minux的源代码,一个非常小的操作系统

				#include 
				#define ptrace	_ptrace
				#include 
				
				PUBLIC long ptrace(req, pid, addr, data)
				int req;
				pid_t pid;
				long addr;
				long data;
				{
				  message m;
				
				  m.m2_i1 = pid;
				  m.m2_i2 = req;
				  m.m2_l1 = addr;
				  m.m2_l2 = data;
				  if (_syscall(MM, PTRACE, &m) < 0) return(-1);
				
				  /* There was no error, but -1 is a legal return value.  Clear errno if
				   * necessary to distinguish this case.  _syscall has set errno to nonzero
				   * for the error case.
				   */
				  if (m.m2_l2 == -1) errno = 0;
				  return(m.m2_l2);
				}