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x86/asm: Move 'status' from thread_struct to thread_info 

The TS_COMPAT bit is very hot and is accessed from code paths that mostly
also touch thread_info::flags.  Move it into struct thread_info to improve
cache locality.

The only reason it was in thread_struct is that there was a brief period
during which arch-specific fields were not allowed in struct thread_info.

Linus suggested further changing:

  ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

to:

  if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED)))
          ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

on the theory that frequently dirtying the cacheline even in pure 64-bit
code that never needs to modify status hurts performance.  That could be a
reasonable followup patch, but I suspect it matters less on top of this
patch.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kernel Hardening <kernel-hardening@lists.openwall.com>
Link: https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2018-01-28 10:38:50 -08:00 committed by Thomas Gleixner
parent d1f7732009
commit 37a8f7c383
7 changed files with 11 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/entry/common.c
View File

@ -206,7 +206,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
* special case only applies after poking regs and before the
* very next return to user mode.
*/
current->thread.status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
#endif
user_enter_irqoff();
@ -304,7 +304,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
unsigned int nr = (unsigned int)regs->orig_ax;
#ifdef CONFIG_IA32_EMULATION
current->thread.status |= TS_COMPAT;
ti->status |= TS_COMPAT;
#endif
if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) {

2
arch/x86/include/asm/processor.h
View File

@ -460,8 +460,6 @@ struct thread_struct {
unsigned short gsindex;
#endif
u32 status; /* thread synchronous flags */
#ifdef CONFIG_X86_64
unsigned long fsbase;
unsigned long gsbase;

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

@ -60,7 +60,7 @@ static inline long syscall_get_error(struct task_struct *task,
* TS_COMPAT is set for 32-bit syscall entries and then
* remains set until we return to user mode.
*/
if (task->thread.status & (TS_COMPAT|TS_I386_REGS_POKED))
if (task->thread_info.status & (TS_COMPAT|TS_I386_REGS_POKED))
/*
* Sign-extend the value so (int)-EFOO becomes (long)-EFOO
* and will match correctly in comparisons.
@ -116,7 +116,7 @@ static inline void syscall_get_arguments(struct task_struct *task,
unsigned long *args)
{
# ifdef CONFIG_IA32_EMULATION
if (task->thread.status & TS_COMPAT)
if (task->thread_info.status & TS_COMPAT)
switch (i) {
case 0:
if (!n--) break;
@ -177,7 +177,7 @@ static inline void syscall_set_arguments(struct task_struct *task,
const unsigned long *args)
{
# ifdef CONFIG_IA32_EMULATION
if (task->thread.status & TS_COMPAT)
if (task->thread_info.status & TS_COMPAT)
switch (i) {
case 0:
if (!n--) break;

3
arch/x86/include/asm/thread_info.h
View File

@ -55,6 +55,7 @@ struct task_struct;
struct thread_info {
unsigned long flags; /* low level flags */
u32 status; /* thread synchronous flags */
};
#define INIT_THREAD_INFO(tsk) \
@ -221,7 +222,7 @@ static inline int arch_within_stack_frames(const void * const stack,
#define in_ia32_syscall() true
#else
#define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \
current->thread.status & TS_COMPAT)
current_thread_info()->status & TS_COMPAT)
#endif
/*

4
arch/x86/kernel/process_64.c
View File

@ -557,7 +557,7 @@ static void __set_personality_x32(void)
* Pretend to come from a x32 execve.
*/
task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT;
current->thread.status &= ~TS_COMPAT;
current_thread_info()->status &= ~TS_COMPAT;
#endif
}
@ -571,7 +571,7 @@ static void __set_personality_ia32(void)
current->personality |= force_personality32;
/* Prepare the first "return" to user space */
task_pt_regs(current)->orig_ax = __NR_ia32_execve;
current->thread.status |= TS_COMPAT;
current_thread_info()->status |= TS_COMPAT;
#endif
}

2
arch/x86/kernel/ptrace.c
View File

@ -935,7 +935,7 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
*/
regs->orig_ax = value;
if (syscall_get_nr(child, regs) >= 0)
child->thread.status |= TS_I386_REGS_POKED;
child->thread_info.status |= TS_I386_REGS_POKED;
break;
case offsetof(struct user32, regs.eflags):

2
arch/x86/kernel/signal.c
View File

@ -787,7 +787,7 @@ static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
* than the tracee.
*/
#ifdef CONFIG_IA32_EMULATION
if (current->thread.status & (TS_COMPAT|TS_I386_REGS_POKED))
if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
return __NR_ia32_restart_syscall;
#endif
#ifdef CONFIG_X86_X32_ABI