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authorTat-Chee Wan2012-02-03 23:57:04 +0100
committerNicolas Schodet2012-02-11 17:30:42 +0100
commitd50dd5ab9567cc308e412c5e9e775dc8e15fb509 (patch)
treeb7d30c1025fb34e65a04d15701c53ee2ca071dec /AT91SAM7S256/armdebug/Debugger/debug_comm.S
parentceb0cbf65a11aed7662eb41ae66157e60ff61d60 (diff)
merge armdebug rc1
This enables the use of GDB or GDB based debuggers to debug the code running on the NXT brick using the USB connection.
Diffstat (limited to 'AT91SAM7S256/armdebug/Debugger/debug_comm.S')
-rw-r--r--AT91SAM7S256/armdebug/Debugger/debug_comm.S555
1 files changed, 555 insertions, 0 deletions
diff --git a/AT91SAM7S256/armdebug/Debugger/debug_comm.S b/AT91SAM7S256/armdebug/Debugger/debug_comm.S
new file mode 100644
index 0000000..4c23912
--- /dev/null
+++ b/AT91SAM7S256/armdebug/Debugger/debug_comm.S
@@ -0,0 +1,555 @@
+/** @file debug_comm.S
+ * @brief GDB Server communications support routines
+ *
+ */
+
+/* Copyright (C) 2007-2011 the NxOS developers
+ *
+ * Module Developed by: TC Wan <tcwan@cs.usm.my>
+ *
+ * See AUTHORS for a full list of the developers.
+ *
+ * See COPYING for redistribution license
+ *
+ */
+
+#define __ASSEMBLY__
+#include "debug_macros.h"
+#include "debug_stub.h"
+#include "debug_internals.h"
+
+ .extern dbg__sendCommMsg
+
+ /* Hexutils function references */
+ .extern hex2char
+ .extern char2hex
+ .extern byte2ascii
+ .extern halfword2ascii_be
+ .extern halfword2ascii_le
+ .extern word2ascii_be
+ .extern word2ascii_le
+ .extern ascii2hex_varlen_be
+ .extern ascii2byte
+ .extern ascii2halfword_be
+ .extern ascii2halfword_le
+ .extern ascii2word_be
+ .extern ascii2word_le
+
+
+.bss
+.align 4
+
+ .global debug_InCommBuf
+ .global debug_OutCommBuf
+debug_InCommBuf:
+ .space USB_BUFSIZE,0
+debug_OutCommBuf:
+ .space USB_BUFSIZE,0
+
+debug_msgRxBufPtr:
+ .word 0x0
+debug_msgTxBufPtr:
+ .word 0x0
+
+debug_msgRxBuf_AppendPtr:
+ .word 0x0
+debug_msgTxBuf_AppendPtr:
+ .word 0x0
+
+ .equ RXAPPENDPTR_OFFSET, (debug_msgRxBuf_AppendPtr - debug_msgRxBufPtr)
+ .equ TXAPPENDPTR_OFFSET, (debug_msgTxBuf_AppendPtr - debug_msgTxBufPtr)
+
+debug_segmentRxNum: /* Current Rx Segment Number */
+ .word 0x0
+
+/* Comm Channel and NXT Received Message Length is now common to both NxOS and NXT Firmware */
+debug_nxtMsgLength:
+ .word 0x0
+
+ .global debug_nxtCommChannel
+debug_nxtCommChannel:
+ .word 0x0
+
+ .global debug_nxtCommOverrun
+debug_nxtCommOverrun:
+ .word 0x0
+
+ .equ NXTCOMMCHANNEL_OFFSET, (debug_nxtCommChannel - debug_nxtMsgLength)
+ .equ NXTCOMMOVERRUN_OFFSET, (debug_nxtCommOverrun - debug_nxtMsgLength)
+
+.data
+.align 4
+
+nxt_commcmd_header:
+ .byte NXT_GDBMSG_TELEGRAMTYPE, 0x00, 0x00 /* padded to 3 bytes */
+
+.code 32
+.text
+.align 4
+/* Debugger Communications Routines
+ * It does not make sense to pass information from the Debugger Module to the Comm. link one character
+ * at a time, especially if we're not using a native serial interface (e.g., EIA-232). Consequently
+ * a Message interface has been defined. This can still call getChar() and putChar() subroutines
+ * if so desired, but it'll be a purely internal matter.
