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 <20220318161528.1531164-6-benjamin.tissoires@redhat.com> <CAPhsuW47s2tUhe-XQHJonBM9P3Upv8CNKpW_Zewgc_3RYW9WMQ@mail.gmail.com>
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From:   Song Liu <song@kernel.org>
Date:   Fri, 18 Mar 2022 14:04:53 -0700
Message-ID: <CAPhsuW5+WQDKDa4ffsABSJ-pY7i9J0oMPweEP+dOrjA4HwnhrQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next v3 05/17] HID: hook up with bpf
To:     Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Jiri Kosina <jikos@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
        Dave Marchevsky <davemarchevsky@fb.com>,
        Joe Stringer <joe@cilium.io>, Jonathan Corbet <corbet@lwn.net>,
        Tero Kristo <tero.kristo@linux.intel.com>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        linux-kselftest@vger.kernel.org,
        Linux Doc Mailing List <linux-doc@vger.kernel.org>
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On Fri, Mar 18, 2022 at 2:02 PM Song Liu <song@kernel.org> wrote:
>
> On Fri, Mar 18, 2022 at 9:17 AM Benjamin Tissoires
> <benjamin.tissoires@redhat.com> wrote:
> >
> > Now that BPF can be compatible with HID, add the capability into HID.
> > drivers/hid/hid-bpf.c takes care of the glue between bpf and HID, and
> > hid-core can then inject any incoming event from the device into a BPF
> > program to filter/analyze it.
>
> So we only need this part for DEVICE EVENT?

NVM, I found other types in the following patches.

>
> >
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >
> > ---
> >
> > changes in v3:
> > - squashed "only call hid_bpf_raw_event() if a ctx is available"
> >   and "bpf: compute only the required buffer size for the device"
> >   into this one
> > - ensure the ctx.size is properly bounded by allocated size
> > - s/link_attach/pre_link_attach/
> > - s/array_detached/array_detach/
> > - fix default switch case when doing nothing
> > - reworked hid_bpf_pre_link_attach() to avoid the switch
> >
> > changes in v2:
> > - split the series by bpf/libbpf/hid/selftests and samples
> > - addressed review comments from v1
> > ---
> >  drivers/hid/Makefile   |   1 +
> >  drivers/hid/hid-bpf.c  | 174 +++++++++++++++++++++++++++++++++++++++++
> >  drivers/hid/hid-core.c |  24 +++++-
> >  include/linux/hid.h    |  11 +++
> >  4 files changed, 207 insertions(+), 3 deletions(-)
> >  create mode 100644 drivers/hid/hid-bpf.c
> >
> > diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
> > index 6d3e630e81af..08d2d7619937 100644
> > --- a/drivers/hid/Makefile
> > +++ b/drivers/hid/Makefile
> > @@ -4,6 +4,7 @@
> >  #
> >  hid-y                  := hid-core.o hid-input.o hid-quirks.o
> >  hid-$(CONFIG_DEBUG_FS)         += hid-debug.o
> > +hid-$(CONFIG_BPF)              += hid-bpf.o
> >
> >  obj-$(CONFIG_HID)              += hid.o
> >  obj-$(CONFIG_UHID)             += uhid.o
> > diff --git a/drivers/hid/hid-bpf.c b/drivers/hid/hid-bpf.c
> > new file mode 100644
> > index 000000000000..5060ebcb9979
> > --- /dev/null
> > +++ b/drivers/hid/hid-bpf.c
> > @@ -0,0 +1,174 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + *  BPF in HID support for Linux
> > + *
> > + *  Copyright (c) 2022 Benjamin Tissoires
> > + */
> > +
> > +#include <linux/filter.h>
> > +#include <linux/mutex.h>
> > +#include <linux/slab.h>
> > +
> > +#include <uapi/linux/bpf_hid.h>
> > +#include <linux/hid.h>
> > +
> > +static int __hid_bpf_match_sysfs(struct device *dev, const void *data)
> > +{
> > +       struct kernfs_node *kn = dev->kobj.sd;
> > +       struct kernfs_node *uevent_kn;
> > +
> > +       uevent_kn = kernfs_find_and_get_ns(kn, "uevent", NULL);
> > +
> > +       return uevent_kn == data;
> > +}
> > +
> > +static struct hid_device *hid_bpf_fd_to_hdev(int fd)
> > +{
> > +       struct device *dev;
> > +       struct hid_device *hdev;
> > +       struct fd f = fdget(fd);
> > +       struct inode *inode;
> > +       struct kernfs_node *node;
> > +
> > +       if (!f.file) {
> > +               hdev = ERR_PTR(-EBADF);
> > +               goto out;
