Hi Song,
many thanks for the quick response.
On Fri, Mar 18, 2022 at 9:48 PM Song Liu <song@xxxxxxxxxx> wrote:
>
> On Fri, Mar 18, 2022 at 9:16 AM Benjamin Tissoires
> <benjamin.tissoires@xxxxxxxxxx> wrote:
> >
> [...]
> >
> > diff --git a/include/linux/bpf-hid.h b/include/linux/bpf-hid.h
> > new file mode 100644
> > index 000000000000..9c8dbd389995
> > --- /dev/null
> > +++ b/include/linux/bpf-hid.h
> >
> [...]
> > +
> > +struct hid_bpf_ctx_kern {
> > + enum hid_bpf_event type; /* read-only */
> > + struct hid_device *hdev; /* read-only */
> > +
> > + u16 size; /* used size in data (RW) */
> > + u8 *data; /* data buffer (RW) */
> > + u32 allocated_size; /* allocated size of data (RO) */
>
> Why u16 size vs. u32 allocated_size?
Probably an oversight because I wrote u32 in the public uapi. Will
change this into u16 too.
> Also, maybe shuffle the members
> to remove some holes?
Ack will do in the next version.
>
> > +
> > + s32 retval; /* in use when BPF_HID_ATTACH_USER_EVENT (RW) */
> > +};
> > +
> [...]
>
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>
> We need to mirror these changes to tools/include/uapi/linux/bpf.h.
OK. I did that in patch 4/17 but I can bring in the changes there too.
>
> > index 99fab54ae9c0..0e8438e93768 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -952,6 +952,7 @@ enum bpf_prog_type {
> > BPF_PROG_TYPE_LSM,
> > BPF_PROG_TYPE_SK_LOOKUP,
> > BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> > + BPF_PROG_TYPE_HID,
> > };
> [...]
> > +
> > /* When BPF ldimm64's insn[0].src_reg != 0 then this can have
> > * the following extensions:
> > *
> > @@ -5129,6 +5145,16 @@ union bpf_attr {
> > * The **hash_algo** is returned on success,
> > * **-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
> > * invalid arguments are passed.
> > + *
> > + * void *bpf_hid_get_data(void *ctx, u64 offset, u64 size)
> > + * Description
> > + * Returns a pointer to the data associated with context at the given
> > + * offset and size (in bytes).
> > + *
> > + * Note: the returned pointer is refcounted and must be dereferenced
> > + * by a call to bpf_hid_discard;
> > + * Return
> > + * The pointer to the data. On error, a null value is returned.
>
> Please use annotations like *size*, **NULL**.
Ack
>
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -5325,6 +5351,7 @@ union bpf_attr {
> > FN(copy_from_user_task), \
> > FN(skb_set_tstamp), \
> > FN(ima_file_hash), \
> > + FN(hid_get_data), \
> > /* */
> >
> > /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> > @@ -5925,6 +5952,10 @@ struct bpf_link_info {
> > struct {
> > __u32 ifindex;
> > } xdp;
> > + struct {
> > + __s32 hidraw_number;
> > + __u32 attach_type;
> > + } hid;
> > };
> > } __attribute__((aligned(8)));
> >
> > diff --git a/include/uapi/linux/bpf_hid.h b/include/uapi/linux/bpf_hid.h
> > new file mode 100644
> > index 000000000000..64a8b9dd8809
> > --- /dev/null
> > +++ b/include/uapi/linux/bpf_hid.h
> > @@ -0,0 +1,31 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later WITH Linux-syscall-note */
> > +
> > +/*
> > + * HID BPF public headers
> > + *
> > + * Copyright (c) 2022 Benjamin Tissoires
> > + */
> > +
> > +#ifndef _UAPI__LINUX_BPF_HID_H__
> > +#define _UAPI__LINUX_BPF_HID_H__
> > +
> > +#include <linux/types.h>
> > +
> > +enum hid_bpf_event {
> > + HID_BPF_UNDEF = 0,
> > + HID_BPF_DEVICE_EVENT, /* when attach type is BPF_HID_DEVICE_EVENT */
> > + HID_BPF_RDESC_FIXUP, /* ................... BPF_HID_RDESC_FIXUP */
> > + HID_BPF_USER_EVENT, /* ................... BPF_HID_USER_EVENT */
>
> Why don't we have a DRIVER_EVENT type here?
For driver event, I want to have a little bit more of information
which tells which event we have:
- HID_BPF_DRIVER_PROBE
- HID_BPF_DRIVER_SUSPEND
- HID_BPF_DRIVER_RAW_REQUEST
- HID_BPF_DRIVER_RAW_REQUEST_ANSWER
- etc...
However, I am not entirely sure on the implementation of all of those,
so I left them aside for now.
