diff --git a/include/ureg_arm.h b/include/ureg_arm.h
new file mode 100644
index 0000000000..c740b03021
--- /dev/null
+++ b/include/ureg_arm.h
@@ -0,0 +1,49 @@
+// Inferno utils/libmach/ureg5.h
+// http://code.google.com/p/inferno-os/source/browse/utils/libmach/ureg5.h
+//
+//	Copyright © 1994-1999 Lucent Technologies Inc.
+//	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
+//	Portions Copyright © 1997-1999 Vita Nuova Limited.
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
+//	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
+//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+struct Ureg {
+	uint	r0;
+	uint	r1;
+	uint	r2;
+	uint	r3;
+	uint	r4;
+	uint	r5;
+	uint	r6;
+	uint	r7;
+	uint	r8;
+	uint	r9;
+	uint	r10;
+	uint	r11;
+	uint	r12;
+	uint	r13;
+	uint	r14;
+	uint	link;
+	uint	type;
+	uint	psr;
+	uint	pc;
+};
diff --git a/src/cmd/5l/asm.c b/src/cmd/5l/asm.c
index 6cd4b2390c..a375b8bf87 100644
--- a/src/cmd/5l/asm.c
+++ b/src/cmd/5l/asm.c
@@ -671,7 +671,10 @@ putsymb(char *s, int t, int32 v, int ver)
 			cput(s[i]);
 		cput(0);
 	}
-	symsize += 4 + 1 + i + 1;
+	// TODO(rsc): handle go parameter
+	lput(0);
+
+	symsize += 4 + 1 + i + 1 + 4;
 
 	if(debug['n']) {
 		if(t == 'z' || t == 'Z') {
diff --git a/src/libmach/5.c b/src/libmach/5.c
new file mode 100644
index 0000000000..67bd88db4c
--- /dev/null
+++ b/src/libmach/5.c
@@ -0,0 +1,92 @@
+// Inferno libmach/5.c
+// http://code.google.com/p/inferno-os/source/browse/utils/libmach/5.c
+//
+//	Copyright © 1994-1999 Lucent Technologies Inc.
+//	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
+//	Portions Copyright © 1997-1999 Vita Nuova Limited.
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
+//	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
+//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+/*
+ * arm definition
+ */
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include "ureg_arm.h"
+#include <mach.h>
+
+#define	REGOFF(x)	(ulong) (&((struct Ureg *) 0)->x)
+
+#define SP		REGOFF(r13)
+#define PC		REGOFF(pc)
+
+#define	REGSIZE		sizeof(struct Ureg)
+
+Reglist armreglist[] =
+{
+	{"LINK",	REGOFF(link),		RINT|RRDONLY, 'X'},
+	{"TYPE",	REGOFF(type),		RINT|RRDONLY, 'X'},
+	{"PSR",		REGOFF(psr),		RINT|RRDONLY, 'X'},
+	{"PC",		PC,			RINT, 'X'},
+	{"SP",		SP,			RINT, 'X'},
+	{"R15",		PC,			RINT, 'X'},
+	{"R14",		REGOFF(r14),		RINT, 'X'},
+	{"R13",		REGOFF(r13),		RINT, 'X'},
+	{"R12",		REGOFF(r12),		RINT, 'X'},
+	{"R11",		REGOFF(r11),		RINT, 'X'},
+	{"R10",		REGOFF(r10),		RINT, 'X'},
+	{"R9",		REGOFF(r9),		RINT, 'X'},
+	{"R8",		REGOFF(r8),		RINT, 'X'},
+	{"R7",		REGOFF(r7),		RINT, 'X'},
+	{"R6",		REGOFF(r6),		RINT, 'X'},
+	{"R5",		REGOFF(r5),		RINT, 'X'},
+	{"R4",		REGOFF(r4),		RINT, 'X'},
+	{"R3",		REGOFF(r3),		RINT, 'X'},
+	{"R2",		REGOFF(r2),		RINT, 'X'},
+	{"R1",		REGOFF(r1),		RINT, 'X'},
+	{"R0",		REGOFF(r0),		RINT, 'X'},
+	{  0 }
+};
+
+	/* the machine description */
+Mach marm =
+{
+	"arm",
+	MARM,		/* machine type */
+	armreglist,	/* register set */
+	REGSIZE,	/* register set size */
+	0,		/* fp register set size */
+	"PC",		/* name of PC */
+	"SP",		/* name of SP */
+	"R15",		/* name of link register */
+	"setR12",	/* static base register name */
+	0,		/* static base register value */
+	0x1000,		/* page size */
+	0xC0000000,	/* kernel base */
+	0,		/* kernel text mask */
+	4,		/* quantization of pc */
+	4,		/* szaddr */
+	4,		/* szreg */
+	4,		/* szfloat */
+	8,		/* szdouble */
+};
diff --git a/src/libmach/5db.c b/src/libmach/5db.c
new file mode 100644
index 0000000000..aea391edfc
--- /dev/null
+++ b/src/libmach/5db.c
@@ -0,0 +1,1095 @@
+// Inferno libmach/5db.c
+// http://code.google.com/p/inferno-os/source/browse/utils/libmach/5db.c
+//
+//	Copyright © 1994-1999 Lucent Technologies Inc.
