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Message-ID: <20220426041950.j37velutd2ckj3s5@MBP-98dd607d3435.dhcp.thefacebook.com>
Date: Mon, 25 Apr 2022 21:19:50 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: Greg KH <gregkh@...uxfoundation.org>,
Jiri Kosina <jikos@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Tero Kristo <tero.kristo@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
bpf@...r.kernel.org
Subject: Re: [RFC bpf-next v4 5/7] HID: initial BPF new way implementation
On Thu, Apr 21, 2022 at 04:07:38PM +0200, Benjamin Tissoires wrote:
> Declare an entry point that can use fmod_ret BPF programs, and
> also an API to access and change the incoming data.
>
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>
> ---
>
> new-ish in v4:
> - far from complete, but gives an overview of what we can do now.
> ---
> drivers/hid/hid-core.c | 115 ++++++++++++++++++++++++++++++++++++++++
> include/linux/hid_bpf.h | 29 ++++++++++
> 2 files changed, 144 insertions(+)
> create mode 100644 include/linux/hid_bpf.h
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index db925794fbe6..ff4e1b47d2fb 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -32,6 +32,9 @@
> #include <linux/hiddev.h>
> #include <linux/hid-debug.h>
> #include <linux/hidraw.h>
> +#include <linux/btf.h>
> +#include <linux/btf_ids.h>
> +#include <linux/hid_bpf.h>
>
> #include "hid-ids.h"
>
> @@ -2008,6 +2011,99 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
> }
> EXPORT_SYMBOL_GPL(hid_report_raw_event);
>
> +struct hid_bpf_ctx_kern {
> + struct hid_device *hdev;
> + struct hid_bpf_ctx ctx;
> + u8 *data;
> + size_t size;
> +};
> +
> +__weak int hid_bpf_device_event(struct hid_bpf_ctx *ctx, s64 type)
> +{
> + return 0;
> +}
> +ALLOW_ERROR_INJECTION(hid_bpf_device_event, NS_ERRNO);
> +
> +noinline __u8 *
> +hid_bpf_kfunc_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t __sz)
> +{
> + struct hid_bpf_ctx_kern *ctx_kern;
> +
> + if (!ctx)
> + return NULL;
> +
> + ctx_kern = container_of(ctx, struct hid_bpf_ctx_kern, ctx);
> +
> + return ctx_kern->data;
> +}
It probably needs to check that "rdonly_buf_sz" or "__sz" constant passed
by the program is less than what was allocated in hid_bpf_ctx_kern->data.
Right?
> +
> +noinline void
> +hid_bpf_kfunc_data_release(__u8 *data)
> +{
> +}
Not clear what release() is for.
hid_bpf_kfunc_get_data() will return PTR_TO_MEM.
There is no need to release it.
> +
> +noinline int
> +hid_bpf_kfunc_hw_request(struct hid_bpf_ctx *ctx)
> +{
> + if (!ctx)
> + return -EINVAL;
> +
> + pr_err("%s test ctx->bus: %04x %s:%d", __func__, ctx->bus, __FILE__, __LINE__);
> +
> + return 0;
> +}
> +
> +/*
> + * The following set contains all functions we agree BPF programs
> + * can use.
> + */
> +BTF_SET_START(hid_bpf_kfunc_ids)
> +BTF_ID(func, hid_bpf_kfunc_get_data)
> +BTF_ID(func, hid_bpf_kfunc_data_release)
> +BTF_ID(func, hid_bpf_kfunc_hw_request)
> +BTF_SET_END(hid_bpf_kfunc_ids)
> +
> +/*
> + * The following set contains all functions to provide a kernel
> + * resource to the BPF program.
> + * We need to add a counterpart release function.
> + */
> +BTF_SET_START(hid_bpf_kfunc_acquire_ids)
> +BTF_ID(func, hid_bpf_kfunc_get_data)
> +BTF_SET_END(hid_bpf_kfunc_acquire_ids)
> +
> +/*
> + * The following set is the release counterpart of the previous
> + * function set.
> + */
> +BTF_SET_START(hid_bpf_kfunc_release_ids)
> +BTF_ID(func, hid_bpf_kfunc_data_release)
> +BTF_SET_END(hid_bpf_kfunc_release_ids)
> +
> +/*
> + * The following set tells which functions are sleepable.
> + */
> +BTF_SET_START(hid_bpf_kfunc_sleepable_ids)
> +BTF_ID(func, hid_bpf_kfunc_hw_request)
> +BTF_SET_END(hid_bpf_kfunc_sleepable_ids)
> +
> +static const struct btf_kfunc_id_set hid_bpf_kfunc_set = {
> + .owner = THIS_MODULE,
> + .check_set = &hid_bpf_kfunc_ids,
> + .acquire_set = &hid_bpf_kfunc_acquire_ids,
> + .release_set = &hid_bpf_kfunc_release_ids,
> + .ret_null_set = &hid_bpf_kfunc_acquire_ids, /* duplicated to force BPF programs to
> + * check the validity of the returned pointer
> + * in acquire function
> + */
> + .sleepable_set = &hid_bpf_kfunc_sleepable_ids,
> +};
> +
> +static int __init hid_bpf_init(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &hid_bpf_kfunc_set);
> +}
> +
> /**
> * hid_input_report - report data from lower layer (usb, bt...)
> *
> @@ -2025,6 +2121,17 @@ int hid_input_report(struct hid_device *hid, int type, u8 *data, u32 size, int i
> struct hid_driver *hdrv;
> struct hid_report *report;
> int ret = 0;
> + struct hid_bpf_ctx_kern ctx_kern = {
> + .hdev = hid,
> + .ctx = {
> + .bus = hid->bus,
> + .group = hid->group,
> + .vendor = hid->vendor,
> + .product = hid->product,
> + },
> + .data = data,
> + .size = size,
> + };
I'm not sure why hid_bpf_ctx_kern is needed.
Just to scope all args into one struct?
> +/*
> + * The following is the HID BPF API.
> + *
> + * It should be treated as UAPI, so extra care is required
> + * when making change to this file.
> + */
> +
> +struct hid_bpf_ctx {
> + __u16 bus; /* BUS ID */
> + __u16 group; /* Report group */
> + __u32 vendor; /* Vendor ID */
> + __u32 product; /* Product ID */
> + __u32 version; /* HID version */
> +};
Your choice of course,
but not clear why kernel has to populate it with explicit:
+ .bus = hid->bus,
+ .group = hid->group,
+ .vendor = hid->vendor,
+ .product = hid->product,
and waste cpu cycles on that while bpf program can read all these fields
on demand when necessary.
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