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).

This commit is contained in:
martin.holst@gmail.com 2013-05-31 19:25:13 +00:00
parent 79c3611cf3
commit a808a224f5

View file

@ -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 '<command> 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");
}
// Wait until the command is received
for(size_t dm_seconds=0; dm_seconds < ms_timeout/10; dm_seconds++) {
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");
}
}
// Check if timeout occured
if(received_command != cmd) return false;
// Copy the received response (if supplied)
if (response) {
memcpy(response, &current_response, sizeof(UsbCommand));
}
// Reset the received command
received_command = CMD_UNKNOWN;
return true;
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(&current_response, UC, sizeof(UsbCommand));
// received_command = UC->cmd;
} break;
}
// Store the last received command
memcpy(&current_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(&current_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;
}