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kernel: Tolerate "count" argument to memcpy being 0.

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It seems GCC2 occasionally will inline a call to memcpy with
a count of 0, which this function did not previously expect
and would result in a "Divide Error Exception."

Hopefully fixes #14613.
This commit is contained in:
Augustin Cavalier 2018-10-29 22:44:01 -04:00
parent 7257735529
commit d1f8f8301c
1 changed files with 9 additions and 1 deletions
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10
src/system/kernel/lib/arch/x86/arch_string.S
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@ -1,10 +1,11 @@
/*
* Copyright 2008, Ingo Weinhold, ingo_weinhold@gmx.de.
* Copyright 2018, Haiku, Inc. All rights reserved.
* Distributed under the terms of the MIT License.
*
* Copyright 2001, Travis Geiselbrecht. All rights reserved.
* Distributed under the terms of the NewOS License.
*/
*/
#include <asm_defs.h>
@ -19,6 +20,12 @@ FUNCTION(memcpy):
movl 16(%esp),%esi /* source */
movl 20(%esp),%ecx /* count */
/* (count == 0 || dest == src) -> quick way out */
testl %ecx, %ecx
je .tail
cmpl %edi, %esi
je .tail
/* move by words */
// TODO: The addresses might not be aligned!
cld
@ -32,6 +39,7 @@ FUNCTION(memcpy):
rep
movsb
.tail:
popl %edi
popl %esi
ret