From: Alan Modra <amodra@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Jan Beulich <jbeulich@suse.com>, Binutils <binutils@sourceware.org>
Subject: Re: [PATCH v5] elf/x86-64: Subtract __ImageBase for R_AMD64_IMAGEBASE
Date: Sat, 6 Mar 2021 10:41:53 +1030 [thread overview]
Message-ID: <20210306001153.GF6042@bubble.grove.modra.org> (raw)
In-Reply-To: <CAMe9rOrK+cR_jJ6L7oKtbT16EKxrmhuxhGWPwDrkszTKWGPJzg@mail.gmail.com>
On Fri, Mar 05, 2021 at 10:26:35AM -0800, H.J. Lu wrote:
> On Fri, Mar 5, 2021 at 5:57 AM Alan Modra <amodra@gmail.com> wrote:
> > This doesn't look like the right place to set up a reference to
> > __executable_start. Doing so in a new check_relocs in pei-x86_64.c
> > that tests for an ELF output would be better. I'm not suggesting that
> > you run over relocs looking for R_AMD64_IMAGEBASE, that could be done
> > but seems unnecessary.
>
> check_relocs is too late. We need to do it in load_symbols (). Otherwise,
> __executable_start won't be defined. I added pex64_link_add_symbols to
> do it.
Ah, I was forgetting that check_relocs now runs much later. Even so,
I would have thought that the PROVIDE would define the symbol? The
question is academic, I'm happy with pex64_link_add_symbols.
> Here is the v5 patch. OK for master?
OK with three further changes.
1) The R_AMD64_IMAGEBASE handling should to be inside the
output_bfd == NULL block. It is wrong to apply the image base
adjustment to the section for relocatable linking. Doing so would
effectively change the reloc addend.
2) I worry about the abort, which I think you might hit if trying to
link PE objects into a pie. One possible fix would be to change
the bfd_link_pde in pex64_link_add_symbols to !bfd_link_relocatable.
That might just be sweeping a problem under the rug, so an
alternative fix would be to remove the abort and instead return
with bfd_reloc_dangerous. Either fix is fine with me.
3) No need to check for bfd_target_elf_flavour in set_output_arch.
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2021-03-06 0:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 12:15 [PATCH] " H.J. Lu
2021-02-23 13:15 ` Jan Beulich
2021-02-23 13:31 ` H.J. Lu
2021-02-23 14:10 ` Jan Beulich
2021-02-23 14:47 ` H.J. Lu
2021-02-23 15:02 ` Jan Beulich
2021-02-23 15:07 ` H.J. Lu
2021-02-23 15:11 ` Jan Beulich
2021-02-23 17:50 ` [PATCH v2] " H.J. Lu
2021-02-25 2:09 ` Alan Modra
2021-02-28 2:38 ` [PATCH v3] " H.J. Lu
2021-03-01 12:19 ` Alan Modra
2021-03-01 13:44 ` H.J. Lu
2021-03-04 13:14 ` Alan Modra
2021-03-04 13:54 ` [PATCH v4] " H.J. Lu
2021-03-05 5:17 ` Alan Modra
2021-03-05 5:29 ` H.J. Lu
2021-03-05 13:57 ` Alan Modra
2021-03-05 18:26 ` [PATCH v5] " H.J. Lu
2021-03-06 0:11 ` Alan Modra [this message]
2021-03-06 1:00 ` [PATCH v6] " H.J. Lu
2021-03-07 4:16 ` Alan Modra
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