Lack of TARGET_ARCH=powerpc support in kgdb from devel/gdb (e.g., -r440115 of /usr/ports): "ABI doesn't support a vmcore target"

[Mark Millard]

[This update just notes that it appears that combination
${MK_GDB} == no && ${MK_GDB_LIBEXEC} == yes is not intended
to be used, effectively eliminating "THING #1" of 0-2.]

On 2017-May-6, at 10:03 PM, Mark Millard <markmi at dsl-only.net> wrote:

> On 2017-May-6, at 5:21 PM, Mark Millard <markmi at dsl-only.net> wrote:
> 
>> On:
>> 
>> # uname -apKU
>> FreeBSD FBSDG4S 12.0-CURRENT FreeBSD 12.0-CURRENT  r317820M  powerpc powerpc 1200030 1200030
>> 
>> When I attempt to use:
>> 
>> # which kgdb
>> /usr/local/bin/kgdb
>> 
>> that was from building devel/gdb for:
>> 
>> # svnlite info /usr/ports | grep "Re[plv]"
>> Relative URL: ^/head
>> Repository Root: https://svn.freebsd.org/ports
>> Repository UUID: 35697150-7ecd-e111-bb59-0022644237b5
>> Revision: 440115
>> Last Changed Rev: 440115
>> 
>> (built via gcc 4.2.1: not via clang: I
>> experiment with clang for powerpc and
>> powerpc64 so I'm being explicit)
>> 
>> I end up getting the following sort of result:
>> 
>> # kgdb /usr/lib/debug/boot/kernel/kernel.debug /var/crash/vmcore.4 
>> . . .
>> Reading symbols from /usr/lib/debug/boot/kernel/kernel.debug...done.
>> ABI doesn't support a vmcore target
>> 
>> That message is from: /usr/ports/devel/gdb/files/kgdb/fbsd-kvm.c . . .
>> 
>> static void
>> kgdb_trgt_open(const char *arg, int from_tty)
>> {
>>       struct fbsd_vmcore_ops *ops = (struct fbsd_vmcore_ops *)
>>           gdbarch_data (target_gdbarch(), fbsd_vmcore_data);
>> . . .
>>       if (ops == NULL || ops->supply_pcb == NULL || ops->cpu_pcb_addr == NULL)
>>               error ("ABI doesn't support a vmcore target");
>> . . .
>> 
>> It appears that there is no kernel debugging
>> supported for TARGET_ARCH=powerpc currently.
>> (The system no longer has its own gdb related
>> materials.)
> 
> I've discovered more context and have found
> a few of issues in how things are currently
> set up.
> 
> THING #0:
> 
> It appears that usr.sbin/crashinfo/crashinfo.sh assumes
> that /usr/local/bin/gdb will work better for all architectures,
> including for kgdb types of activity:
> 
> find_gdb()
> {
>        local binary
> 
>        for binary in /usr/local/bin/gdb /usr/libexec/gdb /usr/bin/gdb; do
>                if [ -x ${binary} ]; then
>                        GDB=${binary}
>                        return
>                fi
>        done
> }
> 
> But it appears that on powerpc /usr/local/bin/gdb and
> /usr/local/bin/kgdb do not support TARGET_ARCH=powerpc
> at all for such activity.
> 
> 
> THING #1:
> 
> Another oddity is for the combination:
> 
> ${MK_GDB} == no && ${MK_GDB_LIBEXEC} == yes
> 
> where the tools/build/mk/OptionalObsoleteFiles.inc
> logic then adds the libexec gdb and kgdb to
> OLD_FILES :
> 
> .if ${MK_GDB} == no || ${MK_GDB_LIBEXEC} == no
> OLD_FILES+=usr/libexec/gdb
> OLD_FILES+=usr/libexec/kgdb
> .endif
> 
> so doing a delete-old removes the only system
> gdb and kgdb that are installed for such a
> context. It does this because of:
> 
> ${MK_GDB} == no
> 
> (And that explains why I thought gdb and kgdb
> were not in the system.)

Looking around at how WITH_GDB and WITH_GDB_LIBEXEC
and the MK_ variants are used it appears that the:

${MK_GDB} == no && ${MK_GDB_LIBEXEC} == yes

combination is not intended to be used.

> THING #2:
> 
> /usr/libexec/kgdb (when present) does not support the
> powerpc architecture for head either . . .
> 
> On a head -r317820 powerpc I attempted:
> 
> # /usr/libexec/kgdb /usr/lib/debug/boot/kernel/kernel.debug /var/crash/vmcore.7
> GNU gdb 6.1.1 [FreeBSD]
> Copyright 2004 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you are
> welcome to change it and/or distribute copies of it under certain conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "powerpc-marcel-freebsd"...
> Failed to open vmcore: unsupported architecture



===
Mark Millard
markmi at dsl-only.net