main.c

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

  /*
   * Setup the root and CWD directories of the process. The root of
   * this process will correspond to the "global" root of the whole
   * system since all the future processes will duplicate it !
   */
  retval = sos_fs_new_opened_file(proc_init, rootfs->root,
				  SOS_FS_OPEN_READ | SOS_FS_OPEN_WRITE,
				  & init_root);
  if (SOS_OK != retval)
    {
      sos_process_unref(proc_init);
      return -SOS_ENOENT;
    }

  /* Duplicate the root file to set the current working directory of
     the init process */
  retval = sos_fs_duplicate_opened_file(init_root, proc_init,
					& init_cwd);
  if (SOS_OK != retval)
    {
      sos_fs_close(init_root);
      sos_process_unref(proc_init);
      return -SOS_ENOENT;
    }

  /* Now update the process ! */
  if ( ( SOS_OK != sos_process_chroot(proc_init, init_root, & unused_of) )
       || ( SOS_OK != sos_process_chdir(proc_init, init_cwd, & unused_of) ) )
    {
      sos_fs_close(init_root);
      sos_fs_close(init_cwd);
      sos_process_chroot(proc_init, NULL, & unused_of);
      sos_process_chdir(proc_init, NULL, & unused_of);
      sos_process_unref(proc_init);
      return -SOS_ENOENT;
    }

  /* Map the 'init' program in user space */
  start_uaddr = sos_binfmt_elf32_map(as_init, "init");
  if (0 == start_uaddr)
    {
      sos_process_unref(proc_init);
      return -SOS_ENOENT;
    }

  /* Allocate the user stack */
  ustack = (SOS_PAGING_TOP_USER_ADDRESS - SOS_DEFAULT_USER_STACK_SIZE) + 1;
  retval = sos_dev_zero_map(as_init, &ustack, SOS_DEFAULT_USER_STACK_SIZE,
			    SOS_VM_MAP_PROT_READ | SOS_VM_MAP_PROT_WRITE,
			    /* PRIVATE */ 0);
  if (SOS_OK != retval)
    {
      sos_process_unref(proc_init);
      return -SOS_ENOMEM;
    }

  /* Now create the user thread */
  new_thr = sos_create_user_thread(NULL,
				   proc_init,
				   start_uaddr,
				   0, 0,
				   ustack + SOS_DEFAULT_USER_STACK_SIZE - 4,
				   SOS_SCHED_PRIO_TS_LOWEST);
  if (! new_thr)
    {
      sos_process_unref(proc_init);
      return -SOS_ENOMEM;
    }

  sos_process_unref(proc_init);
  return SOS_OK;
}


/* ======================================================================
 * The C entry point of our operating system
 */
void sos_main(unsigned long magic, unsigned long arg)
{
  unsigned i;
  sos_paddr_t sos_kernel_core_base_paddr, sos_kernel_core_top_paddr;
  struct sos_time tick_resolution;
  struct sos_fs_manager_instance * rootfs;

  /* Size of RAM above 1MB. Might be undefined ! */
  unsigned long int upper_mem = 0;

  /* 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)
    {
      /* 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 = (multiboot_info_t *) arg;

      /* 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" ;) */
      upper_mem = mbi->mem_upper;
      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 8", ',',
			      (unsigned)(upper_mem >> 10) + 1,
			      (unsigned)upper_mem);
    }
  else if (magic == 0x42244224)
    {
      /* Loaded with SOS bootsect */
      upper_mem = arg;
      sos_x86_videomem_printf(1, 0,
			      SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			      "Welcome to %s%c RAM is %dMB (upper mem = 0x%x kB)",
			      "SOS article 8", ',',
			      (unsigned)(upper_mem >> 10) + 1,
			      (unsigned)upper_mem);
    }
  else
    /* Not loaded with grub, not from an enhanced bootsect */
    sos_x86_videomem_printf(1, 0,
			    SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			    "Welcome to SOS article 8");

  sos_bochs_putstring("Message in a bochs: This is SOS article 8.\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 to know the RAM size */
  if (upper_mem == 0)
    {
      sos_x86_videomem_putstring(20, 0,
				 SOS_X86_VIDEO_FG_LTRED
				   | SOS_X86_VIDEO_BG_BLUE
				   | SOS_X86_VIDEO_FG_BLINKING,
				 "I don't know RAM size ! Load me 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
   */

  SOS_ASSERT_FATAL(SOS_OK
		   == sos_physmem_subsystem_setup((upper_mem<<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 MMU context subsystem
   */
  sos_mm_context_subsystem_setup();

  /*
   * Initialize the CPU context subsystem
   */
  sos_cpu_context_subsystem_setup();

  /*
   * Bind the syscall handler to its software interrupt handler
   */
  sos_swintr_subsystem_setup();


  /*
   * 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,
   					    SOS_SCHED_PRIO_TS_LOWEST) != NULL);

  /* Prepare the stats subsystem */
  sos_load_subsystem_setup();

  /* Declare a thread that prints some stats */
  SOS_ASSERT_FATAL(sos_create_kernel_thread("stat_thread", stat_thread,
					    NULL,
					    SOS_SCHED_PRIO_TS_LOWEST) != NULL);


  /*
   * Initialise user address space management subsystem
   */
  sos_umem_vmm_subsystem_setup();
  sos_dev_zero_subsystem_setup();

  /*
   * Initialize process stuff
   */
  sos_process_subsystem_setup();


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


  SOS_ASSERT_FATAL(SOS_OK == sos_fs_virtfs_subsystem_setup());
  SOS_ASSERT_FATAL(SOS_OK == sos_fs_subsystem_setup(NULL,
						    "virtfs",
						    NULL,
						    & rootfs));


  /* Start the 'init' process, which in turns launches the other
     programs */
  start_init(rootfs);
  /*
   * 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 !");
}