+//	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
+//	Portions Copyright © 1997-1999 Vita Nuova Limited.
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
+//	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
+//	Portions Copyright © 2009 The Go Authors.  All rights reserved.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include "ureg_arm.h"
+#include <mach.h>
+
+static int debug = 0;
+
+#define	BITS(a, b)	((1<<(b+1))-(1<<a))
+
+#define LSR(v, s)	((ulong)(v) >> (s))
+#define ASR(v, s)	((long)(v) >> (s))
+#define ROR(v, s)	(LSR((v), (s)) | (((v) & ((1 << (s))-1)) << (32 - (s))))
+
+
+
+typedef struct	Instr	Instr;
+struct	Instr
+{
+	Map	*map;
+	ulong	w;
+	ulong	addr;
+	uchar	op;			/* super opcode */
+
+	uchar	cond;			/* bits 28-31 */
+	uchar	store;			/* bit 20 */
+
+	uchar	rd;			/* bits 12-15 */
+	uchar	rn;			/* bits 16-19 */
+	uchar	rs;			/* bits 0-11 (shifter operand) */
+
+	long	imm;			/* rotated imm */
+	char*	curr;			/* fill point in buffer */
+	char*	end;			/* end of buffer */
+	char*	err;			/* error message */
+};
+
+typedef struct Opcode Opcode;
+struct Opcode
+{
+	char*	o;
+	void	(*fmt)(Opcode*, Instr*);
+	ulong	(*foll)(Map*, Rgetter, Instr*, ulong);
+	char*	a;
+};
+
+static	void	format(char*, Instr*, char*);
+static	char	FRAMENAME[] = ".frame";
+
+/*
+ * Arm-specific debugger interface
+ */
+
+extern	char	*armexcep(Map*, Rgetter);
+static	int	armfoll(Map*, uvlong, Rgetter, uvlong*);
+static	int	arminst(Map*, uvlong, char, char*, int);
+static	int	armdas(Map*, uvlong, char*, int);
+static	int	arminstlen(Map*, uvlong);
+
+/*
+ *	Debugger interface
+ */
+Machdata armmach =
+{
+	{0, 0, 0, 0xD},		/* break point */
+	4,			/* break point size */
+
+	leswab,			/* short to local byte order */
+	leswal,			/* long to local byte order */
+	leswav,			/* long to local byte order */
+	risctrace,		/* C traceback */
+	riscframe,		/* Frame finder */
+	armexcep,			/* print exception */
+	0,			/* breakpoint fixup */
+	0,			/* single precision float printer */
+	0,			/* double precision float printer */
+	armfoll,		/* following addresses */
+	arminst,		/* print instruction */
+	armdas,			/* dissembler */
+	arminstlen,		/* instruction size */
+};
+
+char*
+armexcep(Map *map, Rgetter rget)
+{
+	long c;
+
+	c = (*rget)(map, "TYPE");
+	switch (c&0x1f) {
+	case 0x11:
+		return "Fiq interrupt";
+	case 0x12:
+		return "Mirq interrupt";
+	case 0x13:
+		return "SVC/SWI Exception";
+	case 0x17:
+		return "Prefetch Abort/Data Abort";
+	case 0x18:
+		return "Data Abort";
+	case 0x1b:
+		return "Undefined instruction/Breakpoint";
+	case 0x1f:
+		return "Sys trap";
+	default:
+		return "Undefined trap";
+	}
+}
+
+static
+char*	cond[16] =
+{
+	"EQ",	"NE",	"CS",	"CC",
+	"MI",	"PL",	"VS",	"VC",
+	"HI",	"LS",	"GE",	"LT",
+	"GT",	"LE",	0,	"NV"
+};
+
+static
+char*	shtype[4] =
+{
+	"<<",	">>",	"->",	"@>"
+};
+
+static
+char *hb[4] =
+{
+	"???",	"HU", "B", "H"
+};
+
+static
+char*	addsub[2] =
+{
+	"-",	"+",
+};
+
+int
+armclass(long w)
+{
+	int op;
+
+	op = (w >> 25) & 0x7;
+	switch(op) {
+	case 0:	/* data processing r,r,r */
+		op = ((w >> 4) & 0xf);
+		if(op == 0x9) {
+			op = 48+16;		/* mul */
+			if(w & (1<<24)) {
+				op += 2;
+				if(w & (1<<22))
+					op++;	/* swap */
+				break;
+			}
+			if(w & (1<<21))
+				op++;		/* mla */
+			break;
+		}
+		if ((op & 0x9) == 0x9)		/* ld/st byte/half s/u */
+		{
+			op = (48+16+4) + ((w >> 22) & 0x1) + ((w >> 19) & 0x2);
+			break;
+		}
+		op = (w >> 21) & 0xf;
+		if(w & (1<<4))
+			op += 32;
+		else
+		if(w & (31<<7))
+			op += 16;
+		break;
+	case 1:	/* data processing i,r,r */
+		op = (48) + ((w >> 21) & 0xf);
+		break;
+	case 2:	/* load/store byte/word i(r) */
+		op = (48+24) + ((w >> 22) & 0x1) + ((w >> 19) & 0x2);
+		break;
+	case 3:	/* load/store byte/word (r)(r) */
+		op = (48+24+4) + ((w >> 22) & 0x1) + ((w >> 19) & 0x2);
+		break;
+	case 4:	/* block data transfer (r)(r) */
+		op = (48+24+4+4) + ((w >> 20) & 0x1);
+		break;
+	case 5:	/* branch / branch link */
+		op = (48+24+4+4+2) + ((w >> 24) & 0x1);
+		break;
+	case 7:	/* coprocessor crap */
+		op = (48+24+4+4+2+2) + ((w >> 3) & 0x2) + ((w >> 20) & 0x1);
+		break;
+	default:
+		op = (48+24+4+4+2+2+4);
+		break;
+	}
+	return op;
+}
+
+static int
+decode(Map *map, ulong pc, Instr *i)
+{
+	uint32 w;
+
+	if(get4(map, pc, &w) < 0) {
+		werrstr("can't read instruction: %r");
+		return -1;
+	}
+	i->w = w;
+	i->addr = pc;
+	i->cond = (w >> 28) & 0xF;
+	i->op = armclass(w);
+	i->map = map;
+	return 1;
+}
+
+static void
+bprint(Instr *i, char *fmt, ...)
