cstart_thumb2.asm

STM32F103RBT6上的USB测试程序

;;  NOTE: To allow the use of this file for both ARMv6M and ARMv7M,
;;        we will only use 16-bit Thumb intructions.

   .extern _lc_ub_stack            ; usr/sys mode stack pointer
   .extern _lc_ue_stack            ; symbol required by debugger
   .extern _lc_ub_table            ; ROM to RAM copy table
   .extern main
   .extern _Exit
;   .global __RESET
   .extern exit
   .weak   exit
   .extern _init_hardware

   .if @defined('__PROF_ENABLE__')
      .extern __prof_init
   .endif
   .if @defined('__POSIX__')
      .extern posix_main
      .extern _posix_boot_stack_top
   .endif

   .global _START

   .section .text.cstart
   .thumb

_START:
      ;; anticipate possible ROM/RAM remapping
      ;; by loading the 'real' program address
      ldr     r1,=_Next
      bx      r1
_Next:
      ;; initialize the stack pointer
      ; this is also part of the vector table
      ldr     r1,=_lc_ub_stack
      mov     sp,r1

      ;; call a user function which initializes hardware
      ;; such as ROM/RAM re-mapping or MMU configuration
      bl      _init_hardware

      ;; copy initialized sections from ROM to RAM
      ;; and clear uninitialized data sections in RAM

      ldr     r3,=_lc_ub_table
      movs    r0,#0
cploop:
      ldr     r4,[r3,#0]      ; load type
      ldr     r5,[r3,#4]      ; dst address
      ldr     r6,[r3,#8]      ; src address
      ldr     r7,[r3,#12]     ; size

      cmp     r4,#1
      beq     copy
      cmp     r4,#2
      beq     clear
      b       done

copy:
      subs    r7,r7,#1
      ldrb    r1,[r6,r7]
      strb    r1,[r5,r7]
      bne     copy

      adds    r3,r3,#16
      b       cploop

clear:
      subs    r7,r7,#1
      strb    r0,[r5,r7]
      bne     clear

      adds    r3,r3,#16
      b       cploop

done:
      ;; initialize or copy the vector table

      .if @defined('__POSIX__')

         ;; posix stack buffer for system upbringing
         ldr     r0,=_posix_boot_stack_top
         ldr     r0, [r0]
         mov     sp,r0

      .else

         ;; load r10 with end of USR/SYS stack, which is
         ;; needed in case stack overflow checking is on
         ;; NOTE: use 16-bit instructions only, for ARMv6M
         ldr     r0,=_lc_ue_stack
         mov     r10,r0

      .endif

      .if @defined('__PROF_ENABLE__')
         bl      __prof_init
      .endif

      .if @defined('__POSIX__')
         ;; call posix_main with no arguments
         bl      posix_main
      .else
         ;; call main with argv[0]==NULL & argc==0
         movs     r0,#0
         movs     r1,#0
         bl       main
      .endif

         ;; call exit using the return value from main()
         ;; Note. Calling exit will also run all functions
         ;; that were supplied through atexit().
         bl      exit

      .ltorg
      .endsec

      .calls  '_START','_init_hardware'
      .calls  '_START','_init_vector_table'
      .if @defined('__PROF_ENABLE__')
         .calls  '_START','__prof_init'
      .endif
      .if @defined('__POSIX__')
         .calls  '_START','posix_main'
      .else
         .calls  '_START','main'
      .endif
         .calls  '_START','exit'
         .calls  '_START','',0

      .end