setup.c

Windows上的精简Linux系统

  uint8_t pad[105];
} __attribute__((packed));

const struct geometry *get_disk_image_geometry(uint32_t where, uint32_t size)
{
  static struct geometry hd_geometry = { 0, 0, 0, 0, 0, 0, 0x80 };
  struct ptab_entry ptab[4];	/* Partition table buffer */
  struct dosemu_header dosemu;
  unsigned int sectors, v;
  unsigned int max_c, max_h, max_s;
  unsigned int c, h, s, offset;
  int i;
  int drive_specified;
  const char *p;

  printf("command line: %s\n", shdr->cmdline);

  offset = 0;
  if ( CMD_HASDATA(p = getcmditem("offset")) && (v = atou(p)) )
    offset = v;

  sectors = (size-offset) >> 9;
  for ( i = 0 ; i < known_geometries ; i++ ) {
    if ( sectors == geometries[i].sectors ) {
      hd_geometry = geometries[i];
      break;
    }
  }

  hd_geometry.sectors = sectors;
  hd_geometry.offset  = offset;

  /* Do we have a DOSEMU header? */
  memcpy(&dosemu, (char *)where+hd_geometry.offset, sizeof dosemu);
  if ( !__builtin_memcmp("DOSEMU", dosemu.magic, 7) ) {
    /* Always a hard disk unless overruled by command-line options */
    hd_geometry.driveno = 0x80;
    hd_geometry.type = 0;
    hd_geometry.c = dosemu.c;
    hd_geometry.h = dosemu.h;
    hd_geometry.s = dosemu.s;
    hd_geometry.offset += dosemu.offset;
    sectors = (size-hd_geometry.offset) >> 9;
  }

  if ( CMD_HASDATA(p = getcmditem("c")) && (v = atou(p)) )
    hd_geometry.c = v;
  if ( CMD_HASDATA(p = getcmditem("h")) && (v = atou(p)) )
    hd_geometry.h = v;
  if ( CMD_HASDATA(p = getcmditem("s")) && (v = atou(p)) )
    hd_geometry.s = v;
  
  if ( getcmditem("floppy") != CMD_NOTFOUND ) {
    hd_geometry.driveno = 0;
    if ( hd_geometry.type == 0 )
      hd_geometry.type = 0x10;	/* ATAPI floppy, e.g. LS-120 */
    drive_specified = 1;
  } else if ( getcmditem("harddisk") != CMD_NOTFOUND ) {
    hd_geometry.driveno = 0x80;
    hd_geometry.type = 0;
    drive_specified = 1;
  }

  if ( (hd_geometry.c == 0) || (hd_geometry.h == 0) ||
       (hd_geometry.s == 0) ) {
    /* Hard disk image, need to examine the partition table for geometry */
    memcpy(&ptab, (char *)where+hd_geometry.offset+(512-2-4*16), sizeof ptab);
    
    max_c = max_h = 0;  max_s = 1;
    for ( i = 0 ; i < 4 ; i++ ) {
      if ( ptab[i].type ) {
	c = ptab[i].start_c + (ptab[i].start_s >> 6);
	s = (ptab[i].start_s & 0x3f);
	h = ptab[i].start_h;
	
	if ( max_c < c ) max_c = c;
	if ( max_h < h ) max_h = h;
	if ( max_s < s ) max_s = s;
	
	c = ptab[i].end_c + (ptab[i].end_s >> 6);
	s = (ptab[i].end_s & 0x3f);
	h = ptab[i].end_h;
	
	if ( max_c < c ) max_c = c;
	if ( max_h < h ) max_h = h;
	if ( max_s < s ) max_s = s;
      }
    }
    
    max_c++; max_h++;		/* Convert to count (1-based) */
    
    if ( !hd_geometry.h )
      hd_geometry.h = max_h;
    if ( !hd_geometry.s )
      hd_geometry.s = max_s;
    if ( !hd_geometry.c )
      hd_geometry.c = sectors/(hd_geometry.h*hd_geometry.s);
  }

  if ( (size-hd_geometry.offset) & 0x1ff ) {
    puts("MEMDISK: Image has fractional end sector\n");
  }
  if ( sectors % (hd_geometry.h*hd_geometry.s) ) {
    puts("MEMDISK: Image seems to have fractional end cylinder\n");
  }
  if ( (hd_geometry.c*hd_geometry.h*hd_geometry.s) > sectors ) {
    puts("MEMDISK: Image appears to be truncated\n");
  }

  return &hd_geometry;
}

/*
 * Jump here if all hope is gone...
 */
void __attribute__((noreturn)) die(void)
{
  asm volatile("sti");
  for(;;)
    asm volatile("hlt");
}