+{
+	va_list arg;
+
+	va_start(arg, fmt);
+	i->curr = vseprint(i->curr, i->end, fmt, arg);
+	va_end(arg);
+}
+
+static int
+plocal(Instr *i)
+{
+	char *reg;
+	Symbol s;
+	char *fn;
+	int class;
+	int offset;
+
+	if(!findsym(i->addr, CTEXT, &s)) {
+		if(debug)fprint(2,"fn not found @%lux: %r\n", i->addr);
+		return 0;
+	}
+	fn = s.name;
+	if (!findlocal(&s, FRAMENAME, &s)) {
+		if(debug)fprint(2,"%s.%s not found @%s: %r\n", fn, FRAMENAME, s.name);
+			return 0;
+	}
+	if(s.value > i->imm) {
+		class = CAUTO;
+		offset = s.value-i->imm;
+		reg = "(SP)";
+	} else {
+		class = CPARAM;
+		offset = i->imm-s.value-4;
+		reg = "(FP)";
+	}
+	if(!getauto(&s, offset, class, &s)) {
+		if(debug)fprint(2,"%s %s not found @%ux: %r\n", fn,
+			class == CAUTO ? " auto" : "param", offset);
+		return 0;
+	}
+	bprint(i, "%s%c%d%s", s.name, class == CPARAM ? '+' : '-', s.value, reg);
+	return 1;
+}
+
+/*
+ * Print value v as name[+offset]
+ */
+int
+gsymoff(char *buf, int n, long v, int space)
+{
+	Symbol s;
+	int r;
+	long delta;
+
+	r = delta = 0;		/* to shut compiler up */
+	if (v) {
+		r = findsym(v, space, &s);
+		if (r)
+			delta = v-s.value;
+		if (delta < 0)
+			delta = -delta;
+	}
+	if (v == 0 || r == 0 || delta >= 4096)
+		return snprint(buf, n, "#%lux", v);
+	if (strcmp(s.name, ".string") == 0)
+		return snprint(buf, n, "#%lux", v);
+	if (!delta)
+		return snprint(buf, n, "%s", s.name);
+	if (s.type != 't' && s.type != 'T')
+		return snprint(buf, n, "%s+%lux", s.name, v-s.value);
+	else
+		return snprint(buf, n, "#%lux", v);
+}
+
+static void
+armdps(Opcode *o, Instr *i)
+{
+	i->store = (i->w >> 20) & 1;
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+	i->rs = (i->w >> 0) & 0xf;
+	if(i->rn == 15 && i->rs == 0) {
+		if(i->op == 8) {
+			format("MOVW", i,"CPSR, R%d");
+			return;
+		} else
+		if(i->op == 10) {
+			format("MOVW", i,"SPSR, R%d");
+			return;
+		}
+	} else
+	if(i->rn == 9 && i->rd == 15) {
+		if(i->op == 9) {
+			format("MOVW", i, "R%s, CPSR");
+			return;
+		} else
+		if(i->op == 11) {
+			format("MOVW", i, "R%s, SPSR");
+			return;
+		}
+	}
+	format(o->o, i, o->a);
+}
+
+static void
+armdpi(Opcode *o, Instr *i)
+{
+	ulong v;
+	int c;
+
+	v = (i->w >> 0) & 0xff;
+	c = (i->w >> 8) & 0xf;
+	while(c) {
+		v = (v<<30) | (v>>2);
+		c--;
+	}
+	i->imm = v;
+	i->store = (i->w >> 20) & 1;
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+	i->rs = i->w&0x0f;
+
+		/* RET is encoded as ADD #0,R14,R15 */
+	if((i->w & 0x0fffffff) == 0x028ef000){
+		format("RET%C", i, "");
+		return;
+	}
+	if((i->w & 0x0ff0ffff) == 0x0280f000){
+		format("B%C", i, "0(R%n)");
+		return;
+	}
+	format(o->o, i, o->a);
+}
+
+static void
+armsdti(Opcode *o, Instr *i)
+{
+	ulong v;
+
+	v = i->w & 0xfff;
+	if(!(i->w & (1<<23)))
+		v = -v;
+	i->store = ((i->w >> 23) & 0x2) | ((i->w >>21) & 0x1);
+	i->imm = v;
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+		/* RET is encoded as LW.P x,R13,R15 */
+	if ((i->w & 0x0ffff000) == 0x049df000)
+	{
+		format("RET%C%p", i, "%I");
+		return;
+	}
+	format(o->o, i, o->a);
+}
+
+/* arm V4 ld/st halfword, signed byte */
+static void
+armhwby(Opcode *o, Instr *i)
+{
+	i->store = ((i->w >> 23) & 0x2) | ((i->w >>21) & 0x1);
+	i->imm = (i->w & 0xf) | ((i->w >> 8) & 0xf);
+	if (!(i->w & (1 << 23)))
+		i->imm = - i->imm;
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+	i->rs = (i->w >> 0) & 0xf;
+	format(o->o, i, o->a);
+}
+
+static void
+armsdts(Opcode *o, Instr *i)
+{
+	i->store = ((i->w >> 23) & 0x2) | ((i->w >>21) & 0x1);
