Re: [patch 2/3] MAP_NOZERO - implement sys_brk2()
From: Rik van Riel
Date: Wed Jun 27 2007 - 00:12:13 EST
Ulrich Drepper wrote:
On 6/26/07, Rik van Riel <riel@xxxxxxxxxx> wrote:
Since programs can get back free()d memory after a malloc(),
with the old contents of the memory intact, surely your
MAP_NONZERO behavior could be the default for programs that
can get away with it?
Maybe we could use some magic ELF header, similar to the
way non-executable stack is handled?
No. This is an implementation detail of the libc version. The malloc
as compiled today is expecting brk-ed memory to be zeroed. This
default can of course be changed (it's a simple define) but you cannot
make this the default behavior for brk.
After going through the first malloc()/free() cycle, surely
the memory will no longer be zeroed on the second malloc() ?
What makes the first brk malloc so special?
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