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HACKING
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HACKING
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* Introduction
Having successfully built ReactOS and been amazed by what it does, you're
now desperate to fill in some of the omissions, this document shows you how.
* Prerequisites
A working knowledge of NT driver development is useful for understanding the
kernel and some of its abstractions. The NT4 ddk is available for free
download from http://www.microsoft.com/hwdev/. The Windows 98 and Windows
2000 DDKs are also available but the NT4 one is the most useful. See
Legal Stuff below however.
There are a number of books on NT driver development, I would recommend
'Windows NT Device Driver Development' (http://www.osr.com/book/) since OSR
seem to know their stuff. There is only one book on NT filesystem
development 'Windows NT File System Internals'. Please don't buy any of
these books unless you need to, and can afford it.
These mailing lists and newsgroups are useful for NT internals related
questions,
ntfsd@atria.com, ntdev@atria.com
(subscribe by email to majordomo@atria.com)
comp.os.????
microsoft.public.????
* Style
There is a coding style used for ReactOS, it's described in a ReactOS's Wiki
page called Coding Style: http://www.reactos.org/wiki/index.php/Coding_Style
However, not all codebase complies with the rules outlined in that page, so
if you need to hack some code which has not been yet formatted, it's wise
to keep the kind of formatting it already has, to make it looking good until
it receives a formatting patch.
* Debugging
Debugging kernel-mode code is tricky, these are some snippets
DbgPrint writes a message to the console using a printf style format
string. The DPRINT macro (defined in internal/debug.h) expands to
DbgPrint unless NDEBUG is defined, this is useful for having copious
output from a module only when a problem is being debugging. DPRINT
also prefixes the message with the file and line number to make it
easier to see where output is coming from. DbgPrint can be used at any
point including in interrupt handlers.
There are options in ntoskrnl/kd/kdebug.c for copying DbgPrint output
to a serial device or bochs logging port (parallel support should also
be added). This can be useful if a lot of output is being generated.
It should be possible to include support for debugging the kernel with
gdb over a serial line. Bochs (a shareware CPU emulator) is also useful
for debugging the kernel, I wrote some patches to allow capture of console
output from within bochs to file and for debugging a kernel running
under bochs with gdb. Contact me (welch@cwcom.net) if you're are
interested.
If CPU reports an exception not handled by the kernel (any page fault
not part of virtual memory support or any other exception) the kernel
will display output like this and halt
General Protection Fault Exception: 13(0)
CS:EIP xxxxxxxx:xxxxxxx
DS xxxx ES xxxx FS xxxx GS xxxxx
EAX: xxxx EBX: xxxx
....
EDI: xxxx EFLAGS: xxxx ESP: xxxx
cr2: xxxx
Stack: xxxx xxxx xxxx ...
....
Frames: xxxx xxxx xxxx ...
....
The fault type will usually be either 'General Protection' or
'Page Fault', see your Intel manual for the more exotic types. The
'EIP' number is the address of the faulting instruction. If the 'CS'
number is 0x20 then the exception occured in kernel mode, if it is 0x11
then the exception occurred in user mode. 'cr2' is the address that the
faulting instruction was trying to access, if the exception was a page
fault. The number printed after 'Frames' are any addresses on the stack
that look like function addresses.
If the kernel detects a serious problem that it will bug check, displaying
output like this
Bug detected (code x, param x x x x)
Frames: xxx xxxx xxxx
....
Again the numbers printed after 'Frames' are any addresses on the stack
that look like function addresss. Usually the kernel will also print a
message describing the problem in more detail, the bug check code isn't
very useful at the moment.
* Contacts
There is a mailing list for kernel development,
ros-dev@reactos.org
The main developers use a svn account to coordinate changes, ask
Aleksey (aleksey@reactos.org) for an account if you are going to be
adding a lot of code. Smaller patches can go to the mailing list or to the
relevant developer (usually the comment at the top of a module will have
an email address). Regular snapshots are made available for download,
see the mailing list for announcements.
* Legal stuff
The ReactOS project is GPL'ed, please make sure any code submitted is
compatible with this.
The NT4 ddk license agreement allows its usage for developing nt drivers
only. Legally therefore it can not be used to develop ReactOS, neither the
documentation or the sample code. I'm not a lawyer, but I doubt the
effiacy of 'shrinkwrap licenses' particularly on freely downloadable
software. The only precendent I know of, in a Scottish court, didn't
upload this type of license.
Also the 'fair use' section of copyright law allows the 'quoting' of small
sections from copyrighted documents, e.g. Windows API or DDK documentation