#define STACK_NEEDED	256	/* Number of bytes of stack */

/*
 * Actual setup routine
 * Returns the drive number (which is then passed in %dl to the
 * called routine.)
 */
syscall_t syscall;
void *sys_bounce;

uint32_t setup(syscall_t cs_syscall, void *cs_bounce)
{
  unsigned int bin_size = (int) &_binary_memdisk_bin_size;
  struct memdisk_header *hptr;
  struct patch_area *pptr;
  uint16_t driverseg;
  uint32_t driverptr, driveraddr;
  uint16_t dosmem_k;
  uint32_t stddosmem;
  const struct geometry *geometry;
  int total_size, cmdlinelen;
  com32sys_t regs;
  uint32_t ramdisk_image, ramdisk_size;

  /* Set up global variables */
  syscall = cs_syscall;
  sys_bounce = cs_bounce;

  /* Show signs of life */
  printf("%s  %s\n", memdisk_version, copyright);

  if ( !shdr->ramdisk_image || !shdr->ramdisk_size ) {
    puts("MEMDISK: No ramdisk image specified!\n");
    die();
  }

  ramdisk_image = shdr->ramdisk_image;
  ramdisk_size  = shdr->ramdisk_size;

  e820map_init();		/* Initialize memory data structure */
  get_mem();			/* Query BIOS for memory map */
  parse_mem();			/* Parse memory map */

  printf("Ramdisk at 0x%08x, length 0x%08x\n",
	 ramdisk_image, ramdisk_size);

  unzip_if_needed(&ramdisk_image, &ramdisk_size);

  geometry = get_disk_image_geometry(ramdisk_image, ramdisk_size);

  printf("Disk is %s, %u K, C/H/S = %u/%u/%u\n",
	 geometry->driveno ? "hard disk" : "floppy",
	 geometry->sectors >> 1,
	 geometry->c, geometry->h, geometry->s);

  /* Reserve the ramdisk memory */
  insertrange(ramdisk_image, ramdisk_size, 2);
  parse_mem();			/* Recompute variables */

  /* Figure out where it needs to go */
  hptr = (struct memdisk_header *) &_binary_memdisk_bin_start;
  pptr = (struct patch_area *)(_binary_memdisk_bin_start + hptr->patch_offs);

  dosmem_k = rdz_16(BIOS_BASEMEM);
  pptr->olddosmem = dosmem_k;
  stddosmem = dosmem_k << 10;
  /* If INT 15 E820 and INT 12 disagree, go with the most conservative */
  if ( stddosmem > dos_mem )
    stddosmem = dos_mem;

  pptr->driveno   = geometry->driveno;
  pptr->drivetype = geometry->type;
  pptr->cylinders = geometry->c;
  pptr->heads     = geometry->h;
  pptr->sectors   = geometry->s;
  pptr->disksize  = geometry->sectors;
  pptr->diskbuf   = ramdisk_image + geometry->offset;
  pptr->statusptr = (geometry->driveno & 0x80) ? 0x474 : 0x441;

  /* Set up a drive parameter table */
  if ( geometry->driveno & 0x80 ) {
    /* Hard disk */
    pptr->dpt.hd.max_cyl  = geometry->c-1;
    pptr->dpt.hd.max_head = geometry->h-1;
    pptr->dpt.hd.ctrl     = (geometry->h > 8) ? 0x08: 0;
  } else {
    /* Floppy - most of these fields are bogus and mimic
       a 1.44 MB floppy drive */
    pptr->dpt.fd.specify1 = 0xdf;
    pptr->dpt.fd.specify2 = 0x02;
    pptr->dpt.fd.delay    = 0x25;
    pptr->dpt.fd.sectors  = geometry->s;
    pptr->dpt.fd.bps      = 0x02;
    pptr->dpt.fd.isgap    = 0x12;
    pptr->dpt.fd.dlen     = 0xff;
    pptr->dpt.fd.fgap     = 0x6c;
    pptr->dpt.fd.ffill    = 0xf6;
    pptr->dpt.fd.settle   = 0x0f;
    pptr->dpt.fd.mstart   = 0x05;

    pptr->dpt.fd.old_fd_dpt = rdz_32(BIOS_INT1E);
  }

  /* The size is given by hptr->total_size plus the size of the E820
     map -- 12 bytes per range; we may need as many as 2 additional
     ranges (each insertrange() can worst-case turn 1 area into 3)
     plus the terminating range, over what nranges currently show. */
  cmdlinelen = strlen(shdr->cmdline)+1;
  total_size  =  hptr->total_size; 		/* Actual memdisk code */
  total_size += (nranges+3)*sizeof(ranges[0]);  /* E820 memory ranges */
  total_size += cmdlinelen;	                /* Command line */
  total_size += STACK_NEEDED;	                /* Stack */
  printf("Total size needed = %u bytes, allocating %uK\n",
	 total_size, (total_size+0x3ff) >> 10);

  if ( total_size > dos_mem ) {
    puts("MEMDISK: Insufficient low memory\n");
    die();
  }

  driveraddr  = stddosmem - total_size;
  driveraddr &= ~0x3FF;

  printf("Old dos memory at 0x%05x (map says 0x%05x), loading at 0x%05x\n",
	 stddosmem, dos_mem, driveraddr);

