Re: Linux syscalls

From: Beth (BethStone21_at_hotmail.NOSPICEDHAM.com)
Date: 06/09/04

  • Next message: rjb: "Re: Locked memory" 
    Date: Wed, 9 Jun 2004 00:41:05 +0100

    Arargh wrote:
    > ntldr (NT4 version) makes NO Int 21h calls. It also enters
    protected
    > mode, which is unlikely for a DOS program. It is a mixed-mode
    16bit
    > real and 32bit protected program from what a quick look tells
    me.
    >
    > IMO, a stand alone program.

    In fact, that sounds like the _perfect description_ of an "OS
    loader" program...

    A raw binary file that doesn't access any OS routines (because,
    being the OS loader, it runs _prior_ to the OS existing - hence
    can't access any OS, obviously - so can only use BIOS and direct
    access)...and then is "mixed 16 / 32 bit code" for making that
    "protected mode switch" from the real mode that the PC naturally
    boots into to 32-bit protected mode that the NT kernel runs
    under...plus, the mnemonical name "NTLDR" is also strongly
    backing this up as most likely standing for: "NT's LOADER"...

    Basically, "NTLDR" is NT's actual OS loader binary file that the
    bootsector loads and transfers control to (after all, a
    bootsector can only be 512 bytes so it can't do the whole
    process for any non-trivial OS in such a small space...well,
    instead, it can load a second file from disk to actually do the
    real OS loading process...a "loader" program..."IO.SYS" used to
    do this with DOS, "NTLDR" does it with NT :)..."BOOT.INI" is, as
    can be seen with Notepad, the actual plain text file with ".ini"
    configuration text for the list of OSes under the "bootmenu" (a
    menu by-passed if there's only one OS installed but a website I
    read suggested that this is one of "NTLDR"'s jobs in printing
    out the "bootmenu" as well as then actually proceeding to load
    the OSes selected from the menu)...

    "NTDETECT.COM" does play a part in this somewhere but I don't
    know exactly what...

    The other files there, though, are, in most cases, basically
    "backwards compatibility"...the "0 bytes" file size being a clue
    that they _can't_ be doing anything because, really, they aren't
    even files...they are more like "placeholder filenames"...just
    directory entries without any actual data file attached...

    Beth :)

  • Next message: rjb: "Re: Locked memory"

    Relevant Pages

    • Re: cloning to a larger drive
      ... *loaded* by a loader that resides on the internal HD, ... and it doesn't make a list of attached hard drives ... minimal OS to load those drivers. ... or a live USB stick tell ntldr how to find the ExpressCard- ...
      (microsoft.public.windowsxp.general)
    • Re: Switching from GRUB to NTLDR
      ... NTLDR uses files to load the boot managers ... You don't have to "reinstall" GRUB ... and it can load all the other OS'es then why make NTLDR the loader? ...
      (Fedora)
    • Re: C 16 bit compiler
      ... first block can't just go and load as many more blocks as it wants to. ... usually in the partition table loader. ... the kernel itself). ...
      (comp.compilers)
    • Problems PXE installing 5.X on RLX Blade
      ... Its like its not finding or able to load the next module in the chain ... echo Loading Kernel... ... IntelBoot Agent Version 4.0.17 ... Building the boot loader arguments ...
      (freebsd-current)
    • Re: Simple Bootloader to Run C program
      ... and get the bootload code to run it. ... A Multiboot loader will load ELF (e.g., produced by GNU toolchain or Unix ... or .coff or ELF .obj's and executables directly. ...
      (comp.lang.asm.x86)