I'll work on that for v4.
>
> >
> [...]
> > +
> > +BPF_CALL_3(bpf_hid_get_data, struct hid_bpf_ctx_kern*, ctx, u64, offset, u64, size)
> > +{
> > + if (!size)
> > + return 0UL;
> > +
> > + if (offset + size > ctx->allocated_size)
> > + return 0UL;
> > +
> > + return (unsigned long)(ctx->data + offset);
> > +}
> > +
> > +static const struct bpf_func_proto bpf_hid_get_data_proto = {
> > + .func = bpf_hid_get_data,
> > + .gpl_only = true,
> > + .ret_type = RET_PTR_TO_ALLOC_MEM_OR_NULL,
> > + .arg1_type = ARG_PTR_TO_CTX,
> > + .arg2_type = ARG_ANYTHING,
> > + .arg3_type = ARG_CONST_ALLOC_SIZE_OR_ZERO,
>
> I think we should use ARG_CONST_SIZE or ARG_CONST_SIZE_OR_ZERO?
I initially tried this with ARG_CONST_SIZE_OR_ZERO but it doesn't work
for 2 reasons:
- we need to pair the argument ARG_CONST_SIZE_* with a pointer to a
memory just before, which doesn't really make sense here
- ARG_CONST_SIZE_* isn't handled in the same way
ARG_CONST_ALLOC_SIZE_OR_ZERO is. The latter tells the verifier that
the given size is the available size of the returned
PTR_TO_ALLOC_MEM_OR_NULL, which is exactly what we want.
>
> > +};
> > +
> > +static const struct bpf_func_proto *
> > +hid_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > +{
> > + switch (func_id) {
> > + case BPF_FUNC_hid_get_data:
> > + return &bpf_hid_get_data_proto;
> > + default:
> > + return bpf_base_func_proto(func_id);
> > + }
> > +}
> [...]
> > +
> > +static int hid_bpf_prog_test_run(struct bpf_prog *prog,
> > + const union bpf_attr *attr,
> > + union bpf_attr __user *uattr)
> > +{
> > + struct hid_device *hdev = NULL;
> > + struct bpf_prog_array *progs;
> > + bool valid_prog = false;
> > + int i;
> > + int target_fd, ret;
> > + void __user *data_out = u64_to_user_ptr(attr->test.data_out);
> > + void __user *data_in = u64_to_user_ptr(attr->test.data_in);
> > + u32 user_size_in = attr->test.data_size_in;
> > + u32 user_size_out = attr->test.data_size_out;
> > + u32 allocated_size = max(user_size_in, user_size_out);
> > + struct hid_bpf_ctx_kern ctx = {
> > + .type = HID_BPF_USER_EVENT,
> > + .allocated_size = allocated_size,
> > + };
> > +
> > + if (!hid_hooks.hdev_from_fd)
> > + return -EOPNOTSUPP;
> > +
> > + if (attr->test.ctx_size_in != sizeof(int))
> > + return -EINVAL;
>
> ctx_size_in is always 4 bytes?
Yes. Basically what I had in mind is that the "ctx" for
user_prog_test_run is the file descriptor to the sysfs that represent
the HID device.
This seemed to me to be the easiest to handle for users.
I'm open to suggestions though.
>
> > +
> > + if (allocated_size > HID_MAX_BUFFER_SIZE)
> > + return -E2BIG;
> > +
> > + if (copy_from_user(&target_fd, (void *)attr->test.ctx_in, attr->test.ctx_size_in))
> > + return -EFAULT;
> > +
> > + hdev = hid_hooks.hdev_from_fd(target_fd);
> > + if (IS_ERR(hdev))
> > + return PTR_ERR(hdev);
> > +
> > + if (allocated_size) {
> > + ctx.data = kzalloc(allocated_size, GFP_KERNEL);
> > + if (!ctx.data)
> > + return -ENOMEM;
> > +
> > + ctx.allocated_size = allocated_size;
> > + }
> > + ctx.hdev = hdev;
> > +
> > + ret = mutex_lock_interruptible(&bpf_hid_mutex);
> > + if (ret)
> > + return ret;
> > +
> > + /* check if the given program is of correct type and registered */
> > + progs = rcu_dereference_protected(hdev->bpf.run_array[BPF_HID_ATTACH_USER_EVENT],
> > + lockdep_is_held(&bpf_hid_mutex));
> > + if (!progs) {
> > + ret = -EFAULT;
> > + goto unlock;
> > + }
> > +
> > + for (i = 0; i < bpf_prog_array_length(progs); i++) {
> > + if (progs->items[i].prog == prog) {
> > + valid_prog = true;
> > + break;
> > + }
> > + }
