/*
 * Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *    * Neither the name of the University 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 THE COPYRIGHT HOLDERS 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 REGENTS 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.
 */

#include <hermit/stdio.h>
#include <hermit/string.h>
#include <hermit/stdlib.h>
#include <hermit/tasks.h>
#include <hermit/errno.h>
#include <hermit/processor.h>
#include <asm/gdt.h>
#include <asm/tss.h>
#include <asm/page.h>

#define MAX_IST		3

gdt_ptr_t		gp;
// currently, our kernel has full access to the ioports
static gdt_entry_t	gdt[GDT_ENTRIES] = {[0 ... GDT_ENTRIES-1] = {0, 0, 0, 0, 0, 0}};
static tss_t		task_state_segments[MAX_CORES] __attribute__ ((aligned (PAGE_SIZE)));
static uint8_t		stack_table[MAX_CORES*KERNEL_STACK_SIZE*MAX_IST] __attribute__ ((aligned (PAGE_SIZE)));

extern const void boot_stack;

/*
 * This is defined in entry.asm. We use this to properly reload
 * the new segment registers
 */
extern void gdt_flush(void);

extern const void boot_stack;

void set_tss(size_t rps0, size_t ist1)
{
	task_state_segments[CORE_ID].rsp0 = rps0;
	task_state_segments[CORE_ID].ist1 = ist1;
}

/* Setup a descriptor in the Global Descriptor Table */
void gdt_set_gate(int num, unsigned long base, unsigned long limit,
			  unsigned char access, unsigned char gran)
{
	configure_gdt_entry(&gdt[num], base, limit, access, gran);
}

void configure_gdt_entry(gdt_entry_t *dest_entry, unsigned long base, unsigned long limit,
		unsigned char access, unsigned char gran)
{
	/* Setup the descriptor base address */
	dest_entry->base_low = (base & 0xFFFF);
	dest_entry->base_middle = (base >> 16) & 0xFF;
	dest_entry->base_high = (base >> 24) & 0xFF;

	/* Setup the descriptor limits */
	dest_entry->limit_low = (limit & 0xFFFF);
	dest_entry->granularity = ((limit >> 16) & 0x0F);

	/* Finally, set up the granularity and access flags */
	dest_entry->granularity |= (gran & 0xF0);
	dest_entry->access = access;
}

/*
 * This will setup the special GDT
 * pointer, set up the entries in our GDT, and then
 * finally call gdt_flush() in our assembler file in order
 * to tell the processor where the new GDT is and update the
 * new segment registers
 */
void gdt_install(void)
{
	int i, num = 0;

	memset(task_state_segments, 0x00, MAX_CORES*sizeof(tss_t));

	/* Setup the GDT pointer and limit */
	gp.limit = (sizeof(gdt_entry_t) * GDT_ENTRIES) - 1;
	gp.base = (size_t) &gdt;

	/* Our NULL descriptor */
	gdt_set_gate(num++, 0, 0, 0, 0);

	/*
	 * The second entry is our Code Segment. The base address
	 * is 0, the limit is 4 GByte, it uses 4KByte granularity,
	 * and is a Code Segment descriptor.
	 */
	gdt_set_gate(num++, 0, 0,
		GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT, GDT_FLAG_64_BIT);

	/*
	 * The third entry is our Data Segment. It's EXACTLY the
	 * same as our code segment, but the descriptor type in
	 * this entry's access byte says it's a Data Segment
	 */
	gdt_set_gate(num++, 0, 0,
		GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT, 0);

	/*
	 * Create code segment for 32bit user-space applications (ring 3)
	 */
	gdt_set_gate(num++, 0, 0xFFFFFFFF,
		GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT, GDT_FLAG_32_BIT | GDT_FLAG_4K_GRAN);

	/*
	 * Create data segment for 32bit user-space applications (ring 3)
	 */
	gdt_set_gate(num++, 0, 0xFFFFFFFF,
		GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT, GDT_FLAG_32_BIT | GDT_FLAG_4K_GRAN);

	/*
	 * Create code segment for 64bit user-space applications (ring 3)
	 */
	gdt_set_gate(num++, 0, 0,
		GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT, GDT_FLAG_64_BIT);

	/*
	 * Create data segment for 64bit user-space applications (ring 3)
	 */
	gdt_set_gate(num++, 0, 0,
		GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT, 0);

	/*
	 * Create TSS for each core (we use these segments for task switching)
	 */
	for(i=0; i<MAX_CORES; i++) {
		task_state_segments[i].rsp0 = (size_t)&boot_stack + (i+1) * KERNEL_STACK_SIZE - 0x10;
		task_state_segments[i].ist1 = 0; // ist will created per task
		task_state_segments[i].ist2 = (size_t)stack_table + MAX_IST*i * KERNEL_STACK_SIZE + (2 /*IST number */ - 1) * KERNEL_STACK_SIZE - 0x10;
		task_state_segments[i].ist3 = (size_t)stack_table + MAX_IST*i * KERNEL_STACK_SIZE + (3 /*IST number */ - 1) * KERNEL_STACK_SIZE - 0x10;
		task_state_segments[i].ist4 = (size_t)stack_table + MAX_IST*i * KERNEL_STACK_SIZE + (4 /*IST number */ - 1) * KERNEL_STACK_SIZE - 0x10;

		gdt_set_gate(num+i*2, (unsigned long) (task_state_segments+i), sizeof(tss_t)-1,
			GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, 0);
	}

	/* Flush out the old GDT and install the new changes! */
	gdt_flush();
}