+ *
+ * Message Format
+ * Since we need to use EP1&2 (Bulk channels) to communicate with the PC Host, the messages should
+ * follow the NXT Direct Commands message structure (this will allow for interoperability with NXT Firmware
+ * in addition to NxOS). The maximum length of any USB communications via the Bulk channel is 64 bytes.
+ * There is a one byte Telegram Type field which identifies the type of telegram, followed by the
+ * Telegram header and actual message.
+ *
+ * The LEGO Mindstorms Communications Protocol Direct Commands GDB Message format (including all headers)
+ * is as follows:
+ *
+ * GDB Command
+ * ===========
+ * Byte 0: Telegram Type Field (0x8d Direct Command, No response required) | NXT Msg Header
+ * Byte 1: Segment No (1-255, 0: Last Segment; limit is MSG_NUMSEGMENTS) |
+ * Byte 2: Telegram Size (Len of USB Buffer - 3, max is MSG_SEGMENTSIZE) |
+ * Byte 3-N: Message data | GDB Command
+ *
+ * The GDB Command (of size M) has the following format:
+ * Offset 0: '+'/'-' Command Received Status (Optional)
+ * Offset 1/0: '$'
+ * Offset 2/1: GDB Command char
+ * Offset 3 - (M-4): Command packet info
+ * Offset M-3: '#'
+ * Offset M-2: MSB of Checksum
+ * Offset M-1: LSB of Checksum
+ *
+ * To be safe, we assume that the Command Received Status is always sent by the GDB server. Therefore,
+ * The maximum size of a GDB Command packet is MSGBUF_SIZE - 5 ('+'/'-', '$', '#', 2 byte checksum)
+ *
+ * GDB Response
+ * ============
+ * Byte 0: Telegram Type Field (0x8d Direct Command, No response required) | NXT Msg Header
+ * Byte 1: Segment No (1-255, 0: Last Segment; limit is MSG_NUMSEGMENTS) |
+ * Byte 2: Telegram Size (Len of USB Buffer - 3, max is MSG_SEGMENTSIZE) |
+ * Byte 3-N: Message data | GDB Response
+ *
+ * The GDB Retransmission Request has the following format:
+ * Offset 0: '-' Command Received Status
+ *
+ * The GDB Response (of size M) has the following format:
+ * Offset 0: '+' Command Received Status
+ * Offset 1: '$'
+ * Offset 2 - (M-4): Response packet info
+ * Offset M-3: '#'
+ * Offset M-2: MSB of Checksum
+ * Offset M-1: LSB of Checksum
+ *
+ * The maximum size of a GDB Response packet is MSGBUF_SIZE - 5 ('+', '$', '#', 2 byte checksum)
+ *
+ * Note: The Telegram Size is the actual size of the Message Data portion
+ * (i.e., excludes the three header bytes, includes the GDB Command/Response Packet checksum bytes
+ * in the last segment)
+ */
+
+ .global dbg__comm_init
+/* dbg__comm_init
+ * Initialize communications channel.
+ * On Entry:
+ * R0: MSG Rx Buf Pointer
+ * R1: MSG Tx Buf Pointer
+ */
+
+dbg__comm_init:
+ stmfd sp!, {lr}
+ ldr r2, =debug_msgRxBufPtr
+ stmia r2!, {r0, r1} /* debug_msgRxBufPtr and debug_msgTxBufPtr */
+ stmia r2!, {r0, r1} /* debug_msgRxBuf_AppendPtr and debug_msgTxBuf_AppendPtr */
+ bl _dbg__comm_readbuf_reset
+ ldr r1, =debug_nxtMsgLength
+ mov r0, #0
+ str r0, [r1, #NXTCOMMCHANNEL_OFFSET] /* Clear NXT Channel on INIT */
+ ldmfd sp!, {pc}
+
+
+_dbg__comm_readbuf_reset:
+ ldr r1, =debug_nxtMsgLength
+ mov r0, #0
+ str r0, [r1] /* Clear Received Comm Message Length */
+ bx lr
+
+ .global dbg__copyNxtDebugMsg
+/* dbg__copyNxtDebugMsg
+ * Copy NXT Debug Message to our own Buffers, indicate Msg Received status.
