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From: meindert@inducom.UUCP (Meindert Kuipers)
Newsgroups: comp.os.os9
Subject: Re: Faulting address on bus errors?
Message-ID: <2023@inducom.UUCP>
Date: 29 Nov 90 08:20:33 GMT
References: <623@oglvee.UUCP>
Distribution: comp
Organization: Inducom Systems BV, Oss Netherlands
Lines: 34

From article <623@oglvee.UUCP>, by jr@oglvee.UUCP (Jim Rosenberg):
> Reading the Motorola book, the information we want is clearly and
> unambiguously saved on the Supervisor Stack when a bus error occurs.  The
> problem is how to get to it.  The OS-9 manual writeup of F$STrap says that a
> routine installed this way is executed in *user* state.  In giving the
> interface to such a routine they don't indicate anywhere that you have access
> to *system* stack.
> 

The exception frame is processed somewhere deep in the kernel, and all the
important parameters are presented in registers on entry in the user
exception routine. You should be able to use this information to get
violation address, program counter and a few other things.
System state exceptions are probably not caught this way, and an error
exception routine must be added to the driver code. I do not know for sure
if this entry is called in the current OS-9 version (2.3).
If you can afford it (eprom space), run the system state debugger in the
"background", although it might be tricky to start it correctly in a
ROM based system.

Succes.

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