diff --git a/src/pkg/crypto/md5/gen.go b/src/pkg/crypto/md5/gen.go
index 275b4aeea3..ccaa7c13d3 100644
--- a/src/pkg/crypto/md5/gen.go
+++ b/src/pkg/crypto/md5/gen.go
@@ -164,7 +164,7 @@ var program = `
 // DO NOT EDIT.
 // Generate with: go run gen.go{{if .Full}} -full{{end}} | gofmt >md5block.go
 
-// +build !amd64
+// +build !amd64,!386,!arm
 
 package md5
 
diff --git a/src/pkg/crypto/md5/md5_test.go b/src/pkg/crypto/md5/md5_test.go
index 4901655e77..b51e304417 100644
--- a/src/pkg/crypto/md5/md5_test.go
+++ b/src/pkg/crypto/md5/md5_test.go
@@ -81,6 +81,30 @@ func TestGolden(t *testing.T) {
 	}
 }
 
+func TestLarge(t *testing.T) {
+	const N = 10000
+	ok := "2bb571599a4180e1d542f76904adc3df" // md5sum of "0123456789" * 1000
+	block := make([]byte, 10004)
+	c := New()
+	for offset := 0; offset < 4; offset++ {
+		for i := 0; i < N; i++ {
+			block[offset+i] = '0' + byte(i%10)
+		}
+		for blockSize := 10; blockSize <= N; blockSize *= 10 {
+			blocks := N / blockSize
+			b := block[offset : offset+blockSize]
+			c.Reset()
+			for i := 0; i < blocks; i++ {
+				c.Write(b)
+			}
+			s := fmt.Sprintf("%x", c.Sum(nil))
+			if s != ok {
+				t.Fatalf("md5 TestLarge offset=%d, blockSize=%d = %s want %s", offset, blockSize, s, ok)
+			}
+		}
+	}
+}
+
 func ExampleNew() {
 	h := New()
 	io.WriteString(h, "The fog is getting thicker!")
diff --git a/src/pkg/crypto/md5/md5block.go b/src/pkg/crypto/md5/md5block.go
index a376fbee99..3e739e36ff 100644
--- a/src/pkg/crypto/md5/md5block.go
+++ b/src/pkg/crypto/md5/md5block.go
@@ -1,7 +1,7 @@
 // DO NOT EDIT.
 // Generate with: go run gen.go -full | gofmt >md5block.go
 
