--- James Courtier-Dutton James@superbug.demon.co.uk wrote:
Damjan Jovanovic wrote:
Hi
I've been trying to add STI (still image) support
to
Wine, and I've made some progress. However, I see
a
deep and unsurmountable need to add (at least user-space) device drivers to Wine, and I would
like
some feedback on these ideas.
Basically, many Windows device drivers are really trivial, but required for many apps. A scanner
driver
typically just accepts commands from a user-space
app,
does minimal processing, and forwards that to
Windows.
I've already hacked up Wine to get the same functionality, and it works - partially.
I propose adding a driver loading system to Wine
that
works as follows: -CreateFile() gets a device filename, like (in my case) \.\MiiScan0 -Currently, Wine's behaviour for such a filename
is to
try load a VXD. -In the case of VXD loading failure, a search is performed in (Wine's) C:\Windows\System32\Drivers
(or
somewhere else?) for a matching driver.
The driver is then loaded and used for (at least): ReadFile() WriteFile() DeviceIoControl() CloseHandle()
The problem is, how is a handle mapped to the appropriate driver? I've thought about it, and
come up
with 3 solutions. The first 3 don't require
changes to
the wineserver but aren't pretty.
- Make the driver a true Linux kernel mode
driver,
and the handle its device file handle. Since ReadFile() and WriteFile() just do read() and
write()
system calls, this can be done. The problem is, DeviceIoControl() has to be implemented using
ioctl(),
and that's dangerous (sending the right codes to
the
wrong device can be catastrophic). Also, it's not portable to other OS's, and requires writing a
kernel
module (which isn't fun).
- The driver is a file giving a process to start
and
some IPC method to use. Wine starts the process
and
uses the IPC method to communicate with the
driver.
This is good as far as Wine's current ReadFile()
and
WriteFile() go, since they don't have to know
they're
not writing to an actual file. The problem here
is,
which IPC method supports both read() and write()
on
the same file descriptor, preserves message boundaries, and carries out-of-band data for DeviceIoControl()? I was thinking TCP sockets, but they don't preserve message boundaries.
- KERNEL32.DLL and / or NTDLL.DLL keep their own
handle table so they know which handles are driver handles and deal with those appropriately. Having
to
look up these tables for every call to ReadFile(), WriteFile() and DeviceIoControl() might be very inefficient, though.
- Use an in-process solution, like a winelib DLL
that
has exports for dealing with ReadFile(),
WriteFile()
and DeviceIoControl(). This could be the most efficient, but then again, you need an efficient
way
to test a handle for being a driver handle, find
the
appropriate driver, and call the right exported function, which likely means the wineserver needs
to
have knowledge of these drivers and provide functionality for testing a handle for being a
driver
handle and have a way to find the driver.
Let me know what you think.
Bye Damjan
I would like this but mainly for a different reason. I help reverse engineer hardware so that we can write linux drivers for it. This reverse engineering task would be easier if I could install the windows drivers on my linux box and run them, and then watch their activity with the hardware. For this to work, we would have to implement the HAL.DLL in wine, a small kernel module for it to communicate with and probably a few other bits.
This would greatly help the hardware reverse engineering requirements in order to get hardware to interoperate with Linux. Currently, I have to installed special .DLLs on a windows box and perform the logging there. I would much prefer to do it all on Linux.
The side effect of this would be that wine will support some hardware even before Linux gets support for it.
This "kernel module" would only be run for the reverse engineering task, as it would most likely make the linux kernel very insecure.
Any comments
James
I am not 100% happy about using the Linux kernel. How would we deal with:
-Portability: It works only on Linux, nowhere else
-ioctl(): how does the DeviceIoControl() functions know whether it is safe to use the native ioctl() function with the same control codes or not?
Bye Damjan
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