[HID,03/13] HID: bpf: implement HID-BPF through bpf_struct_ops

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>
---
 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 | 246 +++++++++++++++++++++++++++++++++++
 include/linux/hid_bpf.h              |  64 ++++++++-
 6 files changed, 362 insertions(+), 9 deletions(-)

On Tue, May 28, 2024 at 6:15 AM Benjamin Tissoires <bentiss@kernel.org> wrote:
>
> 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>
> ---
>  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 | 246 +++++++++++++++++++++++++++++++++++
>  include/linux/hid_bpf.h              |  64 ++++++++-
>  6 files changed, 362 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) {

In the typical case there will be only one prog per device, right?
The for_each is future proofing?

> +               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);

This is for backward compat?
I don't see it's being removed in the later patches.

>         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..be514a98e55b
> --- /dev/null
> +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c
> @@ -0,0 +1,246 @@
> +// 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;
> +

this is good...

> +       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 flags;
> +
> +       switch (member->offset) {
> +       case offsetof(struct hid_bpf_ops, hid_id) * 8:

but here you're open coding it and adding ugly * 8
Just do:
        moff = __btf_member_bit_offset(t, member) / 8;
        switch (moff) {
        case offsetof(struct tcp_congestion_ops, flags):

the way bpf_tcp_ca.c is doing?
Open code of ->offset is asking for trouble.

> +               /* 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) * 8:
> +               flags = ((struct hid_bpf_ops *)udata)->flags;
> +               if (flags & ~HID_BPF_FLAG_MASK)
> +                       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 & HID_BPF_FLAG_INSERT_HEAD)
> +               list_add_rcu(&ops->list, &hdev->bpf.prog_list);
> +       else
> +               list_add_tail_rcu(&ops->list, &hdev->bpf.prog_list);

Looks like future proofing, but I feel it's too little to materialize.
Take a look at include/linux/bpf_mprog.h
I suspect it might be useful here too.

> +
> +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..96495e977204 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 +113,63 @@ 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: &enum hid_bpf_attach_flags to assign flags before ``load()``.
> + *        Writeable only before ``load()``
> + */
> +struct hid_bpf_ops {
> +       /* hid_id needs to stay first so we can easily change it
> +        * from userspace.
> +        */

hmm.
patch 5 just does:
+       skel->struct_ops.mouse_invert->hid_id = hid_id;

I don't see a reason why it needs to be first.

> +       int                     hid_id;
> +       u32                     flags;
> +
> +       /* private: internal use only */
> +       struct list_head        list;
> +
> +       /* public: rest is public */
> +
> +/* fast path fields are put first to fill one cache line */
> +
> +       /**
> +        * @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);
> +
> +/* control/slow paths put last */
> +
> +       /**
> +        * @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);

It's fine since you want to keep the prog mostly unchanged,
but since the whole api is improving maybe it's time
to do something about hid_bpf_ctx in all callbacks?
Pass into prog what prog needs to see.
In the old api all progs had to have a common hid_bpf_ctx.
With struct-ops it can be fine tuned.

Overall it looks great.
hid_id did the trick :)

On May 28 2024, Alexei Starovoitov wrote:
> On Tue, May 28, 2024 at 6:15 AM Benjamin Tissoires <bentiss@kernel.org> wrote:
> >
> > 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>
> > ---
> >  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 | 246 +++++++++++++++++++++++++++++++++++
> >  include/linux/hid_bpf.h              |  64 ++++++++-
> >  6 files changed, 362 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) {
> 
> In the typical case there will be only one prog per device, right?

90% of the time there is only one prog per device, but I need to have
more than one for the following reasons:
- when one prog is loaded, the output data gets modified, so to be able
  to access the raw data from the device I need to add a "tracing" program
  *before* the one that changes data to forward raw data to userspace
- we already have situation where for convenience multiple programs are
  attached to one device (see drivers/hid/bpf/progs/XPPen__ArtistPro16Gen2.bpf.c)
- once firewalling will be in place, we will likely have one program for
  the firewall and one for the device fix

> The for_each is future proofing?
> 
> > +               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);
> 
> This is for backward compat?

yes

> I don't see it's being removed in the later patches.

see patch 8/13, all the tracing capabilities are gone.

I made a backward compatibility step here so I do not break the
selftests while changing the API.

> 
> >         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..be514a98e55b
> > --- /dev/null
> > +++ b/drivers/hid/bpf/hid_bpf_struct_ops.c
> > @@ -0,0 +1,246 @@
> > +// 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;
> > +
> 
> this is good...
> 
> > +       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 flags;
> > +
> > +       switch (member->offset) {
> > +       case offsetof(struct hid_bpf_ops, hid_id) * 8:
> 
> but here you're open coding it and adding ugly * 8
> Just do:
>         moff = __btf_member_bit_offset(t, member) / 8;
>         switch (moff) {
>         case offsetof(struct tcp_congestion_ops, flags):
> 
> the way bpf_tcp_ca.c is doing?
> Open code of ->offset is asking for trouble.

heh, I just monkey-copied tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

Will change it :)

> 
> > +               /* 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) * 8:
> > +               flags = ((struct hid_bpf_ops *)udata)->flags;
> > +               if (flags & ~HID_BPF_FLAG_MASK)
> > +                       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 & HID_BPF_FLAG_INSERT_HEAD)
> > +               list_add_rcu(&ops->list, &hdev->bpf.prog_list);
> > +       else
> > +               list_add_tail_rcu(&ops->list, &hdev->bpf.prog_list);
> 
> Looks like future proofing, but I feel it's too little to materialize.

again, the case already happens, so I need a list (or equivalent of) :)

> Take a look at include/linux/bpf_mprog.h
> I suspect it might be useful here too.

