main.c

Simple Operating Systems （简称SOS）是一个可以运行在X86平台上（包括QEMU

/* Copyright (C) 2004  The SOS Team

   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/time.h>
#include <sos/thread.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++;

  /* Execute the expired timeout actions (if any) */
  sos_time_do_tick();
}


/* ======================================================================
 * Page fault exception handling
 */

/* Helper function to dump a backtrace on bochs and/or the console */
static void dump_backtrace(const struct sos_cpu_state *cpu_state,
			   sos_vaddr_t stack_bottom,
			   sos_size_t  stack_size,
			   sos_bool_t on_console,
			   sos_bool_t on_bochs)
{
  static void backtracer(sos_vaddr_t PC,
			 sos_vaddr_t params,
			 sos_ui32_t depth,
			 void *custom_arg)
    {
      sos_ui32_t invalid = 0xffffffff, *arg1, *arg2, *arg3, *arg4;

      /* Get the address of the first 3 arguments from the
	 frame. Among these arguments, 0, 1, 2, 3 arguments might be
	 meaningful (depending on how many arguments the function may
	 take). */
      arg1 = (sos_ui32_t*)params;
      arg2 = (sos_ui32_t*)(params+4);
      arg3 = (sos_ui32_t*)(params+8);
      arg4 = (sos_ui32_t*)(params+12);

      /* Make sure the addresses of these arguments fit inside the
	 stack boundaries */
#define INTERVAL_OK(b,v,u) ( ((b) <= (sos_vaddr_t)(v)) \
                             && ((sos_vaddr_t)(v) < (u)) )
      if (!INTERVAL_OK(stack_bottom, arg1, stack_bottom + stack_size))
	arg1 = &invalid;
      if (!INTERVAL_OK(stack_bottom, arg2, stack_bottom + stack_size))
	arg2 = &invalid;
      if (!INTERVAL_OK(stack_bottom, arg3, stack_bottom + stack_size))
	arg3 = &invalid;
      if (!INTERVAL_OK(stack_bottom, arg4, stack_bottom + stack_size))
	arg4 = &invalid;

      /* Print the function context for this frame */
      if (on_bochs)
	sos_bochs_printf("[%d] PC=0x%x arg1=0x%x arg2=0x%x arg3=0x%x\n",
			 (unsigned)depth, (unsigned)PC,
			 (unsigned)*arg1, (unsigned)*arg2,
			 (unsigned)*arg3);

      if (on_console)
	sos_x86_videomem_printf(23-depth, 3,
				SOS_X86_VIDEO_BG_BLUE
				  | SOS_X86_VIDEO_FG_LTGREEN,
				"[%d] PC=0x%x arg1=0x%x arg2=0x%x arg3=0x%x arg4=0x%x",
				(unsigned)depth, PC,
				(unsigned)*arg1, (unsigned)*arg2,
				(unsigned)*arg3, (unsigned)*arg4);
      
    }

  sos_backtrace(cpu_state, 15, stack_bottom, stack_size, backtracer, NULL);
}


/* Page fault exception handler with demand paging for the kernel */
static void pgflt_ex(int intid, const struct sos_cpu_state *ctxt)
{
  static sos_ui32_t demand_paging_count = 0;
  sos_vaddr_t faulting_vaddr = sos_cpu_context_get_EX_faulting_vaddr(ctxt);
  sos_paddr_t ppage_paddr;

  /* Check if address is covered by any VMM range */
  if (! sos_kmem_vmm_is_valid_vaddr(faulting_vaddr))
    {
      /* No: The page fault is out of any kernel virtual region. For
	 the moment, we don't handle this. */
      dump_backtrace(ctxt,
		     bootstrap_stack_bottom,
		     bootstrap_stack_size,
		     TRUE, TRUE);
      sos_display_fatal_error("Unresolved page Fault at instruction 0x%x on access to address 0x%x (info=%x)!",
			      sos_cpu_context_get_PC(ctxt),
			      (unsigned)faulting_vaddr,
			      (unsigned)sos_cpu_context_get_EX_info(ctxt));
      SOS_ASSERT_FATAL(! "Got page fault (note: demand paging is disabled)");
    }


