[Info-vax] %SYSTEM-F-ACCVIO in LIBOTS after several hours

[Simon Clubley]

On 2022-03-08, Arne Vajhøj <arne at vajhoej.dk> wrote:
> On 3/8/2022 4:55 PM, Mark Daniel wrote:
>> Reproducible after several hours of continuous execution.
>> 
>>> %SYSTEM-F-ACCVIO, access violation, reason mask=04, virtual 
>>> address=0000000000039B00, PC=FFFFFFFF842341D0, PS=0000001B
>>> %TRACE-F-TRACEBACK, symbolic stack dump follows
>>> image     module    routine               line      rel PC           
>>> abs PC
>>> LIBOTS                                       0 00000000000121D0 
>>> FFFFFFFF842341D0
>>> DECC$SHR  C$TXDOPRINT  putbuf            43567 000000000000CA82 
>>> FFFFFFFF84BC4FA2
>>> DECC$SHR  C$TXDOPRINT  decc$$txdoprint   43658 000000000000CD62 
>>> FFFFFFFF84BC5282
>>> DECC$SHR  C$TXDOPRINT  sprintf           44192 0000000000012492 
>>> FFFFFFFF84BCA9B2
>>> HTTPDMON  HTTPDMON  TcpIpLookup          60709 00000000000109A2 
>>> 00000000000409A2
>>> HTTPDMON  HTTPDMON  AddRequest           60536 0000000000009A62 
>>> 0000000000039A62
>>> HTTPDMON  HTTPDMON  MonitorHttpd         58867 0000000000001392 
>>> 0000000000031392
>>> HTTPDMON  HTTPDMON  main                 58751 0000000000000962 
>>> 0000000000030962
>
>> Line 60790 is
>> 
>>>       3   60709             sprintf (ares[aCacheIdx], "[%s]", 
>>> strerror(errno));
>
>> The ACCVIO is related to the target, ares[aCacheIdx], or to the 
>> argument, strerror(errno)), or...?
>
> The access violation is trying to write to 39B00, so it has to be
> ares[aCacheIdx].
>
> And if ares is a valid array of char arrays, then every indication
> is that aCacheIdx has a bad value.
>

Or alternatively, depending on how the VMS linker gathers any static
data areas within a module when generating a final image, there could
have been a buffer overflow from a writable page into a following R/O
code page.

Take another look at the reported virtual address. Don't you find it
suspicious that the failing VA is exactly at the start of a page boundary ?

Oh, and that sprintf() really should become snprintf() if it's available
to Mark on the systems he supports people running this code on.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.