[PATCH bpf-next v7 17/24] HID: bpf: introduce hid_hw_request()

Benjamin Tissoires
2022-07-21T15:39:56Z

This function can not be called under IRQ, thus it is only available
while in SEC("syscall").
For consistency, this function requires a HID-BPF context to work with,
and so we also provide a helper to create one based on the HID unique
ID.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

--

changes in v7:
- hid_bpf_allocate_context: remove unused variable
- ensures buf is not NULL

changes in v6:
- rename parameter size into buf__sz to teach the verifier about
the actual buffer size used by the call
- remove the allocated data in the user created context, it's not used

new-ish in v5
---
drivers/hid/bpf/hid_bpf_dispatch.c | 147 +++++++++++++++++++++++++++++
drivers/hid/hid-core.c | 2 +
include/linux/hid_bpf.h | 13 ++-
3 files changed, 161 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/bpf/hid_bpf_dispatch.c b/drivers/hid/bpf/hid_bpf_dispatch.c
index 5224af4a1c2a..cc5b29eb27f1 100644
--- a/drivers/hid/bpf/hid_bpf_dispatch.c
+++ b/drivers/hid/bpf/hid_bpf_dispatch.c
@@ -232,14 +232,161 @@ hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags)
return __hid_bpf_attach_prog(hdev, prog_type, prog_fd, flags);
}

+/**
+ * hid_bpf_allocate_context - Allocate a context to the given HID device
+ *
+ * @hid_id: the system unique identifier of the HID device
+ *
+ * @returns A pointer to &struct hid_bpf_ctx on success, %NULL on error.
+ */
+noinline struct hid_bpf_ctx *
+hid_bpf_allocate_context(unsigned int hid_id)
+{
+ struct hid_device *hdev;
+ struct hid_bpf_ctx_kern *ctx_kern = NULL;
+ struct device *dev;
+
+ if (!hid_bpf_ops)
+ return NULL;
+
+ dev = bus_find_device(hid_bpf_ops->bus_type, NULL, &hid_id, device_match_id);
+ if (!dev)
+ return NULL;
+
+ hdev = to_hid_device(dev);
+
+ ctx_kern = kzalloc(sizeof(*ctx_kern), GFP_KERNEL);
+ if (!ctx_kern)
+ return NULL;
+
+ ctx_kern->ctx.hid = hdev;
+
+ return &ctx_kern->ctx;
+}
+
+/**
+ * hid_bpf_release_context - Release the previously allocated context @ctx
+ *
+ * @ctx: the HID-BPF context to release
+ *
+ */
+noinline void
+hid_bpf_release_context(struct hid_bpf_ctx *ctx)
+{
+ struct hid_bpf_ctx_kern *ctx_kern;
+
+ if (!ctx)
+ return;
+
+ ctx_kern = container_of(ctx, struct hid_bpf_ctx_kern, ctx);
+
+ kfree(ctx_kern);
+}
+
+/**
+ * hid_bpf_hw_request - Communicate with a HID device
+ *
+ * @ctx: the HID-BPF context previously allocated in hid_bpf_allocate_context()
+ * @buf: a %PTR_TO_MEM buffer
+ * @buf__sz: the size of the data to transfer
+ * @rtype: the type of the report (%HID_INPUT_REPORT, %HID_FEATURE_REPORT, %HID_OUTPUT_REPORT)
+ * @reqtype: the type of the request (%HID_REQ_GET_REPORT, %HID_REQ_SET_REPORT, ...)
+ *
+ * @returns %0 on success, a negative error code otherwise.
+ */
+noinline int
+hid_bpf_hw_request(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz,
+ enum hid_report_type rtype, enum hid_class_request reqtype)
+{
+ struct hid_device *hdev = (struct hid_device *)ctx->hid; /* discard const */
+ struct hid_report *report;
+ struct hid_report_enum *report_enum;
+ u8 *dma_data;
+ u32 report_len;
+ int ret;
+
+ /* check arguments */
+ if (!ctx || !hid_bpf_ops || !buf)
+ return -EINVAL;
+
+ switch (rtype) {
+ case HID_INPUT_REPORT:
+ case HID_OUTPUT_REPORT:
+ case HID_FEATURE_REPORT:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ switch (reqtype) {
+ case HID_REQ_GET_REPORT:
+ case HID_REQ_GET_IDLE:
+ case HID_REQ_GET_PROTOCOL:
+ case HID_REQ_SET_REPORT:
+ case HID_REQ_SET_IDLE:
+ case HID_REQ_SET_PROTOCOL:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (buf__sz < 1)
+ return -EINVAL;
+
+ report_enum = hdev->report_enum + rtype;
+ report = hid_bpf_ops->hid_get_report(report_enum, buf);
+ if (!report)
+ return -EINVAL;
+
+ report_len = hid_report_len(report);
+
+ if (buf__sz > report_len)
+ buf__sz = report_len;
+
+ dma_data = kmemdup(buf, buf__sz, GFP_KERNEL);
+ if (!dma_data)
+ return -ENOMEM;
+
+ ret = hid_bpf_ops->hid_hw_raw_request(hdev,
+ dma_data[0],
+ dma_data,
+ buf__sz,
+ rtype,
+ reqtype);
+
+ if (ret > 0)
+ memcpy(buf, dma_data, ret);
+
+ kfree(dma_data);
+ return ret;
+}
+
/* for syscall HID-BPF */
BTF_SET_START(hid_bpf_syscall_kfunc_ids)
BTF_ID(func, hid_bpf_attach_prog)
+BTF_ID(func, hid_bpf_allocate_context)
+BTF_ID(func, hid_bpf_release_context)
+BTF_ID(func, hid_bpf_hw_request)
BTF_SET_END(hid_bpf_syscall_kfunc_ids)