Hi Benjamin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 70ec81c2e2b4005465ad0d042e90b36087c36104]

url:    https://github.com/intel-lab-lkp/linux/commits/Benjamin-Tissoires/HID-rename-struct-hid_bpf_ops-into-hid_ops/20240528-212222
base:   70ec81c2e2b4005465ad0d042e90b36087c36104
patch link:    https://lore.kernel.org/r/20240528-hid_bpf_struct_ops-v1-3-8c6663df27d8%40kernel.org
patch subject: [PATCH HID 03/13] HID: bpf: implement HID-BPF through bpf_struct_ops
config: i386-buildonly-randconfig-002-20240531 (https://download.01.org/0day-ci/archive/20240531/202405312035.U1rZN04z-lkp@intel.com/config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240531/202405312035.U1rZN04z-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202405312035.U1rZN04z-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/linux/bpf_verifier.h:7:0,
                    from drivers/hid/bpf/hid_bpf_struct_ops.c:10:
   drivers/hid/bpf/hid_bpf_struct_ops.c: In function 'hid_bpf_struct_ops_init':
>> include/linux/bpf.h:1844:50: warning: statement with no effect [-Wunused-value]
    #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; })
                                                     ^~~~~~~~~~~~~~~~
   drivers/hid/bpf/hid_bpf_struct_ops.c:244:9: note: in expansion of macro 'register_bpf_struct_ops'
     return register_bpf_struct_ops(&bpf_hid_bpf_ops, hid_bpf_ops);
            ^~~~~~~~~~~~~~~~~~~~~~~


vim +1844 include/linux/bpf.h

c196906d50e360d Hou Tao          2021-10-25  1834  
c196906d50e360d Hou Tao          2021-10-25  1835  int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
c196906d50e360d Hou Tao          2021-10-25  1836  			    union bpf_attr __user *uattr);
c196906d50e360d Hou Tao          2021-10-25  1837  #endif
f6be98d19985411 Kui-Feng Lee     2024-01-19  1838  int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
f6be98d19985411 Kui-Feng Lee     2024-01-19  1839  			     struct btf *btf,
f6be98d19985411 Kui-Feng Lee     2024-01-19  1840  			     struct bpf_verifier_log *log);
1338b93346587a2 Kui-Feng Lee     2024-01-19  1841  void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map);
1611603537a4b88 Kui-Feng Lee     2024-02-08  1842  void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc);
27ae7997a66174c Martin KaFai Lau 2020-01-08  1843  #else
f6be98d19985411 Kui-Feng Lee     2024-01-19 @1844  #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; })
85d33df357b6346 Martin KaFai Lau 2020-01-08  1845  static inline bool bpf_try_module_get(const void *data, struct module *owner)
85d33df357b6346 Martin KaFai Lau 2020-01-08  1846  {
85d33df357b6346 Martin KaFai Lau 2020-01-08  1847  	return try_module_get(owner);
85d33df357b6346 Martin KaFai Lau 2020-01-08  1848  }
85d33df357b6346 Martin KaFai Lau 2020-01-08  1849  static inline void bpf_module_put(const void *data, struct module *owner)
85d33df357b6346 Martin KaFai Lau 2020-01-08  1850  {
85d33df357b6346 Martin KaFai Lau 2020-01-08  1851  	module_put(owner);
85d33df357b6346 Martin KaFai Lau 2020-01-08  1852  }
85d33df357b6346 Martin KaFai Lau 2020-01-08  1853  static inline int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map,
85d33df357b6346 Martin KaFai Lau 2020-01-08  1854  						     void *key,
85d33df357b6346 Martin KaFai Lau 2020-01-08  1855  						     void *value)
85d33df357b6346 Martin KaFai Lau 2020-01-08  1856  {
85d33df357b6346 Martin KaFai Lau 2020-01-08  1857  	return -EINVAL;
85d33df357b6346 Martin KaFai Lau 2020-01-08  1858  }
68b04864ca425d1 Kui-Feng Lee     2023-03-22  1859  static inline int bpf_struct_ops_link_create(union bpf_attr *attr)
68b04864ca425d1 Kui-Feng Lee     2023-03-22  1860  {
68b04864ca425d1 Kui-Feng Lee     2023-03-22  1861  	return -EOPNOTSUPP;
68b04864ca425d1 Kui-Feng Lee     2023-03-22  1862  }
1338b93346587a2 Kui-Feng Lee     2024-01-19  1863  static inline void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map)
1338b93346587a2 Kui-Feng Lee     2024-01-19  1864  {
1338b93346587a2 Kui-Feng Lee     2024-01-19  1865  }
68b04864ca425d1 Kui-Feng Lee     2023-03-22  1866