+ * Note: This routine is now used by both NXT Firmware and NxOS
+ * On Entry:
+ * R0: NXT Input Buf Pointer
+ * R1: NXT Communications Channel Enum (CmdBit)
+ * R2: NXT Raw Message Length
+ * On Exit:
+ * R0-R3: Destroyed
+ */
+dbg__copyNxtDebugMsg:
+ ldr r3, =debug_nxtMsgLength
+ str r1, [r3, #NXTCOMMCHANNEL_OFFSET] /* save Communications Channel first */
+ ldr r1, [r3] /* Check if there's an unread message in the buffer */
+ cmp r1, #0
+ beq cont_dbg__copyNxtDebugMsg /* No unread message, so continue */
+exit_dbg__NxtDebugMsgOverrun:
+ ldr r1, [r3, #NXTCOMMOVERRUN_OFFSET]
+ add r1, r1, #1
+ str r1, [r3, #NXTCOMMOVERRUN_OFFSET] /* update message overrun stats */
+ b exit_dbg__copyNxtDebugMsg
+cont_dbg__copyNxtDebugMsg:
+ str r2, [r3]
+ ldr r1, =debug_InCommBuf
+ _dbg_memcpy r1, r0, r2, r3 /* r3: scratch register */
+exit_dbg__copyNxtDebugMsg:
+ bx lr
+
+/* _dbg_reset_msgTxBuf_AppendPtr
+ * Internal variable to reset pointers.
+ * On Exit:
+ * R0: debug_msgTxBuf_AppendPtr
+ * R1: destroyed
+ */
+_dbg_reset_msgTxBuf_AppendPtr:
+ ldr r1, =debug_msgTxBufPtr /* Should not be modified */
+ ldr r0, [r1]
+ str r0, [r1, #TXAPPENDPTR_OFFSET]
+ mov pc, lr
+
+/* _dbg__commHasMsg
+ * Internal Segment Reassembly Routine.
+ * On exit:
+ * r0: !0: (Availale Telegram Message Size), 0: no incoming message/segment
+ * r1: message segment number
+ */
+_dbg__commHasMsg:
+ stmfd sp!, {lr}
+ ldr r0, =debug_nxtMsgLength
+ ldr r0, [r0] /* R0 contains the Comm Buffer Size, including the NXT Direct Command Header */
+
+ ldr r2, =debug_InCommBuf
+ ldrb r1, [r2, #NXT_MSG_TELEGRAMTYPE_OFFSET]
+ cmp r1, #NXT_GDBMSG_TELEGRAMTYPE
+ bne invalid_CommMsg /* Invalid telegram type, ignore */
+
+ ldrb r1, [r2, #NXT_MSG_TELEGRAMSIZE_OFFSET]
+ sub r0, r0, r1 /* Comm Buffer Size - Telegram Size = 3 (header size) */
+ cmp r0, #NXT_GDBMSG_START /* Start offset is equal to header size */
+ bne invalid_CommMsg /* Invalid Message Length, ignore */
+
+ mov r0, r1 /* Telegram Message Size */
+ ldrb r1, [r2, #NXT_MSG_SEGNUM_OFFSET]
+ b _exit_dbg__commHasMsg
+
+invalid_CommMsg:
+ bl _dbg__comm_readbuf_reset /* Next Comm telegram transaction */
+ mov r0, #0
+_exit_dbg__commHasMsg:
+ ldmfd sp!, {pc}
+
+/* _copy_msg_from_commbuf
+ * Internal Comm buffer copy routine, handles segment reassembly.
