diff --git a/Documentation/hid/hid-bpf.rst b/Documentation/hid/hid-bpf.rst
index a55f191d49a33a4482a9935993bf4d451188a10f..c205f92b7bcc43cce95fc04f0ff0fde1ca36bc7b 100644
--- a/Documentation/hid/hid-bpf.rst
+++ b/Documentation/hid/hid-bpf.rst
@@ -427,12 +427,22 @@ program first::
prog_fd = bpf_program__fd(hid_skel->progs.attach_prog);
err = bpf_prog_test_run_opts(prog_fd, &tattrs);
- return err;
+ if (err)
+ return err;
+
+ return args.retval; /* the fd of the created bpf_link */
}
Our userspace program can now listen to notifications on the ring buffer, and
is awaken only when the value changes.
+When the userspace program doesn't need to listen to events anymore, it can just
+close the returned fd from :c:func:`attach_filter`, which will tell the kernel to
+detach the program from the HID device.
+
+Of course, in other use cases, the userspace program can also pin the fd to the
+BPF filesystem through a call to :c:func:`bpf_obj_pin`, as with any bpf_link.
+
Controlling the device
----------------------
diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index 58e608ebf0fa27e8d184d97af2644b21fd3d81af..8d29fd361ab9cabd1fd0ced0d60b25f01449b736 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -249,7 +249,9 @@ int hid_bpf_reconnect(struct hid_device *hdev)
* @prog_fd: an fd in the user process representing the program to attach
* @flags: any logical OR combination of &enum hid_bpf_attach_flags
*
- * @returns %0 on success, an error code otherwise.
+ * @returns an fd of a bpf_link object on success (> %0), an error code otherwise.
+ * Closing this fd will detach the program from the HID device (unless the bpf_link
+ * is pinned to the BPF file system).
*/
/* called from syscall */
noinline int
@@ -257,7 +259,7 @@ hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags)
{
struct hid_device *hdev;
struct device *dev;
- int err, prog_type = hid_bpf_get_prog_attach_type(prog_fd);
+ int fd, err, prog_type = hid_bpf_get_prog_attach_type(prog_fd);
if (!hid_bpf_ops)
return -EINVAL;
@@ -283,17 +285,19 @@ hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags)
return err;
}
- err = __hid_bpf_attach_prog(hdev, prog_type, prog_fd, flags);
- if (err)
- return err;
+ fd = __hid_bpf_attach_prog(hdev, prog_type, prog_fd, flags);
+ if (fd < 0)
+ return fd;
if (prog_type == HID_BPF_PROG_TYPE_RDESC_FIXUP) {
err = hid_bpf_reconnect(hdev);
- if (err)
+ if (err) {
+ close_fd(fd);
return err;
+ }
}
- return 0;
+ return fd;
}
/**
diff --git a/drivers/hid/bpf/hid_bpf_jmp_table.c b/drivers/hid/bpf/hid_bpf_jmp_table.c
index 207972b028d9c4abccc3bc756f33e4b013ea1d31..b7eb5c5e435f938248e14839c688a1455d1976b8 100644
--- a/drivers/hid/bpf/hid_bpf_jmp_table.c
+++ b/drivers/hid/bpf/hid_bpf_jmp_table.c
@@ -322,16 +322,6 @@ static int hid_bpf_insert_prog(int prog_fd, struct bpf_prog *prog)
if (err)
goto out;
- /*
- * The program has been safely inserted, decrement the reference count
- * so it doesn't interfere with the number of actual user handles.
- * This is safe to do because:
- * - we overrite the put_ptr in the prog fd map
- * - we also have a cleanup function that monitors when a program gets
- * released and we manually do the cleanup in the prog fd map
- */
- bpf_prog_sub(prog, 1);
-
/* return the index */
err = index;
@@ -365,14 +355,46 @@ int hid_bpf_get_prog_attach_type(int prog_fd)
return prog_type;
}
+static void hid_bpf_link_release(struct bpf_link *link)
+{
+ struct hid_bpf_link *hid_link =
+ container_of(link, struct hid_bpf_link, link);
+
+ __clear_bit(hid_link->hid_table_index, jmp_table.enabled);
+ schedule_work(&release_work);
+}
+
+static void hid_bpf_link_dealloc(struct bpf_link *link)
+{
+ struct hid_bpf_link *hid_link =
+ container_of(link, struct hid_bpf_link, link);
+
+ kfree(hid_link);
+}
+
+static void hid_bpf_link_show_fdinfo(const struct bpf_link *link,
+ struct seq_file *seq)
+{
+ seq_printf(seq,
+ "attach_type:\tHID-BPF\n");
+}
+
+static const struct bpf_link_ops hid_bpf_link_lops = {
+ .release = hid_bpf_link_release,
+ .dealloc = hid_bpf_link_dealloc,
+ .show_fdinfo = hid_bpf_link_show_fdinfo,
+};
+
/* called from syscall */
noinline int
__hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type,
int prog_fd, __u32 flags)
{
+ struct bpf_link_primer link_primer;
+ struct hid_bpf_link *link;
struct bpf_prog *prog = NULL;
