PL0_test.c


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#include "uart.h"
#include "psr.h"

void PL0_main(void)
{
  uart_puts("hello PL0! Switching to user mode!\n\r");

  asm("cps #0b10000\n\r"
      "isb" ::: "memory");

  // if all went correct, Success! gets printed
  uart_puts("Success!\n\r");

  // if we're indeed i PL0, we should crash now, when trying to access
  // memory we're not allowed to
  char first_kernel_byte[2];

  first_kernel_byte[0] = *(char*) ((uint32_t) 0x8000);
  first_kernel_byte[1] = '\0';
  
  uart_puts(first_kernel_byte);
    
  while (1)
    {
      char c;
      switch(c = uart_getc())
	{
	case '\r':
	  uart_putc('\n');
	default:
	  uart_putc(c);
	}
    }
}