-// +build !amd64,!386
+// +build !amd64,!386,!arm
 
 package md5
 
diff --git a/src/pkg/crypto/md5/md5block_arm.s b/src/pkg/crypto/md5/md5block_arm.s
new file mode 100644
index 0000000000..9a068c3b97
--- /dev/null
+++ b/src/pkg/crypto/md5/md5block_arm.s
@@ -0,0 +1,297 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// ARM version of md5block.go
+
+// Register definitions
+table = 0	// Pointer to MD5 constants table
+data = 1	// Pointer to data to hash
+a = 2		// MD5 accumulator
+b = 3		// MD5 accumulator
+c = 4		// MD5 accumulator
+d = 5		// MD5 accumulator
+c0 = 6		// MD5 constant
+c1 = 7		// MD5 constant
+c2 = 8		// MD5 constant
+// r9, r10 are forbidden
+// r11 is OK provided you check the assembler that no synthetic instructions use it
+c3 = 11		// MD5 constant
+t0 = 12		// temporary
+t1 = 14		// temporary
+
+// func block(dig *digest, p []byte)
+// 0(FP) is *digest
+// 4(FP) is p.array (struct Slice)
+// 8(FP) is p.len
+//12(FP) is p.cap
+//
+// Stack frame
+p_end = -4	// -4(SP) pointer to the end of data
+p_data = -8	// -8(SP) current data pointer
+buf = -8-4*16	//-72(SP) 16 words temporary buffer
+		// 3 words at 4..12(R13) for called routine parameters
+
+TEXT	·block(SB), 7, $84-16
+	MOVW	p+4(FP), R(data)	// pointer to the data
+	MOVW	p_len+8(FP), R(t0)	// number of bytes
+	ADD	R(data), R(t0)
+	MOVW	R(t0), p_end(SP)	// pointer to end of data
+
+loop:
+	MOVW	R(data), p_data(SP)	// Save R(data)
+	AND.S	$3, R(data), R(t0)	// TST $3, R(data) not working see issue 5921
+	BEQ	aligned			// aligned detected - skip copy
+
+	// Copy the unaligned source data into the aligned temporary buffer
+	// memove(to=4(R13), from=8(R13), n=12(R13)) - Corrupts all registers
+	MOVW	$buf(SP), R(table)	// to
+	MOVW	$64, R(c0)		// n
+	MOVM.IB	[R(table),R(data),R(c0)], (R13)
+	BL	runtime·memmove(SB)
+
+	// Point to the local aligned copy of the data
+	MOVW	$buf(SP), R(data)
+
+aligned:
+	// Point to the table of constants
+	// A PC relative add would be cheaper than this
+	MOVW	$·table(SB), R(table)
+
+	// Load up initial MD5 accumulator
+	MOVW	dig+0(FP), R(c0)
+	MOVM.IA (R(c0)), [R(a),R(b),R(c),R(d)]
+
+// a += (((c^d)&b)^d) + X[index] + const
+// a = a<<shift | a>>(32-shift) + b
+#define ROUND1(a, b, c, d, index, shift, const) \
+	EOR	R(c), R(d), R(t0)		; \
+	AND	R(b), R(t0)			; \
+	EOR	R(d), R(t0)			; \
+	MOVW	(index<<2)(R(data)), R(t1)	; \
+	ADD	R(t1), R(t0)			; \
+	ADD	R(const), R(t0)			; \
+	ADD	R(t0), R(a)			; \
+	ADD	R(a)@>(32-shift), R(b), R(a)	;
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND1(a, b, c, d,  0,	7, c0)
+	ROUND1(d, a, b, c,  1, 12, c1)
+	ROUND1(c, d, a, b,  2, 17, c2)
+	ROUND1(b, c, d, a,  3, 22, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND1(a, b, c, d,  4,	7, c0)
+	ROUND1(d, a, b, c,  5, 12, c1)
+	ROUND1(c, d, a, b,  6, 17, c2)
+	ROUND1(b, c, d, a,  7, 22, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND1(a, b, c, d,  8,	7, c0)
+	ROUND1(d, a, b, c,  9, 12, c1)
+	ROUND1(c, d, a, b, 10, 17, c2)
+	ROUND1(b, c, d, a, 11, 22, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND1(a, b, c, d, 12,	7, c0)
+	ROUND1(d, a, b, c, 13, 12, c1)
+	ROUND1(c, d, a, b, 14, 17, c2)
