[PATCH] usb: gadget: functions: add ftrace export over USB

[Felipe Balbi <felipe.balbi@linux.intel.com>]

Allow for ftrace data to be exported over a USB Gadget
Controller. With this, we have a potentially very fast pipe for
transmitting ftrace data to a Host PC for further analysis.

Note that in order to decode the data, one needs access to kernel
symbols in order to convert binary data into function names and what
not.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
---

I wanted to take this through the gadget tree, but there is a
dependency with a previous patch of mine adding and extra argument to
the ->write() function. Hoping someone else will take it.

 drivers/usb/gadget/Kconfig            |  15 ++
 drivers/usb/gadget/function/Makefile  |   2 +
 drivers/usb/gadget/function/f-trace.c | 400 ++++++++++++++++++++++++++++++++++
 3 files changed, 417 insertions(+)
 create mode 100644 drivers/usb/gadget/function/f-trace.c

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index c164d6b788c3..617921f19b5e 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -188,6 +188,9 @@ config USB_F_MASS_STORAGE
 config USB_F_FS
 	tristate
 
+config USB_F_TRACE
+	tristate
+
 config USB_F_UAC1
 	tristate
 
@@ -362,6 +365,18 @@ config USB_CONFIGFS_F_FS
 	  implemented in kernel space (for instance Ethernet, serial or
 	  mass storage) and other are implemented in user space.
 
