/*
 * Copyright (c) 2002 Jonathan Mini <mini@freebsd.org>.
 * Copyright (c) 2001 Daniel Eischen <deischen@freebsd.org>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Neither the name of the author nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY DANIEL EISCHEN AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */

#include <machine/asm.h>
__FBSDID("$FreeBSD$");

/*
 * Where do we define these?
 */
#define	MC_SIZE			640	/* sizeof mcontext_t */
#define	UC_MC_OFFSET		16	/* offset to mcontext from ucontext */
#define	UC_MC_LEN_OFFSET	96	/* offset to mc_len from mcontext */
#define	MC_LEN_OFFSET		80	/* offset to mc_len from mcontext */
#define	MC_FP_REGS_OFFSET	96	/* offset to FP regs from mcontext */
#define	MC_FP_CW_OFFSET		96	/* offset to FP control word */
#define	MC_OWNEDFP_OFFSET	88	/* offset to mc_ownedfp from mcontext */
#define	KM_STACK_SP_OFFSET	36	/* offset to km_stack.ss_sp */
#define	KM_STACK_SIZE_OFFSET	40	/* offset to km_stack.ss_sp */
#define	KM_FUNC_OFFSET		32	/* offset to km_func */
 
/*
 * int uts_to_thread(struct kse_thr_mailbox *tdp,
 *	struct kse_thr_mailbox **curthreadp);
 *
 * Does not return on success, returns -1 otherwise.
 */
ENTRY(uts_to_thread)
	movl	4(%esp), %edx		/* get address of kse_thr_mailbox */
					/* .. ucontext_t is at offset 0 */
	cmpl	$0, %edx		/* check for null pointer */
	jne	1f
	movl	$-1, %eax
	jmp	5f
1:	cmpl	$MC_SIZE, UC_MC_LEN_OFFSET(%edx) /* is context valid? */
	je	2f
	movl	$-1, %eax		/* bzzzt, invalid context */
	jmp	5f
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.
	 */
	addl	$UC_MC_OFFSET, %edx	/* add offset to mcontext */
	movl	4(%edx), %gs
	movl	8(%edx), %fs
	movl	12(%edx), %es
	movl	16(%edx), %ds
	movl	76(%edx), %ss
	movl	20(%edx), %edi
	movl	24(%edx), %esi
	movl	28(%edx), %ebp
	movl	72(%edx), %esp		/* switch to context defined stack */
	subl	$4, %esp		/* leave space for the return address */
	movl	60(%edx), %eax		/* put return address at top of stack */
	movl	%eax, (%esp)
	cmpl	$0, MC_OWNEDFP_OFFSET(%edx) /* are FP regs valid? */
	jz	3f
	frstor	MC_FP_REGS_OFFSET(%edx) /* restore FP regs */
	jmp	4f
3:	fninit
	fldcw	MC_FP_CW_OFFSET(%edx)
4:	movl	48(%edx), %eax		/* restore ax, bx, cx, dx */
	pushl	68(%edx)		/* flags on stack */
	pushl	36(%edx)		/* %ebx on stack */
	pushl	44(%edx)		/* %ecx on stack */
	movl	40(%edx), %edx		/* %edx */
	/* 
	 * all registers are now moved out of mailbox, 
	 * it's safe to set current thread pointer
	 */
	movl	%ebx,(%ecx)
	popl	%ecx			/* %ecx off stack */
	pop	%ebx			/* %ebx off stack */
	popf				/* flags off stack */
5:	ret				/* %eip off stack */
END(uts_to_thread)

/*
 * int thread_to_uts(struct kse_thr_mailbox *tm, struct kse_mailbox *km);
 *
 * Does not return on success, returns -1 otherwise.
 */
ENTRY(thread_to_uts)
	movl	4(%esp), %eax		/* get address of context */
	cmpl	$0, %eax		/* check for null pointer */
	jne	1f
	movl	$-1, %eax
	jmp	2f
1:	pushl	%edx			/* save value of edx */
	movl	%eax, %edx		/* get address of context */
	addl	$UC_MC_OFFSET, %edx	/* add offset to mcontext */
	movl	%gs, 4(%edx)
	movl	%fs, 8(%edx)
	movl	%es, 12(%edx)
	movl	%ds, 16(%edx)
	movl	%edi, 20(%edx)
	movl	%esi, 24(%edx)
	movl	%ebp, 28(%edx)
	movl	%ebx, 36(%edx)
	movl	$0, 48(%edx)		/* store successful return in eax */
	popl	%eax			/* get saved value of edx */
	movl	%eax, 40(%edx)		/* save edx */
	movl	%ecx, 44(%edx)
	movl	(%esp), %eax		/* get return address */
	movl	%eax, 60(%edx)		/* save return address */
	movl	%ss, 76(%edx)
	/*
	 * Don't save floating point registers here.
	 *
	 * This is an explicit call to get the current context, so
	 * the caller is done with the floating point registers.
	 * Contexts formed by involuntary switches, such as signal delivery,
	 * have floating point registers saved by the kernel.
	 */
	fnstcw	MC_FP_CW_OFFSET(%edx)
	movl	$0, MC_OWNEDFP_OFFSET(%edx) /* no FP */
	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 */
	movl	%eax, 72(%edx)		/*   stack; account for this     */
	movl	$MC_SIZE, MC_LEN_OFFSET(%edx) /* context is now valid */
	movl	8(%esp), %edx		/* get address of mailbox */
	movl	KM_STACK_SP_OFFSET(%edx), %eax	/* get bottom of stack */
	addl	KM_STACK_SIZE_OFFSET(%edx), %eax /* add length */
	movl	%eax, %esp		/* switch to the uts's stack */
	pushl	%edx			/* push the address of the mailbox */
	pushl	KM_FUNC_OFFSET(%edx)	/* .. the uts can return to itself */
	pushl	KM_FUNC_OFFSET(%edx)	/* push the address of the uts func */
2:	ret
END(thread_to_uts)