+	i->rs = (i->w >> 0) & 0xf;
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+	format(o->o, i, o->a);
+}
+
+static void
+armbdt(Opcode *o, Instr *i)
+{
+	i->store = (i->w >> 21) & 0x3;		/* S & W bits */
+	i->rn = (i->w >> 16) & 0xf;
+	i->imm = i->w & 0xffff;
+	if(i->w == 0xe8fd8000)
+		format("RFE", i, "");
+	else
+		format(o->o, i, o->a);
+}
+
+/*
+static void
+armund(Opcode *o, Instr *i)
+{
+	format(o->o, i, o->a);
+}
+
+static void
+armcdt(Opcode *o, Instr *i)
+{
+	format(o->o, i, o->a);
+}
+*/
+
+static void
+armunk(Opcode *o, Instr *i)
+{
+	format(o->o, i, o->a);
+}
+
+static void
+armb(Opcode *o, Instr *i)
+{
+	ulong v;
+
+	v = i->w & 0xffffff;
+	if(v & 0x800000)
+		v |= ~0xffffff;
+	i->imm = (v<<2) + i->addr + 8;
+	format(o->o, i, o->a);
+}
+
+static void
+armco(Opcode *o, Instr *i)		/* coprocessor instructions */
+{
+	int op, p, cp;
+
+	char buf[1024];
+
+	i->rn = (i->w >> 16) & 0xf;
+	i->rd = (i->w >> 12) & 0xf;
+	i->rs = i->w&0xf;
+	cp = (i->w >> 8) & 0xf;
+	p = (i->w >> 5) & 0x7;
+	if(i->w&(1<<4)) {
+		op = (i->w >> 21) & 0x07;
+		snprint(buf, sizeof(buf), "#%x, #%x, R%d, C(%d), C(%d), #%x\n", cp, op, i->rd, i->rn, i->rs, p);
+	} else {
+		op = (i->w >> 20) & 0x0f;
+		snprint(buf, sizeof(buf), "#%x, #%x, C(%d), C(%d), C(%d), #%x\n", cp, op, i->rd, i->rn, i->rs, p);
+	}
+	format(o->o, i, buf);
+}
+
+static int
+armcondpass(Map *map, Rgetter rget, uchar cond)
+{
+	ulong psr;
+	uchar n;
+	uchar z;
+	uchar c;
+	uchar v;
+
+	psr = rget(map, "PSR");
+	n = (psr >> 31) & 1;
+	z = (psr >> 30) & 1;
+	c = (psr >> 29) & 1;
+	v = (psr >> 28) & 1;
+
+	switch(cond) {
+		case 0:		return z;
+		case 1:		return !z;
+		case 2:		return c;
+		case 3:		return !c;
+		case 4:		return n;
+		case 5:		return !n;
+		case 6:		return v;
+		case 7:		return !v;
+		case 8:		return c && !z;
+		case 9:		return !c || z;
+		case 10:	return n == v;
+		case 11:	return n != v;
+		case 12:	return !z && (n == v);
+		case 13:	return z && (n != v);
+		case 14:	return 1;
+		case 15:	return 0;
+	}
+	return 0;
+}
+
+static ulong
+armshiftval(Map *map, Rgetter rget, Instr *i)
+{
+	if(i->w & (1 << 25)) {				/* immediate */
+		ulong imm = i->w & BITS(0, 7);
+		ulong s = (i->w & BITS(8, 11)) >> 7; /* this contains the *2 */
+		return ROR(imm, s);
+	} else {
+		char buf[8];
+		ulong v;
+		ulong s = (i->w & BITS(7,11)) >> 7;
+
+		sprint(buf, "R%ld", i->w & 0xf);
+		v = rget(map, buf);
+
+		switch((i->w & BITS(4, 6)) >> 4) {
+		case 0:					/* LSLIMM */
+			return v << s;
+		case 1:					/* LSLREG */
+			sprint(buf, "R%lud", s >> 1);
+			s = rget(map, buf) & 0xFF;
+			if(s >= 32) return 0;
+			return v << s;
+		case 2:					/* LSRIMM */
+			return LSR(v, s);
+		case 3:					/* LSRREG */
+			sprint(buf, "R%ld", s >> 1);
+			s = rget(map, buf) & 0xFF;
+			if(s >= 32) return 0;
+			return LSR(v, s);
+		case 4:					/* ASRIMM */
+			if(s == 0) {
+				if((v & (1U<<31)) == 0)
+					return 0;
+				return 0xFFFFFFFF;
+			}
+			return ASR(v, s);
+		case 5:					/* ASRREG */
+			sprint(buf, "R%ld", s >> 1);
+			s = rget(map, buf) & 0xFF;
+			if(s >= 32) {
+				if((v & (1U<<31)) == 0)
+					return 0;
+				return 0xFFFFFFFF;
+			}
+			return ASR(v, s);
+		case 6:					/* RORIMM */
+			if(s == 0) {
+				ulong c = (rget(map, "PSR") >> 29) & 1;
+
+				return (c << 31) | LSR(v, 1);
+			}
+			return ROR(v, s);
+		case 7:					/* RORREG */
+			sprint(buf, "R%ld", (s>>1)&0xF);
+			s = rget(map, buf);
+			if(s == 0 || (s & 0xF) == 0)
+				return v;
+			return ROR(v, s & 0xF);
+		}
+	}