+ * On entry:
+ * r0: number of bytes to copy
+ * r1: segment number
+ * On exit:
+ * r0: cummulative message length
+ * r1: segment number
+ * r2, r3: Destroyed
+ */
+_copy_msg_from_commbuf:
+ stmfd sp!, {r1,r4,r5,r6,lr}
+ movs r4, r0
+ beq _exit_copy_msg_from_commbuf
+
+ ldr r6, =debug_msgRxBufPtr /* Address of Pointers */
+ ldr r5, [r6] /* Rx buffer Start Address */
+ ldr r2, [r6, #RXAPPENDPTR_OFFSET] /* Append Pointer */
+
+ sub r3, r2, r5 /* r3: current length of message */
+ add r3, r3, r4 /* new cummulative length of message */
+ cmp r3, #MSGBUF_SIZE
+ movhi r4, #0 /* Buffer overflow! */
+ strhi r5, [r6, #RXAPPENDPTR_OFFSET] /* Reset AppendPtr to beginning of Rx Buffer */
+ bhi _exit_copy_msg_from_commbuf
+
+ ldr r3, =debug_InCommBuf
+ add r3, r3, #NXT_GDBMSG_START
+ _dbg_memcpy r2, r3, r4, r0 /* r2 updated to point to next empty char slot in Rx buffer */
+ sub r4, r2, r5 /* r4: cummulative length of message */
+
+ /* Update debug_msgRxBuf_AppendPtr */
+ teq r1, #0 /* Check if this is last segment (segment 0) */
+ streq r5, [r6, #RXAPPENDPTR_OFFSET] /* Reset AppendPtr to beginning of Rx Buffer if so */
+ strne r2, [r6, #RXAPPENDPTR_OFFSET] /* Otherwise, update Append Pointer to receive next segment */
+
+_exit_copy_msg_from_commbuf:
+ bl _dbg__comm_readbuf_reset /* Next Comm telegram transaction */
+ mov r0, r4 /* Return cummulative message length in R0 */
+ ldmfd sp!, {r1,r4,r5,r6,pc} /* Return segment number in R1 */
+
+
+/* _msgbuf_checksum
+ * Internal routine to calculate checksum character buffer.
+ * On entry:
+ * r0: pointer to character buffer to checksum (assume ASCIIZ terminated)
+ * On exit:
+ * r0: pointer to character buffer after ASCIIZ
+ * r1: checksum (8-bit binary)
+ * r2: message length
+ * r3: destroyed
+ */
+_msgbuf_checksum:
+ mov r1, #0 /* clear checksum */
+ mov r2, #0 /* clear length */
+1: ldrb r3, [r0], #1 /* Iterate through buffer */
+ add r1, r1, r3 /* cummulative sum of char */
+ teq r3, #0
+ addne r2, r2, #1 /* increment message length */
+ bne 1b /* until ASCIIZ found */
+ and r1, #BYTE0 /* Modulo 256 */
+ mov pc, lr
+
+ .global dbg__getDebugMsg
+/* dbg__getDebugMsg
+ * Retrieve pending Debugger Message if available (Non-Blocking).
+ * On entry:
+ * No parameters (assume pointers were initialized previously using dbg__comm_init)
+ * On exit:
+ * r0: >0 = Valid GDB Message Length (incl '$', excluding '#' and checksum),
+ * 0 = no valid message (yet), -1 = error
+ * r1: GDB Message Buffer Pointer (incl '$', excluding '#' and checksum)
+ * r2, r3: Destroyed
+ * Note: If GDB Message were returned, it is ASCIIZ terminated, does not include '#' and checksum
+ */
+dbg__getDebugMsg:
+ stmfd sp!, {r4,r5,lr}
+ bl _dbg__commHasMsg /* r0: message length, r1: segment number */
+ teq r0, #0
+ beq exit_dbg__getDebugMsg /* no new message, exit with R0 = 0 */
+
+ ldr r4, =debug_segmentRxNum
+ ldr r2, [r4] /* Get current Segment Number */
+ add r2, r2, #1 /* Expected Segment Number for comparison */
+ teq r1, #0
+ streq r1, [r4] /* Update current Segment Number with 0 since it is the last segment */
+ beq _hasMsg2Copy
+ cmp r1, #MSG_NUMSEGMENTS /* Segment Number < MSG_NUMSEGMENTS? */
+ bhs _invalid_segment
+ teq r1, r2 /* Valid Segment Number, check against Expected Segment Number */
+ beq _hasMsg2Copy /* Segment Number matches Expected Segment Number, update buffers */
+
+_invalid_segment:
