[OpenAFS] Re: "unable to authenticate to AFS" error- linux distribution, specific?

[Joseph Kiniry]

Hi all,
After applying Christof's suggested patches OpenAFS 1.3.74 builds for 
me, and klog works, but all attempts at examining my cell's root volume 
(e.g., fs examine /afs/) result in hangs, segmentation faults, or other 
bizarre behavior.

Joe
On 19 Nov, 2004, at 11:08, Christof Hanke wrote:
Douglas E. Engert wrote:
It could also mean that the stack was being overlayed, and moving this
variabe to static means something else on the stack is being 
overlayed.

Two other things to try:
 Compile without optimizatrion.
 Use the debugger s to set a watch point on the ans_label before 
calling
 the ka_Authenticate. Hopefully the debugger will catch the location 
where
 it ws being modified.

You were right.
The gdb found it was modified in ubik/ubikclient.c: ubik_CallIter()
This function takes 20 parameters :
afs_int32
ubik_CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, p6, 
p7, p8,
             p9, p10, p11, p12, p13, p14, p15, p16)
In kauth/authclient.c:kawrap_ubik_Call() it is called with only 12 
parameters :
477 : code = ubik_CallIter(aproc, aclient, aflags, &count, p1, p2, p3, 
p4,
478 :                             p5, p6, p7, p8);

Which is not uncommon, a wee grep showed up all sorts of numbers of 
paramters with wich ubik_CallIter() is called.

The real trick is now in ubik_CallIter() itself :
changing
777: code = CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, 
p6, p7,
                   p8, p9, p10, p11, p12, p13, p14, p15, 
p16,NEED_LOCK);
to
777 :code = CallIter(aproc, aclient, aflags, apos, NEED_LOCK, p1, p2, 
p3, p4, p5, p6, p7,
778:                     p8, p9, p10, p11, p12, p13, p14, p15, p16);

and all following seems to fix the problem.
Here the patch :
# diff ubikclient.c ubikclient_new.c
584,585c584,585
< CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, p5, p6, p7, 
p8, p9,
<        p10, p11, p12, p13, p14, p15, p16, needlock)
---
> CallIter(aproc, aclient, aflags, apos, needlock,p1, p2, p3, p4, p5, 
p6, p7, p8, p9,
>        p10, p11, p12, p13, p14, p15, p16)
718,720c718,720
<               CallIter(aproc, aclient, aflags, &count, p1, p2, p3, 
p4, p5,
<                        p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, 
p16,
<                        NO_LOCK);
---
>               CallIter(aproc, aclient, aflags, &count, NO_LOCK,p1, 
p2, p3, p4, p5,
>                        p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, 
p16
>                        );
776,777c776,777
<     return CallIter(aproc, aclient, aflags, apos, p1, p2, p3, p4, 
p5, p6, p7,
<                   p8, p9, p10, p11, p12, p13, p14, p15, p16, 
NEED_LOCK);
---
>     return CallIter(aproc, aclient, aflags, apos, NEED_LOCK, p1, p2, 
p3, p4, p5,
>                    p6,p7,p8, p9, p10, p11, p12, p13, p14, p15, p16);

Apparently, you cannot use a variable after the "optional ones", 
otherwise you corrupt the stack (?).

Then there is the question :
Wouldn't it be cleaner to call the function with the exact (real) 
number of parameters ?
I guess it would imply some performance penalties, but would they 
matter?

-Christof  Hanke
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