/*
 * Copyright (c) 2009 Corey Tabaka
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include <sys/types.h>
#include <string.h>
#include <stdlib.h>
#include <debug.h>
#include <kernel/thread.h>
#include <arch/x86.h>
#include <arch/x86/descriptor.h>

/*struct context_switch_frame {
	uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax;
	uint32_t ds, es, fs, gs;
	uint32_t eip, cs, eflags;
};*/
struct context_switch_frame {
	uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax;
	uint32_t eflags;
	uint32_t eip;
};

extern void x86_context_switch(addr_t *old_sp, addr_t new_sp);

static void initial_thread_func(void) __NO_RETURN;
static void initial_thread_func(void)
{
	int ret;

//	dprintf("initial_thread_func: thread %p calling %p with arg %p\n", current_thread, current_thread->entry, current_thread->arg);
//	dump_thread(current_thread);

	/* exit the implicit critical section we're within */
	exit_critical_section();

	ret = current_thread->entry(current_thread->arg);

//	dprintf("initial_thread_func: thread %p exiting with %d\n", current_thread, ret);

	thread_exit(ret);
}

void arch_thread_initialize(thread_t *t)
{
	// create a default stack frame on the stack
	vaddr_t stack_top = (vaddr_t)t->stack + t->stack_size;

	// make sure the top of the stack is 8 byte aligned for EABI compliance
	stack_top = ROUNDDOWN(stack_top, 8);

	struct context_switch_frame *frame = (struct context_switch_frame *)(stack_top);
	frame--;

	// fill it in
	memset(frame, 0, sizeof(*frame));
	
	frame->eip = (vaddr_t) &initial_thread_func;
	frame->eflags = 0x3002; // IF = 0, NT = 0, IOPL = 3
	//frame->cs = CODE_SELECTOR;
	//frame->fs = DATA_SELECTOR;
	//frame->gs = DATA_SELECTOR;
	//frame->es = DATA_SELECTOR;
	//frame->ds = DATA_SELECTOR;
	
	// set the stack pointer
	t->arch.esp = (vaddr_t)frame;
}

void arch_context_switch(thread_t *oldthread, thread_t *newthread)
{
	//dprintf(DEBUG, "arch_context_switch: old %p (%s), new %p (%s)\n", oldthread, oldthread->name, newthread, newthread->name);
	
	__asm__ __volatile__ (
		"pushl $1f			\n\t"
		"pushf				\n\t"
		"pusha				\n\t"
		"movl %%esp,(%%edx)	\n\t"
		"movl %%eax,%%esp	\n\t"
		"popa				\n\t"
		"popf				\n\t"
		"ret				\n\t"
		"1:					\n\t"
		
		:
		: "d" (&oldthread->arch.esp), "a" (newthread->arch.esp)
	);
	
	/*__asm__ __volatile__ (
		"pushf				\n\t"
		"pushl %%cs			\n\t"
		"pushl $1f			\n\t"
		"pushl %%gs			\n\t"
		"pushl %%fs			\n\t"
		"pushl %%es			\n\t"
		"pushl %%ds			\n\t"
		"pusha				\n\t"
		"movl %%esp,(%%edx)	\n\t"
		"movl %%eax,%%esp	\n\t"
		"popa				\n\t"
		"popl %%ds			\n\t"
		"popl %%es			\n\t"
		"popl %%fs			\n\t"
		"popl %%gs			\n\t"
		"iret				\n\t"
		"1:	"
		:
		: "d" (&oldthread->arch.esp), "a" (newthread->arch.esp)
	);*/
}