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/* 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/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 */
static 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++;
}
/* Division by zero exception handler */
static void divide_ex(int exid)
{
static sos_ui32_t div_count = 0;
display_bits(0, 0,
SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
div_count);
div_count++;
}
/* The C entry point of our operating system */
void sos_main(unsigned long magic, unsigned long addr)
{
unsigned i;
/* 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);
/* Binding some HW interrupts and exceptions to software routines */
sos_irq_set_routine(SOS_IRQ_TIMER,
clk_it);
sos_exception_set_routine(SOS_EXCEPT_DIVIDE_ERROR,
divide_ex);
/* Enabling the HW interrupts here, this will make the timer HW
interrupt call our clk_it handler */
asm volatile ("sti\n");
/* Raise a rafale of 'division by 0' exceptions. All this code is
not really needed (equivalent to a bare "i=1/0;"), except when
compiling with -O3: "i=1/0;" is considered dead code with gcc
-O3. */
i = 10;
while (1)
{
/* Stupid function call to fool gcc optimizations */
sos_bochs_printf("i = 1 / %d...\n", i);
i = 1 / i;
}
/* Will never print this since the "divide by zero" exception always
returns to the faulting instruction (see Intel x86 doc vol 3,
section 5.12), thus re-evaluating the "divide-by-zero" exprssion
and raising the "divide by zero" exception again and again... */
sos_x86_videomem_putstring(2, 0,
SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
"Invisible");
return;
}
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