From a808a224f54ef44b7399b291ec9d8bcf758e43da Mon Sep 17 00:00:00 2001 From: "martin.holst@gmail.com" Date: Fri, 31 May 2013 19:25:13 +0000 Subject: [PATCH] Found that USBcommands from the device are silently overwritten if the host does not quickly enough read them, which causes problems in several places. Implemented a circular buffer which stores up to 50 commands (still tiny, memorywise) and prints out a message if the buffer wraps around (overwrites). --- client/cmdmain.c | 135 +++++++++++++++++++++++++++++------------------ 1 file changed, 84 insertions(+), 51 deletions(-) diff --git a/client/cmdmain.c b/client/cmdmain.c index a9a37ad1..7f34d543 100644 --- a/client/cmdmain.c +++ b/client/cmdmain.c @@ -33,6 +33,14 @@ UsbCommand current_response_user; static int CmdHelp(const char *Cmd); static int CmdQuit(const char *Cmd); +//For storing command that are received from the device +#define CMD_BUFFER_SIZE 50 +static UsbCommand cmdBuffer[CMD_BUFFER_SIZE]; +//Points to the next empty position to write to +static int cmd_head;//Starts as 0 +//Points to the position of the last unread command +static int cmd_tail = -1;//Starts as -1 + static command_t CommandTable[] = { {"help", CmdHelp, 1, "This help. Use ' help' for details of the following commands:\n"}, @@ -56,30 +64,31 @@ int CmdQuit(const char *Cmd) exit(0); return 0; } - +/** + * Waits for a certain response type. This method waits for a maximum of + * ms_timeout milliseconds for a specified response command. + *@brief WaitForResponseTimeout + * @param cmd command to wait for + * @param response struct to copy received command into. + * @param ms_timeout + * @return true if command was returned, otherwise false + */ bool WaitForResponseTimeout(uint32_t cmd, UsbCommand* response, size_t ms_timeout) { - // Wait until the command is received - for(size_t i=0; received_command != cmd && i < ms_timeout/10; i++) { - msleep(10); // XXX ugh - if (i == 200) { // Two seconds elapsed - PrintAndLog("Waiting for a response from the proxmark..."); - PrintAndLog("Don't forget to cancel its operation first by pressing on the button"); - } - } - - // Check if timeout occured - if(received_command != cmd) return false; - - // Copy the received response (if supplied) - if (response) { - memcpy(response, ¤t_response, sizeof(UsbCommand)); - } - - // Reset the received command - received_command = CMD_UNKNOWN; + // Wait until the command is received + for(size_t dm_seconds=0; dm_seconds < ms_timeout/10; dm_seconds++) { - return true; + if(getCommand(response) && response->cmd == cmd){ + //We got what we expected + return true; + } + msleep(10); // XXX ugh + if (dm_seconds == 200) { // Two seconds elapsed + PrintAndLog("Waiting for a response from the proxmark..."); + PrintAndLog("Don't forget to cancel its operation first by pressing on the button"); + } + } + return false; } bool WaitForResponse(uint32_t cmd, UsbCommand* response) { @@ -183,37 +192,61 @@ void UsbCommandReceived(UsbCommand *UC) default: { } break; } -// // Store the last received command -// memcpy(¤t_response, UC, sizeof(UsbCommand)); -// received_command = UC->cmd; } break; } - // Store the last received command - memcpy(¤t_response, UC, sizeof(UsbCommand)); - received_command = UC->cmd; -/* - // Maybe it's a response: - switch(current_command) { - case CMD_DOWNLOAD_RAW_ADC_SAMPLES_125K: - if (UC->cmd != CMD_DOWNLOADED_RAW_ADC_SAMPLES_125K) goto unexpected_response; - int i; - for(i=0; i<48; i++) sample_buf[i] = UC->d.asBytes[i]; - received_command = UC->cmd; - return; - case CMD_ACQUIRE_RAW_ADC_SAMPLES_125K: - case CMD_DOWNLOADED_SIM_SAMPLES_125K: - if (UC->cmd != CMD_ACK) goto unexpected_response; - // got ACK - received_command = UC->cmd; - return; - default: - unexpected_response: - - if(UC->cmd != CMD_ACK) - PrintAndLog("unrecognized command %08x \n", UC->cmd); - else - memcpy(¤t_response, UC, sizeof(UsbCommand)); - received_command = UC->cmd; - } + + storeCommand(UC); + +} +/** + * @brief storeCommand stores a USB command in a circular buffer + * @param UC + */ +void storeCommand(UsbCommand *command) +{ + if(cmd_head == cmd_tail) + { + //If these two are equal, we're about to overwrite in the + // circular buffer. + PrintAndLog("WARNING: Command buffer about to overwrite command! This needs to be fixed!"); + } + //Store the command at the 'head' location + UsbCommand* destination = &cmdBuffer[cmd_head]; + memcpy(destination, command, sizeof(UsbCommand)); + + //Also, if cmd_tail is still -1 because the buffer was + // previously empty, set it to head + if(cmd_tail < 0) { + cmd_tail = cmd_head; + } + + cmd_head++; //increment head + cmd_head %= CMD_BUFFER_SIZE;//wrap around + +} +/** + * @brief getCommand gets a command from an internal circular buffer. + * @param response location to write command + * @return 1 if response was returned, 0 if nothing has been received */ +int getCommand(UsbCommand* response) +{ + //If head == tail, there's nothing to read, or if we just got initialized + if(cmd_head == cmd_tail || cmd_tail == -1){ + return 0; + } + //Pick out the next unread command + UsbCommand* last_unread = &cmdBuffer[cmd_tail]; + memcpy(response, last_unread, sizeof(UsbCommand)); + //Increment tail - this is a circular buffer, so modulo buffer size + cmd_tail = (cmd_tail +1 ) % CMD_BUFFER_SIZE; + //In order to detect when the buffer overwrites itself, we set the + // tail to -1 whenever it 'catches up' with head : this means the buffer is empty. + // Otherwise, head==tail could mean both: either empty or full. + if(cmd_tail == cmd_head){ + cmd_tail = -1 ; + } + + return 1; + } -- 2.39.2