Auth SEGV on sparc64, alignment problem?

[Josef 'Jeff' Sipek]

On Tue, Feb 20, 2018 at 19:08:27 -0500, Chris Ross wrote:
> 
>   Apologies first for using two addresses, but I can’t currently read my email at distal.com.  :-)
> 
>   I was previously running dovecot2-2.2.29.1_2 on FreeBSD 11 on sparc64.
>   Trying to debug a problem I was having with one of my clients, I
>   upgraded to dovecot-2.2.33.2_4 on that same server.  However, I cannot
>   connect now, log shows:
> 
...
>   Loading the core file, as described
>   https://www.dovecot.org/bugreport.html , shows the error in libc
>   somewhere:

I read the your other mails in this thread; can you run things as before and
do a 'bt full' on the core file with the debug-symbol-enabled libdovecot?
gdb seems to be catching the SIGTRAPs, which is making things a bit confusing.

> (gdb) bt full
> #0  __unaligned_load (
>     p=0x617070656e640e6d <Address 0x617070656e640e6d out of bounds>, size=4)

This address looks like ASCII - "append\x0em", so my theory at the moment
is:

(1) something clobbers a pointer
(2) the CPU attempts to execute a load from the address
(3) a utrap is generated to handle unaligned load
(4) the utrap code attempts to emulate the unaligned load
(5) the CPU fails to access the address since it is bogus, and a SIGSEGV is
    generated

Now, I'm have no idea why it'd first try to work around the alignment
requirement before doing a quick sanity check and generating SIGSEGV to
begin with, but that's my theory based on the info available so far.
Hopefully, a stack trace from a core file will help.

Thanks,

Jeff.

>     at /usr/src/release-11.1.0/lib/libc/sparc64/sys/__sparc_utrap_align.c:45
> 	val = 0
> 	i = 0
> #1  0x00000000109f9f6c in __unaligned_fixup (uf=0x7fdffffee40)
>     at /usr/src/release-11.1.0/lib/libc/sparc64/sys/__sparc_utrap_align.c:78
> 	addr = <value optimized out>
> 	val = <value optimized out>
> 	insn = 3254807616
> 	sig = <value optimized out>
> #2  0x00000000109f9d50 in __sparc_utrap (uf=0x7fdffffee40)
>     at /usr/src/release-11.1.0/lib/libc/sparc64/sys/__sparc_utrap.c:100
> 	sig = 272013984
> #3  0x000000001094a10c in __sparc_utrap_gen () from /lib/libc.so.7
> No symbol table info available.
> #4  0x000000001094a10c in __sparc_utrap_gen () from /lib/libc.so.7
> No symbol table info available.
> Previous frame identical to this frame (corrupt stack?)
> (gdb) 
> 
>   As this is a sparc64, with 8-byte alignment requirements, I’m guessing that’s the issue.  Many a piece of software has failed to respect that and crashed.  But, I’m not sure.
> 
>   Does anyone have any suggestions?  I’ve built it locally (via ports), so if there are compiler options I can/should try, I certainly can try.
> 
>   Thanks…
> 
>                          - Chris

-- 
If I have trouble installing Linux, something is wrong. Very wrong.
		- Linus Torvalds