text: #include <u.h>
  #include <libc.h>
  #include <mach.h>
  
  Regdesc*
  regdesc(char *name)
  {
  	Regdesc *r;
  
  	for(r=mach->reglist; r->name; r++)
  		if(strcmp(r->name, name) == 0)
  			return r;
  	return nil;
  }
  
  int
  rput(Regs *regs, char *name, u64int u)
  {
  	if(regs == nil){
  		werrstr("registers not mapped");
  		return -1;
  	}
  	return regs->rw(regs, name, &u, 0);
  }
  
  int
  rget(Regs *regs, char *name, u64int *u)
  {
  	if(regs == nil){
  		*u = ~(u64int)0;
  		werrstr("registers not mapped");
  		return -1;
  	}
  	return regs->rw(regs, name, u, 1);
  }
  
  int
  _uregrw(Regs *regs, char *name, u64int *u, int isr)
  {
  	Regdesc *r;
  	uchar *ureg;
  
  	if(!isr){
  		werrstr("cannot write registers");
  		return -1;
  	}
  
  	if((r = regdesc(name)) == nil)
  		return -1;
  	ureg = ((UregRegs*)regs)->ureg + r->offset;
  
  	switch(r->format){
  	default:
  	case 'X':
  		*u = mach->swap4(*(u32int*)ureg);
  		return 0;
  	case 'Y':
  		*u = mach->swap8(*(u64int*)ureg);
  		return 0;
  	}
  }
  