linux-kernel - [tip:x86/asm] x86/asm/entry: Simplify task_pt

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Date:	Mon, 16 Mar 2015 05:09:49 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, rostedt@...dmis.org, oleg@...hat.com,
	tglx@...utronix.de, keescook@...omium.org, dvlasenk@...hat.com,
	wad@...omium.org, torvalds@...ux-foundation.org, bp@...en8.de,
	ast@...mgrid.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, luto@...capital.net
Subject: [tip:x86/asm] x86/asm/entry: Simplify task_pt_regs()
  macro definition

Commit-ID:  42503341cde213c5928a19f7c6e1eb8c85f2df3d
Gitweb:     http://git.kernel.org/tip/42503341cde213c5928a19f7c6e1eb8c85f2df3d
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Fri, 13 Mar 2015 15:09:03 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 16 Mar 2015 11:05:36 +0100

x86/asm/entry: Simplify task_pt_regs() macro definition

Before this change, task_pt_regs() was using KSTK_TOP(),
and it was the only use of that macro. In turn, KSTK_TOP used
THREAD_SIZE_LONGS, and it was the only use of that macro too.

Fold these macros into task_pt_regs(). Tweak comment
about "- 8" - we now use a symbolic constant, not literal 8.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Reviewed-by: Steven Rostedt <rostedt@...dmis.org>
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: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Drewry <wad@...omium.org>
Link: http://lkml.kernel.org/r/1426255743-5394-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/processor.h | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c3a037b..d157f94 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -846,15 +846,8 @@ static inline void spin_lock_prefetch(const void *x)
 
 extern unsigned long thread_saved_pc(struct task_struct *tsk);
 
-#define THREAD_SIZE_LONGS      (THREAD_SIZE/sizeof(unsigned long))
-#define KSTK_TOP(info)                                                 \
-({                                                                     \
-       unsigned long *__ptr = (unsigned long *)(info);                 \
-       (unsigned long)(&__ptr[THREAD_SIZE_LONGS]);                     \
-})
-
 /*
- * The below -8 is to reserve 8 bytes on top of the ring0 stack.
+ * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack.
  * This is necessary to guarantee that the entire "struct pt_regs"
  * is accessible even if the CPU haven't stored the SS/ESP registers
  * on the stack (interrupt gate does not save these registers
@@ -863,12 +856,11 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
  * "struct pt_regs" is possible, but they may contain the
  * completely wrong values.
  */
-#define task_pt_regs(task)                                             \
-({                                                                     \
-       struct pt_regs *__regs__;                                       \
-       __regs__ = (struct pt_regs *)(KSTK_TOP(task_stack_page(task)) - \
-				     TOP_OF_KERNEL_STACK_PADDING);     \
-       __regs__ - 1;                                                   \
+#define task_pt_regs(task) \
+({									\
+	unsigned long __ptr = (unsigned long)task_stack_page(task);	\
+	__ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;		\
+	((struct pt_regs *)__ptr) - 1;					\
 })
 
 #define KSTK_ESP(task)		(task_pt_regs(task)->sp)
--
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