+	ROUND1(b, c, d, a, 15, 22, c3)
+
+// a += (((b^c)&d)^c) + X[index] + const
+// a = a<<shift | a>>(32-shift) + b
+#define ROUND2(a, b, c, d, index, shift, const) \
+	EOR	R(b), R(c), R(t0)		; \
+	AND	R(d), R(t0)			; \
+	EOR	R(c), R(t0)			; \
+	MOVW	(index<<2)(R(data)), R(t1)	; \
+	ADD	R(t1), R(t0)			; \
+	ADD	R(const), R(t0)			; \
+	ADD	R(t0), R(a)			; \
+	ADD	R(a)@>(32-shift), R(b), R(a)	;
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND2(a, b, c, d,  1,	5, c0)
+	ROUND2(d, a, b, c,  6,	9, c1)
+	ROUND2(c, d, a, b, 11, 14, c2)
+	ROUND2(b, c, d, a,  0, 20, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND2(a, b, c, d,  5,	5, c0)
+	ROUND2(d, a, b, c, 10,	9, c1)
+	ROUND2(c, d, a, b, 15, 14, c2)
+	ROUND2(b, c, d, a,  4, 20, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND2(a, b, c, d,  9,	5, c0)
+	ROUND2(d, a, b, c, 14,	9, c1)
+	ROUND2(c, d, a, b,  3, 14, c2)
+	ROUND2(b, c, d, a,  8, 20, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND2(a, b, c, d, 13,	5, c0)
+	ROUND2(d, a, b, c,  2,	9, c1)
+	ROUND2(c, d, a, b,  7, 14, c2)
+	ROUND2(b, c, d, a, 12, 20, c3)
+
+// a += (b^c^d) + X[index] + const
+// a = a<<shift | a>>(32-shift) + b
+#define ROUND3(a, b, c, d, index, shift, const) \
+	EOR	R(b), R(c), R(t0)		; \
+	EOR	R(d), R(t0)			; \
+	MOVW	(index<<2)(R(data)), R(t1)	; \
+	ADD	R(t1), R(t0)			; \
+	ADD	R(const), R(t0)			; \
+	ADD	R(t0), R(a)			; \
+	ADD	R(a)@>(32-shift), R(b), R(a)	;
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND3(a, b, c, d,  5,	4, c0)
+	ROUND3(d, a, b, c,  8, 11, c1)
+	ROUND3(c, d, a, b, 11, 16, c2)
+	ROUND3(b, c, d, a, 14, 23, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND3(a, b, c, d,  1,	4, c0)
+	ROUND3(d, a, b, c,  4, 11, c1)
+	ROUND3(c, d, a, b,  7, 16, c2)
+	ROUND3(b, c, d, a, 10, 23, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND3(a, b, c, d, 13,	4, c0)
+	ROUND3(d, a, b, c,  0, 11, c1)
+	ROUND3(c, d, a, b,  3, 16, c2)
+	ROUND3(b, c, d, a,  6, 23, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND3(a, b, c, d,  9,	4, c0)
+	ROUND3(d, a, b, c, 12, 11, c1)
+	ROUND3(c, d, a, b, 15, 16, c2)
+	ROUND3(b, c, d, a,  2, 23, c3)
+
+// a += (c^(b|^d)) + X[index] + const
+// a = a<<shift | a>>(32-shift) + b
+#define ROUND4(a, b, c, d, index, shift, const) \
+	MVN	R(d), R(t0)			; \
+	ORR	R(b), R(t0)			; \
+	EOR	R(c), R(t0)			; \
+	MOVW	(index<<2)(R(data)), R(t1)	; \
+	ADD	R(t1), R(t0)			; \
+	ADD	R(const), R(t0)			; \
+	ADD	R(t0), R(a)			; \
+	ADD	R(a)@>(32-shift), R(b), R(a)	;
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND4(a, b, c, d,  0,	6, c0)
+	ROUND4(d, a, b, c,  7, 10, c1)
+	ROUND4(c, d, a, b, 14, 15, c2)
+	ROUND4(b, c, d, a,  5, 21, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND4(a, b, c, d, 12,	6, c0)
+	ROUND4(d, a, b, c,  3, 10, c1)
+	ROUND4(c, d, a, b, 10, 15, c2)
+	ROUND4(b, c, d, a,  1, 21, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND4(a, b, c, d,  8,	6, c0)
+	ROUND4(d, a, b, c, 15, 10, c1)
+	ROUND4(c, d, a, b,  6, 15, c2)
+	ROUND4(b, c, d, a, 13, 21, c3)
+
+	MOVM.IA.W (R(table)), [R(c0),R(c1),R(c2),R(c3)]
+	ROUND4(a, b, c, d,  4,	6, c0)
+	ROUND4(d, a, b, c, 11, 10, c1)
+	ROUND4(c, d, a, b,  2, 15, c2)
+	ROUND4(b, c, d, a,  9, 21, c3)
+
