We do this implementation in several steps to not have the CI failing: - first (this patch), we add struct_ops while keeping the existing infra available - then we change the selftests, the examples and the existing in-tree HID-BPF programs - then we remove the existing trace points making old HID-BPF obsolete
There are a few advantages of struct_ops over tracing: - compatibility with sleepable programs (for hid_hw_raw_request() in a later patch) - a lot simpler in the kernel: it's a simple rcu protected list - we can add more parameters to the function called without much trouble - the "attach" is now generic through BPF-core: the caller just needs to set hid_id and flags before calling __load(). - all the BPF tough part is not handled in BPF-core through generic processing - hid_bpf_ctx is now only writable where it needs be
Signed-off-by: Benjamin Tissoires bentiss@kernel.org
---
changes in v3: - change private/public misleading comments - remove cache line comments/attribute - change mutex prog_list_lock comment
changes in v2: - drop custom enum hid_bpf_attach_flags (use BPF_F_BEFORE instead) - fix member offset in .ops_init_member() --- drivers/hid/bpf/Makefile | 2 +- drivers/hid/bpf/hid_bpf_dispatch.c | 52 +++++++- drivers/hid/bpf/hid_bpf_dispatch.h | 4 + drivers/hid/bpf/hid_bpf_jmp_table.c | 3 + drivers/hid/bpf/hid_bpf_struct_ops.c | 247 +++++++++++++++++++++++++++++++++++ include/linux/hid_bpf.h | 61 ++++++++- 6 files changed, 360 insertions(+), 9 deletions(-)
diff --git a/drivers/hid/bpf/Makefile b/drivers/hid/bpf/Makefile index cf55120cf7d6..1cb3f31e9335 100644 --- a/drivers/hid/bpf/Makefile +++ b/drivers/hid/bpf/Makefile @@ -8,4 +8,4 @@ LIBBPF_INCLUDE = $(srctree)/tools/lib obj-$(CONFIG_HID_BPF) += hid_bpf.o CFLAGS_hid_bpf_dispatch.o += -I$(LIBBPF_INCLUDE) CFLAGS_hid_bpf_jmp_table.o += -I$(LIBBPF_INCLUDE) -hid_bpf-objs += hid_bpf_dispatch.o hid_bpf_jmp_table.o +hid_bpf-objs += hid_bpf_dispatch.o hid_bpf_jmp_table.o hid_bpf_struct_ops.o diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c index c8bb79ce2354..7216c3c7713d 100644 --- a/drivers/hid/bpf/hid_bpf_dispatch.c +++ b/drivers/hid/bpf/hid_bpf_dispatch.c @@ -58,6 +58,7 @@ dispatch_hid_bpf_device_event(struct hid_device *hdev, enum hid_report_type type }, .data = hdev->bpf.device_data, }; + struct hid_bpf_ops *e; int ret;
if (type >= HID_REPORT_TYPES) @@ -70,9 +71,25 @@ dispatch_hid_bpf_device_event(struct hid_device *hdev, enum hid_report_type type memset(ctx_kern.data, 0, hdev->bpf.allocated_data); memcpy(ctx_kern.data, data, *size);
+ rcu_read_lock(); + list_for_each_entry_rcu(e, &hdev->bpf.prog_list, list) { + if (e->hid_device_event) { + ret = e->hid_device_event(&ctx_kern.ctx, type); + if (ret < 0) { + rcu_read_unlock(); + return ERR_PTR(ret); + } + + if (ret) + ctx_kern.ctx.retval = ret; + } + } + rcu_read_unlock(); + ret = hid_bpf_prog_run(hdev, HID_BPF_PROG_TYPE_DEVICE_EVENT, &ctx_kern); if (ret < 0) return ERR_PTR(ret); + ret = ctx_kern.ctx.retval;
if (ret) { if (ret > ctx_kern.ctx.allocated_size) @@ -122,7 +139,10 @@ u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *s
memcpy(ctx_kern.data, rdesc, min_t(unsigned int, *size, HID_MAX_DESCRIPTOR_SIZE));
