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<chapter id="implementation">
<title>Low-level Implementation</title>
<para>Details of Wine's Low-level Implementation...</para>
<sect1 id="config-keyboard">
<title>Keyboard</title>
<para>
Wine now needs to know about your keyboard layout. This
requirement comes from a need from many apps to have the
correct scancodes available, since they read these directly,
instead of just taking the characters returned by the X
server. This means that Wine now needs to have a mapping from
X keys to the scancodes these programs expect.
</para>
<para>
On startup, Wine will try to recognize the active X layout by
seeing if it matches any of the defined tables. If it does,
everything is alright. If not, you need to define it.
</para>
<para>
To do this, open the file
<filename>dlls/x11drv/keyboard.c</filename> and take a look
at the existing tables. Make a backup copy of it, especially
if you don't use CVS.
</para>
<para>
What you really would need to do, is find out which scancode
each key needs to generate. Find it in the
<function>main_key_scan</function> table, which looks like
this:
</para>
<programlisting>
static const int main_key_scan[MAIN_LEN] =
{
/* this is my (102-key) keyboard layout, sorry if it doesn't quite match yours */
0x29,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,
0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,
0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,0x2B,
0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0x34,0x35,
0x56 /* the 102nd key (actually to the right of l-shift) */
};
</programlisting>
<para>
Next, assign each scancode the characters imprinted on the
keycaps. This was done (sort of) for the US 101-key keyboard,
which you can find near the top in
<filename>keyboard.c</filename>. It also shows that if there
is no 102nd key, you can skip that.
</para>
<para>
However, for most international 102-key keyboards, we have
done it easy for you. The scancode layout for these already
pretty much matches the physical layout in the
<function>main_key_scan</function>, so all you need to do is
to go through all the keys that generate characters on your
main keyboard (except spacebar), and stuff those into an
appropriate table. The only exception is that the 102nd key,
which is usually to the left of the first key of the last line
(usually <keycap>Z</keycap>), must be placed on a separate
line after the last line.
</para>
<para>
For example, my Norwegian keyboard looks like this
</para>
<screen>
<EFBFBD> ! " # <20> % & / ( ) = ? ` Back-
| 1 2@ 3<> 4$ 5 6 7{ 8[ 9] 0} + \<5C> space
Tab Q W E R T Y U I O P <20> ^
<20>~
Enter
Caps A S D F G H J K L <20> <20> *
Lock '
Sh- > Z X C V B N M ; : _ Shift
ift &lt; , . -
Ctrl Alt Spacebar AltGr Ctrl
</screen>
<para>
Note the 102nd key, which is the <keycap>&lt;></keycap> key, to
the left of <keycap>Z</keycap>. The character to the right of
the main character is the character generated by
<keycap>AltGr</keycap>.
</para>
<para>
This keyboard is defined as follows:
</para>
<programlisting>
static const char main_key_NO[MAIN_LEN][4] =
{
"|<7C>","1!","2\"@","3#<23>","4<>$","5%","6&","7/{","8([","9)]","0=}","+?","\\<5C>",
"qQ","wW","eE","rR","tT","yY","uU","iI","oO","pP","<22><>","<22>^~",
"aA","sS","dD","fF","gG","hH","jJ","kK","lL","<22><>","<22><>","'*",
"zZ","xX","cC","vV","bB","nN","mM",",;",".:","-_",
"&lt;>"
};
</programlisting>
<para>
Except that " and \ needs to be quoted with a backslash, and
that the 102nd key is on a separate line, it's pretty
straightforward.
</para>
<para>
After you have written such a table, you need to add it to the
<function>main_key_tab[]</function> layout index table. This
will look like this:
</para>
<programlisting>
static struct {
WORD lang, ansi_codepage, oem_codepage;
const char (*key)[MAIN_LEN][4];
} main_key_tab[]={
...
...
{MAKELANGID(LANG_NORWEGIAN,SUBLANG_DEFAULT), 1252, 865, &amp;main_key_NO},
...
</programlisting>
<para>
After you have added your table, recompile Wine and test that
it works. If it fails to detect your table, try running
</para>
<screen>
WINEDEBUG=+key,+keyboard wine > key.log 2>&1
</screen>
<para>
and look in the resulting <filename>key.log</filename> file to
find the error messages it gives for your layout.
