linux-kernel - [PATCH 0/2] x86_64: LRET to userspace

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Date:	Wed, 23 Jul 2014 08:34:10 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	x86@...nel.org, Borislav Petkov <bp@...en8.de>
Cc:	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH 0/2] x86_64: LRET to userspace

This series is based on tip/perf/urgent.  It should apply to any
recent kernel, but my test case [1] will OOPS without the fix in
tip/perf/urgent.

The first patch or something like it is needed for 3.16, regardless
of any lret hackery -- I think it's making its way toward a pull
request this week, but I haven't seen it land in -tip yet.

I'm repeating it here because the LRET stuff won't work on paravirt,
and patch 1 puts the machinery for that in place.

tl;dr Read patch 2.  To test, apply patch 1 and consider basing on
tip/perf/urgent.

[1] sigreturn_32 from https://gitorious.org/linux-test-utils/linux-clock-tests/

Andy Lutomirski (2):
  x86_64,entry,xen: Do not invoke espfix64 on Xen
  x86_64,entry: Use lret to return to userspace when possible

 arch/x86/include/asm/irqflags.h     |   3 +-
 arch/x86/include/asm/paravirt.h     |   4 ++
 arch/x86/include/asm/traps.h        |   6 ++
 arch/x86/kernel/cpu/mcheck/mce.c    |   2 +
 arch/x86/kernel/entry_64.S          | 121 ++++++++++++++++++++++++++++++------
 arch/x86/kernel/nmi.c               |  21 +++++++
 arch/x86/kernel/paravirt_patch_64.c |   2 -
 7 files changed, 136 insertions(+), 23 deletions(-)

-- 
1.9.3

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