Re: [PATCH bpf-next v2 03/28] HID: hook up with bpf

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.

Signed-off-by: Benjamin Tissoires <redacted>

---

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  | 157 +++++++++++++++++++++++++++++++++++++++++
  drivers/hid/hid-core.c |  21 +++++-
  include/linux/hid.h    |  11 +++
  4 files changed, 187 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..8120e598de9f
--- /dev/null
+++ b/drivers/hid/hid-bpf.c

@@ -0,0 +1,157 @@
+// 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_link_attach(struct hid_device *hdev, enum bpf_hid_attach_type type)
+{
+	int err = 0;
+
+	switch (type) {
+	case BPF_HID_ATTACH_DEVICE_EVENT:
+		if (!hdev->bpf.ctx) {
+			hdev->bpf.ctx = bpf_hid_allocate_ctx(hdev, HID_BPF_MAX_BUFFER_SIZE);
+			if (IS_ERR(hdev->bpf.ctx)) {
+				err = PTR_ERR(hdev->bpf.ctx);
+				hdev->bpf.ctx = NULL;
+			}
+		}
+		break;
+	default:
+		/* do nothing */