  /*
   * Demand paging
   */
 
  /* Update the number of demand paging requests handled */
  demand_paging_count ++;
  display_bits(0, 0,
	       SOS_X86_VIDEO_FG_LTRED | SOS_X86_VIDEO_BG_BLUE,
	       demand_paging_count);

  /* Allocate a new page for the virtual address */
  ppage_paddr = sos_physmem_ref_physpage_new(FALSE);
  if (! ppage_paddr)
    SOS_ASSERT_FATAL(! "TODO: implement swap. (Out of mem in demand paging because no swap for kernel yet !)");
  SOS_ASSERT_FATAL(SOS_OK == sos_paging_map(ppage_paddr,
					    SOS_PAGE_ALIGN_INF(faulting_vaddr),
					    FALSE,
					    SOS_VM_MAP_PROT_READ
					    | SOS_VM_MAP_PROT_WRITE
					    | SOS_VM_MAP_ATOMIC));
  sos_physmem_unref_physpage(ppage_paddr);

  /* Ok, we can now return to interrupted context */
}


/* ======================================================================
 * Demonstrate the use of SOS kernel threads
 *  - Kernel Threads are created with various priorities and their
 *    state is printed on both the console and the bochs' 0xe9 port
 *  - For tests regarding threads' synchronization, see mouse_sim.c
 */

struct thr_arg
{
  char character;
  int  color;

  int col;
  int row;
};


static void demo_thread(void *arg)
{
  struct thr_arg *thr_arg = (struct thr_arg*)arg;
  int progress = 0;

  sos_bochs_printf("start %c", thr_arg->character);
  while (1)
    {
      progress ++;
      display_bits(thr_arg->row, thr_arg->col+1, thr_arg->color, progress);

      sos_bochs_putchar(thr_arg->character);

      /* Yield the CPU to another thread sometimes... */
      if ((random() % 100) == 0)
	{
	  sos_bochs_printf("yield(%c)\n", thr_arg->character);
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 'Y');
	  SOS_ASSERT_FATAL(SOS_OK == sos_thread_yield());
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 'R');
	}

      /* Go to sleep some other times... */
      else if ((random() % 200) == 0)
	{
	  struct sos_time t = (struct sos_time){ .sec=0, .nanosec=50000000 };
	  sos_bochs_printf("sleep1(%c)\n", thr_arg->character);
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 's');
	  SOS_ASSERT_FATAL(SOS_OK == sos_thread_sleep(& t));
	  SOS_ASSERT_FATAL(sos_time_is_zero(& t));
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 'R');
	}

      /* Go to sleep for a longer time some other times... */
      else if ((random() % 300) == 0)
	{
	  struct sos_time t = (struct sos_time){ .sec=0, .nanosec=300000000 };
	  sos_bochs_printf("sleep2(%c)\n", thr_arg->character);
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 'S');
	  SOS_ASSERT_FATAL(SOS_OK == sos_thread_sleep(& t));
	  SOS_ASSERT_FATAL(sos_time_is_zero(& t));
	  sos_x86_videomem_putchar(thr_arg->row, thr_arg->col, 0x1e, 'R');
	}

      /* Infinite loop otherwise */
    }
}


static void test_thread()
{
  /* "static" variables because we want them to remain even when the
     function returns */
  static struct thr_arg arg_b, arg_c, arg_d, arg_e, arg_R, arg_S;
  sos_ui32_t flags;

  sos_disable_IRQs(flags);

  arg_b = (struct thr_arg) { .character='b', .col=0, .row=21, .color=0x14 };
  sos_create_kernel_thread("YO[b]", demo_thread, (void*)&arg_b);

  arg_c = (struct thr_arg) { .character='c', .col=46, .row=21, .color=0x14 };
  sos_create_kernel_thread("YO[c]", demo_thread, (void*)&arg_c);

