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Modify bcopy (and memcpy/memmove) so that the length value is not

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re-read from the stack mid copy.  This may help mitigate the recent
Apache buffer overrun and future overruns of the sort.

Reviewed by:	jdp
MFC after:	2 days
This commit is contained in:
Mike Silbersack 2002-06-27 03:55:36 +00:00
parent 80536ead7f
commit 1228a1c634
1 changed files with 4 additions and 2 deletions
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6
lib/libc/i386/string/bcopy.S
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@ -69,10 +69,11 @@ ENTRY(bcopy)
cmpl %ecx,%eax /* overlapping? */
jb 1f
cld /* nope, copy forwards. */
movl %ecx, %eax
shrl $2,%ecx /* copy by words */
rep
movsl
movl 20(%esp),%ecx
movl %eax, %ecx
andl $3,%ecx /* any bytes left? */
rep
movsb
@ -86,12 +87,13 @@ ENTRY(bcopy)
addl %ecx,%edi /* copy backwards. */
addl %ecx,%esi
std
movl %ecx, %eax
andl $3,%ecx /* any fractional bytes? */
decl %edi
decl %esi
rep
movsb
movl 20(%esp),%ecx /* copy remainder by words */
movl %eax, %ecx /* copy remainder by words */
shrl $2,%ecx
subl $3,%esi
subl $3,%edi