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Commit b30f3ae5 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

x86-64: Clean up 'save/restore_i387()' usage 



Suresh Siddha wants to fix a possible FPU leakage in error conditions,
but the fact that save/restore_i387() are inlines in a header file makes
that harder to do than necessary.  So start off with an obvious cleanup.

This just moves the x86-64 version of save/restore_i387() out of the
header file, and moves it to the only file that it is actually used in:
arch/x86/kernel/signal_64.c.  So exposing it in a header file was wrong
to begin with.

[ Side note: I'd like to fix up some of the games we play with the
  32-bit version of these functions too, but that's a separate
  matter.  The 32-bit versions are shared - under different names
  at that! - by both the native x86-32 code and the x86-64 32-bit
  compatibility code ]

Acked-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b5684b83

arch/x86/kernel/signal_64.c

+53 −0
Original line number Diff line number Diff line
@@ -53,6 +53,59 @@ sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss, 
	return do_sigaltstack(uss, uoss, regs->sp);

}



/*

 * Signal frame handlers.

 */



static inline int save_i387(struct _fpstate __user *buf)

{

	struct task_struct *tsk = current;

	int err = 0;



	BUILD_BUG_ON(sizeof(struct user_i387_struct) !=

			sizeof(tsk->thread.xstate->fxsave));



	if ((unsigned long)buf % 16)

		printk("save_i387: bad fpstate %p\n", buf);



	if (!used_math())

		return 0;

	clear_used_math(); /* trigger finit */

	if (task_thread_info(tsk)->status & TS_USEDFPU) {

		err = save_i387_checking((struct i387_fxsave_struct __user *)

					 buf);

		if (err)

			return err;

		task_thread_info(tsk)->status &= ~TS_USEDFPU;

		stts();

	} else {

		if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,

				   sizeof(struct i387_fxsave_struct)))

			return -1;

	}

	return 1;

}



/*

 * This restores directly out of user space. Exceptions are handled.

 */

static inline int restore_i387(struct _fpstate __user *buf)

{

	struct task_struct *tsk = current;

	int err;



	if (!used_math()) {

		err = init_fpu(tsk);

		if (err)

			return err;

	}



	if (!(task_thread_info(current)->status & TS_USEDFPU)) {

		clts();

		task_thread_info(current)->status |= TS_USEDFPU;

	}

	return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);

}



/*

 * Do a signal return; undo the signal stack.

include/asm-x86/i387.h

+0 −54
Original line number Diff line number Diff line
@@ -137,60 +137,6 @@ static inline void __save_init_fpu(struct task_struct *tsk) 
	task_thread_info(tsk)->status &= ~TS_USEDFPU;

}



/*

 * Signal frame handlers.

 */



static inline int save_i387(struct _fpstate __user *buf)

{

	struct task_struct *tsk = current;

	int err = 0;



	BUILD_BUG_ON(sizeof(struct user_i387_struct) !=

			sizeof(tsk->thread.xstate->fxsave));



	if ((unsigned long)buf % 16)

		printk("save_i387: bad fpstate %p\n", buf);



	if (!used_math())

		return 0;

	clear_used_math(); /* trigger finit */

	if (task_thread_info(tsk)->status & TS_USEDFPU) {

		err = save_i387_checking((struct i387_fxsave_struct __user *)

					 buf);

		if (err)

			return err;

		task_thread_info(tsk)->status &= ~TS_USEDFPU;

		stts();

	} else {

		if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,

				   sizeof(struct i387_fxsave_struct)))

			return -1;

	}

	return 1;

}



/*

 * This restores directly out of user space. Exceptions are handled.

 */

static inline int restore_i387(struct _fpstate __user *buf)

{

	struct task_struct *tsk = current;

	int err;



	if (!used_math()) {

		err = init_fpu(tsk);

		if (err)

			return err;

	}



	if (!(task_thread_info(current)->status & TS_USEDFPU)) {

		clts();

		task_thread_info(current)->status |= TS_USEDFPU;

	}

	return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);

}



#else  /* CONFIG_X86_32 */



extern void finit(void);