path: root/sos-code-article5/sos/main.c

/* Copyright (C) 2004  The SOS Team
   Copyright (C) 1999  Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
   USA. 
*/

/* Include definitions of the multiboot standard */
#include <bootstrap/multiboot.h>
#include <hwcore/idt.h>
#include <hwcore/gdt.h>
#include <hwcore/irq.h>
#include <hwcore/exception.h>
#include <hwcore/i8254.h>
#include <sos/list.h>
#include <sos/physmem.h>
#include <hwcore/paging.h>
#include <sos/kmem_vmm.h>
#include <sos/kmalloc.h>
#include <sos/klibc.h>
#include <sos/assert.h>
#include <drivers/x86_videomem.h>
#include <drivers/bochs.h>


/* Helper function to display each bits of a 32bits integer on the
   screen as dark or light carrets */
void display_bits(unsigned char row, unsigned char col,
		  unsigned char attribute,
		  sos_ui32_t integer)
{
  int i;
  /* Scan each bit of the integer, MSb first */
  for (i = 31 ; i >= 0 ; i--)
    {
      /* Test if bit i of 'integer' is set */
      int bit_i = (integer & (1 << i));
      /* Ascii 219 => dark carret, Ascii 177 => light carret */
      unsigned char ascii_code = bit_i?219:177;
      sos_x86_videomem_putchar(row, col++,
			       attribute,
			       ascii_code);
    }
}


/* Clock IRQ handler */
static void clk_it(int intid)
{
  static sos_ui32_t clock_count = 0;

  display_bits(0, 48,
	       SOS_X86_VIDEO_FG_LTGREEN | SOS_X86_VIDEO_BG_BLUE,
	       clock_count);
  clock_count++;
}
struct digit
{
  struct digit *prev, *next;
  char value;
};

/* Representation of a big (positive) integer: Most Significant Digit
   (MSD) is the HEAD of the list. Least Significant Digit (LSD) is the
   TAIL of the list */
typedef struct digit * big_number_t;


/* Add a new digit after the LSD */
void bn_push_lsd(big_number_t * bn, char value)
{
  struct digit *d;
  d = (struct digit*) sos_kmalloc(sizeof(struct digit), 0);
  SOS_ASSERT_FATAL(d != NULL);
  d->value = value;
  list_add_tail(*bn, d);
}


/* Add a new digit before the MSD */
void bn_push_msd(big_number_t * bn, char value)
{
  struct digit *d;
  d = (struct digit*) sos_kmalloc(sizeof(struct digit), 0);
  SOS_ASSERT_FATAL(d != NULL);
  d->value = value;
  list_add_head(*bn, d);
}


/* Construct a big integer from a (machine) integer */
big_number_t bn_new(unsigned long int i)
{
  big_number_t retval;

  list_init(retval);
  do
    {
      bn_push_msd(&retval, i%10);
      i /= 10;
    }
  while (i != 0);

  return retval;
}


/* Create a new big integer from another big integer */
big_number_t bn_copy(const big_number_t bn)
{
  big_number_t retval;
  int nb_elts;
  struct digit *d;

  list_init(retval);
  list_foreach(bn, d, nb_elts)
    {
      bn_push_lsd(&retval, d->value);
    }

  return retval;
}


/* Free the memory used by a big integer */
void bn_del(big_number_t * bn)
{
  struct digit *d;

  list_collapse(*bn, d)
    {
      sos_kfree((sos_vaddr_t)d);
    }
}


/* Shift left a big integer: bn := bn*10^shift */
void bn_shift(big_number_t *bn, int shift)
{
  for ( ; shift > 0 ; shift --)
    {
      bn_push_lsd(bn, 0);
    }
}


/* Dump the big integer in bochs */
void bn_print_bochs(const big_number_t bn)
{
  int nb_elts;
  const struct digit *d;

  if (list_is_empty(bn))
    sos_bochs_printf("0");
  else
    list_foreach(bn, d, nb_elts)
      sos_bochs_printf("%d", d->value);
}

