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

tip-bot for Denys Vlasenko
2015-03-31T12:37:51Z

Commit-ID: a3675b32aac81c2c4733568844f8276527a37423
Gitweb: http://git.kernel.org/tip/a3675b32aac81c2c4733568844f8276527a37423
Author: Denys Vlasenko <dvlasenk@redhat.com>
AuthorDate: Mon, 30 Mar 2015 20:09:34 +0200
Committer: Ingo Molnar <mingo@kernel.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@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427738975-7391-5-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.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.
*/