+	return 0;
+}
+
+static int
+nbits(ulong v)
+{
+	int n = 0;
+	int i;
+
+	for(i=0; i < 32 ; i++) {
+		if(v & 1) ++n;
+		v >>= 1;
+	}
+
+	return n;
+}
+
+static ulong
+armmaddr(Map *map, Rgetter rget, Instr *i)
+{
+	ulong v;
+	ulong nb;
+	char buf[8];
+	ulong rn;
+
+	rn = (i->w >> 16) & 0xf;
+	sprint(buf,"R%ld", rn);
+
+	v = rget(map, buf);
+	nb = nbits(i->w & ((1 << 15) - 1));
+
+	switch((i->w >> 23) & 3) {
+		case 0: return (v - (nb*4)) + 4;
+		case 1: return v;
+		case 2: return v - (nb*4);
+		case 3: return v + 4;
+	}
+	return 0;
+}
+
+static ulong
+armaddr(Map *map, Rgetter rget, Instr *i)
+{
+	char buf[8];
+	ulong rn;
+
+	sprint(buf, "R%ld", (i->w >> 16) & 0xf);
+	rn = rget(map, buf);
+
+	if((i->w & (1<<24)) == 0) {			/* POSTIDX */
+		sprint(buf, "R%ld", rn);
+		return rget(map, buf);
+	}
+
+	if((i->w & (1<<25)) == 0) {			/* OFFSET */
+		sprint(buf, "R%ld", rn);
+		if(i->w & (1U<<23))
+			return rget(map, buf) + (i->w & BITS(0,11));
+		return rget(map, buf) - (i->w & BITS(0,11));
+	} else {					/* REGOFF */
+		ulong index = 0;
+		uchar c;
+		uchar rm;
+
+		sprint(buf, "R%ld", i->w & 0xf);
+		rm = rget(map, buf);
+
+		switch((i->w & BITS(5,6)) >> 5) {
+		case 0: index = rm << ((i->w & BITS(7,11)) >> 7);	break;
+		case 1: index = LSR(rm, ((i->w & BITS(7,11)) >> 7));	break;
+		case 2: index = ASR(rm, ((i->w & BITS(7,11)) >> 7));	break;
+		case 3:
+			if((i->w & BITS(7,11)) == 0) {
+				c = (rget(map, "PSR") >> 29) & 1;
+				index = c << 31 | LSR(rm, 1);
+			} else {
+				index = ROR(rm, ((i->w & BITS(7,11)) >> 7));
+			}
+			break;
+		}
+		if(i->w & (1<<23))
+			return rn + index;
+		return rn - index;
+	}
+}
+
+static ulong
+armfadd(Map *map, Rgetter rget, Instr *i, ulong pc)
+{
+	char buf[8];
+	int r;
+
+	r = (i->w >> 12) & 0xf;
+	if(r != 15 || !armcondpass(map, rget, (i->w >> 28) & 0xf))
+		return pc+4;
+
+	r = (i->w >> 16) & 0xf;
+	sprint(buf, "R%d", r);
+
+	return rget(map, buf) + armshiftval(map, rget, i);
+}
+
+static ulong
+armfmovm(Map *map, Rgetter rget, Instr *i, ulong pc)
+{
+	uint32 v;
+	ulong addr;
+
+	v = i->w & 1<<15;
+	if(!v || !armcondpass(map, rget, (i->w>>28)&0xf))
+		return pc+4;
+
+	addr = armmaddr(map, rget, i) + nbits(i->w & BITS(0,15));
+	if(get4(map, addr, &v) < 0) {
+		werrstr("can't read addr: %r");
+		return -1;
+	}
+	return v;
+}
+
+static ulong
+armfbranch(Map *map, Rgetter rget, Instr *i, ulong pc)
+{
+	if(!armcondpass(map, rget, (i->w >> 28) & 0xf))
+		return pc+4;
+
+	return pc + (((signed long)i->w << 8) >> 6) + 8;
+}
+
+static ulong
+armfmov(Map *map, Rgetter rget, Instr *i, ulong pc)
+{
+	ulong rd;
+	uint32 v;
+
+	rd = (i->w >> 12) & 0xf;
+	if(rd != 15 || !armcondpass(map, rget, (i->w>>28)&0xf))
+		return pc+4;
+
+	 /* LDR */
+	/* BUG: Needs LDH/B, too */
+	if(((i->w>>26)&0x3) == 1) {
+		if(get4(map, armaddr(map, rget, i), &v) < 0) {
+			werrstr("can't read instruction: %r");
+			return pc+4;
+		}
+		return v;
+	}
+
+	 /* MOV */
+	return armshiftval(map, rget, i);
+}
+
+static Opcode opcodes[] =
+{
+	"AND%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"EOR%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"SUB%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"RSB%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"ADD%C%S",	armdps, armfadd,	"R%s,R%n,R%d",
+	"ADC%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"SBC%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"RSC%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"TST%C%S",	armdps, 0,	"R%s,R%n",
+	"TEQ%C%S",	armdps, 0,	"R%s,R%n",
