linux-kernel - [PATCHv3 0/2] Salted build ids via linker sections

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Date:   Tue, 22 May 2018 17:19:37 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Andy Lutomirski <luto@...nel.org>, mjw@...oraproject.org,
        "H . J . Lu" <hjl.tools@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Laura Abbott <labbott@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        X86 ML <x86@...nel.org>, linux-kernel@...r.kernel.org,
        Nick Clifton <nickc@...hat.com>,
        Cary Coutant <ccoutant@...il.com>, linux-kbuild@...r.kernel.org
Subject: [PATCHv3 0/2] Salted build ids via linker sections

Hi,

This is v3 of the series to allow unique build-ids in the kernel. As
a reminder of the context:

""
In Fedora, the debug information is packaged separately (foo-debuginfo) and
can be installed separately. There's been a long standing issue where only one
version of a debuginfo info package can be installed at a time. Mark Wielaard
made an effort for Fedora 27 to allow parallel installation of debuginfo (see
https://fedoraproject.org/wiki/Changes/ParallelInstallableDebuginfo for
more details)

Part of the requirement to allow this to work is that build ids are
unique between builds. The existing upstream rpm implementation ensures
this by re-calculating the build-id using the version and release as a
seed. This doesn't work 100% for the kernel because of the vDSO which is
its own binary and doesn't get updated. After poking holes in a few of my
ideas, there was a discussion with some people from the binutils team about
adding --build-id-salt to let ld do the calculation debugedit is doing. There
was a counter proposal made about adding some extra information via a .comment
which will affect the build id calculation but just get stripped out.
""

I mentioned in the previous version that there were problems with
sporadic build failures. v3 switches to generating the linker script
directly instead of a header + a linker script to avoid this problem. I
also dropped the Kconfig completely (I can add it back as a guard if
this seems not small enough to want all the time). I've also dropped the
RFC tag since it's well formed enough at this point.

Laura Abbott (2):
  kbuild: Introduce build-salt linker script
  x86/vdso: Add build salt to the vDSO

 Makefile                     |  4 +++-
 arch/x86/entry/vdso/Makefile |  4 +++-
 scripts/.gitignore           |  1 +
 scripts/Makefile             |  9 ++++++++-
 scripts/gensalt              | 22 ++++++++++++++++++++++
 scripts/link-vmlinux.sh      |  3 ++-
 6 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100755 scripts/gensalt

-- 
2.17.0