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Re: [Xen-devel][PATCH][RFC] _chk_fail and _chk canaries for minios and n

To: "George S. Coker, II" <gscoker@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel][PATCH][RFC] _chk_fail and _chk canaries for minios and newlib
From: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
Date: Mon, 9 Mar 2009 19:13:17 +0100
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George S. Coker, II, le Mon 09 Mar 2009 13:08:04 -0500, a écrit :
> This patch implements a minios version of the stack_chk_fail from glibc.
> fprintf_chk and sprintf_chk functions have been added to newlib.

Cool!  That'd be useful indeed.  I'm however wondering whether
your patch is enough for the stack protection: in my memory, gcc
assumes that the glibc is used, and on e.g. i386, it uses gs:(0x14)
for the stack canary (see a disassembly of a program compiled with
-fstack-protector-all, there's a mov %gs:0x14,%eax lying in functions),
and as a result we need to define a proper gs in MiniOS that follows
glibc's tcbhead_t.

The fortified printfs should be fine.


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