6ebbf2ce43
ARMv6 and greater introduced a new instruction ("bx") which can be used
to return from function calls. Recent CPUs perform better when the
"bx lr" instruction is used rather than the "mov pc, lr" instruction,
and this sequence is strongly recommended to be used by the ARM
architecture manual (section A.4.1.1).
We provide a new macro "ret" with all its variants for the condition
code which will resolve to the appropriate instruction.
Rather than doing this piecemeal, and miss some instances, change all
the "mov pc" instances to use the new macro, with the exception of
the "movs" instruction and the kprobes code. This allows us to detect
the "mov pc, lr" case and fix it up - and also gives us the possibility
of deploying this for other registers depending on the CPU selection.
Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S
Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood
Tested-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385
Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci
Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M
Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
125 lines
2.8 KiB
ArmAsm
125 lines
2.8 KiB
ArmAsm
/*
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* linux/arch/arm/lib/memzero.S
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*
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* Copyright (C) 1995-2000 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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.text
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.align 5
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.word 0
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/*
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* Align the pointer in r0. r3 contains the number of bytes that we are
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* mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
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* don't bother; we use byte stores instead.
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*/
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1: subs r1, r1, #4 @ 1 do we have enough
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blt 5f @ 1 bytes to align with?
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cmp r3, #2 @ 1
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strltb r2, [r0], #1 @ 1
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strleb r2, [r0], #1 @ 1
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strb r2, [r0], #1 @ 1
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add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
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/*
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* The pointer is now aligned and the length is adjusted. Try doing the
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* memzero again.
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*/
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ENTRY(__memzero)
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mov r2, #0 @ 1
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ands r3, r0, #3 @ 1 unaligned?
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bne 1b @ 1
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/*
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* r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
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*/
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cmp r1, #16 @ 1 we can skip this chunk if we
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blt 4f @ 1 have < 16 bytes
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#if ! CALGN(1)+0
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/*
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* We need an extra register for this loop - save the return address and
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* use the LR
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*/
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str lr, [sp, #-4]! @ 1
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mov ip, r2 @ 1
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mov lr, r2 @ 1
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3: subs r1, r1, #64 @ 1 write 32 bytes out per loop
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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stmgeia r0!, {r2, r3, ip, lr} @ 4
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bgt 3b @ 1
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ldmeqfd sp!, {pc} @ 1/2 quick exit
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/*
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* No need to correct the count; we're only testing bits from now on
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*/
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tst r1, #32 @ 1
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stmneia r0!, {r2, r3, ip, lr} @ 4
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stmneia r0!, {r2, r3, ip, lr} @ 4
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tst r1, #16 @ 1 16 bytes or more?
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stmneia r0!, {r2, r3, ip, lr} @ 4
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ldr lr, [sp], #4 @ 1
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#else
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/*
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* This version aligns the destination pointer in order to write
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* whole cache lines at once.
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*/
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stmfd sp!, {r4-r7, lr}
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mov r4, r2
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mov r5, r2
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mov r6, r2
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mov r7, r2
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mov ip, r2
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mov lr, r2
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cmp r1, #96
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andgts ip, r0, #31
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ble 3f
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rsb ip, ip, #32
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sub r1, r1, ip
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movs ip, ip, lsl #(32 - 4)
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stmcsia r0!, {r4, r5, r6, r7}
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stmmiia r0!, {r4, r5}
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movs ip, ip, lsl #2
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strcs r2, [r0], #4
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3: subs r1, r1, #64
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stmgeia r0!, {r2-r7, ip, lr}
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stmgeia r0!, {r2-r7, ip, lr}
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bgt 3b
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ldmeqfd sp!, {r4-r7, pc}
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tst r1, #32
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stmneia r0!, {r2-r7, ip, lr}
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tst r1, #16
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stmneia r0!, {r4-r7}
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ldmfd sp!, {r4-r7, lr}
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#endif
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4: tst r1, #8 @ 1 8 bytes or more?
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stmneia r0!, {r2, r3} @ 2
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tst r1, #4 @ 1 4 bytes or more?
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strne r2, [r0], #4 @ 1
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/*
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* When we get here, we've got less than 4 bytes to zero. We
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* may have an unaligned pointer as well.
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*/
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5: tst r1, #2 @ 1 2 bytes or more?
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strneb r2, [r0], #1 @ 1
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strneb r2, [r0], #1 @ 1
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tst r1, #1 @ 1 a byte left over
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strneb r2, [r0], #1 @ 1
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ret lr @ 1
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ENDPROC(__memzero)
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