diff options
| -rw-r--r-- | Documentation/hid/hid-bpf.rst | 12 | ||||
| -rw-r--r-- | drivers/hid/bpf/hid_bpf_dispatch.c | 18 | ||||
| -rw-r--r-- | drivers/hid/bpf/hid_bpf_jmp_table.c | 126 | ||||
| -rw-r--r-- | include/linux/hid_bpf.h | 7 |
4 files changed, 95 insertions, 68 deletions
diff --git a/Documentation/hid/hid-bpf.rst b/Documentation/hid/hid-bpf.rst index a55f191d49a3..c205f92b7bcc 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 58e608ebf0fa..8d29fd361ab9 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 207972b028d9..b7eb5c5e435f 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 3ca85ab91325..e9afb61e6ee0 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); |