From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001
From: root <root@artemis.panaceas.org>
Date: Fri, 25 Dec 2015 04:40:36 +0000
Subject: initial_commit

---
 arch/arm/lib/memzero.S | 125 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 arch/arm/lib/memzero.S

(limited to 'arch/arm/lib/memzero.S')

diff --git a/arch/arm/lib/memzero.S b/arch/arm/lib/memzero.S
new file mode 100644
index 00000000..3fbdef5f
--- /dev/null
+++ b/arch/arm/lib/memzero.S
@@ -0,0 +1,125 @@
+/*
+ *  linux/arch/arm/lib/memzero.S
+ *
+ *  Copyright (C) 1995-2000 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+	.text
+	.align	5
+	.word	0
+/*
+ * Align the pointer in r0.  r3 contains the number of bytes that we are
+ * mis-aligned by, and r1 is the number of bytes.  If r1 < 4, then we
+ * don't bother; we use byte stores instead.
+ */
+1:	subs	r1, r1, #4		@ 1 do we have enough
+	blt	5f			@ 1 bytes to align with?
+	cmp	r3, #2			@ 1
+	strltb	r2, [r0], #1		@ 1
+	strleb	r2, [r0], #1		@ 1
+	strb	r2, [r0], #1		@ 1
+	add	r1, r1, r3		@ 1 (r1 = r1 - (4 - r3))
+/*
+ * The pointer is now aligned and the length is adjusted.  Try doing the
+ * memzero again.
+ */
+
+ENTRY(__memzero)
+	mov	r2, #0			@ 1
+	ands	r3, r0, #3		@ 1 unaligned?
+	bne	1b			@ 1
+/*
+ * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
+ */
+	cmp	r1, #16			@ 1 we can skip this chunk if we
+	blt	4f			@ 1 have < 16 bytes
+
+#if ! CALGN(1)+0
+
+/*
+ * We need an extra register for this loop - save the return address and
+ * use the LR
+ */
+	str	lr, [sp, #-4]!		@ 1
+	mov	ip, r2			@ 1
+	mov	lr, r2			@ 1
+
+3:	subs	r1, r1, #64		@ 1 write 32 bytes out per loop
+	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
+	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
+	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
+	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
+	bgt	3b			@ 1
+	ldmeqfd	sp!, {pc}		@ 1/2 quick exit
+/*
+ * No need to correct the count; we're only testing bits from now on
+ */
+	tst	r1, #32			@ 1
+	stmneia	r0!, {r2, r3, ip, lr}	@ 4
+	stmneia	r0!, {r2, r3, ip, lr}	@ 4
+	tst	r1, #16			@ 1 16 bytes or more?
+	stmneia	r0!, {r2, r3, ip, lr}	@ 4
+	ldr	lr, [sp], #4		@ 1
+
+#else
+
+/*
+ * This version aligns the destination pointer in order to write
+ * whole cache lines at once.
+ */
+
+	stmfd	sp!, {r4-r7, lr}
+	mov	r4, r2
+	mov	r5, r2
+	mov	r6, r2
+	mov	r7, r2
+	mov	ip, r2
+	mov	lr, r2
+
+	cmp	r1, #96
+	andgts	ip, r0, #31
+	ble	3f
+
+	rsb	ip, ip, #32
+	sub	r1, r1, ip
+	movs	ip, ip, lsl #(32 - 4)
+	stmcsia	r0!, {r4, r5, r6, r7}
+	stmmiia	r0!, {r4, r5}
+	movs	ip, ip, lsl #2
+	strcs	r2, [r0], #4
+
+3:	subs	r1, r1, #64
+	stmgeia	r0!, {r2-r7, ip, lr}
+	stmgeia	r0!, {r2-r7, ip, lr}
+	bgt	3b
+	ldmeqfd	sp!, {r4-r7, pc}
+
+	tst	r1, #32
+	stmneia	r0!, {r2-r7, ip, lr}
+	tst	r1, #16
+	stmneia	r0!, {r4-r7}
+	ldmfd	sp!, {r4-r7, lr}
+
+#endif
+
+4:	tst	r1, #8			@ 1 8 bytes or more?
+	stmneia	r0!, {r2, r3}		@ 2
+	tst	r1, #4			@ 1 4 bytes or more?
+	strne	r2, [r0], #4		@ 1
+/*
+ * When we get here, we've got less than 4 bytes to zero.  We
+ * may have an unaligned pointer as well.
+ */
+5:	tst	r1, #2			@ 1 2 bytes or more?
+	strneb	r2, [r0], #1		@ 1
+	strneb	r2, [r0], #1		@ 1
+	tst	r1, #1			@ 1 a byte left over
+	strneb	r2, [r0], #1		@ 1
+	mov	pc, lr			@ 1
+ENDPROC(__memzero)
-- 
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