+	MOVW	dig+0(FP), R(t0)
+	MOVM.IA (R(t0)), [R(c0),R(c1),R(c2),R(c3)]
+
+	ADD	R(c0), R(a)
+	ADD	R(c1), R(b)
+	ADD	R(c2), R(c)
+	ADD	R(c3), R(d)
+
+	MOVM.IA [R(a),R(b),R(c),R(d)], (R(t0))
+
+	MOVW	p_data(SP), R(data)
+	MOVW	p_end(SP), R(t0)
+	ADD	$64, R(data)
+	CMP	R(t0), R(data)
+	BLO	loop
+
+	RET
+
+// MD5 constants table
+
+	// Round 1
+	DATA	·table+0x00(SB)/4, $0xd76aa478
+	DATA	·table+0x04(SB)/4, $0xe8c7b756
+	DATA	·table+0x08(SB)/4, $0x242070db
+	DATA	·table+0x0c(SB)/4, $0xc1bdceee
+	DATA	·table+0x10(SB)/4, $0xf57c0faf
+	DATA	·table+0x14(SB)/4, $0x4787c62a
+	DATA	·table+0x18(SB)/4, $0xa8304613
+	DATA	·table+0x1c(SB)/4, $0xfd469501
+	DATA	·table+0x20(SB)/4, $0x698098d8
+	DATA	·table+0x24(SB)/4, $0x8b44f7af
+	DATA	·table+0x28(SB)/4, $0xffff5bb1
+	DATA	·table+0x2c(SB)/4, $0x895cd7be
+	DATA	·table+0x30(SB)/4, $0x6b901122
+	DATA	·table+0x34(SB)/4, $0xfd987193
+	DATA	·table+0x38(SB)/4, $0xa679438e
+	DATA	·table+0x3c(SB)/4, $0x49b40821
+	// Round 2
+	DATA	·table+0x40(SB)/4, $0xf61e2562
+	DATA	·table+0x44(SB)/4, $0xc040b340
+	DATA	·table+0x48(SB)/4, $0x265e5a51
+	DATA	·table+0x4c(SB)/4, $0xe9b6c7aa
+	DATA	·table+0x50(SB)/4, $0xd62f105d
+	DATA	·table+0x54(SB)/4, $0x02441453
+	DATA	·table+0x58(SB)/4, $0xd8a1e681
+	DATA	·table+0x5c(SB)/4, $0xe7d3fbc8
+	DATA	·table+0x60(SB)/4, $0x21e1cde6
+	DATA	·table+0x64(SB)/4, $0xc33707d6
+	DATA	·table+0x68(SB)/4, $0xf4d50d87
+	DATA	·table+0x6c(SB)/4, $0x455a14ed
+	DATA	·table+0x70(SB)/4, $0xa9e3e905
+	DATA	·table+0x74(SB)/4, $0xfcefa3f8
+	DATA	·table+0x78(SB)/4, $0x676f02d9
+	DATA	·table+0x7c(SB)/4, $0x8d2a4c8a
+	// Round 3
+	DATA	·table+0x80(SB)/4, $0xfffa3942
+	DATA	·table+0x84(SB)/4, $0x8771f681
+	DATA	·table+0x88(SB)/4, $0x6d9d6122
+	DATA	·table+0x8c(SB)/4, $0xfde5380c
+	DATA	·table+0x90(SB)/4, $0xa4beea44
+	DATA	·table+0x94(SB)/4, $0x4bdecfa9
+	DATA	·table+0x98(SB)/4, $0xf6bb4b60
+	DATA	·table+0x9c(SB)/4, $0xbebfbc70
+	DATA	·table+0xa0(SB)/4, $0x289b7ec6
+	DATA	·table+0xa4(SB)/4, $0xeaa127fa
+	DATA	·table+0xa8(SB)/4, $0xd4ef3085
+	DATA	·table+0xac(SB)/4, $0x04881d05
+	DATA	·table+0xb0(SB)/4, $0xd9d4d039
+	DATA	·table+0xb4(SB)/4, $0xe6db99e5
+	DATA	·table+0xb8(SB)/4, $0x1fa27cf8
+	DATA	·table+0xbc(SB)/4, $0xc4ac5665
+	// Round 4
+	DATA	·table+0xc0(SB)/4, $0xf4292244
+	DATA	·table+0xc4(SB)/4, $0x432aff97
+	DATA	·table+0xc8(SB)/4, $0xab9423a7
+	DATA	·table+0xcc(SB)/4, $0xfc93a039
+	DATA	·table+0xd0(SB)/4, $0x655b59c3
+	DATA	·table+0xd4(SB)/4, $0x8f0ccc92
+	DATA	·table+0xd8(SB)/4, $0xffeff47d
+	DATA	·table+0xdc(SB)/4, $0x85845dd1
+	DATA	·table+0xe0(SB)/4, $0x6fa87e4f
+	DATA	·table+0xe4(SB)/4, $0xfe2ce6e0
+	DATA	·table+0xe8(SB)/4, $0xa3014314
+	DATA	·table+0xec(SB)/4, $0x4e0811a1
+	DATA	·table+0xf0(SB)/4, $0xf7537e82
+	DATA	·table+0xf4(SB)/4, $0xbd3af235
+	DATA	·table+0xf8(SB)/4, $0x2ad7d2bb
+	DATA	·table+0xfc(SB)/4, $0xeb86d391
+	// Global definition
+	GLOBL	·table(SB),8,$256
diff --git a/src/pkg/crypto/md5/md5block_decl.go b/src/pkg/crypto/md5/md5block_decl.go
index 3365200860..c4d6aaaf03 100644
--- a/src/pkg/crypto/md5/md5block_decl.go
+++ b/src/pkg/crypto/md5/md5block_decl.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build amd64 386
+// +build amd64 386 arm
 
 package md5