+ bl _dbg__comm_readbuf_reset /* Invalid, Next Comm telegram transaction */
+ mov r0, #0 /* Reset Segment Number */
+ str r0, [r4] /* Update current Segment Number with 0 to prepare for new message */
+ b exit_dbg__getMsgError /* Exit with error */
+
+_hasMsg2Copy:
+ str r1, [r4] /* Update current Segment Number */
+ bl _copy_msg_from_commbuf /* r0: cummulative message length, r1: segment number */
+ teq r1, #0
+ movne r0, #0 /* Incomplete message, ignore for now */
+ bne exit_dbg__getDebugMsg /* Message not complete yet, exit */
+
+ /* Check for valid GDB message */
+ mov r4, r0 /* keep message length in R4, assume to be within MSGBUF_SIZE */
+ ldr r5, =debug_msgRxBufPtr
+ ldr r5, [r5] /* Rx buffer Start Address */
+
+/* Need to account for Packet Acknowledgement */
+1: ldrb r0, [r5]
+ teq r0, #MSGBUF_CTRLC /* Look for Ctrl-C */
+ moveq r0, r4 /* If found, set R0 to current message length */
+ beq exit_dbg__getDebugMsg /* and return */
+ teq r0, #MSGBUF_NAKCHAR /* Look for '-' */
+ beq exit_dbg__getMsgError /* Error from Host, Retransmit previous message */
+ teq r0, #MSGBUF_ACKCHAR /* Look for '+' */
+ addeq r5, r5, #1 /* Adjust Buffer Start Pointer (excl '+') */
+ subeq r4, r4, #1 /* Adjust Message Length */
+ beq 1b /* Skip all Packet Acknowledgements */
+
+ /* Note: Here we assume that we won't get a single ACK '+' or NAK '-' character message.
+ * If we do, it'll be flagged as an error
+ */
+ subs r2, r4, #MSGBUF_CHKSUMOFFSET /* Look for '#': Message Length - 3 = '#' offset */
+ blt exit_dbg__getMsgError /* Message Length is too short, exit with error */
+ ldrb r0, [r5, r2]
+ teq r0, #MSGBUF_CHKSUMCHAR
+ bne exit_dbg__getMsgError /* No checksum char '#', exit with error */
+
+ mov r1, #0
+ strb r1, [r5, r2] /* Zero out '#' char for checksum calc later */
+
+#ifdef CHECK_GDBSTARTCHAR
+ /* Checked in dbg__bkpt_waitCMD */
+ ldrb r0, [r5]
+ teq r0, #MSGBUF_STARTCHAR /* Look for '$' */
+ bne exit_dbg__getMsgError /* No start char '$', exit with error */
+#endif
+
+ add r0, r5, #1 /* Checksum packet data (excl '$') */
+ bl _msgbuf_checksum /* R2: length (excl '$'), R1: calculated checksum, R0: pointer to checksum in receive buffer */
+ mov r3, r1 /* Keep calculated checksum in R3 (R1 destroyed by ascii2byte) */
+ bl ascii2byte /* R0: received checksum, R1: address of next buffer location */
+ teq r0, r3 /* Compare calculated checksum in R3 against received checksum in R0 */
+ bne exit_dbg__getMsgError /* Checksums do not match, exit with error */
+
+ subeq r0, r4, #MSGBUF_CHKSUMOFFSET /* Update message length (incl '$') as return parameter */
+ add r2, r2, #1 /* expected message length (from _msgbuf_checksum) */
+ teq r0, r2
+ beq exit_dbg__getDebugMsg /* Valid length, return */
+
+exit_dbg__getMsgError:
+ /* We must first clear the existing message checksum */
+ ldr r1, =debug_msgTxBufPtr /* R5: data structure base pointer */
+ ldr r1, [r1] /* Tx buffer Start Address */
+
+1: ldrb r0, [r1], #1
+ teq r0, #MSGBUF_CHKSUMCHAR
+ bne 1b
+
+ mov r0, #0 /* ASCIIZ */
+ strb r0, [r1, #-1] /* Pointer R1 is now one past the MSGBUF_CHKSUMCHAR */
+
+ bl dbg__putDebugMsg /* Retransmit message */
+ mov r0, #0 /* Flag no message received */
+
+#if 0
+ mov r0, #MSGBUF_MSGERROR
+#endif
+
+exit_dbg__getDebugMsg:
+ mov r1, r5 /* Return GDB Message Buffer Pointer in R1 */
+ ldmfd sp!, {r4,r5,pc}
+
+
+/* _copy_msg_to_commbuf
+ * Internal Comm buffer copy routine, handles segment fragmentation.
