谁可以帮我注释一下这段汇编程序?很多地方都读不懂,谢谢

_syscall1(int,setuid,uid_t,uid);
将被展开成下面的汇编指令

_setuid:
subl $4,%exp
pushl %ebx
movzwl 12(%esp) , %eax
movl %eax,4(%esp)
movl $23, %eax
movl 4(%esp), %ebx
int $0x80
movl %eax,%edx
testl %edx,%edx
jge L2
negl %edx
movl %edx, _errno
movl $-1,%eax
popl %ebx
addl $4,%esp
ret
L2:
movl %edx,%eax
popl %ebx
addl $4, %esp
ret