Cortex M. McGee

ARM Cortex M0-4 machine code generator

WORK IN PROGRESS

Debug on stm32f4-discovery GDB

• Run the debug.sh to start OpenOCD and connect to the board

• Start gdb (arm-none-eabi-gdb)

  • Issue command target extended-remote localhost:3333 or short version tar ext :3333

Debug on stm32f4-discovery Telnet

• Run the debug.sh to start OpenOCD and connect to the board

• Telnet telnet localhost 4444

  • load binary code into memory with command: load_image filename address For example: load_image out.bin 0x20000000

  • Disassemble loaded code arm disassemble address number-of-instructions Example:

    > arm disassemble 0x20000000 10
    0x20000000  0x20ff    	MOVS	r0, #0xff
    0x20000002  0x21de    	MOVS	r1, #0xde
    0x20000004  0x22ad    	MOVS	r2, #0xad
    0x20000006  0x230f    	MOVS	r3, #0x0f
    0x20000008  0x24f0    	MOVS	r4, #0xf0
    0x2000000a  0x25ab    	MOVS	r5, #0xab
    0x2000000c  0x26dc    	MOVS	r6, #0xdc
    0x2000000e  0x2712    	MOVS	r7, #0x12
    0x20000010  0x2043    	MOVS	r0, #0x43
    0x20000012  0x2199    	MOVS	r1, #0x99
    

  • Display registers contents: reg

  • Set register contents: reg name value Example: reg pc 0x20000000

  • Set breakpoint bp address length Example: bp 0x20000012 2

  • Run: resume

  • Step through code: step

Quick debug with xxd

• View binary file contents as HEX values: xxd filename
• View binary file contents as BIN values: xxd -b filename

To figure out

• Byte ordering for 32bit thumb
• Generation of elf header and sections.