</para>
<para>
Note that the <constant>LANG_*</constant> and
<constant>SUBLANG_*</constant> definitions are in
<filename>include/winnls.h</filename>, which you might need to
know to find out which numbers your language is assigned, and
find it in the WINEDEBUG output. The numbers will be
<literal>(SUBLANG * 0x400 + LANG)</literal>, so, for example
the combination <literal>LANG_NORWEGIAN (0x14)</literal> and
<literal>SUBLANG_DEFAULT (0x1)</literal> will be (in hex)
<literal>14 + 1*400 = 414</literal>, so since I'm Norwegian, I
could look for <literal>0414</literal> in the WINEDEBUG output
to find out why my keyboard won't detect.
</para>
<para>
Once it works, submit it to the Wine project. If you use CVS,
you will just have to do
</para>
<screen>
cvs -z3 diff -u dlls/x11drv/keyboard.c > layout.diff
</screen>
<para>
from your main Wine directory, then submit
<filename>layout.diff</filename> to
<email>wine-patches@winehq.org</email> along with a brief note
of what it is.
</para>
<para>
If you don't use CVS, you need to do
</para>
<screen>
diff -u the_backup_file_you_made dlls/x11drv/keyboard.c > layout.diff
</screen>
<para>
and submit it as explained above.
</para>
<para>
If you did it right, it will be included in the next Wine
release, and all the troublesome programs (especially
remote-control programs) and games that use scancodes will
be happily using your keyboard layout, and you won't get those
annoying fixme messages either.
</para>
</sect1>
<sect1 id="undoc-func">
<title>Undocumented APIs</title>
<para>
Some background: On the i386 class of machines, stack entries are
usually dword (4 bytes) in size, little-endian. The stack grows
downward in memory. The stack pointer, maintained in the
<literal>esp</literal> register, points to the last valid entry;
thus, the operation of pushing a value onto the stack involves
decrementing <literal>esp</literal> and then moving the value into
the memory pointed to by <literal>esp</literal>
(i.e., <literal>push p</literal> in assembly resembles
<literal>*(--esp) = p;</literal> in C). Removing (popping)
values off the stack is the reverse (i.e., <literal>pop p</literal>
corresponds to <literal>p = *(esp++);</literal> in C).
</para>
<para>
In the <literal>stdcall</literal> calling convention, arguments are
pushed onto the stack right-to-left. For example, the C call
<function>myfunction(40, 20, 70, 30);</function> is expressed in
Intel assembly as:
<screen>
push 30
push 70
push 20
push 40
call myfunction
</screen>
The called function is responsible for removing the arguments
off the stack. Thus, before the call to myfunction, the
stack would look like:
<screen>
[local variable or temporary]
[local variable or temporary]
30
70
20
esp -> 40
</screen>
After the call returns, it should look like:
<screen>
[local variable or temporary]
esp -> [local variable or temporary]
</screen>
</para>
<para>
To restore the stack to this state, the called function must know how
many arguments to remove (which is the number of arguments it takes).
This is a problem if the function is undocumented.
</para>
<para>
One way to attempt to document the number of arguments each function
takes is to create a wrapper around that function that detects the
stack offset. Essentially, each wrapper assumes that the function will
take a large number of arguments. The wrapper copies each of these
arguments into its stack, calls the actual function, and then calculates
the number of arguments by checking esp before and after the call.
</para>
<para>
The main problem with this scheme is that the function must actually
be called from another program. Many of these functions are seldom
used. An attempt was made to aggressively query each function in a
given library (<filename>ntdll.dll</filename>) by passing 64 arguments,
all 0, to each function. Unfortunately, Windows NT quickly goes to a
blue screen of death, even if the program is run from a
non-administrator account.
</para>
<para>
Another method that has been much more successful is to attempt to
figure out how many arguments each function is removing from the
stack. This instruction, <literal>ret hhll</literal> (where
<symbol>hhll</symbol> is the number of bytes to remove, i.e. the
number of arguments times 4), contains the bytes
<literal>0xc2 ll hh</literal> in memory. It is a reasonable
assumption that few, if any, functions take more than 16 arguments;
therefore, simply searching for
<literal>hh == 0 && ll &lt; 0x40</literal> starting from the
address of a function yields the correct number of arguments most
of the time.
</para>
<para>
Of course, this is not without errors. <literal>ret 00ll</literal>
is not the only instruction that can have the byte sequence
<literal>0xc2 ll 0x0</literal>; for example,
<literal>push 0x000040c2</literal> has the byte sequence
<literal>0x68 0xc2 0x40 0x0 0x0</literal>, which matches
the above. Properly, the utility should look for this sequence
only on an instruction boundary; unfortunately, finding
instruction boundaries on an i386 requires implementing a full
disassembler -- quite a daunting task. Besides, the probability
of having such a byte sequence that is not the actual return
instruction is fairly low.