+	"CMP%C%S",	armdps, 0,	"R%s,R%n",
+	"CMN%C%S",	armdps, 0,	"R%s,R%n",
+	"ORR%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"MOVW%C%S",	armdps, armfmov,	"R%s,R%d",
+	"BIC%C%S",	armdps, 0,	"R%s,R%n,R%d",
+	"MVN%C%S",	armdps, 0,	"R%s,R%d",
+
+/* 16 */
+	"AND%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"EOR%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"SUB%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"RSB%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"ADD%C%S",	armdps, armfadd,	"(R%s%h%m),R%n,R%d",
+	"ADC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"SBC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"RSC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"TST%C%S",	armdps, 0,	"(R%s%h%m),R%n",
+	"TEQ%C%S",	armdps, 0,	"(R%s%h%m),R%n",
+	"CMP%C%S",	armdps, 0,	"(R%s%h%m),R%n",
+	"CMN%C%S",	armdps, 0,	"(R%s%h%m),R%n",
+	"ORR%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"MOVW%C%S",	armdps, armfmov,	"(R%s%h%m),R%d",
+	"BIC%C%S",	armdps, 0,	"(R%s%h%m),R%n,R%d",
+	"MVN%C%S",	armdps, 0,	"(R%s%h%m),R%d",
+
+/* 32 */
+	"AND%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"EOR%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"SUB%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"RSB%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"ADD%C%S",	armdps, armfadd,	"(R%s%hR%M),R%n,R%d",
+	"ADC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"SBC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"RSC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"TST%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
+	"TEQ%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
+	"CMP%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
+	"CMN%C%S",	armdps, 0,	"(R%s%hR%M),R%n",
+	"ORR%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"MOVW%C%S",	armdps, armfmov,	"(R%s%hR%M),R%d",
+	"BIC%C%S",	armdps, 0,	"(R%s%hR%M),R%n,R%d",
+	"MVN%C%S",	armdps, 0,	"(R%s%hR%M),R%d",
+
+/* 48 */
+	"AND%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"EOR%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"SUB%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"RSB%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"ADD%C%S",	armdpi, armfadd,	"$#%i,R%n,R%d",
+	"ADC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"SBC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"RSC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"TST%C%S",	armdpi, 0,	"$#%i,R%n",
+	"TEQ%C%S",	armdpi, 0,	"$#%i,R%n",
+	"CMP%C%S",	armdpi, 0,	"$#%i,R%n",
+	"CMN%C%S",	armdpi, 0,	"$#%i,R%n",
+	"ORR%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"MOVW%C%S",	armdpi, armfmov,	"$#%i,R%d",
+	"BIC%C%S",	armdpi, 0,	"$#%i,R%n,R%d",
+	"MVN%C%S",	armdpi, 0,	"$#%i,R%d",
+
+/* 48+16 */
+	"MUL%C%S",	armdpi, 0,	"R%s,R%M,R%n",
+	"MULA%C%S",	armdpi, 0,	"R%s,R%M,R%n,R%d",
+	"SWPW",		armdpi, 0,	"R%s,(R%n),R%d",
+	"SWPB",		armdpi, 0,	"R%s,(R%n),R%d",
+
+/* 48+16+4 */
+	"MOV%u%C%p",	armhwby, 0,	"R%d,(R%n%UR%M)",
+	"MOV%u%C%p",	armhwby, 0,	"R%d,%I",
+	"MOV%u%C%p",	armhwby, armfmov,	"(R%n%UR%M),R%d",
+	"MOV%u%C%p",	armhwby, armfmov,	"%I,R%d",
+
+/* 48+24 */
+	"MOVW%C%p",	armsdti, 0,	"R%d,%I",
+	"MOVB%C%p",	armsdti, 0,	"R%d,%I",
+	"MOVW%C%p",	armsdti, armfmov,	"%I,R%d",
+	"MOVBU%C%p",	armsdti, armfmov,	"%I,R%d",
+
+	"MOVW%C%p",	armsdts, 0,	"R%d,(R%s%h%m)(R%n)",
+	"MOVB%C%p",	armsdts, 0,	"R%d,(R%s%h%m)(R%n)",
+	"MOVW%C%p",	armsdts, armfmov,	"(R%s%h%m)(R%n),R%d",
+	"MOVBU%C%p",	armsdts, armfmov,	"(R%s%h%m)(R%n),R%d",