+config USB_CONFIGFS_F_TRACE
+	bool "Linux FTrace Export Over USB"
+	depends on USB_CONFIGFS
+	select USB_F_TRACE
+	help
+	  The Linux FTrace Export Over USB lets one export ftrace buffer
+	  over a USB cable to a host computer for further processing.
+
+	  If you want support for that, say Y or M here. Otherwise say N.
+
+	  If unsure, say N.
+
 config USB_CONFIGFS_F_UAC1
 	bool "Audio Class 1.0"
 	depends on USB_CONFIGFS
diff --git a/drivers/usb/gadget/function/Makefile b/drivers/usb/gadget/function/Makefile
index cb8c225e8549..1433e8ad7675 100644
--- a/drivers/usb/gadget/function/Makefile
+++ b/drivers/usb/gadget/function/Makefile
@@ -46,3 +46,5 @@ usb_f_printer-y			:= f_printer.o
 obj-$(CONFIG_USB_F_PRINTER)	+= usb_f_printer.o
 usb_f_tcm-y			:= f_tcm.o
 obj-$(CONFIG_USB_F_TCM)		+= usb_f_tcm.o
+usb_f_trace-y			:= f-trace.o
+obj-$(CONFIG_USB_F_TRACE)	+= usb_f_trace.o
diff --git a/drivers/usb/gadget/function/f-trace.c b/drivers/usb/gadget/function/f-trace.c
new file mode 100644
index 000000000000..7de92950c0e7
--- /dev/null
+++ b/drivers/usb/gadget/function/f-trace.c
@@ -0,0 +1,400 @@
+/*
+ * f_trace.c -- USB FTrace Export
+ *
+ * Copyright (C) 2017 Intel Corporation
+ * Author: Felipe Balbi <felipe.balbi@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License v2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/trace.h>
+#include <linux/usb.h>
+#include <linux/usb/composite.h>
+#include <linux/usb/gadget.h>
+#include <linux/workqueue.h>
+
+struct usb_ftrace {
+	struct trace_export ftrace;
+	struct usb_function function;
+	struct work_struct queue_work;
+	spinlock_t lock;
+
+	struct list_head list;
+	struct list_head pending;
+	struct list_head queued;
+
+	struct usb_ep *in;
+
+	u8 intf_id;
+};
+#define ftrace_to_trace(f)	(container_of((f), struct usb_ftrace, ftrace))
+#define work_to_trace(w)	(container_of((w), struct usb_ftrace, queue_work))
+#define to_trace(f)		(container_of((f), struct usb_ftrace, function))
+
+#define FTRACE_REQUEST_QUEUE_LENGTH	250
+
+static inline struct usb_request *next_request(struct list_head *list)
+{
+	return list_first_entry_or_null(list, struct usb_request, list);
+}
+
+struct usb_ftrace_opts {
+	struct usb_function_instance func_inst;
+};
+#define to_opts(fi)	(container_of((fi), struct usb_ftrace_opts, func_inst))
+
+static struct usb_interface_descriptor ftrace_intf_desc = {
+	.bLength		= USB_DT_INTERFACE_SIZE,
+	.bDescriptorType	= USB_DT_INTERFACE,
+
+	.bAlternateSetting	= 0,
+	.bNumEndpoints		= 1,
+	.bInterfaceClass	= USB_CLASS_VENDOR_SPEC,
+	.bInterfaceSubClass	= USB_SUBCLASS_VENDOR_SPEC,
+};
+
+/* Super-Speed Support */
+static struct usb_endpoint_descriptor ftrace_ss_in_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+
+	.bEndpointAddress	= USB_DIR_IN,
+	.bmAttributes		= USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize		= cpu_to_le16(1024),
+};
+
+static struct usb_ss_ep_comp_descriptor ftrace_ss_in_comp_desc = {
+	.bLength		= USB_DT_SS_EP_COMP_SIZE,
+	.bDescriptorType	= USB_DT_SS_ENDPOINT_COMP,
+
+	.bMaxBurst		= 15,
+};
+
+static struct usb_descriptor_header *ftrace_ss_function[] = {
+	(struct usb_descriptor_header *) &ftrace_intf_desc,
+	(struct usb_descriptor_header *) &ftrace_ss_in_desc,
+	(struct usb_descriptor_header *) &ftrace_ss_in_comp_desc,
+	NULL,
+};
+
+/* High-Speed Support */
+static struct usb_endpoint_descriptor ftrace_hs_in_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+
+	.bEndpointAddress	= USB_DIR_IN,
+	.bmAttributes		= USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize		= cpu_to_le16(512),
+};
+
+static struct usb_descriptor_header *ftrace_hs_function[] = {
+	(struct usb_descriptor_header *) &ftrace_intf_desc,
+	(struct usb_descriptor_header *) &ftrace_hs_in_desc,
+	NULL,
+};
+
+/* Full-Speed Support */
+static struct usb_endpoint_descriptor ftrace_fs_in_desc = {
+	.bLength		= USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType	= USB_DT_ENDPOINT,
+
+	.bEndpointAddress	= USB_DIR_IN,
+	.bmAttributes		= USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize		= cpu_to_le16(64),
+};
+
+static struct usb_descriptor_header *ftrace_fs_function[] = {
+	(struct usb_descriptor_header *) &ftrace_intf_desc,
+	(struct usb_descriptor_header *) &ftrace_fs_in_desc,
+	NULL,
+};
+
+static struct usb_string ftrace_string_defs[] = {
+	[0].s = "Linux Ftrace Export",
+	{ },
+};
+
+static struct usb_gadget_strings ftrace_string_table = {
+	.language		= 0x0409, /* en-US */
+	.strings		= ftrace_string_defs,
+};
+
+static struct usb_gadget_strings *ftrace_strings[] = {
+	&ftrace_string_table,
+	NULL,
+};
+
+/* ------------------------------------------------------------------------ */
+
+static void ftrace_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct usb_ftrace		*trace = req->context;
+
+	kfree(req->buf);
+	list_move_tail(&req->list, &trace->list);
+}
+
+static void ftrace_queue_work(struct work_struct *work)
+{
+	struct usb_ftrace		*trace = work_to_trace(work);
+	struct usb_request		*req;
+	struct usb_request		*tmp;
+	struct list_head		local_list;
+
+	spin_lock_irq(&trace->lock);
+restart:
+	list_replace_init(&trace->pending, &local_list);
+	spin_unlock_irq(&trace->lock);
+
+	list_for_each_entry_safe(req, tmp, &local_list, list) {
+		int			ret;
+
+		ret = usb_ep_queue(trace->in, req, GFP_KERNEL);
+		if (!ret)
+			list_move_tail(&req->list, &trace->queued);
+	}
+
+	spin_lock_irq(&trace->lock);