+ * On entry:
+ * r0: number of bytes to copy
+ * r1: segment number
+ * On exit:
+ * r0: cummulative message length
+ * r1: segment number
+ * r2, r3: Destroyed
+ */
+_copy_msg_to_commbuf:
+ stmfd sp!, {r1,r4,r5,r6,lr}
+ ldr r6, =debug_msgTxBufPtr /* Address of Pointers */
+ ldr r5, [r6, #TXAPPENDPTR_OFFSET] /* Retrieve Tx Append Pointer */
+
+ movs r4, r0
+ beq _exit_copy_msg_to_commbuf
+
+#ifdef CHECK_TXLEN
+ add r0, r4, #NXT_GDBMSG_START /* offset = header size */
+ cmp r0, #USB_BUFSIZE
+ bhi _exit_copy_msg_to_commbuf /* We let calling routine detect problem (segment number will increment) */
+#endif
+
+ /* Fill in Comm Message Header */
+ ldr r3, =debug_OutCommBuf
+ mov r2, #NXT_GDBMSG_TELEGRAMTYPE
+ strb r2, [r3], #1 /* Telegram type */
+ strb r1, [r3], #1 /* Segment Number */
+ strb r0, [r3], #1 /* Message Length */
+
+ mov r2, r5 /* Copy to R2 for updating */
+ mov r1, r4 /* actual GDB message fragment length (exclude Comm header) */
+ _dbg_memcpy r3, r2, r1, r0 /* This copies over the message fragment, r3, r2 updated */
+ mov r5, r2 /* Updated Tx Append Pointer, keep in R5 for now */
+
+ add r0, r4, #NXT_GDBMSG_START /* Total Comm Buffer Size for Tx (NXT_GDBMSG_START offset = header size) */
+ bl dbg__sendCommMsg /* Common interface routine to commnuncations drivers */
+ cmp r0, #TRUE
+ ldrne r5, [r6, #TXAPPENDPTR_OFFSET] /* Tx failed, Retrieve Original Tx Append Pointer */
+ streq r5, [r6, #TXAPPENDPTR_OFFSET] /* Tx succeeded, Update Tx Append Pointer to new position */
+
+_exit_copy_msg_to_commbuf:
+ ldr r6, [r6] /* Retrieve Tx Buffer Start Address */
+ sub r0, r5, r6 /* Return calculated cummulative message length (R0) */
+ ldmfd sp!, {r1,r4,r5,r6,pc} /* Return segment number in R1 */
+
+ .global dbg__putDebugMsg
+/* dbg__putDebugMsg
+ * Sends Debugger Message from calling routine after appending checksum (Blocking) .