/* Dump the big integer on the console */
void bn_print_console(unsigned char row, unsigned char col,
		      unsigned char attribute,
		      const big_number_t bn,
		      int nb_decimals)
{
  if (list_is_empty(bn))
    sos_x86_videomem_printf(row, col, attribute, "0");
  else
    {
      int nb_elts;
      const struct digit *d;
      unsigned char x = col;

      list_foreach(bn, d, nb_elts)
	{
	  if (nb_elts == 0)
	    {
	      sos_x86_videomem_printf(row, x, attribute, "%d.", d->value);
	      x += 2;
	    }
	  else if (nb_elts < nb_decimals)
	    {
	      sos_x86_videomem_printf(row, x, attribute, "%d", d->value);
	      x ++;
	    }
	}

      sos_x86_videomem_printf(row, x, attribute, " . 10^{%d}  ", nb_elts-1);
    }
}


/* Result is the addition of 2 big integers */
big_number_t bn_add (const big_number_t bn1, const big_number_t bn2)
{
  big_number_t retval;
  const struct digit *d1, *d2;
  sos_bool_t  bn1_end = FALSE, bn2_end = FALSE;
  char carry = 0;

  list_init(retval);
  d1 = list_get_tail(bn1);
  bn1_end = list_is_empty(bn1);
  d2 = list_get_tail(bn2);
  bn2_end = list_is_empty(bn2);
  do
    {
      if (! bn1_end)
	carry += d1->value;
      if (! bn2_end)
	carry += d2->value;

      bn_push_msd(&retval, carry % 10);
      carry  /= 10;

      if (! bn1_end)
	d1 = d1->prev;
      if (! bn2_end)
	d2 = d2->prev;
      if (d1 == list_get_tail(bn1))
	bn1_end = TRUE;
      if (d2 == list_get_tail(bn2))
	bn2_end = TRUE;
    }
  while (!bn1_end || !bn2_end);

  if (carry > 0)
    {
      bn_push_msd(&retval, carry);
    }

  return retval;
}


/* Result is the multiplication of a big integer by a single digit */
big_number_t bn_muli (const big_number_t bn, char digit)
{
  big_number_t retval;
  int nb_elts;
  char   carry = 0;
  const struct digit *d;

  list_init(retval);
  list_foreach_backward(bn, d, nb_elts)
    {
      carry += d->value * digit;
      bn_push_msd(&retval, carry % 10);
      carry /= 10;
    }

  if (carry > 0)
    {
      bn_push_msd(&retval, carry);
    }

  return retval;
}


/* Result is the multiplication of 2 big integers */
big_number_t bn_mult(const big_number_t bn1, const big_number_t bn2)
{
  int shift = 0;
  big_number_t retval;
  int nb_elts;
  struct digit *d;

  list_init(retval);
  list_foreach_backward(bn2, d, nb_elts)
    {
      big_number_t retmult = bn_muli(bn1, d->value);
      big_number_t old_retval = retval;
      bn_shift(& retmult, shift);
      retval = bn_add(old_retval, retmult);
      bn_del(& retmult);
      bn_del(& old_retval);
      shift ++;
    }

  return retval;
}


/* Result is the factorial of an integer */
big_number_t bn_fact(unsigned long int v)
{
  unsigned long int i;
  big_number_t retval = bn_new(1);
  for (i = 1 ; i <= v ; i++)
    {
      big_number_t I   = bn_new(i);
      big_number_t tmp = bn_mult(retval, I);
      sos_x86_videomem_printf(4, 0,
			      SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_LTGREEN,
			      "%d! = ", (int)i);
      bn_print_console(4, 8, SOS_X86_VIDEO_BG_BLUE | SOS_X86_VIDEO_FG_WHITE,
		       tmp, 55);
      bn_del(& I);
      bn_del(& retval);
      retval = tmp;
    }

  return retval;
}


void bn_test()
{
  big_number_t bn = bn_fact(1000);
  sos_bochs_printf("1000! = ");
  bn_print_bochs(bn);
  sos_bochs_printf("\n");
  