</para>
<para>
Much more troublesome is the non-linear flow of a function. For
example, consider the following two functions:
<screen>
somefunction1:
jmp somefunction1_impl
somefunction2:
ret 0004
somefunction1_impl:
ret 0008
</screen>
In this case, we would incorrectly detect both
<function>somefunction1</function> and
<function>somefunction2</function> as taking only a single
argument, whereas <function>somefunction1</function> really
takes two arguments.
</para>
<para>
With these limitations in mind, it is possible to implement more stubs
in Wine and, eventually, the functions themselves.
</para>
</sect1>
<sect1 id="accel-impl">
<title>Accelerators</title>
<para>
There are <emphasis>three</emphasis> differently sized
accelerator structures exposed to the user:
</para>
<orderedlist>
<listitem>
<para>
Accelerators in NE resources. This is also the internal
layout of the global handle <type>HACCEL</type> (16 and
32) in Windows 95 and Wine. Exposed to the user as Win16
global handles <type>HACCEL16</type> and
<type>HACCEL32</type> by the Win16/Win32 API.
These are 5 bytes long, with no padding:
<programlisting>
BYTE fVirt;
WORD key;
WORD cmd;
</programlisting>
</para>
</listitem>
<listitem>
<para>
Accelerators in PE resources. They are exposed to the user
only by direct accessing PE resources.
These have a size of 8 bytes:
</para>
<programlisting>
BYTE fVirt;
BYTE pad0;
WORD key;
WORD cmd;
WORD pad1;
</programlisting>
</listitem>
<listitem>
<para>
Accelerators in the Win32 API. These are exposed to the
user by the <function>CopyAcceleratorTable</function>
and <function>CreateAcceleratorTable</function> functions
in the Win32 API.
These have a size of 6 bytes:
</para>
<programlisting>
BYTE fVirt;
BYTE pad0;
WORD key;
WORD cmd;
</programlisting>
</listitem>
</orderedlist>
<para>
Why two types of accelerators in the Win32 API? We can only
guess, but my best bet is that the Win32 resource compiler
can/does not handle struct packing. Win32 <type>ACCEL</type>
is defined using <function>#pragma(2)</function> for the
compiler but without any packing for RC, so it will assume
<function>#pragma(4)</function>.
</para>
</sect1>
<sect1 id="hardware-trace">
<title>Doing A Hardware Trace</title>
<para>
The primary reason to do this is to reverse engineer a
hardware device for which you don't have documentation, but
can get to work under Wine.
</para>
<para>
This lot is aimed at parallel port devices, and in particular
parallel port scanners which are now so cheap they are
virtually being given away. The problem is that few
manufactures will release any programming information which
prevents drivers being written for Sane, and the traditional
technique of using DOSemu to produce the traces does not work
as the scanners invariably only have drivers for Windows.
</para>
<para>
Presuming that you have compiled and installed wine the first
thing to do is is to enable direct hardware access to your
parallel port. To do this edit <filename>config</filename>
(usually in <filename>~/.wine/</filename>) and in the
ports section add the following two lines
</para>
<programlisting>
read=0x378,0x379,0x37a,0x37c,0x77a
write=0x378,x379,0x37a,0x37c,0x77a
</programlisting>
<para>
This adds the necessary access required for SPP/PS2/EPP/ECP
parallel port on LPT1. You will need to adjust these number
accordingly if your parallel port is on LPT2 or LPT0.
</para>
<para>
When starting wine use the following command line, where
<literal>XXXX</literal> is the program you need to run in
order to access your scanner, and <literal>YYYY</literal> is
the file your trace will be stored in:
</para>
<programlisting>
WINEDEBUG=+io wine XXXX 2&gt; &gt;(sed 's/^[^:]*:io:[^ ]* //' &gt; YYYY)
</programlisting>
<para>
You will need large amounts of hard disk space (read hundreds
of megabytes if you do a full page scan), and for reasonable
performance a really fast processor and lots of RAM.
