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From: Michael Ellerman <mpe@ellerman.id.au>
To: Alan Modra <amodra@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org, Joel Stanley <joel@jms.id.au>
Subject: Re: [PATCH] powerpc/32: Include .branch_lt in data section
Date: Wed, 19 Dec 2018 20:51:13 +1100	[thread overview]
Message-ID: <87tvj9rgj2.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <20181118082652.GA21617@bubble.grove.modra.org>

Alan Modra <amodra@gmail.com> writes:
> On Thu, Nov 15, 2018 at 11:47:52PM +1100, Michael Ellerman wrote:
>> Alan Modra <amodra@gmail.com> writes:
>> 
>> > On Wed, Nov 14, 2018 at 01:32:18PM +1030, Joel Stanley wrote:
>> >> I wasn't sure where this should go or if the ordering matters.
>> >
>> > The usual answer is: "Look at where the section goes in the standard
>> > linker scripts."   But that doesn't apply here.  The section will be
>> > empty for a kernel build so it doesn't matter where it goes.
>> 
>> If it's empty why don't we just discard it?
>
> That can be a recipe for finding linker bugs.  Not that I'm against
> you finding linker bugs.  ;-)

Seems we might have found a linker bug :)

With a binutils 2.29 toolchain discarding .branch_lt causes a segfault
when linking:

  http://kisskb.ellerman.id.au/kisskb/buildresult/13618838/log/

  /kisskb/src/scripts/link-vmlinux.sh: line 85: 74627 Segmentation fault      (core dumped) ${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} -T ${lds} ${objects}


That toolchain is here:

  https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/5.5.0/x86_64-gcc-5.5.0-nolibc-powerpc64-linux.tar.xz

It seems to be better with binutils 2.30, it doesn't crash but still
doesn't link:

  http://kisskb.ellerman.id.au/kisskb/buildresult/13620269/log/

  /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld: linkage table error against `0002bf55.xdp_rxq_info_reg_mem_model'
  /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld: stubs don't match calculated size
  /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld: can not build stubs: Bad value
  make[1]: *** [/kisskb/src/Makefile:1036: vmlinux] Error 1

So I guess I'll take this version of the patch for now.

cheers

  reply	other threads:[~2018-12-19  9:53 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14  3:02 [PATCH] powerpc/32: Include .branch_lt in data section Joel Stanley
2018-11-14  4:00 ` Alan Modra
2018-11-15 12:47   ` Michael Ellerman
2018-11-18  8:26     ` Alan Modra
2018-12-19  9:51       ` Michael Ellerman [this message]
2019-02-08 13:02 ` Michael Ellerman

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