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ba999a0402
The memcpy template is a bit unusual in the way it manages the stack
pointer: depending on the execution path through the function, the SP
assumes different values as different subsets of the register file are
preserved and restored again. This is problematic when it comes to EHABI
unwind info, as it is not instruction accurate, and does not allow
tracking the SP value as it changes.
Commit 279f487e0b ("ARM: 8225/1: Add unwinding support for memory
copy functions") addressed this by carving up the function in different
chunks as far as the unwinder is concerned, and keeping a set of unwind
directives for each of them, each corresponding with the state of the
stack pointer during execution of the chunk in question. This not only
duplicates unwind info unnecessarily, but it also complicates unwinding
the stack upon overflow.
Instead, let's do what the compiler does when the SP is updated halfway
through a function, which is to use a frame pointer and emit the
appropriate unwind directives to communicate this to the unwinder.
Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's
avoid touching R7 in the body of the template, so that Thumb-2 can use
it as the frame pointer. R11 was not modified in the first place.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
66 lines
1.3 KiB
ArmAsm
66 lines
1.3 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* linux/arch/arm/lib/memcpy.S
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*
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* Author: Nicolas Pitre
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* Created: Sep 28, 2005
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* Copyright: MontaVista Software, Inc.
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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#include <asm/unwind.h>
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#define LDR1W_SHIFT 0
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#define STR1W_SHIFT 0
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.macro ldr1w ptr reg abort
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W(ldr) \reg, [\ptr], #4
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.endm
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.macro ldr4w ptr reg1 reg2 reg3 reg4 abort
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ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4}
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.endm
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.macro ldr8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
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ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
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.endm
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.macro ldr1b ptr reg cond=al abort
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ldrb\cond \reg, [\ptr], #1
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.endm
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.macro str1w ptr reg abort
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W(str) \reg, [\ptr], #4
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.endm
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.macro str8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
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stmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
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.endm
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.macro str1b ptr reg cond=al abort
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strb\cond \reg, [\ptr], #1
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.endm
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.macro enter regs:vararg
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UNWIND( .save {r0, \regs} )
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stmdb sp!, {r0, \regs}
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.endm
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.macro exit regs:vararg
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ldmfd sp!, {r0, \regs}
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.endm
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.text
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/* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
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ENTRY(__memcpy)
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ENTRY(mmiocpy)
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WEAK(memcpy)
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#include "copy_template.S"
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ENDPROC(memcpy)
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ENDPROC(mmiocpy)
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ENDPROC(__memcpy)
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