text: /*
   * Copyright (c) 2019 LuoZhongYao
   * SPDX-License-Identifier: Apache-2.0
   */
  
  #include <kernel.h>
  #include <device.h>
  #include <init.h>
  
  extern void __stdout_hook_install(int (*fn)(int));
  
  #define SYS_WRITEC 0x03
  
  int arch_printk_char_out(int _c)
  {
  	char c = _c;
  
  #if defined(CONFIG_CPU_CORTEX_M)
  
  	register unsigned long r0 __asm__("r0") = SYS_WRITEC;
  	register void *r1 __asm__("r1") = &c;
  
  	__asm__ __volatile__ ("bkpt 0xab" : : "r" (r0), "r" (r1) : "memory");
  
  #elif defined(CONFIG_ARM64)
  
  	register unsigned long x0 __asm__("x0") = SYS_WRITEC;
  	register void *x1 __asm__("x1") = &c;
  
  	__asm__ volatile ("hlt 0xf000" : : "r" (x0), "r" (x1) : "memory");
  
  #else
  #error "unsupported CPU type"
  #endif
  
  	return 0;
  }
  
  static int semihost_console_init(const struct device *dev)
  {
  	ARG_UNUSED(dev);
  
  	/*
  	 * The printk output callback is arch_printk_char_out by default and
  	 * is installed at link time. That makes printk() usable very early.
  	 *
  	 * We still need to install the stdout callback manually at run time.
  	 */
  	__stdout_hook_install(arch_printk_char_out);
  
  	return 0;
  }
  
  SYS_INIT(semihost_console_init, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
  