  arg_d = (struct thr_arg) { .character='d', .col=0, .row=20, .color=0x14 };
  sos_create_kernel_thread("YO[d]", demo_thread, (void*)&arg_d);

  arg_e = (struct thr_arg) { .character='e', .col=0, .row=19, .color=0x14 };
  sos_create_kernel_thread("YO[e]", demo_thread, (void*)&arg_e);

  arg_R = (struct thr_arg) { .character='R', .col=0, .row=17, .color=0x1c };
  sos_create_kernel_thread("YO[R]", demo_thread, (void*)&arg_R);

  arg_S = (struct thr_arg) { .character='S', .col=0, .row=16, .color=0x1c };
  sos_create_kernel_thread("YO[S]", demo_thread, (void*)&arg_S);

  sos_restore_IRQs(flags);
}


/* ======================================================================
 * An operating system MUST always have a ready thread ! Otherwise:
 * what would the CPU have to execute ?!
 */
static void idle_thread()
{
  sos_ui32_t idle_twiddle = 0;

  while (1)
    {
      /* Remove this instruction if you get an "Invalid opcode" CPU
	 exception (old 80386 CPU) */
      asm("hlt\n");

      idle_twiddle ++;
      display_bits(0, 0, SOS_X86_VIDEO_FG_GREEN | SOS_X86_VIDEO_BG_BLUE,
		   idle_twiddle);
      
      /* Lend the CPU to some other thread */
      sos_thread_yield();
    }
}


/* ======================================================================
 * 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;
  struct sos_time tick_resolution;

  /* 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 article 6.5", ',',
			    (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 article 6.5");

  sos_bochs_putstring("Message in a bochs: This is SOS article 6.5.\n");

  /* Setup CPU segmentation and IRQ subsystem */
  sos_gdt_subsystem_setup();
  sos_idt_subsystem_setup();

  /* Setup SOS IRQs and exceptions subsystem */
  sos_exception_subsystem_setup();
  sos_irq_subsystem_setup();

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

  /* Setup the kernel time subsystem to get prepared to take the timer
     ticks into account */
  tick_resolution = (struct sos_time) { .sec=0, .nanosec=10000000UL };
  sos_time_subsysem_setup(& tick_resolution);

  /* 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_subsystem_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 */
  SOS_ASSERT_FATAL(SOS_OK ==
		   sos_paging_subsystem_setup(sos_kernel_core_base_paddr,
					      sos_kernel_core_top_paddr));
  
  /* Bind the page fault exception */
  sos_exception_set_routine(SOS_EXCEPT_PAGE_FAULT,
			    pgflt_ex);

  /*
   * Setup kernel virtual memory allocator
   */

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

  /*
   * Initialize the Kernel thread and scheduler subsystems
   */
  
  /* Initialize kernel thread subsystem */
  sos_thread_subsystem_setup(bootstrap_stack_bottom,
			     bootstrap_stack_size);

  /* Initialize the scheduler */
  sos_sched_subsystem_setup();

  /* Declare the IDLE thread */
  SOS_ASSERT_FATAL(sos_create_kernel_thread("idle", idle_thread, NULL) != NULL);

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


  /* Now run some Kernel threads just for fun ! */
  extern void MouseSim();
  MouseSim();
  test_thread();

  /*
   * We can safely exit from this function now, for there is already
   * an idle Kernel thread ready to make the CPU busy working...
   *
   * However, we must EXPLICITELY call sos_thread_exit() because a
   * simple "return" will return nowhere ! Actually this first thread
   * was initialized by the Grub bootstrap stage, at a time when the
   * word "thread" did not exist. This means that the stack was not
   * setup in order for a return here to call sos_thread_exit()
   * automagically. Hence we must call it manually. This is the ONLY
   * kernel thread where we must do this manually.
   */
  sos_bochs_printf("Bye from primary thread !\n");
  sos_thread_exit();
  SOS_FATAL_ERROR("No trespassing !");
}