- ret = hid_bpf_prog_run(hdev, HID_BPF_PROG_TYPE_RDESC_FIXUP, &ctx_kern); + if (hdev->bpf.rdesc_ops) + ret = hdev->bpf.rdesc_ops->hid_rdesc_fixup(&ctx_kern.ctx); + else + ret = hid_bpf_prog_run(hdev, HID_BPF_PROG_TYPE_RDESC_FIXUP, &ctx_kern); if (ret < 0) goto ignore_bpf;
@@ -150,7 +170,7 @@ static int device_match_id(struct device *dev, const void *id) return hdev->id == *(int *)id; }
-static struct hid_device *hid_get_device(unsigned int hid_id) +struct hid_device *hid_get_device(unsigned int hid_id) { struct device *dev;
@@ -164,7 +184,7 @@ static struct hid_device *hid_get_device(unsigned int hid_id) return to_hid_device(dev); }
-static void hid_put_device(struct hid_device *hid) +void hid_put_device(struct hid_device *hid) { put_device(&hid->dev); } @@ -205,7 +225,7 @@ static int __hid_bpf_allocate_data(struct hid_device *hdev, u8 **data, u32 *size return 0; }
-static int hid_bpf_allocate_event_data(struct hid_device *hdev) +int hid_bpf_allocate_event_data(struct hid_device *hdev) { /* hdev->bpf.device_data is already allocated, abort */ if (hdev->bpf.device_data) @@ -592,14 +612,22 @@ static const struct btf_kfunc_id_set hid_bpf_syscall_kfunc_set = {
int hid_bpf_connect_device(struct hid_device *hdev) { - struct hid_bpf_prog_list *prog_list; + bool need_to_allocate = false; + struct hid_bpf_ops *e;
rcu_read_lock(); - prog_list = rcu_dereference(hdev->bpf.progs[HID_BPF_PROG_TYPE_DEVICE_EVENT]); + list_for_each_entry_rcu(e, &hdev->bpf.prog_list, list) { + if (e->hid_device_event) { + need_to_allocate = true; + break; + } + } + if (rcu_dereference(hdev->bpf.progs[HID_BPF_PROG_TYPE_DEVICE_EVENT])) + need_to_allocate = true; rcu_read_unlock();
/* only allocate BPF data if there are programs attached */ - if (!prog_list) + if (!need_to_allocate) return 0;
return hid_bpf_allocate_event_data(hdev); @@ -623,12 +651,15 @@ void hid_bpf_destroy_device(struct hid_device *hdev) hdev->bpf.destroyed = true;
__hid_bpf_destroy_device(hdev); + __hid_bpf_ops_destroy_device(hdev); } EXPORT_SYMBOL_GPL(hid_bpf_destroy_device);
void hid_bpf_device_init(struct hid_device *hdev) { spin_lock_init(&hdev->bpf.progs_lock); + INIT_LIST_HEAD(&hdev->bpf.prog_list); + mutex_init(&hdev->bpf.prog_list_lock); } EXPORT_SYMBOL_GPL(hid_bpf_device_init);
@@ -662,6 +693,13 @@ static int __init hid_bpf_init(void) return 0; }
+ /* register struct_ops kfuncs after we are sure we can load our preloaded bpf program */ + err = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &hid_bpf_kfunc_set); + if (err) { + pr_warn("error while setting HID BPF tracing kfuncs: %d", err); + return 0; + } + /* register syscalls after we are sure we can load our preloaded bpf program */ err = register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &hid_bpf_syscall_kfunc_set); if (err) { diff --git a/drivers/hid/bpf/hid_bpf_dispatch.h b/drivers/hid/bpf/hid_bpf_dispatch.h index fbe0639d09f2..e52c43d81650 100644 --- a/drivers/hid/bpf/hid_bpf_dispatch.h +++ b/drivers/hid/bpf/hid_bpf_dispatch.h @@ -10,12 +10,16 @@ struct hid_bpf_ctx_kern { u8 *data; };
