arch/arm-cortex-m0/crt.c

   1 /* Author: Domen Puncer <domen@cba.si>.  License: WTFPL, see file LICENSE */
   2 #include "arch/crt.h"
   3
   4 extern void _ram_end;
   5
   6 void __naked reset_handler()
   7 {
   8         /* cortex-m3 trm 2.2.1 main stack and process stack */
   9         asm volatile (
  10                         /* select PSP as current stack pointer */
  11                         "mrs    r0, CONTROL\n"
  12                         "mov    r1, #2\n"
  13                         "orr    r0, r1\n"
  14                         "msr    CONTROL, r0\n"
  15                         "isb\n"
  16
  17                         /* hrm... this stack is ignored laters anyways, as the scheduler starts,
  18                          * so it could just be the same as for exceptions, yes? */
  19                         "ldr    r0, =_ram_end-1024\n" /* 1k for main stack */
  20                         "mov    sp, r0\n"
  21
  22                         "bl     init\n"
  23                         "bl     main\n"
  24                         "b      generic_exception_handler\n"
  25         );
  26 }
  27
  28 /* cortex-m3 trm, 5.5.1, mcu stacks xPSR, PC, LR, R12, R3, R2, R1, R0 */
  29 void __naked generic_exception_handler()
  30 {
  31         asm volatile (
  32                         "mov    r2, lr\n"
  33                         "mov    r1, #0x4\n"
  34                         "tst    r2, r1\n" /* process task, see EXC_RETURN */
  35
  36                         "mrs    r0, MSP\n"
  37                         "beq    1f\n"
  38                         "mrs    r0, PSP\n"
  39                         "1:\n"
  40
  41                         /* yeah, on cortex-m3 this is push {r4-r11, lr} :P */
  42                         "push   {lr}\n"
  43                         "mov    lr, r0\n" /* tmp for sp */
  44                         "mov    r0, r8\n"
  45                         "mov    r1, r9\n"
  46                         "mov    r2, r10\n"
  47                         "mov    r3, r11\n"
  48                         "push   {r0-r3}\n" /* r8-r11 */
  49                         "push   {r4-r7}\n"
  50                         "mov    r0, lr\n" /* restore sp to r0 */
  51
  52                         "mov    r1, sp\n\t"
  53                         "mrs    r2, IPSR\n\t"
  54                         "b      generic_exception_handler_c\n\t"
  55         );
  56 }
  57