media/doc/HACKING

   1 * Introduction
   2
   3 Having successfully built ReactOS and been amazed by what it does, you're
   4 now desperate to fill in some of the omissions, this document shows you how.
   5
   6 * Prerequisites
   7
   8 A working knowledge of NT driver development is useful for understanding the
   9 kernel and some of its abstractions. The NT4 ddk is available for free
  10 download from http://www.microsoft.com/hwdev/. The Windows 98 and Windows
  11 2000 DDKs are also available but the NT4 one is the most useful. See
  12 Legal Stuff below however.
  13
  14 There are a number of books on NT driver development, I would recommend
  15 'Windows NT Device Driver Development' (http://www.osr.com/book/) since OSR
  16 seem to know their stuff. There is only one book on NT filesystem
  17 development 'Windows NT File System Internals'. Please don't buy any of
  18 these books unless you need to, and can afford it.
  19
  20 These mailing lists and newsgroups are useful for NT internals related
  21 questions,
  22            ntfsd@atria.com, ntdev@atria.com
  23                             (subscribe by email to majordomo@atria.com)
  24            comp.os.????
  25            microsoft.public.????
  26
  27 * Style
  28
  29 There is a coding style used for ReactOS, it's described in a ReactOS's Wiki
  30 page called Coding Style: http://www.reactos.org/wiki/index.php/Coding_Style
  31
  32 However, not all codebase complies with the rules outlined in that page, so
  33 if you need to hack some code which has not been yet formatted, it's wise
  34 to keep the kind of formatting it already has, to make it looking good until
  35 it receives a formatting patch.
  36
  37
  38 * Debugging
  39
  40 Debugging kernel-mode code is tricky, these are some snippets
  41
  42     DbgPrint writes a message to the console using a printf style format
  43     string. The DPRINT macro (defined in internal/debug.h) expands to
  44     DbgPrint unless NDEBUG is defined, this is useful for having copious
  45     output from a module only when a problem is being debugging. DPRINT
  46     also prefixes the message with the file and line number to make it
  47     easier to see where output is coming from. DbgPrint can be used at any
  48     point including in interrupt handlers.
  49
  50     There are options in ntoskrnl/kd/kdebug.c for copying DbgPrint output
  51     to a serial device or bochs logging port (parallel support should also
  52     be added). This can be useful if a lot of output is being generated.
  53
  54     It should be possible to include support for debugging the kernel with
  55     gdb over a serial line. Bochs (a shareware CPU emulator) is also useful
  56     for debugging the kernel, I wrote some patches to allow capture of console
  57     output from within bochs to file and for debugging a kernel running
  58     under bochs with gdb. Contact me (welch@cwcom.net) if you're are
  59     interested.
  60
  61     If CPU reports an exception not handled by the kernel (any page fault
  62     not part of virtual memory support or any other exception) the kernel
  63     will display output like this and halt
  64
  65             General Protection Fault Exception: 13(0)
  66             CS:EIP  xxxxxxxx:xxxxxxx
  67             DS xxxx ES xxxx FS xxxx GS xxxxx
  68             EAX: xxxx EBX: xxxx
  69             ....
  70             EDI: xxxx EFLAGS: xxxx ESP: xxxx
  71             cr2: xxxx
  72             Stack: xxxx xxxx xxxx ...
  73                    ....
  74             Frames: xxxx xxxx xxxx ...
  75                    ....
  76
  77     The fault type will usually be either 'General Protection' or
  78     'Page Fault', see your Intel manual for the more exotic types. The
  79     'EIP' number is the address of the faulting instruction. If the 'CS'
  80     number is 0x20 then the exception occured in kernel mode, if it is 0x11
  81     then the exception occurred in user mode. 'cr2' is the address that the
  82     faulting instruction was trying to access, if the exception was a page
  83     fault. The number printed after 'Frames' are any addresses on the stack
  84     that look like function addresses.
  85
  86
  87     If the kernel detects a serious problem that it will bug check, displaying
  88     output like this
  89
  90            Bug detected (code x, param x x x x)
  91            Frames: xxx xxxx xxxx
  92                    ....
  93
  94     Again the numbers printed after 'Frames' are any addresses on the stack
  95     that look like function addresss. Usually the kernel will also print a
  96     message describing the problem in more detail, the bug check code isn't
  97     very useful at the moment.
  98
  99 * Contacts
 100
 101     There is a mailing list for kernel development,
 102
 103             ros-dev@reactos.org
 104
 105     The main developers use a svn account to coordinate changes, ask
 106     Aleksey (aleksey@reactos.org) for an account if you are going to be
 107     adding a lot of code. Smaller patches can go to the mailing list or to the
 108     relevant developer (usually the comment at the top of a module will have
 109     an email address). Regular snapshots are made available for download,
 110     see the mailing list for announcements.
 111
 112 * Legal stuff
 113
 114     The ReactOS project is GPL'ed, please make sure any code submitted is
 115     compatible with this.
 116
 117     The NT4 ddk license agreement allows its usage for developing nt drivers
 118     only. Legally therefore it can not be used to develop ReactOS, neither the
 119     documentation or the sample code. I'm not a lawyer, but I doubt the
 120     effiacy of 'shrinkwrap licenses' particularly on freely downloadable
 121     software. The only precendent I know of, in a Scottish court, didn't
 122     upload this type of license.
 123
 124     Also the 'fair use' section of copyright law allows the 'quoting' of small
 125     sections from copyrighted documents, e.g. Windows API or DDK documentation