ftdi: fix overflow if last field of a scan is empty

[openocd.git] / src / jtag / drivers / ftdi.c

diff --git a/src/jtag/drivers/ftdi.c b/src/jtag/drivers/ftdi.c
index 72b08fd4c95e65c058469136b4bc158dbb7d7db5..46797d7dfe3952d0e3ca221849e0d4fb0c8dfef9 100644 (file)
--- a/src/jtag/drivers/ftdi.c
+++ b/src/jtag/drivers/ftdi.c
@@ -389,6 +389,18 @@ static int ftdi_execute_scan(struct jtag_command *cmd)
        DEBUG_JTAG_IO("%s type:%d", cmd->cmd.scan->ir_scan ? "IRSCAN" : "DRSCAN",
                jtag_scan_type(cmd->cmd.scan));
 
+       /* Make sure there are no trailing fields with num_bits == 0, or the logic below will fail. */
+       while (cmd->cmd.scan->num_fields > 0
+                       && cmd->cmd.scan->fields[cmd->cmd.scan->num_fields - 1].num_bits == 0) {
+               cmd->cmd.scan->num_fields--;
+               LOG_DEBUG("discarding trailing empty field");
+       }
+
+       if (cmd->cmd.scan->num_fields == 0) {
+               LOG_DEBUG("empty scan, doing nothing");
+               return retval;
+       }
+
        if (cmd->cmd.scan->ir_scan) {
                if (tap_get_state() != TAP_IRSHIFT)
                        move_to_state(TAP_IRSHIFT);
@@ -413,7 +425,7 @@ static int ftdi_execute_scan(struct jtag_command *cmd)
 
                if (i == cmd->cmd.scan->num_fields - 1 && tap_get_state() != tap_get_end_state()) {
                        /* Last field, and we're leaving IRSHIFT/DRSHIFT. Clock last bit during tap
-                        *movement */
+                        * movement. This last field can't have length zero, it was checked above. */
                        mpsse_clock_data(mpsse_ctx,
                                field->out_value,
                                0,