1 files changed, 42 insertions, 0 deletions
diff --git a/src/lib9/tas-power.c b/src/lib9/tas-power.c
new file mode 100644
index 00000000..2ed71d47
--- /dev/null
+++ b/src/lib9/tas-power.c
@@ -0,0 +1,42 @@
+#include "u.h"
+#include "libc.h"
+
+/*
+ * first argument (l) is in r3 at entry.
+ * r3 contains return value upon return.
+ */
+int
+_tas(int *x)
+{
+	int     v;
+	int	tmp, tmp2, tmp3;
+
+	/*
+	 * this __asm__ works with gcc on linux
+	 */
+	__asm__("\n	sync\n"
+	"	li	%1,0\n"
+	"	mr	%2,%4		/* &x->val */\n"
+	"	lis	%3,0xdead	/* assemble constant 0xdeaddead */\n"
+	"	ori	%3,%3,0xdead	/* \" */\n"
+	"tas1:\n"
+	"	dcbf	%2,%1	/* cache flush; \"fix for 603x bug\" */\n"
+	"	lwarx	%0,%2,%1	/* v = x->val with reservation */\n"
+	"	cmp	cr0,0,%0,%1	/* v == 0 */\n"
+	"	bne	tas0\n"
+	"	stwcx.	%3,%2,%1   /* if (x->val same) x->val = 0xdeaddead */\n"
+	"	bne	tas1\n"
+	"tas0:\n"
+	"	sync\n"
+	"	isync\n"
+	: "=r" (v), "=&r" (tmp), "=&r"(tmp2), "=&r"(tmp3)
+	: "r"  (x)
+	: "cr0", "memory"
+	);
+	switch(v) {
+	case 0:		return 0;
+	case 0xdeaddead: return 1;
+	default:	fprint(2, "tas: corrupted 0x%lux\n", v);
+	}
+	return 0;
+}