x86: Keep thread_info on thread stack in x86_32

x86_64 uses a per_cpu variable kernel_stack to always point to
the thread stack of current. This is where the thread_info is stored
and is accessed from this location even when the irq or exception stack
is in use. This removes the complexity of having to maintain the
thread info on the stack when interrupts are running and having to
copy the preempt_count and other fields to the interrupt stack.

x86_32 uses the old method of copying the thread_info from the thread
stack to the exception stack just before executing the exception.

Having the two different requires #ifdefs and also the x86_32 way
is a bit of a pain to maintain. By converting x86_32 to the same
method of x86_64, we can remove #ifdefs, clean up the x86_32 code
a little, and remove the overhead of the copy.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110806012354.263834829@goodmis.org
Link: http://lkml.kernel.org/r/20140206144321.852942014@goodmis.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 5 insertions, 44 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index ca2de1b48fa..47e5de25ba7 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -9,6 +9,7 @@
 
 #include <linux/compiler.h>
 #include <asm/page.h>
+#include <asm/percpu.h>
 #include <asm/types.h>
 
 /*
@@ -34,12 +35,6 @@ struct thread_info {
 	void __user		*sysenter_return;
 	unsigned int		sig_on_uaccess_error:1;
 	unsigned int		uaccess_err:1;	/* uaccess failed */
-#ifdef CONFIG_X86_32
-	unsigned long           previous_esp;   /* ESP of the previous stack in
-						   case of nested (IRQ) stacks
-						   (Moved to end, to be removed soon)
-						*/
-#endif
 };
 
 #define INIT_THREAD_INFO(tsk)			\
@@ -153,9 +148,9 @@ struct thread_info {
 #define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
 #define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
 
-#ifdef CONFIG_X86_32
+#define STACK_WARN		(THREAD_SIZE/8)
+#define KERNEL_STACK_OFFSET	(5*(BITS_PER_LONG/8))
 
-#define STACK_WARN	(THREAD_SIZE/8)
 /*
  * macros/functions for gaining access to the thread information structure
  *
@@ -163,38 +158,6 @@ struct thread_info {
  */
 #ifndef __ASSEMBLY__
 
-#define current_stack_pointer ({		\
-	unsigned long sp;			\
-	asm("mov %%esp,%0" : "=g" (sp));	\
-	sp;					\
-})
-
-/* how to get the thread information struct from C */
-static inline struct thread_info *current_thread_info(void)
-{
-	return (struct thread_info *)
-		(current_stack_pointer & ~(THREAD_SIZE - 1));
-}
-
-#else /* !__ASSEMBLY__ */
-
-/* how to get the thread information struct from ASM */
-#define GET_THREAD_INFO(reg)	 \
-	movl $-THREAD_SIZE, reg; \
-	andl %esp, reg
-
-#endif
-
-#else /* X86_32 */
-
-#include <asm/percpu.h>
-#define KERNEL_STACK_OFFSET (5*8)
-
-/*
- * macros/functions for gaining access to the thread information structure
- * preempt_count needs to be 1 initially, until the scheduler is functional.
- */
-#ifndef __ASSEMBLY__
 DECLARE_PER_CPU(unsigned long, kernel_stack);
 
 static inline struct thread_info *current_thread_info(void)
@@ -209,8 +172,8 @@ static inline struct thread_info *current_thread_info(void)
 
 /* how to get the thread information struct from ASM */
 #define GET_THREAD_INFO(reg) \
-	movq PER_CPU_VAR(kernel_stack),reg ; \
-	subq $(THREAD_SIZE-KERNEL_STACK_OFFSET),reg
+	_ASM_MOV PER_CPU_VAR(kernel_stack),reg ; \
+	_ASM_SUB $(THREAD_SIZE-KERNEL_STACK_OFFSET),reg ;
 
 /*
  * Same if PER_CPU_VAR(kernel_stack) is, perhaps with some offset, already in
@@ -220,8 +183,6 @@ static inline struct thread_info *current_thread_info(void)
 
 #endif
 
-#endif /* !X86_32 */
-
 /*
  * Thread-synchronous status.
  *