In _thread_enter_uts, fix eflags saving bug.

In _thread_switch, set current thread pointer in kse mailbox
only after all registers copied out of thread mailbox, kernel will do
upcall at trap time, if set current thread pointer before loading all
registers from thread mailbox, at trap time, the thread mailbox data
will be overwritten by kernel, result is junk data is loaded into CPU.

lib/libkse/arch/i386/i386/thr_enter_uts.S

@@ -79,7 +79,8 @@ ENTRY(_thread_enter_uts)
 	 */
 	fnstcw	MC_FP_CW_OFFSET(%edx)
 	movl	$0, MC_OWNEDFP_OFFSET(%edx) /* no FP */
-	lahf				/* get eflags */
+	pushfl				/* get eflags */
+	popl	%eax
 	movl	%eax, 68(%edx)		/* store eflags */
 	movl	%esp, %eax		/* setcontext pushes the return  */
 	addl	$4, %eax		/*   address onto the top of the */

lib/libpthread/arch/i386/i386/thr_enter_uts.S

@@ -79,7 +79,8 @@ ENTRY(_thread_enter_uts)
 	 */
 	fnstcw	MC_FP_CW_OFFSET(%edx)
 	movl	$0, MC_OWNEDFP_OFFSET(%edx) /* no FP */
-	lahf				/* get eflags */
+	pushfl				/* get eflags */
+	popl	%eax
 	movl	%eax, 68(%edx)		/* store eflags */
 	movl	%esp, %eax		/* setcontext pushes the return  */
 	addl	$4, %eax		/*   address onto the top of the */

lib/libpthread/arch/i386/i386/thr_switch.S

@@ -54,8 +54,8 @@ ENTRY(_thread_switch)
 	je	2f
 	movl	$-1, %eax		/* bzzzt, invalid context */
 	jmp	5f
-2:	movl	8(%esp), %eax		/* get address of curthreadp */
-	movl	%edx, (%eax)		/* we're now the current thread */
+2:	movl	8(%esp), %ecx		/* get address of curthreadp */
+	movl	%edx, %ebx		/* save the pointer for later */
 	/*
 	 * From here on, we don't touch the old stack.
 	 */
@@ -78,12 +78,19 @@ ENTRY(_thread_switch)
 	jmp	4f
 3:	fninit
 	fldcw	MC_FP_CW_OFFSET(%edx)
-4:	movl	48(%edx), %eax		/* restore ax, bx, cx */
-	movl	36(%edx), %ebx
-	movl	44(%edx), %ecx
+4:	movl	48(%edx), %eax		/* restore ax, bx, cx, dx */
 	pushl	68(%edx)		/* flags on stack */
-	pushl	40(%edx)		/* %edx on stack  */
+	pushl	36(%edx)		/* %ebx on stack */
+	pushl	44(%edx)		/* %ecx on stack */
+	pushl	40(%edx)		/* %edx on stack */
+	/* 
+	 * all registers are now moved out of mailbox 
+	 * it's now safe to set current thread pointer
+	 */
+	movl	%ebx,(%ecx)
 	popl	%edx			/* %edx off stack */
+	popl	%ecx			/* %ecx off stack */
+	popl	%ebx			/* %ebx off stack */
 	popf				/* flags off stack */
 5:	ret				/* %eip off stack */