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SubjectRe: [PATCH v3] x86/vmlinux: Fix with pre-2.23 binutils
On Tue, Jan 14, 2020 at 05:51:35PM +0100, Borislav Petkov wrote:
> On Mon, Jan 13, 2020 at 05:53:32PM -0800, Kees Cook wrote:
> > NAK: linkers can add things at the end of .text that will go missing from
> > the kernel if _etext isn't _outside_ the .text section, truly beyond the
> > end of the .text section. This patch will break Control Flow Integrity
> > checking since the jump tables are at the end of .text.
> Err, which linkers are those? Please elaborate.
> In any case, after reading the thread, I can't help but favor the idea
> of us bumping min binutils version to 2.23.
> Michael (on Cc) says that the 2.21 was kinda broken wrt to the symbols
> fun outside of sections, 2.22 tried to fix it, see
> fd952815307f ("x86-32, relocs: Whitelist more symbols for ld bug workaround")
> which Arvind pointed out and 2.23 fixed it for real.
> Now, 2.23 is still very ancient. I'm looking at our releases: openSUSE
> 12.1 has the minimum supported gcc version 4.6 by the kernel and
> also the minimum binutils version 2.21 which we support according to
> Documentation/process/changes.rst
> Now, openSUSE 12.1 is ancient and we ourselves advise people to update
> to current distros so I don't think anyone would still run it.

RHEL7 looks to have been released with 2.23 and we already don't
support the version in RHEL6, so that should be good too.

> So, considering that upping the binutils version would save us from all
> this trouble I say we try it after 5.5 releases for a maximum time of a
> full 5.6 release cycle and see who complains.
> Considering how no one triggered this yet until Arvind, I think no one
> would complain. But I might be wrong.
> So what do people think? hpa?

Thumbs up from me -- I had thought there were a few other reports
earlier about these, but looking at those threads, it seems like they're
all actually with, which we already decided to drop support for
in commit 75959d44f9dc ("kbuild: Fail if gold linker is detected").

> --
> Regards/Gruss,
> Boris.

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