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Commit d375cf15 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

x86/entry/64: Remove thread_struct::sp0 



On x86_64, we can easily calculate sp0 when needed instead of
storing it in thread_struct.

On x86_32, a similar cleanup would be possible, but it would require
cleaning up the vm86 code first, and that can wait for a later
cleanup series.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/719cd9c66c548c4350d98a90f050aee8b17f8919.1509609304.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent cd493a6d

arch/x86/include/asm/compat.h

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
 */

#include <linux/types.h>

#include <linux/sched.h>

#include <linux/sched/task_stack.h>

#include <asm/processor.h>

#include <asm/user32.h>

#include <asm/unistd.h>

arch/x86/include/asm/processor.h

+9 −19
Original line number Diff line number Diff line
@@ -430,7 +430,9 @@ typedef struct { 
struct thread_struct {

	/* Cached TLS descriptors: */

	struct desc_struct	tls_array[GDT_ENTRY_TLS_ENTRIES];

#ifdef CONFIG_X86_32

	unsigned long		sp0;

#endif

	unsigned long		sp;

#ifdef CONFIG_X86_32

	unsigned long		sysenter_cs;
@@ -797,6 +799,13 @@ static inline void spin_lock_prefetch(const void *x) 


#define task_top_of_stack(task) ((unsigned long)(task_pt_regs(task) + 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;					\

})



#ifdef CONFIG_X86_32

/*

 * User space process size: 3GB (default).
@@ -816,23 +825,6 @@ static inline void spin_lock_prefetch(const void *x) 
	.addr_limit		= KERNEL_DS,				  \

}



/*

 * 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

 * when switching to the same priv ring).

 * Therefore beware: accessing the ss/esp fields of the

 * "struct pt_regs" is possible, but they may contain the

 * completely wrong values.

 */

#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)



#else
@@ -866,11 +858,9 @@ static inline void spin_lock_prefetch(const void *x) 
#define STACK_TOP_MAX		TASK_SIZE_MAX



#define INIT_THREAD  {						\

	.sp0			= TOP_OF_INIT_STACK,		\

	.addr_limit		= KERNEL_DS,			\

}



#define task_pt_regs(tsk)	((struct pt_regs *)(tsk)->thread.sp0 - 1)

extern unsigned long KSTK_ESP(struct task_struct *task);



#endif /* CONFIG_X86_64 */

arch/x86/include/asm/switch_to.h

+6 −0
Original line number Diff line number Diff line 
#ifndef _ASM_X86_SWITCH_TO_H

#define _ASM_X86_SWITCH_TO_H



#include <linux/sched/task_stack.h>



struct task_struct; /* one of the stranger aspects of C forward declarations */



struct task_struct *__switch_to_asm(struct task_struct *prev,
@@ -87,7 +89,11 @@ static inline void refresh_sysenter_cs(struct thread_struct *thread) 
/* This is used when switching tasks or entering/exiting vm86 mode. */

static inline void update_sp0(struct task_struct *task)

{

#ifdef CONFIG_X86_32

	load_sp0(task->thread.sp0);

#else

	load_sp0(task_top_of_stack(task));

#endif

}



#endif /* _ASM_X86_SWITCH_TO_H */

arch/x86/kernel/process_64.c

+0 −1
Original line number Diff line number Diff line
@@ -274,7 +274,6 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, 
	struct inactive_task_frame *frame;

	struct task_struct *me = current;



	p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;

	childregs = task_pt_regs(p);

	fork_frame = container_of(childregs, struct fork_frame, regs);

	frame = &fork_frame->frame;