  /* Reserve this range of memory */
  wrz_16(BIOS_BASEMEM, driveraddr >> 10);
  insertrange(driveraddr, dos_mem-driveraddr, 2);
  parse_mem();

  pptr->mem1mb     = low_mem  >> 10;
  pptr->mem16mb    = high_mem >> 16;
  if ( low_mem == (15 << 20) ) {
    /* lowmem maxed out */
    uint32_t int1588mem = (high_mem >> 10)+(low_mem >> 10);
    pptr->memint1588 = (int1588mem > 0xffff) ? 0xffff : int1588mem;
  } else {
    pptr->memint1588 = low_mem >> 10;
  }

  printf("1588: 0x%04x  15E801: 0x%04x 0x%04x\n",
	 pptr->memint1588, pptr->mem1mb, pptr->mem16mb);

  driverseg = driveraddr >> 4;
  driverptr = driverseg  << 16;

  /* Anything beyond the end is for the stack */
  pptr->mystack    = (uint16_t)(stddosmem-driveraddr);

  pptr->oldint13 = rdz_32(BIOS_INT13);
  pptr->oldint15 = rdz_32(BIOS_INT15);

  /* Adjust the E820 table: if there are null ranges (type 0)
     at the end, change them to type end of list (-1).
     This is necessary for the driver to be able to report end
     of list correctly. */
  while ( nranges && ranges[nranges-1].type == 0 ) {
    ranges[--nranges].type = -1;
  }

  /* Query drive parameters of this type */
  memset(&regs, 0, sizeof regs);
  regs.es = 0;
  regs.eax.b[1] = 0x08;
  regs.edx.b[0] = geometry->driveno;
  syscall(0x13, &regs, &regs);
  
  if ( regs.eflags.l & 1 ) {
    printf("INT 13 08: Failure, assuming this is the only drive\n");
    pptr->drivecnt = 1;
  } else {
    printf("INT 13 08: Success, count = %u, BPT = %04x:%04x\n",
	   regs.edx.b[0], regs.es, regs.edi.w[0]);
    pptr->drivecnt = regs.edx.b[0]+1;
  }

  /* Pointer to the command line */
  pptr->cmdline_off = bin_size + (nranges+1)*sizeof(ranges[0]);
  pptr->cmdline_seg = driverseg;

  /* Copy driver followed by E820 table followed by command line */
  {
    unsigned char *dpp = (unsigned char *)(driverseg << 4);
    dpp = memcpy_endptr(dpp, &_binary_memdisk_bin_start, bin_size);
    dpp = memcpy_endptr(dpp, ranges, (nranges+1)*sizeof(ranges[0]));
    dpp = memcpy_endptr(dpp, shdr->cmdline, cmdlinelen+1);
  }

  /* Install the interrupt handlers */
  printf("old: int13 = %08x  int15 = %08x\n",
	 rdz_32(BIOS_INT13), rdz_32(BIOS_INT15));
  
  wrz_32(BIOS_INT13, driverptr+hptr->int13_offs);
  wrz_32(BIOS_INT15, driverptr+hptr->int15_offs);
  
  printf("new: int13 = %08x  int15 = %08x\n",
	 rdz_32(BIOS_INT13), rdz_32(BIOS_INT15));

  /* Update various BIOS magic data areas (gotta love this shit) */

  if ( geometry->driveno & 0x80 ) {
    /* Update BIOS hard disk count */
    wrz_8(BIOS_HD_COUNT, rdz_8(BIOS_HD_COUNT)+1);
  } else {
    /* Update BIOS floppy disk count */
    uint8_t equip = rdz_8(BIOS_EQUIP);
    if ( equip & 1 ) {
      if ( (equip & (3 << 6)) != (3 << 6) ) {
	equip += (1 << 6);
      }
    } else {
      equip |= 1;
      equip &= ~(3 << 6);
    }
    wrz_8(BIOS_EQUIP, equip);
  }

  /* Reboot into the new "disk"; this is also a test for the interrupt hooks */
  puts("Loading boot sector... ");

  memset(&regs, 0, sizeof regs);
  // regs.es = 0;
  regs.eax.w[0] = 0x0201;	/* Read sector */
  regs.ebx.w[0] = 0x7c00;	/* 0000:7C00 */
  regs.ecx.w[0] = 1;		/* One sector */
  regs.edx.w[0] = geometry->driveno;
  syscall(0x13, &regs, &regs);

  if ( regs.eflags.l & 1 ) {
    puts("MEMDISK: Failed to load new boot sector\n");
    die();
  }
  
  if ( getcmditem("pause") != CMD_NOTFOUND ) {
    puts("press any key to boot... ");
    regs.eax.w[0] = 0;
    syscall(0x16, &regs, NULL);
  }

  puts("booting...\n");

  /* On return the assembly code will jump to the boot vector */
  return geometry->driveno;
}