> > +       }
> > +
> > +       inode = file_inode(f.file);
> > +       node = inode->i_private;
> > +
> > +       dev = bus_find_device(&hid_bus_type, NULL, node, __hid_bpf_match_sysfs);
> > +
> > +       if (dev)
> > +               hdev = to_hid_device(dev);
> > +       else
> > +               hdev = ERR_PTR(-EINVAL);
> > +
> > + out:
> > +       fdput(f);
> > +       return hdev;
> > +}
> > +
> > +static int hid_bpf_pre_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type)
> > +{
> > +       int err = 0;
> > +       unsigned int i, j, max_report_len = 0;
> > +       unsigned int alloc_size = 0;
> > +
> > +       if (type != BPF_HID_ATTACH_DEVICE_EVENT)
> > +               return 0;
> > +
> > +       /* hdev->bpf.device_data is already allocated, abort */
> > +       if (hdev->bpf.device_data)
> > +               return 0;
> > +
> > +       /* compute the maximum report length for this device */
> > +       for (i = 0; i < HID_REPORT_TYPES; i++) {
> > +               struct hid_report_enum *report_enum = hdev->report_enum + i;
> > +
> > +               for (j = 0; j < HID_MAX_IDS; j++) {
> > +                       struct hid_report *report = report_enum->report_id_hash[j];
> > +
> > +                       if (report)
> > +                               max_report_len = max(max_report_len, hid_report_len(report));
> > +               }
> > +       }
> > +
> > +       /*
> > +        * Give us a little bit of extra space and some predictability in the
> > +        * buffer length we create. This way, we can tell users that they can
> > +        * work on chunks of 64 bytes of memory without having the bpf verifier
> > +        * scream at them.
> > +        */
> > +       alloc_size = DIV_ROUND_UP(max_report_len, 64) * 64;
> > +
> > +       hdev->bpf.device_data = kzalloc(alloc_size, GFP_KERNEL);
> > +       if (!hdev->bpf.device_data)
> > +               err = -ENOMEM;
> > +       else
> > +               hdev->bpf.allocated_data = alloc_size;
> > +
> > +       return err;
> > +}
> > +
> > +static void hid_bpf_array_detach(struct hid_device *hdev, enum bpf_hid_attach_type type)
> > +{
> > +       switch (type) {
> > +       case BPF_HID_ATTACH_DEVICE_EVENT:
> > +               kfree(hdev->bpf.device_data);
> > +               hdev->bpf.device_data = NULL;
> > +               break;
> > +       default:
> > +               /* do nothing */
> > +               break;
> > +       }
> > +}
> > +
> > +static int hid_bpf_run_progs(struct hid_device *hdev, struct hid_bpf_ctx_kern *ctx)
> > +{
> > +       enum bpf_hid_attach_type type;
> > +
> > +       if (!ctx)
> > +               return -EINVAL;
> > +
> > +       switch (ctx->type) {
> > +       case HID_BPF_DEVICE_EVENT:
> > +               type = BPF_HID_ATTACH_DEVICE_EVENT;
> > +               break;
> > +       default:
> > +               return -EINVAL;
> > +       }
> > +
> > +       if (!hdev->bpf.run_array[type])
> > +               return 0;
> > +
> > +       return BPF_PROG_RUN_ARRAY(hdev->bpf.run_array[type], ctx, bpf_prog_run);
> > +}
> > +
> > +u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *data, int *size)
> > +{
> > +       int ret;
> > +       struct hid_bpf_ctx_kern ctx = {
> > +               .type = HID_BPF_DEVICE_EVENT,
> > +               .hdev = hdev,
> > +               .size = *size,
> > +               .data = hdev->bpf.device_data,
> > +               .allocated_size = hdev->bpf.allocated_data,
> > +       };
> > +
> > +       if (bpf_hid_link_empty(&hdev->bpf, BPF_HID_ATTACH_DEVICE_EVENT))
> > +               return data;
> > +
> > +       memset(ctx.data, 0, hdev->bpf.allocated_data);
> > +       memcpy(ctx.data, data, *size);
> > +
> > +       ret = hid_bpf_run_progs(hdev, &ctx);
> > +       if (ret)
> > +               return ERR_PTR(-EIO);
> > +
> > +       if (!ctx.size || ctx.size > ctx.allocated_size)
> > +               return ERR_PTR(-EINVAL);
> > +
> > +       *size = ctx.size;
> > +
> > +       return ctx.data;
> > +}
> > +
> > +int __init hid_bpf_module_init(void)
