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Re: [x86-64 psABI] RFC: Extend x86-64 PLT entry to support MPX
- From: Florian Weimer <fweimer at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>, GCC Development <gcc at gcc dot gnu dot org>, Binutils <binutils at sourceware dot org>, "Girkar, Milind" <milind dot girkar at intel dot com>, "Kreitzer, David L" <david dot l dot kreitzer at intel dot com>
- Date: Wed, 24 Jul 2013 10:43:52 +0200
- Subject: Re: [x86-64 psABI] RFC: Extend x86-64 PLT entry to support MPX
- References: <CAMe9rOp=1v38F_aV-pbv50YOGSEr_ju+byZP1L_G_h4bm5Ad3w at mail dot gmail dot com>
On 07/23/2013 09:49 PM, H.J. Lu wrote:
2. Extend the current 16-byte PLT entry:
ff 25 32 8b 21 00 jmpq *name@GOTPCREL(%rip)
68 00 00 00 00 pushq $index
e9 00 00 00 00 jmpq PLT0
which clear bound registers, to 32-byte to add BND prefix to branch
instructions.
Would it be possible to use a different instruction sequence that stays
in the 16 byte limit? Or restrict MPX support to BIND_NOW relocations?
--
Florian Weimer / Red Hat Product Security Team