+BTF_SET_START(hid_bpf_syscall_kfunc_ret_null_ids)
+BTF_ID(func, hid_bpf_allocate_context)
+BTF_SET_END(hid_bpf_syscall_kfunc_ret_null_ids)
+
+BTF_SET_START(hid_bpf_syscall_kfunc_alloc_ids)
+BTF_ID(func, hid_bpf_allocate_context)
+BTF_SET_END(hid_bpf_syscall_kfunc_alloc_ids)
+
+BTF_SET_START(hid_bpf_syscall_kfunc_release_ids)
+BTF_ID(func, hid_bpf_release_context)
+BTF_SET_END(hid_bpf_syscall_kfunc_release_ids)
+
static const struct btf_kfunc_id_set hid_bpf_syscall_kfunc_set = {
.owner = THIS_MODULE,
.check_set = &hid_bpf_syscall_kfunc_ids,
+ .ret_null_set = &hid_bpf_syscall_kfunc_ret_null_ids,
+ .acquire_set = &hid_bpf_syscall_kfunc_alloc_ids,
+ .release_set = &hid_bpf_syscall_kfunc_release_ids,
};

int hid_bpf_connect_device(struct hid_device *hdev)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index c2589106ea4b..356d3822f17d 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2917,6 +2917,8 @@ int hid_check_keys_pressed(struct hid_device *hid)
EXPORT_SYMBOL_GPL(hid_check_keys_pressed);

static struct hid_bpf_ops hid_ops = {
+ .hid_get_report = hid_get_report,
+ .hid_hw_raw_request = hid_hw_raw_request,
.owner = THIS_MODULE,
.bus_type = &hid_bus_type,
};
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h
index 86af0a79e6be..9d1cc1ceb942 100644
--- a/include/linux/hid_bpf.h
+++ b/include/linux/hid_bpf.h
@@ -61,11 +61,15 @@ struct hid_bpf_ctx {
int hid_bpf_device_event(struct hid_bpf_ctx *ctx);

/* Following functions are kfunc that we export to BPF programs */
-/* only available in tracing */
+/* available everywhere in HID-BPF */
__u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t __sz);

/* only available in syscall */
int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags);
+int hid_bpf_hw_request(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz,
+ enum hid_report_type rtype, enum hid_class_request reqtype);
+struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id);
+void hid_bpf_release_context(struct hid_bpf_ctx *ctx);

/*
* Below is HID internal
@@ -84,7 +88,14 @@ enum hid_bpf_prog_type {
HID_BPF_PROG_TYPE_MAX,
};

+struct hid_report_enum;
+
struct hid_bpf_ops {
+ struct hid_report *(*hid_get_report)(struct hid_report_enum *report_enum, const u8 *data);
+ int (*hid_hw_raw_request)(struct hid_device *hdev,
+ unsigned char reportnum, __u8 *buf,
+ size_t len, enum hid_report_type rtype,
+ enum hid_class_request reqtype);
struct module *owner;
struct bus_type *bus_type;
};
--
2.36.1