KD System Rewrite:
[reactos.git] / reactos / 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 no coding style used for ReactOS, however the following guidelines
30 make things easier
31
32 Include information at the top of a module about its purpose, contact
33 information for its programmer and any useful notes.
34
35 Include a comment by each non-trival function describing its arguments,
36 purpose and any other notes.
37
38 Update the documentation in this directory
39
40 These guidelines are an ideal, no one manages to implement them all the
41 time, straightforward working code is probably just as good.
42
43 * Debugging
44
45 Debugging kernel-mode code is tricky, these are some snippets
46
47 DbgPrint writes a message to the console using a printf style format
48 string. The DPRINT macro (defined in internal/debug.h) expands to
49 DbgPrint unless NDEBUG is defined, this is useful for having copious
50 output from a module only when a problem is being debugging. DPRINT
51 also prefixes the message with the file and line number to make it
52 easier to see where output is coming from. DbgPrint can be used at any
53 point including in interrupt handlers.
54
55 There are options in ntoskrnl/kd/kdebug.c for copying DbgPrint output
56 to a serial device or bochs logging port (parallel support should also
57 be added). This can be useful if a lot of output is being generated.
58
59 It should be possible to include support for debugging the kernel with
60 gdb over a serial line. Bochs (a shareware CPU emulator) is also useful
61 for debugging the kernel, I wrote some patches to allow capture of console
62 output from within bochs to file and for debugging a kernel running
63 under bochs with gdb. Contact me (welch@cwcom.net) if you're are
64 interested.
65
66 If CPU reports an exception not handled by the kernel (any page fault
67 not part of virtual memory support or any other exception) the kernel
68 will display output like this and halt
69
70 General Protection Fault Exception: 13(0)
71 CS:EIP xxxxxxxx:xxxxxxx
72 DS xxxx ES xxxx FS xxxx GS xxxxx
73 EAX: xxxx EBX: xxxx
74 ....
75 EDI: xxxx EFLAGS: xxxx ESP: xxxx
76 cr2: xxxx
77 Stack: xxxx xxxx xxxx ...
78 ....
79 Frames: xxxx xxxx xxxx ...
80 ....
81
82 The fault type will usually be either 'General Protection' or
83 'Page Fault', see your Intel manual for the more exotic types. The
84 'EIP' number is the address of the faulting instruction. If the 'CS'
85 number is 0x20 then the exception occured in kernel mode, if it is 0x11
86 then the exception occurred in user mode. 'cr2' is the address that the
87 faulting instruction was trying to access, if the exception was a page
88 fault. The number printed after 'Frames' are any addresses on the stack
89 that look like function addresses.
90
91
92 If the kernel detects a serious problem that it will bug check, displaying
93 output like this
94
95 Bug detected (code x, param x x x x)
96 Frames: xxx xxxx xxxx
97 ....
98
99 Again the numbers printed after 'Frames' are any addresses on the stack
100 that look like function addresss. Usually the kernel will also print a
101 message describing the problem in more detail, the bug check code isn't
102 very useful at the moment.
103
104 * Contacts
105
106 There is a mailing list for kernel development,
107
108 ros-kernel@reactos.com
109
110 The main developers use a cvs account to coordinate changes, ask
111 rex (rex@lvcablemodem.com) for an account if you are going to be adding
112 a lot of code. Smaller patches can go to the mailing list or to the
113 relevant developer (usually the comment at the top of a module will have
114 an email address). Regular snapshots are made available for download,
115 see the mailing list for announcements.
116
117 * Legal stuff
118
119 The ReactOS project is GPL'ed, please make sure any code submitted is
120 compatible with this.
121
122 The NT4 ddk license agreement allows its usage for developing nt drivers
123 only. Legally therefore it can not be used to develop ReactOS, neither the
124 documentation or the sample code. I'm not a lawyer, but I doubt the
125 effiacy of 'shrinkwrap licenses' particularly on freely downloadable
126 software. The only precendent I know of, in a Scottish court, didn't
127 upload this type of license.
128
129 Also the 'fair use' section of copyright law allows the 'quoting' of small
130 sections from copyrighted documents, e.g. Windows API or DDK documentation