+struct hid_device *hid_get_device(unsigned int hid_id); +void hid_put_device(struct hid_device *hid); +int hid_bpf_allocate_event_data(struct hid_device *hdev); int hid_bpf_preload_skel(void); void hid_bpf_free_links_and_skel(void); int hid_bpf_get_prog_attach_type(struct bpf_prog *prog); int __hid_bpf_attach_prog(struct hid_device *hdev, enum hid_bpf_prog_type prog_type, int prog_fd, struct bpf_prog *prog, __u32 flags); void __hid_bpf_destroy_device(struct hid_device *hdev); +void __hid_bpf_ops_destroy_device(struct hid_device *hdev); int hid_bpf_prog_run(struct hid_device *hdev, enum hid_bpf_prog_type type, struct hid_bpf_ctx_kern *ctx_kern); int hid_bpf_reconnect(struct hid_device *hdev); diff --git a/drivers/hid/bpf/hid_bpf_jmp_table.c b/drivers/hid/bpf/hid_bpf_jmp_table.c index aa8e1c79cdf5..8a54ba447718 100644 --- a/drivers/hid/bpf/hid_bpf_jmp_table.c +++ b/drivers/hid/bpf/hid_bpf_jmp_table.c @@ -81,6 +81,9 @@ static int hid_bpf_program_count(struct hid_device *hdev, if (type >= HID_BPF_PROG_TYPE_MAX) return -EINVAL;
+ if (type == HID_BPF_PROG_TYPE_RDESC_FIXUP && hdev->bpf.rdesc_ops) + n += 1; + FOR_ENTRIES(i, jmp_table.tail, jmp_table.head) { struct hid_bpf_prog_entry *entry = &jmp_table.entries[i];
diff --git a/drivers/hid/bpf/hid_bpf_struct_ops.c b/drivers/hid/bpf/hid_bpf_struct_ops.c new file mode 100644 index 000000000000..9192c66cde20 --- /dev/null +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c @@ -0,0 +1,247 @@ +// SPDX-License-Identifier: GPL-2.0-only + +/* + * HID-BPF support for Linux + * + * Copyright (c) 2024 Benjamin Tissoires + */ + +#include <linux/bitops.h> +#include <linux/bpf_verifier.h> +#include <linux/bpf.h> +#include <linux/btf.h> +#include <linux/btf_ids.h> +#include <linux/filter.h> +#include <linux/hid.h> +#include <linux/hid_bpf.h> +#include <linux/init.h> +#include <linux/module.h> +#include <linux/workqueue.h> +#include "hid_bpf_dispatch.h" + +static struct btf *hid_bpf_ops_btf; + +static int hid_bpf_ops_init(struct btf *btf) +{ + hid_bpf_ops_btf = btf; + return 0; +} + +static bool hid_bpf_ops_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + return bpf_tracing_btf_ctx_access(off, size, type, prog, info); +} + +static int hid_bpf_ops_check_member(const struct btf_type *t, + const struct btf_member *member, + const struct bpf_prog *prog) +{ + u32 moff = __btf_member_bit_offset(t, member) / 8; + + switch (moff) { + case offsetof(struct hid_bpf_ops, hid_rdesc_fixup): + break; + default: + if (prog->sleepable) + return -EINVAL; + } + + return 0; +} + +static int hid_bpf_ops_btf_struct_access(struct bpf_verifier_log *log, + const struct bpf_reg_state *reg, + int off, int size) +{ + const struct btf_type *state; + const struct btf_type *t; + s32 type_id; + + type_id = btf_find_by_name_kind(reg->btf, "hid_bpf_ctx", + BTF_KIND_STRUCT); + if (type_id < 0) + return -EINVAL; + + t = btf_type_by_id(reg->btf, reg->btf_id); + state = btf_type_by_id(reg->btf, type_id); + if (t != state) { + bpf_log(log, "only access to hid_bpf_ctx is supported\n"); + return -EACCES; + } + + /* out-of-bound access in hid_bpf_ctx */ + if (off + size > sizeof(struct hid_bpf_ctx)) { + bpf_log(log, "write access at off %d with size %d\n", off, size); + return -EACCES; + } + + if (off < offsetof(struct hid_bpf_ctx, retval)) { + bpf_log(log, + "write access at off %d with size %d on read-only part of hid_bpf_ctx\n", + off, size); + return -EACCES; + } + + return NOT_INIT; +} + +static const struct bpf_verifier_ops hid_bpf_verifier_ops = { + .is_valid_access = hid_bpf_ops_is_valid_access, + .btf_struct_access = hid_bpf_ops_btf_struct_access, +}; + +static int hid_bpf_ops_init_member(const struct btf_type *t, + const struct btf_member *member, + void *kdata, const void *udata) +{ + u32 moff = __btf_member_bit_offset(t, member) / 8; + u32 flags; + + switch (moff) { + case offsetof(struct hid_bpf_ops, hid_id): + /* For hid_id and flags fields, this function has to copy it + * and return 1 to indicate that the data has been handled by + * the struct_ops type, or the verifier will reject the map if + * the value of those fields is not zero. + */ + ((struct hid_bpf_ops *)kdata)->hid_id = ((struct hid_bpf_ops *)udata)->hid_id; + return 1; + case offsetof(struct hid_bpf_ops, flags): + flags = ((struct hid_bpf_ops *)udata)->flags; + if (flags & ~BPF_F_BEFORE) + return -EINVAL; + ((struct hid_bpf_ops *)kdata)->flags = flags; + return 1; + } + return 0; +} + +static int hid_bpf_reg(void *kdata) +{ + struct hid_bpf_ops *ops = kdata; + struct hid_device *hdev; + int count, err = 0; + + hdev = hid_get_device(ops->hid_id); + if (IS_ERR(hdev)) + return PTR_ERR(hdev); + + ops->hdev = hdev; + + mutex_lock(&hdev->bpf.prog_list_lock); + + count = list_count_nodes(&hdev->bpf.prog_list); + if (count >= HID_BPF_MAX_PROGS_PER_DEV) { + err = -E2BIG; + goto out_unlock; + } + + if (ops->hid_rdesc_fixup) { + if (hdev->bpf.rdesc_ops) { + err = -EINVAL; + goto out_unlock; + } + + hdev->bpf.rdesc_ops = ops; + } + + if (ops->hid_device_event) { + err = hid_bpf_allocate_event_data(hdev); + if (err) + goto out_unlock; + } + + if (ops->flags & BPF_F_BEFORE) + list_add_rcu(&ops->list, &hdev->bpf.prog_list); + else + list_add_tail_rcu(&ops->list, &hdev->bpf.prog_list); + +out_unlock: + mutex_unlock(&hdev->bpf.prog_list_lock); + + if (err) { + if (hdev->bpf.rdesc_ops == ops) + hdev->bpf.rdesc_ops = NULL; + hid_put_device(hdev); + } else if (ops->hid_rdesc_fixup) { + hid_bpf_reconnect(hdev); + } + + return err; +} + +static void hid_bpf_unreg(void *kdata) +{ + struct hid_bpf_ops *ops = kdata; + struct hid_device *hdev; + bool reconnect = false; + + hdev = ops->hdev; + + /* check if __hid_bpf_ops_destroy_device() has been called */ + if (!hdev) + return; + + mutex_lock(&hdev->bpf.prog_list_lock); + + list_del_rcu(&ops->list); + + reconnect = hdev->bpf.rdesc_ops == ops; + if (reconnect) + hdev->bpf.rdesc_ops = NULL; + + mutex_unlock(&hdev->bpf.prog_list_lock); + + if (reconnect) + hid_bpf_reconnect(hdev); + + hid_put_device(hdev); +} + +static int __hid_bpf_device_event(struct hid_bpf_ctx *ctx, enum hid_report_type type) +{ + return 0; +} + +static int __hid_bpf_rdesc_fixup(struct hid_bpf_ctx *ctx) +{ + return 0; +} + +static struct hid_bpf_ops __bpf_hid_bpf_ops = { + .hid_device_event = __hid_bpf_device_event, + .hid_rdesc_fixup = __hid_bpf_rdesc_fixup, +}; + +static struct bpf_struct_ops bpf_hid_bpf_ops = { + .verifier_ops = &hid_bpf_verifier_ops, + .init = hid_bpf_ops_init, + .check_member = hid_bpf_ops_check_member, + .init_member = hid_bpf_ops_init_member, + .reg = hid_bpf_reg, + .unreg = hid_bpf_unreg, + .name = "hid_bpf_ops", + .cfi_stubs = &__bpf_hid_bpf_ops, + .owner = THIS_MODULE, +}; + +void __hid_bpf_ops_destroy_device(struct hid_device *hdev) +{ + struct hid_bpf_ops *e; + + rcu_read_lock(); + list_for_each_entry_rcu(e, &hdev->bpf.prog_list, list) { + hid_put_device(hdev); + e->hdev = NULL; + } + rcu_read_unlock(); +} + +static int __init hid_bpf_struct_ops_init(void) +{ + return register_bpf_struct_ops(&bpf_hid_bpf_ops, hid_bpf_ops); +} +late_initcall(hid_bpf_struct_ops_init); diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h index a66103618e6e..c4f4ce10b7dd 100644 --- a/include/linux/hid_bpf.h +++ b/include/linux/hid_bpf.h @@ -65,11 +65,12 @@ struct hid_bpf_ctx { * @HID_BPF_FLAG_INSERT_HEAD: insert the given program before any other program * currently attached to the device. This doesn't * guarantee that this program will always be first - * @HID_BPF_FLAG_MAX: sentinel value, not to be used by the callers */ enum hid_bpf_attach_flags { HID_BPF_FLAG_NONE = 0, HID_BPF_FLAG_INSERT_HEAD = _BITUL(0), + + /* private: internal use only */ HID_BPF_FLAG_MAX, };
@@ -112,6 +113,60 @@ struct hid_ops {
extern struct hid_ops *hid_ops;
+/** + * struct hid_bpf_ops - A BPF struct_ops of callbacks allowing to attach HID-BPF + * programs to a HID device + * @hid_id: the HID uniq ID to attach to. This is writeable before ``load()``, and + * cannot be changed after + * @flags: flags used while attaching the struct_ops to the device. Currently only + * available value is %0 or ``BPF_F_BEFORE``. + * Writeable only before ``load()`` + */ +struct hid_bpf_ops { + /* hid_id needs to stay first so we can easily change it + * from userspace. + */ + int hid_id; + u32 flags; + + /* private: do not show up in the docs */ + struct list_head list; + + /* public: rest should show up in the docs */ + + /** + * @hid_device_event: called whenever an event is coming in from the device + * + * It has the following arguments: + * + * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx + * + * Return: %0 on success and keep processing; a positive + * value to change the incoming size buffer; a negative + * error code to interrupt the processing of this event + * + * Context: Interrupt context. + */ + int (*hid_device_event)(struct hid_bpf_ctx *ctx, enum hid_report_type report_type); + + /** + * @hid_rdesc_fixup: called when the probe function parses the report descriptor + * of the HID device + * + * It has the following arguments: + * + * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx + * + * Return: %0 on success and keep processing; a positive + * value to change the incoming size buffer; a negative + * error code to interrupt the processing of this device + */ + int (*hid_rdesc_fixup)(struct hid_bpf_ctx *ctx); + + /* private: do not show up in the docs */ + struct hid_device *hdev; +}; + struct hid_bpf_prog_list { u16 prog_idx[HID_BPF_MAX_PROGS_PER_DEV]; u8 prog_cnt; @@ -129,6 +184,10 @@ struct hid_bpf { bool destroyed; /* prevents the assignment of any progs */
spinlock_t progs_lock; /* protects RCU update of progs */ + + struct hid_bpf_ops *rdesc_ops; + struct list_head prog_list; + struct mutex prog_list_lock; /* protects prog_list update */ };
/* specific HID-BPF link when a program is attached to a device */