Re: libc6.1 signal handling bug on alpha
Greetings!
Paul Slootman <paul@debian.org> writes:
> On Tue 24 Feb 2004, Camm Maguire wrote:
>
> > Greetings! Just wondering if I should cripple gcl/maxima/acl2/axiom
> > on alpha to work around this bug, or if its going to get fixed
> > sometime soon.....
>
> Don't hold your breath... :-(
:-) Seriously though, this is a pity, as its a major bug which has
only recently been introduced on alpha only. I like alpha. I think
it should be one of the strongest Debian options. But there don't
appear to be even as many users as m68k :-(.
> I don't expect that a kernel change would be responsible for this;
> my alpha is still running 2.4.19-rc2 (the latest at the time of last
> boot :-) and I guess you see the same problem there. Perhaps some libc
> change?
Yes, this is a libc6.1 issue only. The signal is being delivered
(kernel), but sigaction (libc6.1) can't setup the handler to return to
the right place.
Take care,
>
> Paul Slootman
>
> > =============================================================================
> > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=221969
> > =============================================================================
> >
> > * To: paul@debian.org, debian-alpha@lists.debian.org,camm@m.enhanced.com
> > * Subject: Apparent signal handling errors recently introduced
> > * From: Camm Maguire <camm@m.enhanced.com>
> > * Date: Fri, 06 Feb 2004 12:15:02 -0500
> > * Message-id: <[🔎] E1Ap9ZG-0006Y9-00@wisdom.m.enhanced.com>
> > * Old-return-path: <camm@m.enhanced.com>
> >
> > Greetings! GCL and its compiled programs (maxima, acl2, axiom) can
> > make use of a more efficient garbage collection algorithm by
> > mprotecting certain pages read only, trapping segmentation faults, and
> > then reprotecting the pages read write as necessary. This has been
> > working on alpha for a long time. acl2 in particular was last build
> > on 20021210 on lully successfully using this mechanism. I've made
> > some minor modifications to the acl2 package, and now the build breaks
> > on alpha only, apparently.
> >
> > Debugging on escher shows that apparently the stack is damaged in such
> > a way as the program cannot determine where to return after the signal
> > handler, in particular the return is one stack level up from where the
> > segmentation signal was caught. Is there any recent kernel change
> > that could have caused this?
> >
> > Here is a gdb session:
> >
> > Starting program: /home/camm/acl2-2.7/raw_nsaved_acl2 /home/camm/gcl-2.6.1/unixport/ <init_nsaved_acl2.lsp
> > GCL (GNU Common Lisp) April 1994 131072 pages
> > Building symbol table for /home/camm/acl2-2.7/raw_nsaved_acl2 ..
> > loading /home/camm/gcl-2.6.1/unixport/../lsp/gcl_export.lsp
> > ...
> > [GC for 5242 RELOCATABLE-BLOCKS pages..(T=764).GC finished]
> > [SGC on]
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x0000000120667b8c in LI20 (V83=0x120d74570) at gcl_sloop.c:530
> > 530 bds_bind(VV[34],(V83));
> > (gdb) bt 5
> > #0 0x0000000120667b8c in LI20 (V83=0x120d74570) at gcl_sloop.c:530
> > #1 0x0000000120666ad8 in L7 () at gcl_sloop.c:230
> > #2 0x00000001204eb984 in funcall (fun=0x120b51380) at eval.c:173
> > #3 0x00000001205336ac in IapplyVector (fun=0x120b51380, nargs=2,
> > base=0x12084ea10) at nfunlink.c:239
> > #4 0x00000001204ef2f8 in fLfuncall (fun=0x120b51380) at eval.c:1140
> > (More stack frames follow...)
> > (gdb) up
> > #1 0x0000000120666ad8 in L7 () at gcl_sloop.c:230
> > 230 base[3]= (*(LnkLI247))(base[2]);
> > (gdb) p base
> > $35 = (object *) 0x12084ea10
> > (gdb) p &base
> > $36 = (object **) 0x11fffe6f8
> > (gdb) c
> > Continuing.
> >
> > Breakpoint 1, memprotect_handler (sig=11, code=4831830752, scp=0x11fffe360,
> > addr=0x0) at sgbc.c:1404
> > 1404 int j=page_multiple;
> > (gdb) p *(object **) 0x11fffe6f8
> > $37 = (union lispunion **) 0x12084ea10
> > (gdb) display *(object **) 0x11fffe6f8
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb) n
> > 1408 faddr=GET_FAULT_ADDR(sig,code,scp,addr);
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1409 debug_fault = (long) faddr;
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1413 if (faddr >= core_end || (unsigned long)faddr < DBEGIN) {
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1422 p = page(faddr);
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1423 p = ROUND_DOWN_PAGE_NO(p);
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1424 if (p >= first_protectable_page
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1433 mprotect(pagetochar(p),page_multiple * PAGESIZE, PROT_READ_WRITE);
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1434 while (--j >= 0)
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb) p j
> > $38 = 1
> > (gdb) n
> > 1435 sgc_type_map[p+j] = sgc_type_map[p+j] | SGC_TEMP_WRITABLE;
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1434 while (--j >= 0)
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb)
> > 1457 }
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb) bt
> > #0 memprotect_handler (sig=11, code=4831830752, scp=0x11fffe360, addr=0x0)
> > at sgbc.c:1457
> > #1 0x000002000022c858 in __open_catalog () from /lib/libc.so.6.1
> > #2 0x0000000120666ad8 in L7 () at gcl_sloop.c:230
> > (gdb) c
> > Continuing.
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x0000000120666ae4 in L7 () at gcl_sloop.c:230
> > 230 base[3]= (*(LnkLI247))(base[2]);
> > 1: *(union lispunion ***) 4831831800 = (union lispunion **) 0x12084ea10
> > (gdb) bt
> > #0 0x0000000120666ae4 in L7 () at gcl_sloop.c:230
> > (gdb) p &base
> > $39 = (object **) 0x12080b74c
> > (gdb) p base[0]
> > Cannot access memory at address 0x20add6c800000000
> > (gdb)
>
>
>
--
Camm Maguire camm@enhanced.com
==========================================================================
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