Date: Fri, 8 Jul 2011 17:32:23 +1000 (EST) From: Peter Jeremy <peterjeremy@acm.org> To: FreeBSD-gnats-submit@FreeBSD.org Subject: gnu/158719: [patch] Fix kgdb on sparc64 Message-ID: <201107080732.p687WNRw090826@server.vk2pj.dyndns.org> Resent-Message-ID: <201107080740.p687e1GP095747@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 158719
>Category: gnu
>Synopsis: [patch] Fix kgdb on sparc64
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Jul 08 07:40:01 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator: Peter Jeremy
>Release: FreeBSD 8.2-STABLE amd64
>Organization:
n/a
>Environment:
System: FreeBSD sb1500.vk2pj.dyndns.org 9.0-CURRENT FreeBSD 9.0-CURRENT #1: Wed\
Jun 22 17:53:58 EST 2011 root@sb1500.vk2pj.dyndns.org:/usr/obj/usr/src/sys/sb1\
500 sparc64
Patch also tested on: FreeBSD server.vk2pj.dyndns.org 8.2-STABLE FreeBSD 8.2-STABLE #11: Fri Apr 22 11:55:58 EST 2011 root@server.vk2pj.dyndns.org:/var/obj/usr/src/sys/server amd64
>Description:
kgdb does not work on sparc64. Following some investigation,
the problem is that the sparc64 kgdb has two "core_stratum"
target_ops structures active - the default "Local core dump file"
defined in contrib/gdb/gdb/corelow.c and the FreeBSD-specific
"kernel core dump file" defined in gnu/usr.bin/gdb/kgdb/trgt.c
On at least i386 and amd64, the "Local core dump file" is
inhibited by statically defining coreops_suppress_target as
non-zero in gnu/usr.bin/gdb/libgdb/fbsd-threads.c (this file
defines "FreeBSD multithreaded core dump file" target_ops
which is itself inhibited by fbsdcoreops_suppress_target in
gnu/usr.bin/gdb/kgdb/trgt.c).
sparc64 does not include fbsd-threads.c and therefore
the "Local core dump file" is not inhibited. As a result,
contrib/gdb/gdb/target.c::find_core_target() finds multiple
targets and returns NULL.
Note that it's possible that similar problems exist on other
architectures.
>How-To-Repeat:
Run "kgdb /boot/kernel/kernel /dev/mem" as root on sparc64.
It will report "GDB can't read core files on this machine."
>Fix:
It's not possible to directly inhibit the "Local core dump file"
by defining coreops_suppress_target in trgt.c because that
results in a duplicate definition on (eg) amd64. Likewise a
weak DATA symbol does not override a strong BSS symbol.
The following patch therefore defines coreops_suppress_target
in a file that is only active on sparc64 kgdb.
Index: gnu/usr.bin/gdb/kgdb/trgt_sparc64.c
===================================================================
RCS file: /usr/ncvs/src/gnu/usr.bin/gdb/kgdb/trgt_sparc64.c,v
retrieving revision 1.8
diff -u -r1.8 trgt_sparc64.c
--- gnu/usr.bin/gdb/kgdb/trgt_sparc64.c 1 May 2008 20:36:48 -0000 1.8
+++ gnu/usr.bin/gdb/kgdb/trgt_sparc64.c 8 Jul 2011 06:17:55 -0000
@@ -197,3 +197,9 @@
/* printf("%s: %lx =%s\n", __func__, pc, pname); */
return (NULL);
}
+/*
+** Disable the default "Local core dump file" target. This is done in
+** libgdb/fbsd-threads.c for most targets but that file is not used on
+** sparc64
+*/
+int coreops_suppress_target = 1;
>Release-Note:
>Audit-Trail:
>Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201107080732.p687WNRw090826>