Felipe Balbi <felipe.ba...@linux.intel.com> writes: > Felipe Balbi <felipe.ba...@linux.intel.com> writes: > >> 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.ba...@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. > > just as an extra note here. In order for this to be really useful, it > would be nice to be able to control what is going to be traced over USB > as well, but that means exporting a few extra functions to GPL drivers. > > Would that be okay? I could have a set of vendor-specific control > requests to set buffer size and to read/write ftrace filter functions. > > The idea is that things like e.g. Android SDK could rely on this on > debug builds and the SDK itself would make sure to keep a copy of > vmlinux around to processing of the data coming through USB.
something along these lines (although I think trace buffer size doesn't matter for trace export, but it serves well enough to illustrate a point): modified drivers/usb/gadget/function/f-trace.c @@ -33,6 +33,8 @@ struct usb_ftrace { struct usb_ep *in; + u32 buffer_size; + u16 version; u8 intf_id; }; #define ftrace_to_trace(f) (container_of((f), struct usb_ftrace, ftrace)) @@ -40,6 +42,12 @@ struct usb_ftrace { #define to_trace(f) (container_of((f), struct usb_ftrace, function)) #define FTRACE_REQUEST_QUEUE_LENGTH 250 +#define FTRACE_VERSION 0x0100 /* bcd 1.00 */ + +/* FTrace vendor-specific requests */ +#define USB_FTRACE_GET_VERSION 0x00 +#define USB_FTRACE_GET_TRACE_BUF_SIZE 0x01 +#define USB_FTRACE_SET_TRACE_BUF_SIZE 0x02 static inline struct usb_request *next_request(struct list_head *list) { @@ -142,6 +150,13 @@ static void ftrace_complete(struct usb_ep *ep, struct usb_request *req) list_move_tail(&req->list, &trace->list); } +static void ftrace_set_trace_buf_size_complete(struct usb_ep *ep, struct usb_request *req) +{ + struct usb_ftrace *trace = req->context; + + trace_set_buf_size(le32_to_cpu(trace->buffer_size)); +} + static void ftrace_queue_work(struct work_struct *work) { struct usb_ftrace *trace = work_to_trace(work); @@ -237,6 +252,71 @@ static int ftrace_set_alt(struct usb_function *f, unsigned intf, unsigned alt) return -EINVAL; } +extern unsigned long trace_get_buf_size(void); + +static int ftrace_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl) +{ + struct usb_configuration *c = f->config; + struct usb_request *req = c->cdev->req; + struct usb_ftrace *trace = to_trace(f); + + int ret; + + u16 index = le16_to_cpu(ctrl->wIndex); + u16 value = le16_to_cpu(ctrl->wValue); + u16 length = le16_to_cpu(ctrl->wLength); + + if (value != 0 || index != 0) + return -EINVAL; + + switch (ctrl->bRequest) { + case USB_FTRACE_GET_VERSION: + if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_VENDOR | + USB_RECIP_INTERFACE)) + return -EINVAL; + + if (length != 2) + return -EINVAL; + + req->zero = 0; + req->length = 2; + req->buf = &trace->version; + break; + case USB_FTRACE_GET_TRACE_BUF_SIZE: + if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_VENDOR | + USB_RECIP_INTERFACE)) + return -EINVAL; + + if (length != 2) + return -EINVAL; + + trace->buffer_size = cpu_to_le32(trace_get_buf_size()); + + req->zero = 0; + req->length = 2; + req->buf = &trace->buffer_size; + break; + case USB_FTRACE_SET_TRACE_BUF_SIZE: + if (ctrl->bRequestType != (USB_DIR_OUT | USB_TYPE_VENDOR | + USB_RECIP_INTERFACE)) + return -EINVAL; + + if (length != 4) + return -EINVAL; + + req->zero = 0; + req->length = 4; + req->context = trace; + req->complete = ftrace_set_trace_buf_size_complete; + req->buf = &trace->buffer_size; + break; + default: + return -EINVAL; + } + + return usb_ep_queue(c->cdev->gadget->ep0, req, GFP_ATOMIC); +} + static int ftrace_bind(struct usb_configuration *c, struct usb_function *f) { struct usb_composite_dev *cdev = c->cdev; @@ -247,6 +327,8 @@ static int ftrace_bind(struct usb_configuration *c, struct usb_function *f) int ret; int i; + trace->version = cpu_to_le16(FTRACE_VERSION); + us = usb_gstrings_attach(cdev, ftrace_strings, ARRAY_SIZE(ftrace_string_defs)); if (IS_ERR(us)) modified kernel/trace/trace.c @@ -618,6 +618,12 @@ int tracing_is_enabled(void) static unsigned long trace_buf_size = TRACE_BUF_SIZE_DEFAULT; +unsigned long trace_get_buf_size(void) +{ + return trace_buf_size; +} +EXPORT_SYMBOL_GPL(trace_get_buf_size); + /* trace_types holds a link list of available tracers. */ static struct tracer *trace_types __read_mostly; -- balbi
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