On Fri, Mar 18, 2022 at 2:02 PM Song Liu <song@xxxxxxxxxx> wrote:
>
> 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?
NVM, I found other types in the following patches.
>
> >
> > 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
> >
