Make use of BPF_HID_ATTACH_RDESC_FIXUP so we can trigger an rdesc fixup
in the bpf world.
Whenever the program gets attached/detached, the device is reconnected
meaning that userspace will see it disappearing and reappearing with
the new report descriptor.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
---
changes in v3:
- ensure the ctx.size is properly bounded by allocated size
- s/link_attached/post_link_attach/
- removed the switch statement with only one case
changes in v2:
- split the series by bpf/libbpf/hid/selftests and samples
---
drivers/hid/hid-bpf.c | 62 ++++++++++++++++++++++++++++++++++++++++++
drivers/hid/hid-core.c | 3 +-
include/linux/hid.h | 6 ++++
3 files changed, 70 insertions(+), 1 deletion(-)
diff --git a/drivers/hid/hid-bpf.c b/drivers/hid/hid-bpf.c
index 5060ebcb9979..45c87ff47324 100644
--- a/drivers/hid/hid-bpf.c
+++ b/drivers/hid/hid-bpf.c
@@ -50,6 +50,14 @@ static struct hid_device *hid_bpf_fd_to_hdev(int fd)
return hdev;
}
+static int hid_reconnect(struct hid_device *hdev)
+{
+ if (!test_and_set_bit(ffs(HID_STAT_REPROBED), &hdev->status))
+ return device_reprobe(&hdev->dev);
+
+ return 0;
+}
+
static int hid_bpf_pre_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type)
{
int err = 0;
@@ -92,6 +100,12 @@ static int hid_bpf_pre_link_attach(struct hid_device *hdev, enum bpf_hid_attach_
return err;
}
+static void hid_bpf_post_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type)
+{
+ if (type == BPF_HID_ATTACH_RDESC_FIXUP)
+ hid_reconnect(hdev);
+}
+
static void hid_bpf_array_detach(struct hid_device *hdev, enum bpf_hid_attach_type type)
{
switch (type) {
@@ -99,6 +113,9 @@ static void hid_bpf_array_detach(struct hid_device *hdev, enum bpf_hid_attach_ty
kfree(hdev->bpf.device_data);
hdev->bpf.device_data = NULL;
break;
+ case BPF_HID_ATTACH_RDESC_FIXUP:
+ hid_reconnect(hdev);
+ break;
default:
/* do nothing */
break;
@@ -116,6 +133,9 @@ static int hid_bpf_run_progs(struct hid_device *hdev, struct hid_bpf_ctx_kern *c
case HID_BPF_DEVICE_EVENT:
type = BPF_HID_ATTACH_DEVICE_EVENT;
break;
+ case HID_BPF_RDESC_FIXUP:
+ type = BPF_HID_ATTACH_RDESC_FIXUP;
+ break;
default:
return -EINVAL;
}
@@ -155,11 +175,53 @@ u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *data, int *size)
return ctx.data;
}
+u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size)
+{
+ int ret;
+ struct hid_bpf_ctx_kern ctx = {
+ .type = HID_BPF_RDESC_FIXUP,
+ .hdev = hdev,
+ .size = *size,
+ };
+
+ if (bpf_hid_link_empty(&hdev->bpf, BPF_HID_ATTACH_RDESC_FIXUP))
+ goto ignore_bpf;
+
+ ctx.data = kmemdup(rdesc, HID_MAX_DESCRIPTOR_SIZE, GFP_KERNEL);
+ if (!ctx.data)
+ goto ignore_bpf;
+
+ ctx.allocated_size = HID_MAX_DESCRIPTOR_SIZE;
+
+ ret = hid_bpf_run_progs(hdev, &ctx);
+ if (ret)
+ goto ignore_bpf;
+
+ if (ctx.size > ctx.allocated_size)
+ goto ignore_bpf;
+
+ *size = ctx.size;
+
+ if (*size) {
+ rdesc = krealloc(ctx.data, *size, GFP_KERNEL);
+ } else {
+ rdesc = NULL;
+ kfree(ctx.data);
+ }
+
+ return rdesc;
+
+ ignore_bpf:
+ kfree(ctx.data);
+ return kmemdup(rdesc, *size, GFP_KERNEL);
+}
+
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,
+ .post_link_attach = hid_bpf_post_link_attach,
.array_detach = hid_bpf_array_detach,
};
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 937fab7eb9c6..3182c39db006 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1213,7 +1213,8 @@ int hid_open_report(struct hid_device *device)
return -ENODEV;
size = device->dev_rsize;
- buf = kmemdup(start, size, GFP_KERNEL);
+ /* hid_bpf_report_fixup() ensures we work on a copy of rdesc */
+ buf = hid_bpf_report_fixup(device, start, &size);
if (buf == NULL)
return -ENOMEM;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 8fd79011f461..66d949d10b78 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1213,10 +1213,16 @@ do { \
#ifdef CONFIG_BPF
u8 *hid_bpf_raw_event(struct hid_device *hdev, u8 *rd, int *size);
+u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc, unsigned 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 u8 *hid_bpf_report_fixup(struct hid_device *hdev, u8 *rdesc,
+ unsigned int *size)
+{
+ return kmemdup(rdesc, *size, GFP_KERNEL);
+}
static inline int hid_bpf_module_init(void) { return 0; }
static inline void hid_bpf_module_exit(void) {}
#endif
--
2.35.1