struct hid_bpf_prog_entry *prog_entry;
- int cnt, err = -EINVAL, prog_idx = -1;
+ int cnt, err = -EINVAL, prog_table_idx = -1;
/* take a ref on the prog itself */
prog = bpf_prog_get(prog_fd);
@@ -381,23 +403,32 @@ __hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type,
mutex_lock(&hid_bpf_attach_lock);
+ link = kzalloc(sizeof(*link), GFP_USER);
+ if (!link) {
+ err = -ENOMEM;
+ goto err_unlock;
+ }
+
+ bpf_link_init(&link->link, BPF_LINK_TYPE_UNSPEC,
+ &hid_bpf_link_lops, prog);
+
/* do not attach too many programs to a given HID device */
cnt = hid_bpf_program_count(hdev, NULL, prog_type);
if (cnt < 0) {
err = cnt;
- goto out_unlock;
+ goto err_unlock;
}
if (cnt >= hid_bpf_max_programs(prog_type)) {
err = -E2BIG;
- goto out_unlock;
+ goto err_unlock;
}
- prog_idx = hid_bpf_insert_prog(prog_fd, prog);
+ prog_table_idx = hid_bpf_insert_prog(prog_fd, prog);
/* if the jmp table is full, abort */
- if (prog_idx < 0) {
- err = prog_idx;
- goto out_unlock;
+ if (prog_table_idx < 0) {
+ err = prog_table_idx;
+ goto err_unlock;
}
if (flags & HID_BPF_FLAG_INSERT_HEAD) {
@@ -412,22 +443,32 @@ __hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type,
/* we steal the ref here */
prog_entry->prog = prog;
- prog_entry->idx = prog_idx;
+ prog_entry->idx = prog_table_idx;
prog_entry->hdev = hdev;
prog_entry->type = prog_type;
/* finally store the index in the device list */
err = hid_bpf_populate_hdev(hdev, prog_type);
+ if (err) {
+ hid_bpf_release_prog_at(prog_table_idx);
+ goto err_unlock;
+ }
+
+ link->hid_table_index = prog_table_idx;
+
+ err = bpf_link_prime(&link->link, &link_primer);
if (err)
- hid_bpf_release_prog_at(prog_idx);
+ goto err_unlock;
- out_unlock:
mutex_unlock(&hid_bpf_attach_lock);
- /* we only use prog as a key in the various tables, so we don't need to actually
- * increment the ref count.
- */
+ return bpf_link_settle(&link_primer);
+
+ err_unlock:
+ mutex_unlock(&hid_bpf_attach_lock);
+
bpf_prog_put(prog);
+ kfree(link);
return err;
}
@@ -460,36 +501,10 @@ void __hid_bpf_destroy_device(struct hid_device *hdev)
void call_hid_bpf_prog_put_deferred(struct work_struct *work)
{
- struct bpf_prog_aux *aux;
- struct bpf_prog *prog;
- bool found = false;
- int i;
-
- aux = container_of(work, struct bpf_prog_aux, work);
- prog = aux->prog;
-
- /* we don't need locking here because the entries in the progs table
- * are stable:
- * if there are other users (and the progs entries might change), we
- * would simply not have been called.
- */
- for (i = 0; i < HID_BPF_MAX_PROGS; i++) {
- if (jmp_table.progs[i] == prog) {
- __clear_bit(i, jmp_table.enabled);
- found = true;
- }
- }
-
- if (found)
- /* schedule release of all detached progs */
- schedule_work(&release_work);
-}
-
-static void hid_bpf_prog_fd_array_put_ptr(void *ptr)
-{
+ /* kept around for patch readability, to be dropped in the next commmit */
}
-#define HID_BPF_PROGS_COUNT 2
+#define HID_BPF_PROGS_COUNT 1
static struct bpf_link *links[HID_BPF_PROGS_COUNT];
static struct entrypoints_bpf *skel;
@@ -528,8 +543,6 @@ void hid_bpf_free_links_and_skel(void)
idx++; \
} while (0)
-static struct bpf_map_ops hid_bpf_prog_fd_maps_ops;
-
int hid_bpf_preload_skel(void)
{
int err, idx = 0;
@@ -548,14 +561,7 @@ int hid_bpf_preload_skel(void)
goto out;
}
- /* our jump table is stealing refs, so we should not decrement on removal of elements */
- hid_bpf_prog_fd_maps_ops = *jmp_table.map->ops;
- hid_bpf_prog_fd_maps_ops.map_fd_put_ptr = hid_bpf_prog_fd_array_put_ptr;
-
- jmp_table.map->ops = &hid_bpf_prog_fd_maps_ops;
-
ATTACH_AND_STORE_LINK(hid_tail_call);
- ATTACH_AND_STORE_LINK(hid_bpf_prog_put_deferred);
return 0;
out:
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h
index 3ca85ab913258a259ded5ef09057c4e70f5a84b5..e9afb61e6ee019edfcaa74eb78c01da5dcb75d5e 100644
--- a/include/linux/hid_bpf.h
+++ b/include/linux/hid_bpf.h
@@ -3,6 +3,7 @@
#ifndef __HID_BPF_H
#define __HID_BPF_H
+#include <linux/bpf.h>
#include <linux/spinlock.h>
#include <uapi/linux/hid.h>
@@ -138,6 +139,12 @@ struct hid_bpf {
spinlock_t progs_lock; /* protects RCU update of progs */
};
+/* specific HID-BPF link when a program is attached to a device */
+struct hid_bpf_link {
+ struct bpf_link link;
+ int hid_table_index;
+};
+
#ifdef CONFIG_HID_BPF
u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
u32 *size, int interrupt);