> > +
> > + if (!valid_prog) {
> > + ret = -EINVAL;
> > + goto unlock;
> > + }
> > +
> > + /* copy data_in from userspace */
> > + if (user_size_in) {
> > + if (copy_from_user(ctx.data, data_in, user_size_in)) {
> > + ret = -EFAULT;
> > + goto unlock;
> > + }
> > +
> > + ctx.size = user_size_in;
> > + }
> > +
> > + migrate_disable();
> > +
> > + ret = bpf_prog_run(prog, &ctx);
> > +
> > + migrate_enable();
> > +
> > + if (user_size_out && data_out) {
> > + user_size_out = min3(user_size_out, (u32)ctx.size, allocated_size);
> > +
> > + if (copy_to_user(data_out, ctx.data, user_size_out)) {
> > + ret = -EFAULT;
> > + goto unlock;
> > + }
> > +
> > + if (copy_to_user(&uattr->test.data_size_out,
> > + &user_size_out,
> > + sizeof(user_size_out))) {
> > + ret = -EFAULT;
> > + goto unlock;
> > + }
> > + }
> > +
> > + if (copy_to_user(&uattr->test.retval, &ctx.retval, sizeof(ctx.retval)))
> > + ret = -EFAULT;
> > +
> > +unlock:
> > + kfree(ctx.data);
> > +
> > + mutex_unlock(&bpf_hid_mutex);
> > + return ret;
> > +}
> > +
> > +const struct bpf_prog_ops hid_prog_ops = {
> > + .test_run = hid_bpf_prog_test_run,
> > +};
> > +
> > +int bpf_hid_init(struct hid_device *hdev)
> > +{
> > + int type;
> > +
> > + for (type = 0; type < MAX_BPF_HID_ATTACH_TYPE; type++)
> > + INIT_LIST_HEAD(&hdev->bpf.links[type]);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(bpf_hid_init);
> > +
> > +void bpf_hid_exit(struct hid_device *hdev)
> > +{
> > + enum bpf_hid_attach_type type;
> > + struct bpf_hid_link *hid_link;
> > +
> > + mutex_lock(&bpf_hid_mutex);
> > + for (type = 0; type < MAX_BPF_HID_ATTACH_TYPE; type++) {
> > + bpf_hid_run_array_detach(hdev, type);
> > + list_for_each_entry(hid_link, &hdev->bpf.links[type], node) {
> > + hid_link->hdev = NULL; /* auto-detach link */
> > + }
> > + }
> > + mutex_unlock(&bpf_hid_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(bpf_hid_exit);
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index b88688264ad0..d1c05011e5ab 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -3,6 +3,7 @@
> > */
> > #include <linux/bpf.h>
> > #include <linux/bpf-cgroup.h>
> > +#include <linux/bpf-hid.h>
> > #include <linux/bpf_trace.h>
> > #include <linux/bpf_lirc.h>
> > #include <linux/bpf_verifier.h>
> > @@ -2205,6 +2206,7 @@ static bool is_sys_admin_prog_type(enum bpf_prog_type prog_type)
> > {
> > switch (prog_type) {
> > case BPF_PROG_TYPE_LIRC_MODE2:
> > + case BPF_PROG_TYPE_HID:
> > return true;
> > default:
> > return false;
> > @@ -3199,6 +3201,11 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
> > return BPF_PROG_TYPE_SK_LOOKUP;
> > case BPF_XDP:
> > return BPF_PROG_TYPE_XDP;
> > + case BPF_HID_DEVICE_EVENT:
> > + case BPF_HID_RDESC_FIXUP:
> > + case BPF_HID_USER_EVENT:
> > + case BPF_HID_DRIVER_EVENT:
> > + return BPF_PROG_TYPE_HID;
> > default:
> > return BPF_PROG_TYPE_UNSPEC;
> > }
> > @@ -3342,6 +3349,11 @@ static int bpf_prog_query(const union bpf_attr *attr,
> > case BPF_SK_MSG_VERDICT:
> > case BPF_SK_SKB_VERDICT:
> > return sock_map_bpf_prog_query(attr, uattr);
> > + case BPF_HID_DEVICE_EVENT:
> > + case BPF_HID_RDESC_FIXUP:
> > + case BPF_HID_USER_EVENT:
> > + case BPF_HID_DRIVER_EVENT:
> > + return bpf_hid_prog_query(attr, uattr);
> > default:
> > return -EINVAL;
> > }
> > @@ -4336,6 +4348,8 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
> > ret = bpf_perf_link_attach(attr, prog);
> > break;
> > #endif
> > + case BPF_PROG_TYPE_HID:
> > + return bpf_hid_link_create(attr, prog);
> > default:
> > ret = -EINVAL;
> > }
> > --
> > 2.35.1
> >
>
Cheers,
Benjamin
