[ros-dev] serial.sys

[Alex Ionescu]

Rick Parrish wrote:
> This email is directed mostly to Herve and anyone else familiar with 
> SERIAL.SYS and how it works.
> 
> Two years ago I implemented a small (5 kilobyte) WDM driver that 
> "wrapped" SERIAL.SYS. It's an ugly hack that (almost) works. What I did 
> was "hook" the interrupt service routine by directly modifying the IDT. 
> It works most of the time but occassionally I get BSOD (and I don't know 
> why).
> 
> The driver installed ISR reads the MSR (modem status register) of the 
> UART. The RDTSC instruction is used to generate a timestamp of when the 
> MSR changed. Both pieces of data are stored in a FIFO - on every 
> interrupt. A user mode program can later retrieve the information at 
> regular time intervals.
> 
> Hint: using the CTS, DCD, and DSR pins on a standard RS232 port, you can 
> create a Poor Man's 3 Channel Logic Analyzer. Other applications include 
> packet radio interface for amateur radio.
> 
> What I'd like to do is merge the functionality directly into SERIAL.SYS 
> (eg. work with the OS instead of around it). The extra functionality 
> would be exposed through IOCTL or some other means but would not break 
> ordinary serial COMM functionality.
> 
> Disclaimer: I'm not a veteran author of kernel mode drivers.
> 
> This is a relatively obscure application so if you want to reply 
> off-list, that's perfectly fine by me.
> 
> Here are my questions:
> 
> 1. how robust is the current SERIAL.SYS driver (I see a few "FIXME"s in 
> the comments) ?
> 2. does ReactOS support or require code-signing of drivers? (probably 
> not yet)
> 3. Can I run the "Genuine" Reactos SERIAL.SYS on "Genuine" Windows 
> 2K/XP? I think so (setting WFP aside). 4. is anyone in the ReactOS 
> community interested in such a driver extension as described above? 
> (probably not)
> 
> Also, if anyone would like to see the logic analyzer program and related 
> driver - please send me an email.
> 
> Regards,
> Rick
> 
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> 


Besides what Hervé wrote, have a look at Microsoft's serial.sys driver
in the WDK/DDK sample source code. It's the working driver used in XP+,
and you can easily modify it to test your changes on it.

-- 
Best regards,
Alex Ionescu
Project Lead, TinyKRNL
Kernel-Mode Software Design Engineer, ReactOS