check that the hardware supports 32 bit before starting

Reference: /n/atom/patch/applied/ipl64chk
Date: Thu Apr 17 23:13:05 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/boot/pcipl/cpuid.s	Thu Jan  1 00:00:00 1970
+++ /sys/src/boot/pcipl/cpuid.s	Thu Apr 17 23:13:05 2014
@@ -0,0 +1,13 @@
+TEXT cpuid(SB), 1, $0
+	MOVL	regs+0(FP), BP
+	MOVL	0(BP), AX
+	MOVL	4(BP), BX
+	MOVL	8(BP), CX
+	MOVL	8(BP), DX
+	BYTE $0x0F; BYTE $0xA2
+	MOVL	regs+0(FP), BP
+	MOVL	AX, 0(BP)
+	MOVL	BX, 4(BP)
+	MOVL	CX, 8(BP)
+	MOVL	DX, 12(BP)
+	RET
--- /sys/src/boot/pcipl/mkfile	Thu Apr 17 23:13:05 2014
+++ /sys/src/boot/pcipl/mkfile	Thu Apr 17 23:13:05 2014
@@ -34,7 +34,7 @@
 iplpbs:	iplpbs.$O
 	$LD -o $target -H3 -T0x0800 -l $prereq
 
-ipl&:	l%.$O %.$O sub.$O e820.$O a20.$O  edd.$O eddif.$O
+ipl&:	l%.$O %.$O sub.$O e820.$O a20.$O cpuid.$O edd.$O eddif.$O
 	$LD -o $target -H3 -T0x7c00 -l $prereq
 
 install:V:
--- /sys/src/boot/pcipl/sub.c	Thu Apr 17 23:13:05 2014
+++ /sys/src/boot/pcipl/sub.c	Thu Apr 17 23:13:05 2014
@@ -517,12 +517,36 @@
 	return "i/o error";
 }
 
+typedef struct Cpuidreg Cpuidreg;
+struct Cpuidreg {
+	u32int	ax;
+	u32int	bx;
+	u32int	cx;
+	u32int	dx;
+};
+void cpuid(Cpuidreg*);
+
+int
+check64(void)
+{
+	Cpuidreg r;
+
+	memset(&r, 0, sizeof r);
+	r.ax = 0x80000001;
+	cpuid(&r);
+	if(r.dx & 1<<29)
+		return 0;
+	return -1;
+}
+
 char*
 warp64(Exec ex, void *f)
 {
 	uchar *e, *d, *b, *t, ulv[8];
 	ulong n;
 
+	if(check64() == -1)
+		return "hw not 64bit";
 	if(readn(f, ulv, 8) != 8)
 		return "bad header";
 	e = (uchar*)(getbe(&ex.entry, 4) & ~0xF0000000UL);