
    >> + * @size: Valid data in the data field.
    >> + *
    >> + * Programs can get the available valid size in data by fetching this field.
    >> + */
    >> +struct hid_bpf_ctx {
    >> + __u32 index;
    >> + const struct hid_device *hid;
    >> + enum hid_report_type report_type;
    >> + __s32 size;
    >> +};
    >> +
    >> +/* Following functions are tracepoints that BPF programs can attach to */
    >> +int hid_bpf_device_event(struct hid_bpf_ctx *ctx);
    >> +
    >> +/* Following functions are kfunc that we export to BPF programs */
    >> +/* only available in tracing */
    >> +__u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t __sz);
    >> +
    >> +/* only available in syscall */
    >> +int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags);
    >> +
    >> +/*
    >> + * Below is HID internal
    >> + */
    >> +
    >> +/* internal function to call eBPF programs, not to be used by anybody */
    >> +int __hid_bpf_tail_call(struct hid_bpf_ctx *ctx);
    >> +
    >> +#define HID_BPF_MAX_PROGS_PER_DEV 64
    >> +#define HID_BPF_FLAG_MASK (((HID_BPF_FLAG_MAX - 1) << 1) - 1)
    >> +
    >> +/* types of HID programs to attach to */
    >> +enum hid_bpf_prog_type {
    >> + HID_BPF_PROG_TYPE_UNDEF = -1,
    >> + HID_BPF_PROG_TYPE_DEVICE_EVENT, /* an event is emitted from the device */
    >> + HID_BPF_PROG_TYPE_MAX,
    >> +};
    >> +
    >> +struct hid_bpf_ops {
    >> + struct module *owner;
    >> + struct bus_type *bus_type;
    >> +};
    >> +
    >> +extern struct hid_bpf_ops *hid_bpf_ops;
    >> +
    >> +struct hid_bpf_prog_list {
    >> + u16 prog_idx[HID_BPF_MAX_PROGS_PER_DEV];
    >> + u8 prog_cnt;
    >> +};
    >> +
    >> +/* stored in each device */
    >> +struct hid_bpf {
    >> + struct hid_bpf_prog_list __rcu *progs[HID_BPF_PROG_TYPE_MAX]; /* attached BPF progs */
    >> + bool destroyed; /* prevents the assignment of any progs */
    >> +
    >> + spinlock_t progs_lock; /* protects RCU update of progs */
    >> +};
    >> +
    >> +#ifdef CONFIG_HID_BPF
    >> +int dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
    >> + u32 size, int interrupt);
    >> +void hid_bpf_destroy_device(struct hid_device *hid);
    >> +void hid_bpf_device_init(struct hid_device *hid);
    >> +#else /* CONFIG_HID_BPF */
    >> +static inline int dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
    >> + u32 size, int interrupt) { return 0; }
    >> +static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
    >> +static inline void hid_bpf_device_init(struct hid_device *hid) {}
    >> +#endif /* CONFIG_HID_BPF */
    >> +
    >> +#endif /* __HID_BPF_H */
    >> diff --git a/include/uapi/linux/hid_bpf.h b/include/uapi/linux/hid_bpf.h
    >> new file mode 100644
    >> index 000000000000..ba8caf9b60ee
    >> --- /dev/null
    >> +++ b/include/uapi/linux/hid_bpf.h
    >> @@ -0,0 +1,25 @@
    >> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
    >
    > This is fine, it is in include/uapi/
    >
    > Other than those minor comments, this all looks good to me!
    >
    > Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >

    Great!
    And thanks a lot for the other reviews.

    I finally managed to get some time to work on it after some time off and
    urgent sh**t happening, so I'll send a new version of the series today.

    Cheers,
    Benjamin

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