linux-kernel - Updated version of RD/WR FS/GS BASE patchkit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1458576969-13309-1-git-send-email-andi@firstfloor.org>
Date:	Mon, 21 Mar 2016 09:16:00 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	x86@...nel.org
Cc:	luto@...capital.net, linux-kernel@...r.kernel.org
Subject: Updated version of RD/WR FS/GS BASE patchkit

This is a reworked version of my older fsgsbase patchkit.
Main changes:
- Ported to new entry/* code, which simplified it somewhat
- Now has a test program
- Fixed ptrace/core dump support
- Better documentation
- Some minor fixes improvement

This adds kernel support for some Intel instructions that
allow fast access to the FS and GS 64bit base. They need
some changes to entry_64.S because they allow user
to fully control the GS base.

Advantages:
- NMIs (and other "paranoid" interrupts) avoid
one RDMSR which makes them faster
- User space can use these instructions, mainly
for efficient context switching with user thread libraries
- Context switches do not need to use MSR writes
anymore to context switch FS/GS base >4GB. This
will speed up applications that have enough thread
local data that it won't fit below 4GB.
- User space can use GS efficiently as an additional
global pointer register

I also included one minor (unrelated) optimization to
disable an unneeded old SWAPGS workaround.

-Andi