}



/* The C entry point of our operating system */
void sos_main(unsigned long magic, unsigned long addr)
{
  unsigned i;
  sos_paddr_t sos_kernel_core_base_paddr, sos_kernel_core_top_paddr;

  /* Grub sends us a structure, called multiboot_info_t with a lot of
     precious informations about the system, see the multiboot
     documentation for more information. */
  multiboot_info_t *mbi;
  mbi = (multiboot_info_t *) addr;

  /* Setup bochs and console, and clear the console */
  sos_bochs_setup();

  sos_x86_videomem_setup();
  sos_x86_videomem_cls(SOS_X86_VIDEO_BG_BLUE);

  /* Greetings from SOS */
  if (magic == MULTIBOOT_BOOTLOADER_MAGIC)
    /* Loaded with Grub */
    sos_x86_videomem_printf(1, 0,
			    SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			    "Welcome From GRUB to %s%c RAM is %dMB (upper mem = 0x%x kB)",
			    "SOS", ',',
			    (unsigned)(mbi->mem_upper >> 10) + 1,
			    (unsigned)mbi->mem_upper);
  else
    /* Not loaded with grub */
    sos_x86_videomem_printf(1, 0,
			    SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			    "Welcome to SOS");

  sos_bochs_putstring("Message in a bochs\n");

  /* Setup CPU segmentation and IRQ subsystem */
  sos_gdt_setup();
  sos_idt_setup();

  /* Setup SOS IRQs and exceptions subsystem */
  sos_exceptions_setup();
  sos_irq_setup();

  /* Configure the timer so as to raise the IRQ0 at a 100Hz rate */
  sos_i8254_set_frequency(100);

  /* We need a multiboot-compliant boot loader to get the size of the RAM */
  if (magic != MULTIBOOT_BOOTLOADER_MAGIC)
    {
      sos_x86_videomem_putstring(20, 0,
				 SOS_X86_VIDEO_FG_LTRED
				   | SOS_X86_VIDEO_BG_BLUE
				   | SOS_X86_VIDEO_FG_BLINKING,
				 "I'm not loaded with Grub !");
      /* STOP ! */
      for (;;)
	continue;
    }

  /*
   * Some interrupt handlers
   */

  /* Binding some HW interrupts and exceptions to software routines */
  sos_irq_set_routine(SOS_IRQ_TIMER,
		      clk_it);

  /*
   * Setup physical memory management
   */

  /* Multiboot says: "The value returned for upper memory is maximally
     the address of the first upper memory hole minus 1 megabyte.". It
     also adds: "It is not guaranteed to be this value." aka "YMMV" ;) */
  sos_physmem_setup((mbi->mem_upper<<10) + (1<<20),
		    & sos_kernel_core_base_paddr,
		    & sos_kernel_core_top_paddr);
  
  /*
   * Switch to paged-memory mode
   */

  /* Disabling interrupts should seem more correct, but it's not really
     necessary at this stage */
  if (sos_paging_setup(sos_kernel_core_base_paddr,
		       sos_kernel_core_top_paddr))
    sos_bochs_printf("Could not setup paged memory mode\n");
  sos_x86_videomem_printf(2, 0,
			  SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			  "Paged-memory mode is activated");


  /*
   * Setup kernel virtual memory allocator
   */ 

  if (sos_kmem_vmm_setup(sos_kernel_core_base_paddr,
			 sos_kernel_core_top_paddr,
			 bootstrap_stack_bottom,
			 bootstrap_stack_bottom + bootstrap_stack_size))
    sos_bochs_printf("Could not setup the Kernel virtual space allocator\n");

  if (sos_kmalloc_setup())
    sos_bochs_printf("Could not setup the Kmalloc subsystem\n");

  /* Run some kmalloc tests */
  bn_test();

  /*
   * Enabling the HW interrupts here, this will make the timer HW
   * interrupt call our clk_it handler
   */
  asm volatile ("sti\n");

  /* An operatig system never ends */
  for (;;)
    continue;

  return;
}