On Fri, Mar 18, 2022 at 9:17 AM Benjamin Tissoires
<benjamin.tissoires@xxxxxxxxxx> 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?
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
>
> ---
>
> 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
>