+ * On entry:
+ * No parameters (assume pointers were initialized previously using dbg__comm_init)
+ * On exit:
+ * r0: status (0: success, -1: error)
+ * Note: GDB Message to be sent must be ASCIIZ terminated, does not include '#' and checksum
+ * Response packets start with '+' followed by '$' (2 bytes prefix)
+ */
+dbg__putDebugMsg:
+ stmfd sp!, {r4,r5,lr}
+ /* Perform Checksum Calculation */
+ ldr r5, =debug_msgTxBufPtr /* R5: data structure base pointer */
+ ldr r4, [r5] /* Tx buffer Start Address */
+ str r4, [r5, #TXAPPENDPTR_OFFSET] /* Reset Tx buffer Append Pointer */
+ add r0, r4, #2 /* skip '+' and '$' */
+ bl _msgbuf_checksum /* R2: length (excl '+' and '$'), R1: calculated checksum, R0: pointer to checksum in tx buffer */
+
+#ifdef CHECK_TXLEN
+ add r2, r2, #2 /* r2: returned length from _msgbuf_checksum, added with prefix length */
+ sub r3, r0, r4 /* r3: calculated length from pointers (incl. prefix length) */
+ teq r2, r3
+ bne exit_dbg__putMsgError
+#endif
+
+ mov r3, #MSGBUF_CHKSUMCHAR
+ strb r3, [r0, #-1] /* Insert '#' */
+ bl byte2ascii /* On return, R0 points to location after checksum bytes, R1 is original pointer to checksum */
+ sub r4, r0, r4 /* R4 = Calculated total message length (incl '+' and '$', '#' and checksum bytes */
+ cmp r4, #MSG_SEGMENTSIZE /* If total message length > MSG_SEGMENTSIZE */
+ mov r1, #0 /* Initialize Segment Number = 0 (last segment) first */
+ mov r0, #0 /* Initial cummulative message length */
+ mov r5, #0 /* Previous cummulative message length */
+
+ /* We assume unsigned message lengths, so the arithmetic MUST NOT result in negative values */
+_cont_putMsg:
+ cmp r4, r0
+ movls r0, #0 /* R0: Exit status (success) */
+ bls exit_dbg__putDebugMsg /* If Total message length (r4) <= Cummulative message length (r0), we're done */
+ add r2, r0, #MSG_SEGMENTSIZE /* R2: calculate new Max cummulative message length */
+ cmp r4, r2 /* Check total message length (R4) against new Max cummulative message length (R2) */
+ subls r0, r4, r0 /* if total message length (R4) <= new Max cummulative message length (R2), send remainder */
+ movls r1, #0 /* Flag as last segment (Segment Number = 0) */
+ movhi r0, #MSG_SEGMENTSIZE /* else send MSG_SEGMENTSIZE bytes */
+ addhi r1, r1, #1 /* Increment Segment Number */
+ cmp r1, #MSG_NUMSEGMENTS
+ bhs exit_dbg__putMsgError /* If Segment Number >= MSG_NUMSEGMENTS, flag error */
+ bl _copy_msg_to_commbuf /* R0: cummulative message length, R1: segment number */
+ teq r5, r0 /* Check if we managed to transmit the previous message */
+ beq exit_dbg__putMsgError /* No, flag error */
+ movne r5, r0 /* Update previous cummulative message length */
+ b _cont_putMsg
+
+exit_dbg__putMsgError:
+ mov r0, #MSGBUF_MSGERROR
+exit_dbg__putDebugMsg:
+ ldmfd sp!, {r4,r5,pc}
+
+ .global dbg__sendAckOrNak
+/* dbg__sendAckOrNak
+ * Send Ack (for successful receipt of message)
+ * or Nak (for Retransmission due to received message Checksum error) (Blocking) .
+ * On entry:
+ * No parameters (assume pointers were initialized previously using dbg__comm_init)
+ * On exit:
+ * r0: status (0: success, -1: error)
+ * r1: destroyed
+ * Note: An Ack Or Nak is indicated by '+' or '-', which is prepended with the Comm header and sent (without checksum)
+ * Sending Ack is only done for Continue and Step commands, where GDB does not expect any replies.
+ */
+dbg__sendAckOrNak:
+ stmfd sp!, {lr}
+ ldr r1, =debug_msgTxBufPtr /* R2: data structure base pointer */
+ ldr r0, [r1] /* Tx buffer Start Address */
+ str r0, [r1, #TXAPPENDPTR_OFFSET] /* Reset Tx buffer Append Pointer */
+
+ mov r1, #0 /* Initialize Segment Number = 0 (last segment) */
+ mov r0, #1 /* Retransmission message length = 1 */
+ bl _copy_msg_to_commbuf /* R0: cummulative message length, R1: segment number */
+ cmp r0, #1 /* Check if we managed to transmit the previous message */
+ moveq r0, #0 /* R0: Exit status (success) */
+ movne r0, #MSGBUF_MSGERROR /* R0: Exit status (error) */
+ ldmfd sp!, {pc}
+