1 #include "u.h"
2 #include "libc.h"
3 
4 /*
5  * first argument (l) is in r3 at entry.
6  * r3 contains return value upon return.
7  */
8 int
9 _tas(int *x)
10 {
11 	int     v;
12 	int	tmp, tmp2, tmp3;
13 
14 	/*
15 	 * this __asm__ works with gcc on linux
16 	 */
17 	__asm__("\n	sync\n"
18 	"	li	%1,0\n"
19 	"	mr	%2,%4		/* &x->val */\n"
20 	"	lis	%3,0xdead	/* assemble constant 0xdeaddead */\n"
21 	"	ori	%3,%3,0xdead	/* \" */\n"
22 	"tas1:\n"
23 	"	dcbf	%2,%1	/* cache flush; \"fix for 603x bug\" */\n"
24 	"	lwarx	%0,%2,%1	/* v = x->val with reservation */\n"
25 	"	cmp	cr0,0,%0,%1	/* v == 0 */\n"
26 	"	bne	tas0\n"
27 	"	stwcx.	%3,%2,%1   /* if (x->val same) x->val = 0xdeaddead */\n"
28 	"	bne	tas1\n"
29 	"tas0:\n"
30 	"	sync\n"
31 	"	isync\n"
32 	: "=r" (v), "=&r" (tmp), "=&r"(tmp2), "=&r"(tmp3)
33 	: "r"  (x)
34 	: "cr0", "memory"
35 	);
36 	switch(v) {
37 	case 0:		return 0;
38 	case 0xdeaddead: return 1;
39 	default:	fprint(2, "tas: corrupted 0x%lux\n", v);
40 	}
41 	return 0;
42 }