Xen上的miniOS

原文：

http://qyrekcah.spaces.live.com/blog/cns!D691A70904EDECB0!228.entry?wa=wsignin1.0&sa=674975121

    在Xen上可以运行的最小OS，该miniOS直接用汇编程序编写，实现了Xen的hypercall的调用。下面是它的实现代码：

# helloworld.s 
 
 
 

   .section __xen_guest 
  
  .ascii "GUEST_OS=MyOS" 
  
  .ascii ",XEN_VER=xen-3.0" 
  
  .ascii ",HYPERCALL_PAGE=0x2" 
  
  .ascii ",LOADER=generic" 
  
  .ascii ",PT_MODE_WRITABLE" 
  
  .byte 0 
  
 .text   # text section为可执行的程序代码(executable program code) 
  
  .globl _start # Guest OS的入口为_start 
  
 _start: 
  
  cld  #cld(Clear Decimal Flag) 设置ALU为二进制模式 
  
  #设置hypercall 参数 
  
  movl $18, %eax # __Hypervisor_console_io 
  
  movl $0, %ebx # CONSOLEIO_write 
  
  movl $hello_message_len, %ecx # buffer length 
  
  movl $hello_message, %edx # buffer virtual address 
  
  int $0x82 #使用int $0x82执行hypercall 
  
 

    #调用关机和关闭电源hypercall 
  
  movl $6, %eax # __Hypervisor_sched_op_compat 
  
  movl $2, %ebx # SCHEDOP_shutdown 
  
  movl $0, %ecx # SHUTDOWN_poweroff 
  
  int $0x82 
  
 hang: 
  
  jmp hang # shouldn't get here 
  
 .data  # 数据段(data section) 
  
  hello_message: .ascii "This is the hello world program./n" 
  
  hello_message_len = . -hello_message  #hello消息的长度，.表示当前offset

编译时使用的Makefile为

helloworld: helloworld.s 
  
  as -o helloworld.o -a=helloworld.l helloworld.s 
  
  ld -Ttext 0x100000 -o helloworld.elf helloworld.o

该虚拟机的配置文件为

kernel = "helloworld.elf" 
 
 
 

   memory = 32 
 
 
 

   name = "HelloWorld" 
 
 
 

   on_crash = 'destroy' #当domain crash时指定guest的行动(behaviour)