+
+	"MOVM%C%P%a",	armbdt, armfmovm,		"[%r],(R%n)",
+	"MOVM%C%P%a",	armbdt, armfmovm,		"(R%n),[%r]",
+
+	"B%C",		armb, armfbranch,		"%b",
+	"BL%C",		armb, armfbranch,		"%b",
+
+	"CDP%C",	armco, 0,		"",
+	"CDP%C",	armco, 0,		"",
+	"MCR%C",	armco, 0,		"",
+	"MRC%C",	armco, 0,		"",
+
+	"UNK",		armunk, 0,	"",
+};
+
+static void
+gaddr(Instr *i)
+{
+	*i->curr++ = '$';
+	i->curr += gsymoff(i->curr, i->end-i->curr, i->imm, CANY);
+}
+
+static	char *mode[] = { 0, "IA", "DB", "IB" };
+static	char *pw[] = { "P", "PW", 0, "W" };
+static	char *sw[] = { 0, "W", "S", "SW" };
+
+static void
+format(char *mnemonic, Instr *i, char *f)
+{
+	int j, k, m, n;
+	int g;
+	char *fmt;
+
+	if(mnemonic)
+		format(0, i, mnemonic);
+	if(f == 0)
+		return;
+	if(mnemonic)
+		if(i->curr < i->end)
+			*i->curr++ = '\t';
+	for ( ; *f && i->curr < i->end; f++) {
+		if(*f != '%') {
+			*i->curr++ = *f;
+			continue;
+		}
+		switch (*++f) {
+
+		case 'C':	/* .CONDITION */
+			if(cond[i->cond])
+				bprint(i, ".%s", cond[i->cond]);
+			break;
+
+		case 'S':	/* .STORE */
+			if(i->store)
+				bprint(i, ".S");
+			break;
+
+		case 'P':	/* P & U bits for block move */
+			n = (i->w >>23) & 0x3;
+			if (mode[n])
+				bprint(i, ".%s", mode[n]);
+			break;
+
+		case 'p':	/* P & W bits for single data xfer*/
+			if (pw[i->store])
+				bprint(i, ".%s", pw[i->store]);
+			break;
+
+		case 'a':	/* S & W bits for single data xfer*/
+			if (sw[i->store])
+				bprint(i, ".%s", sw[i->store]);
+			break;
+
+		case 's':
+			bprint(i, "%d", i->rs & 0xf);
+			break;
+
+		case 'M':
+			bprint(i, "%d", (i->w>>8) & 0xf);
+			break;
+
+		case 'm':
+			bprint(i, "%d", (i->w>>7) & 0x1f);
+			break;
+
+		case 'h':
+			bprint(i, shtype[(i->w>>5) & 0x3]);
+			break;
+
+		case 'u':		/* Signed/unsigned Byte/Halfword */
+			bprint(i, hb[(i->w>>5) & 0x3]);
+			break;
+
+		case 'I':
+			if (i->rn == 13) {
+				if (plocal(i))
+					break;
+			}
+			g = 0;
+			fmt = "#%lx(R%d)";
+			if (i->rn == 15) {
+				/* convert load of offset(PC) to a load immediate */
+				uint32 x;
+				if (get4(i->map, i->addr+i->imm+8, &x) > 0)
+				{
+					i->imm = (int32)x;
+					g = 1;
+					fmt = "";
+				}
+			}
+			if (mach->sb)
+			{
+				if (i->rd == 11) {
+					uint32 nxti;
+
+					if (get4(i->map, i->addr+4, &nxti) > 0) {
+						if ((nxti & 0x0e0f0fff) == 0x060c000b) {
+							i->imm += mach->sb;
+							g = 1;
+							fmt = "-SB";
+						}
+					}
+				}
+				if (i->rn == 12)
+				{
+					i->imm += mach->sb;
+					g = 1;
+					fmt = "-SB(SB)";
+				}
+			}
+			if (g)
+			{
+				gaddr(i);
+				bprint(i, fmt, i->rn);
+			}
+			else
+				bprint(i, fmt, i->imm, i->rn);
+			break;
+		case 'U':		/* Add/subtract from base */
+			bprint(i, addsub[(i->w >> 23) & 1]);
+			break;
+
+		case 'n':
+			bprint(i, "%d", i->rn);
+			break;
+
+		case 'd':
+			bprint(i, "%d", i->rd);
+			break;
+
+		case 'i':
+			bprint(i, "%lux", i->imm);
+			break;
+
+		case 'b':
+			i->curr += symoff(i->curr, i->end-i->curr,
+				i->imm, CTEXT);
+			break;
+
+		case 'g':
+			i->curr += gsymoff(i->curr, i->end-i->curr,
+				i->imm, CANY);
+			break;
+
+		case 'r':
+			n = i->imm&0xffff;
+			j = 0;
+			k = 0;
+			while(n) {
+				m = j;
+				while(n&0x1) {
+					j++;
+					n >>= 1;
+				}
+				if(j != m) {
+					if(k)
+						bprint(i, ",");
+					if(j == m+1)
+						bprint(i, "R%d", m);
+					else
+						bprint(i, "R%d-R%d", m, j-1);
+					k = 1;
+				}
+				j++;
+				n >>= 1;
+			}
+			break;
+
+		case '\0':
+			*i->curr++ = '%';
+			return;
+
