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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: Andy 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2017-11-02 00:59:16 -07:00 committed by Ingo Molnar
parent cd493a6deb
commit d375cf1530
4 changed files with 16 additions and 20 deletions
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1
arch/x86/include/asm/compat.h
View File

@ -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>

28
arch/x86/include/asm/processor.h
View File

@ -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 */

6
arch/x86/include/asm/switch_to.h
View File

@ -1,6 +1,8 @@
#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 */

1
arch/x86/kernel/process_64.c
View File

@ -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;