> > +{
> > +       struct bpf_hid_hooks hooks = {
> > +               .hdev_from_fd = hid_bpf_fd_to_hdev,
> > +               .pre_link_attach = hid_bpf_pre_link_attach,
> > +               .array_detach = hid_bpf_array_detach,
> > +       };
> > +
> > +       bpf_hid_set_hooks(&hooks);
> > +
> > +       return 0;
> > +}
> > +
> > +void __exit hid_bpf_module_exit(void)
> > +{
> > +       bpf_hid_set_hooks(NULL);
> > +}
> > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> > index f1aed5bbd000..937fab7eb9c6 100644
> > --- a/drivers/hid/hid-core.c
> > +++ b/drivers/hid/hid-core.c
> > @@ -1748,13 +1748,24 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
> >         struct hid_driver *hdrv;
> >         unsigned int a;
> >         u32 rsize, csize = size;
> > -       u8 *cdata = data;
> > +       u8 *cdata;
> >         int ret = 0;
> >
> > +       /* we pre-test if device_data is available here to cut the calls at the earliest */
> > +       if (hid->bpf.device_data) {
> > +               data = hid_bpf_raw_event(hid, data, &size);
> > +               if (IS_ERR(data)) {
> > +                       ret = PTR_ERR(data);
> > +                       goto out;
> > +               }
> > +       }
> > +
> >         report = hid_get_report(report_enum, data);
> >         if (!report)
> >                 goto out;
> >
> > +       cdata = data;
> > +
> >         if (report_enum->numbered) {
> >                 cdata++;
> >                 csize--;
> > @@ -2528,10 +2539,12 @@ int hid_add_device(struct hid_device *hdev)
> >
> >         hid_debug_register(hdev, dev_name(&hdev->dev));
> >         ret = device_add(&hdev->dev);
> > -       if (!ret)
> > +       if (!ret) {
> >                 hdev->status |= HID_STAT_ADDED;
> > -       else
> > +       } else {
> >                 hid_debug_unregister(hdev);
> > +               bpf_hid_exit(hdev);
> > +       }
> >
> >         return ret;
> >  }
> > @@ -2567,6 +2580,7 @@ struct hid_device *hid_allocate_device(void)
> >         spin_lock_init(&hdev->debug_list_lock);
> >         sema_init(&hdev->driver_input_lock, 1);
> >         mutex_init(&hdev->ll_open_lock);
> > +       bpf_hid_init(hdev);
> >
> >         return hdev;
> >  }
> > @@ -2574,6 +2588,7 @@ EXPORT_SYMBOL_GPL(hid_allocate_device);
> >
> >  static void hid_remove_device(struct hid_device *hdev)
> >  {
> > +       bpf_hid_exit(hdev);
> >         if (hdev->status & HID_STAT_ADDED) {
> >                 device_del(&hdev->dev);
> >                 hid_debug_unregister(hdev);
> > @@ -2700,6 +2715,8 @@ static int __init hid_init(void)
> >
> >         hid_debug_init();
> >
> > +       hid_bpf_module_init();
> > +
> >         return 0;
> >  err_bus:
> >         bus_unregister(&hid_bus_type);
> > @@ -2709,6 +2726,7 @@ static int __init hid_init(void)
> >
> >  static void __exit hid_exit(void)
> >  {
> > +       hid_bpf_module_exit();
> >         hid_debug_exit();
> >         hidraw_exit();
> >         bus_unregister(&hid_bus_type);
> > diff --git a/include/linux/hid.h b/include/linux/hid.h
> > index 56f6f4ad45a7..8fd79011f461 100644
> > --- a/include/linux/hid.h
> > +++ b/include/linux/hid.h
> > @@ -27,6 +27,7 @@
> >  #include <linux/mutex.h>
> >  #include <linux/power_supply.h>
> >  #include <uapi/linux/hid.h>
> > +#include <uapi/linux/bpf_hid.h>
> >
> >  /*
> >   * We parse each description item into this structure. Short items data
> > @@ -1210,4 +1211,14 @@ do {                                                                     \
> >  #define hid_dbg_once(hid, fmt, ...)                    \
> >         dev_dbg_once(&(hid)->dev, fmt, ##__VA_ARGS__)
> >
> > +#ifdef CONFIG_BPF
> > +u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size);
> > +int hid_bpf_module_init(void);
> > +void hid_bpf_module_exit(void);
> > +#else
> > +static inline u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size) { return rd; }
> > +static inline int hid_bpf_module_init(void) { return 0; }
> > +static inline void hid_bpf_module_exit(void) {}
> > +#endif
> > +
> >  #endif
> > --
> > 2.35.1
> >