linux-kernel - [tip:x86/asm] x86/asm/entry/64: Do not GET_THREAD

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Date:	Tue, 31 Mar 2015 05:37:18 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	ast@...mgrid.com, wad@...omium.org, dvlasenk@...hat.com,
	torvalds@...ux-foundation.org, hpa@...or.com,
	keescook@...omium.org, bp@...en8.de, fweisbec@...il.com,
	luto@...capital.net, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org, oleg@...hat.com,
	mingo@...nel.org
Subject: [tip:x86/asm] x86/asm/entry/64: Do not GET_THREAD_INFO()
  too early

Commit-ID:  a3675b32aac81c2c4733568844f8276527a37423
Gitweb:     http://git.kernel.org/tip/a3675b32aac81c2c4733568844f8276527a37423
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Mon, 30 Mar 2015 20:09:34 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 31 Mar 2015 09:31:11 +0200

x86/asm/entry/64: Do not GET_THREAD_INFO() too early

At exit_intr, we GET_THREAD_INFO(%rcx) and then jump to
retint_kernel if saved CS was from kernel. But the code at
retint_kernel doesn't need %rcx.

Move GET_THREAD_INFO(%rcx) down, after CS check and branch.

While at it, remove "has a correct top of stack" comment.
After recent changes which eliminated FIXUP_TOP_OF_STACK,
we always have a correct pt_regs layout.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Will Drewry <wad@...omium.org>
Link: http://lkml.kernel.org/r/1427738975-7391-5-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/entry_64.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 34d60c3..6f251a5 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -658,13 +658,12 @@ ret_from_intr:
 	CFI_ADJUST_CFA_OFFSET	RBP
 
 exit_intr:
-	GET_THREAD_INFO(%rcx)
 	testl $3,CS(%rsp)
 	je retint_kernel
-
 	/* Interrupt came from user space */
+
+	GET_THREAD_INFO(%rcx)
 	/*
-	 * Has a correct top of stack.
 	 * %rcx: thread info. Interrupts off.
 	 */
 retint_with_reschedule:
--
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