+		default:
+			bprint(i, "%%%c", *f);
+			break;
+		}
+	}
+	*i->curr = 0;
+}
+
+static int
+printins(Map *map, ulong pc, char *buf, int n)
+{
+	Instr i;
+
+	i.curr = buf;
+	i.end = buf+n-1;
+	if(decode(map, pc, &i) < 0)
+		return -1;
+
+	(*opcodes[i.op].fmt)(&opcodes[i.op], &i);
+	return 4;
+}
+
+static int
+arminst(Map *map, uvlong pc, char modifier, char *buf, int n)
+{
+	USED(modifier);
+	return printins(map, pc, buf, n);
+}
+
+static int
+armdas(Map *map, uvlong pc, char *buf, int n)
+{
+	Instr i;
+
+	i.curr = buf;
+	i.end = buf+n;
+	if(decode(map, pc, &i) < 0)
+		return -1;
+	if(i.end-i.curr > 8)
+		i.curr = _hexify(buf, i.w, 7);
+	*i.curr = 0;
+	return 4;
+}
+
+static int
+arminstlen(Map *map, uvlong pc)
+{
+	Instr i;
+
+	if(decode(map, pc, &i) < 0)
+		return -1;
+	return 4;
+}
+
+static int
+armfoll(Map *map, uvlong pc, Rgetter rget, uvlong *foll)
+{
+	ulong d;
+	Instr i;
+
+	if(decode(map, pc, &i) < 0)
+		return -1;
+
+	if(opcodes[i.op].foll) {
+		d = (*opcodes[i.op].foll)(map, rget, &i, pc);
+		if(d == -1)
+			return -1;
+	} else
+		d = pc+4;
+
+	foll[0] = d;
+	return 1;
+}
diff --git a/src/libmach/Makefile b/src/libmach/Makefile
index b0031486ab..cde2cdf66c 100644
--- a/src/libmach/Makefile
+++ b/src/libmach/Makefile
@@ -39,8 +39,10 @@ OFILES=\
 	access.$O\
 	machdata.$O\
 	setmach.$O\
+	5.$O\
 	6.$O\
 	8.$O\
+	5db.$O\
 	8db.$O\
 	5obj.$O\
 	6obj.$O\
diff --git a/src/libmach/executable.c b/src/libmach/executable.c
index 075738e9c8..6bde5b5a44 100644
--- a/src/libmach/executable.c
+++ b/src/libmach/executable.c
@@ -108,7 +108,6 @@ Mach	mmips2be;
 Mach	msparc;
 Mach	msparc64;
 Mach	m68020;
-Mach	marm;
 Mach	mpower;
 Mach	mpower64;
 Mach	malpha;
diff --git a/src/libmach/setmach.c b/src/libmach/setmach.c
index b887781867..0fa4d31920 100644
--- a/src/libmach/setmach.c
+++ b/src/libmach/setmach.c
@@ -1,11 +1,11 @@
 // Inferno libmach/setmach.c
 // http://code.google.com/p/inferno-os/source/browse/utils/libmach/setmach.c
 //
-// 	Copyright © 1994-1999 Lucent Technologies Inc.
-// 	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
-// 	Portions Copyright © 1997-1999 Vita Nuova Limited.
-// 	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
-// 	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
+//	Copyright © 1994-1999 Lucent Technologies Inc.
+//	Power PC support Copyright © 1995-2004 C H Forsyth (forsyth@terzarima.net).
+//	Portions Copyright © 1997-1999 Vita Nuova Limited.
+//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).
+//	Revisions Copyright © 2000-2004 Lucent Technologies Inc. and others.
 //	Portions Copyright © 2009 The Go Authors.  All rights reserved.
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -50,8 +50,8 @@ extern	Mach		mmips, msparc, m68020, mi386, mamd64,
 extern	Machdata	mipsmach, sparcmach, m68020mach, i386mach,
 			armmach, mipsmach2le, powermach, alphamach, sparc64mach;
 */
-extern	Mach		mi386, mamd64;
-extern	Machdata		i386mach;
+extern	Mach		mi386, mamd64, marm;
+extern	Machdata		i386mach, armmach;
 
 /*
  *	machine selection table.  machines with native disassemblers should
@@ -72,6 +72,12 @@ Machtab	machines[] =
 		AAMD64,
 		&mamd64,
 		&i386mach,	},
+	{	"arm",				/*ARM*/
+		FARM,
+		FARMB,
+		AARM,
+		&marm,
+		&armmach,	},
 #ifdef unused
 	{	"68020",			/*68020*/
 		F68020,
@@ -127,12 +133,6 @@ Machtab	machines[] =
 		AI8086,
 		&mi386,
 		&i386mach,	},
-	{	"arm",				/*ARM*/
-		FARM,
-		FARMB,
-		AARM,
-		&marm,
-		&armmach,	},
 	{	"power",			/*PowerPC*/
 		FPOWER,
 		FPOWERB,