</para>
<para>
You will need to postprocess the output into a more manageable
format, using the <command>shrink</command> program. First
you need to compile the source (which is located at the end of
this section):
<programlisting>
cc shrink.c -o shrink
</programlisting>
</para>
<para>
Use the <command>shrink</command> program to reduce the
physical size of the raw log as follows:
</para>
<programlisting>
cat log | shrink &gt; log2
</programlisting>
<para>
The trace has the basic form of
</para>
<programlisting>
XXXX &gt; YY @ ZZZZ:ZZZZ
</programlisting>
<para>
where <literal>XXXX</literal> is the port in hexadecimal being
accessed, <literal>YY</literal> is the data written (or read)
from the port, and <literal>ZZZZ:ZZZZ</literal> is the address
in memory of the instruction that accessed the port. The
direction of the arrow indicates whether the data was written
or read from the port.
</para>
<programlisting>
&gt; data was written to the port
&lt; data was read from the port
</programlisting>
<para>
My basic tip for interpreting these logs is to pay close
attention to the addresses of the IO instructions. Their
grouping and sometimes proximity should reveal the presence of
subroutines in the driver. By studying the different versions
you should be able to work them out. For example consider the
following section of trace from my UMAX Astra 600P
</para>
<programlisting>
0x378 &gt; 55 @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
0x378 &gt; aa @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
0x378 &gt; 00 @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
0x378 &gt; 00 @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
0x378 &gt; 00 @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
0x378 &gt; 00 @ 0297:01ec
0x37a &gt; 05 @ 0297:01f5
0x379 &lt; 8f @ 0297:01fa
0x37a &gt; 04 @ 0297:0211
</programlisting>
<para>
As you can see there is a repeating structure starting at
address <literal>0297:01ec</literal> that consists of four io
accesses on the parallel port. Looking at it the first io
access writes a changing byte to the data port the second
always writes the byte <literal>0x05</literal> to the control
port, then a value which always seems to
<literal>0x8f</literal> is read from the status port at which
point a byte <literal>0x04</literal> is written to the control
port. By studying this and other sections of the trace we can
write a C routine that emulates this, shown below with some
macros to make reading/writing on the parallel port easier to
read.
</para>
<programlisting>
#define r_dtr(x) inb(x)
#define r_str(x) inb(x+1)
#define r_ctr(x) inb(x+2)
#define w_dtr(x,y) outb(y, x)
#define w_str(x,y) outb(y, x+1)
#define w_ctr(x,y) outb(y, x+2)
/* Seems to be sending a command byte to the scanner */
int udpp_put(int udpp_base, unsigned char command)
{
int loop, value;
w_dtr(udpp_base, command);
w_ctr(udpp_base, 0x05);
for (loop=0; loop &lt; 10; loop++)
if ((value = r_str(udpp_base)) & 0x80)
{
w_ctr(udpp_base, 0x04);
return value & 0xf8;
}
return (value & 0xf8) | 0x01;
}
</programlisting>
<para>
For the UMAX Astra 600P only seven such routines exist (well
14 really, seven for SPP and seven for EPP). Whether you
choose to disassemble the driver at this point to verify the
routines is your own choice. If you do, the address from the
trace should help in locating them in the disassembly.
</para>
<para>
You will probably then find it useful to write a script/perl/C
program to analyse the logfile and decode them futher as this
can reveal higher level grouping of the low level routines.
For example from the logs from my UMAX Astra 600P when decoded
further reveal (this is a small snippet)
</para>
<programlisting>
start:
put: 55 8f
put: aa 8f
put: 00 8f
put: 00 8f
put: 00 8f
put: c2 8f
wait: ff
get: af,87
wait: ff
get: af,87
end: cc
start:
put: 55 8f
put: aa 8f
put: 00 8f
put: 03 8f
put: 05 8f
put: 84 8f
wait: ff
</programlisting>
<para>
From this it is easy to see that <varname>put</varname>
routine is often grouped together in five successive calls
sending information to the scanner. Once these are understood
it should be possible to process the logs further to show the
higher level routines in an easy to see format. Once the
highest level format that you can derive from this process is
understood, you then need to produce a series of scans varying
only one parameter between them, so you can discover how to
set the various parameters for the scanner.
</para>
<para>
The following is the <filename>shrink.c</filename> program:
<programlisting>
/* Copyright David Campbell &lt;campbell@torque.net&gt; */
#include &lt;stdio.h&gt;
#include &lt;string.h&gt;
int main (void)
{
char buff[256], lastline[256] = "";
int count = 0;
while (!feof (stdin))
{
fgets (buff, sizeof (buff), stdin);
if (strcmp (buff, lastline))
{
if (count &gt; 1)
printf ("# Last line repeated %i times #\n", count);
printf ("%s", buff);
strcpy (lastline, buff);
count = 1;
}
else count++;
}
return 0;
}
</programlisting>
</para>
</sect1>
</chapter>
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