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 <sos/errno.h>

/* 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 <hwcore/mm_context.h>
#include <hwcore/swintr.h>
#include <sos/kmem_vmm.h>
#include <sos/kmalloc.h>
#include <sos/time.h>
#include <sos/thread.h>
#include <sos/process.h>
#include <sos/umem_vmm.h>
#include <sos/klibc.h>
#include <sos/assert.h>
#include <drivers/x86_videomem.h>
#include <drivers/bochs.h>
#include <sos/calcload.h>
#include <sos/umem_vmm.h>
#include <sos/binfmt_elf32.h>
#include <drivers/zero.h>
#include <sos/fs.h>
#include <drivers/fs_virtfs.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();

  /* Update scheduler statistics and status */
  sos_sched_do_timer_tick();
}


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


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

  if (sos_cpu_context_is_in_user_mode(ctxt)
      || (cur_thr->fixup_uaccess.return_vaddr))
    {
      __label__ unforce_address_space;
      sos_bool_t need_to_setup_mmu;
      sos_ui32_t errcode = sos_cpu_context_get_EX_info(ctxt);

      /* Make sure to always stay in the interrupted thread's MMU
	 configuration */
      need_to_setup_mmu = (cur_thr->squatted_mm_context
			   != sos_process_get_mm_context(cur_thr->process));
      if (need_to_setup_mmu)
	sos_thread_prepare_user_space_access(NULL, 0);

      if (SOS_OK ==
	  sos_umem_vmm_try_resolve_page_fault(faulting_vaddr,
					      errcode & (1 << 1),
					      TRUE))
	goto unforce_address_space;

      /* If the page fault occured in kernel mode, return to kernel to
	 the fixup address */
      if (! sos_cpu_context_is_in_user_mode(ctxt))
	{
	  cur_thr->fixup_uaccess.faulted_uaddr = faulting_vaddr;
	  sos_cpu_context_set_EX_return_address(ctxt,
						cur_thr->fixup_uaccess.return_vaddr);
	  goto unforce_address_space;
	}

      if (need_to_setup_mmu)
	sos_thread_end_user_space_access();

      sos_bochs_printf("Unresolved USER page Fault at instruction 0x%x on access to address 0x%x (info=%x)!\n",
		       sos_cpu_context_get_PC(ctxt),
		       (unsigned)faulting_vaddr,
		       (unsigned)sos_cpu_context_get_EX_info(ctxt));
      sos_bochs_printf("Terminating User thread\n");
      sos_thread_exit();

    unforce_address_space:
      if (need_to_setup_mmu)
	sos_thread_end_user_space_access();
      return;
    }

  /* 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. */
      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 in kernel space
   */
 
  /* 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 */
}



/* ======================================================================
 * 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();
    }
}


/* ======================================================================
 * Kernel thread showing some CPU usage statistics on the console every 1s
 */
static void stat_thread()
{
  while (1)
    {
      sos_ui32_t flags;
      sos_ui32_t load1, load5, load15;
      char str1[11], str5[11], str15[11];
      struct sos_time t;
      t.sec = 1;
      t.nanosec = 0;

      sos_thread_sleep(& t);

      sos_disable_IRQs(flags);

      /* The IDLE task is EXcluded in the following computation */
      sos_load_get_sload(&load1, &load5, &load15);
      sos_load_to_string(str1, load1);
      sos_load_to_string(str5, load5);
      sos_load_to_string(str15, load15);
      sos_x86_videomem_printf(16, 34,
			      SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			      "Kernel (- Idle): %s %s %s    ",
			      str1, str5, str15);

      sos_load_get_uload(&load1, &load5, &load15);
      sos_load_to_string(str1, load1);
      sos_load_to_string(str5, load5);
      sos_load_to_string(str15, load15);
      sos_x86_videomem_printf(17, 34,
			      SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			      "User: %s %s %s        ",
			      str1, str5, str15);

      sos_load_get_uratio(&load1, &load5, &load15);
      sos_load_to_string(str1, load1);
      sos_load_to_string(str5, load5);
      sos_load_to_string(str15, load15);
      sos_x86_videomem_printf(18, 34,
			      SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			      "User CPU %%: %s %s %s        ",
			      str1, str5, str15);

      /* The IDLE task is INcluded in the following computation */
      sos_load_get_sratio(&load1, &load5, &load15);
      sos_load_to_string(str1, load1);
      sos_load_to_string(str5, load5);
      sos_load_to_string(str15, load15);
      sos_x86_videomem_printf(19, 34,
			      SOS_X86_VIDEO_FG_YELLOW | SOS_X86_VIDEO_BG_BLUE,
			      "Kernel CPU %% (+ Idle): %s %s %s    ",
			      str1, str5, str15);
      sos_restore_IRQs(flags);
    }
}


/* ======================================================================
 * Start the "init" (userland) process
 */
static sos_ret_t
start_init(struct sos_fs_manager_instance * rootfs)
{
  sos_ret_t retval;
  struct sos_umem_vmm_as *as_init;
  struct sos_process *proc_init;
  struct sos_thread *new_thr;
  sos_uaddr_t ustack, start_uaddr;
  struct sos_fs_opened_file * init_root, * init_cwd, * unused_of;

  /* Create the new process */
  proc_init = sos_process_create("init", FALSE);
  if (! proc_init)
    return -SOS_ENOMEM;
  as_init = sos_process_get_address_space(proc_init);