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: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 47c3d24..b45ef8d 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -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.