+	if (!list_empty(&trace->pending))
+		goto restart;
+	spin_unlock_irq(&trace->lock);
+}
+
+static void notrace ftrace_write(struct trace_export *ftrace, const void *buf,
+				 unsigned int len)
+{
+	struct usb_ftrace		*trace = ftrace_to_trace(ftrace);
+	struct usb_request		*req = next_request(&trace->list);
+
+	if (!req)
+		return;
+
+	if (!trace->in->enabled)
+		return;
+
+	req->buf = kmemdup(buf, len, GFP_ATOMIC);
+	req->length = len;
+	req->context = trace;
+	req->complete = ftrace_complete;
+	list_move_tail(&req->list, &trace->pending);
+
+	schedule_work(&trace->queue_work);
+}
+
+/* ------------------------------------------------------------------------ */
+
+static void ftrace_disable_endpoint(struct usb_ftrace *trace)
+{
+	if (trace->in->enabled)
+		WARN_ON(usb_ep_disable(trace->in));
+}
+
+static int ftrace_enable_endpoint(struct usb_ftrace *trace)
+{
+	if (trace->in->enabled)
+		return 0;
+
+	return usb_ep_enable(trace->in);
+}
+
+static int ftrace_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+	struct usb_ftrace		*trace = to_trace(f);
+	struct usb_composite_dev	*cdev = f->config->cdev;
+	int				ret;
+
+	if (alt != 0)
+		goto fail;
+
+	if (intf != trace->intf_id)
+		goto fail;
+
+	ftrace_disable_endpoint(trace);
+
+	if (!trace->in->desc) {
+		ret = config_ep_by_speed(cdev->gadget, f, trace->in);
+		if (ret) {
+			trace->in->desc = NULL;
+			goto fail;
+		}
+	}
+
+	ret = ftrace_enable_endpoint(trace);
+	if (ret)
+		goto fail;
+
+	return 0;
+
+fail:
+	return -EINVAL;
+}
+
+static int ftrace_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev	*cdev = c->cdev;
+	struct usb_ftrace		*trace = to_trace(f);
+	struct usb_string		*us;
+	struct usb_ep			*ep;
+
+	int				ret;
+	int				i;
+
+	us = usb_gstrings_attach(cdev, ftrace_strings,
+				 ARRAY_SIZE(ftrace_string_defs));
+	if (IS_ERR(us))
+		return PTR_ERR(us);
+
+	ftrace_intf_desc.iInterface = us[0].id;
+
+	ret = usb_interface_id(c, f);
+	if (ret < 0)
+		goto err0;
+	trace->intf_id = ret;
+	ftrace_intf_desc.bInterfaceNumber = ret;
+
+	ep = usb_ep_autoconfig(cdev->gadget, &ftrace_fs_in_desc);
+	if (!ep)
+		goto err0;
+	trace->in = ep;
+
+	ftrace_hs_in_desc.bEndpointAddress = ftrace_fs_in_desc.bEndpointAddress;
+	ftrace_ss_in_desc.bEndpointAddress = ftrace_fs_in_desc.bEndpointAddress;
+
+	trace->ftrace.write = ftrace_write;
+
+	spin_lock_init(&trace->lock);
+	INIT_WORK(&trace->queue_work, ftrace_queue_work);
+	INIT_LIST_HEAD(&trace->list);
+	INIT_LIST_HEAD(&trace->pending);
+	INIT_LIST_HEAD(&trace->queued);
+
+	ret = usb_assign_descriptors(f, ftrace_fs_function, ftrace_hs_function,
+				     ftrace_ss_function, NULL);
+	if (ret)
+		goto err0;
+
+	for (i = 0; i < FTRACE_REQUEST_QUEUE_LENGTH; i++) {
+		struct usb_request *req;
+
+		req = usb_ep_alloc_request(trace->in, GFP_KERNEL);
+		if (!req)
+			goto err1;
+
+		list_add_tail(&req->list, &trace->list);
+	}
+
+	ret = register_ftrace_export(&trace->ftrace);
+	if (ret)
+		goto err1;
+
+	return 0;
+
+err1:
+	while (!list_empty(&trace->list)) {
+		struct usb_request *req = next_request(&trace->list);
+
+		usb_ep_free_request(trace->in, req);
+		list_del(&req->list);
+	}
+
+	usb_free_all_descriptors(f);
+
+err0:
+	ERROR(cdev, "%s: can't bind --> err %d\n", f->name, ret);
+
+	return ret;
+}
+
+static void ftrace_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_ftrace		*trace = to_trace(f);
+	struct usb_request		*req;
+	struct usb_request		*tmp;
+
+	unregister_ftrace_export(&trace->ftrace);
+	cancel_work_sync(&trace->queue_work);
+	usb_free_all_descriptors(f);
+
+	list_for_each_entry(req, &trace->queued, list)
+		usb_ep_dequeue(trace->in, req);
+
+	list_for_each_entry_safe(req, tmp, &trace->pending, list) {
+		usb_ep_free_request(trace->in, req);
+		list_del(&req->list);
+	}
+
+	list_for_each_entry_safe(req, tmp, &trace->list, list) {
+		usb_ep_free_request(trace->in, req);
+		list_del(&req->list);
+	}
+}
+
+static void ftrace_disable(struct usb_function *f)
+{
+	struct usb_ftrace		*trace = to_trace(f);
+
+	ftrace_disable_endpoint(trace);
+}
+
+static void ftrace_free_func(struct usb_function *f)
+{
+	kfree(to_trace(f));
+}
+
+static struct config_item_type ftrace_func_type = {
+	.ct_owner		= THIS_MODULE,
+};
+
+static void ftrace_free_inst(struct usb_function_instance *fi)
+{
+	struct usb_ftrace_opts		*opts = to_opts(fi);
+
+	kfree(opts);
+}
+
+static struct usb_function_instance *ftrace_alloc_inst(void)
+{
+	struct usb_ftrace_opts		*opts;
+
+	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+	if (!opts)
+		return ERR_PTR(-ENOMEM);
+
+	opts->func_inst.free_func_inst = ftrace_free_inst;
+
+	config_group_init_type_name(&opts->func_inst.group, "",
+				    &ftrace_func_type);
+
+	return &opts->func_inst;
+}
+
+static struct usb_function *ftrace_alloc(struct usb_function_instance *fi)
+{
+	struct usb_ftrace		*trace;
+
+	trace = kzalloc(sizeof(*trace), GFP_KERNEL);
+	if (!trace)
+		return NULL;
+
+	trace->function.name = "ftrace";
+	trace->function.bind = ftrace_bind;
+	trace->function.unbind = ftrace_unbind;
+	trace->function.set_alt = ftrace_set_alt;
+	trace->function.disable = ftrace_disable;
+	trace->function.strings = ftrace_strings;
+	trace->function.free_func = ftrace_free_func;
+
+	return &trace->function;
+}
+
+DECLARE_USB_FUNCTION_INIT(ftrace, ftrace_alloc_inst, ftrace_alloc);
+MODULE_AUTHOR("Felipe Balbi <felipe.balbi@linux.intel.com>");
+MODULE_LICENSE("GPL v2");
-- 
2.11.0.295.gd7dffce1ce