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• #3 Pizzafutar aktív tag Pizzafutar #2

  2004-07-27 00:05:08 #3

  Összes hozzászólása itt Válaszok az összes hozzászólására itt Válaszok erre a hozzászólásra

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  Pizzafutar

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  válasz Pizzafutar #2 üzenetére

  Na, ha senki nem szolt hozza, akkor ide másolom a kérdéses részt.
  arch/i386/boot/setup.S
  
  # Well, now's the time to actually move into protected mode. To make
  # things as simple as possible, we do no register set-up or anything,
  # we let the gnu-compiled 32-bit programs do that. We just jump to
  # absolute address 0x1000 (or the loader supplied one),
  # in 32-bit protected mode.
  #
  # Note that the short jump isn't strictly needed, although there are
  # reasons why it might be a good idea. It won't hurt in any case.
  movw $1, %ax # protected mode (PE) bit
  lmsw %ax # This is it!
  jmp flush_instr
  
  flush_instr:
  xorw %bx, %bx # Flag to indicate a boot
  xorl %esi, %esi # Pointer to real-mode code
  movw %cs, %si
  subw $DELTA_INITSEG, %si
  shll $4, %esi # Convert to 32-bit pointer
  
  # jump to startup_32 in arch/i386/boot/compressed/head.S
  #
  # NOTE: For high loaded big kernels we need a
  # jmpi 0x100000,__BOOT_CS
  #
  # but we yet haven't reloaded the CS register, so the default size
  # of the target offset still is 16 bit.
  # However, using an operand prefix (0x66), the CPU will properly
  # take our 48 bit far pointer. (INTeL 80386 Programmer's Reference
  # Manual, Mixing 16-bit and 32-bit code, page 16-6)
  
  .byte 0x66, 0xea # prefix + jmpi-opcode
  code32: .long 0x1000 # will be set to 0x100000
  # for big kernels
  

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