Re: [GIT PULL] Clang feature updates for v5.14-rc1

[Kees Cook]

On Tue, Jun 29, 2021 at 02:14:00PM +0100, Mark Rutland wrote:
> Hi Kees,
> 
> On Mon, Jun 28, 2021 at 12:32:24PM -0700, Kees Cook wrote:
> > Hi Linus,
> > 
> > Please pull these Clang feature updates for v5.14-rc1.
> > 
> > Thanks!
> > 
> > -Kees
> > 
> > The following changes since commit d07f6ca923ea0927a1024dfccafc5b53b61cfecc:
> > 
> >   Linux 5.13-rc2 (2021-05-16 15:27:44 -0700)
> > 
> > are available in the Git repository at:
> > 
> >   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git tags/clang-features-v5.14-rc1
> > 
> > for you to fetch changes up to 6a0544606ec7f03e4a2534c87ea989de4bac41ae:
> > 
> >   pgo: rectify comment to proper kernel-doc syntax (2021-06-28 12:10:31 -0700)
> > 
> > ----------------------------------------------------------------
> > Clang feature updates for v5.14-rc1
> > 
> > The big addition for this merge window is the core support for Clang's
> > Profile Guided Optimization, which lets Clang build the kernel for
> > improved performance when running specific kernel workloads. This
> > currently covers only vmlinux, but module support is under active
> > development. (Sami Tolvanen, Bill Wendling, Kees Cook, Jarmo Tiitto,
> > Lukas Bulwahn)
> 
> I thought the PGO stuff was on hold given Peter had open concerns, e.g.
> 
> https://lore.kernel.org/r/20210614154639.GB68749@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ... and there didn't seem to be a strong conclusion to the contrary.

Hi! Whoops, I think you weren't CCed on the later threads over noinstr:
https://lore.kernel.org/lkml/YNGQV09E9xAvvppO@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

I understood that as the blocker for Peter from the earlier thread.

> 
> > Added CC_HAS_NO_PROFILE_FN_ATTR in preparation for PGO support in
> > the face of the noinstr attribute, paving the way for PGO and fixing
> > GCOV. (Nick Desaulniers)
> > 
> > x86_64 LTO coverage is expaned to 32-bit x86. (Nathan Chancellor)
> > 
> > Small fixes to CFI. (Mark Rutland, Nathan Chancellor)
> 
> FWIW, all the rest of this looks good to me.

Thanks!

-Kees

> 
> Thanks,
> Mark.
> 
> > 
> > ----------------------------------------------------------------
> > Bill Wendling (1):
> >       pgo: rename the raw profile file to vmlinux.profraw
> > 
> > Jarmo Tiitto (2):
> >       pgo: Limit allocate_node() to vmlinux sections
> >       pgo: Fix sleep in atomic section in prf_open()
> > 
> > Kees Cook (2):
> >       MAINTAINERS: Expand and relocate PGO entry
> >       pgo: Clean up prf_open() error paths
> > 
> > Lukas Bulwahn (1):
> >       pgo: rectify comment to proper kernel-doc syntax
> > 
> > Mark Rutland (1):
> >       CFI: Move function_nocfi() into compiler.h
> > 
> > Nathan Chancellor (2):
> >       MAINTAINERS: Add Clang CFI section
> >       x86, lto: Enable Clang LTO for 32-bit as well
> > 
> > Nick Desaulniers (3):
> >       compiler_attributes.h: define __no_profile, add to noinstr
> >       compiler_attributes.h: cleanups for GCC 4.9+
> >       Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR
> > 
> > Sami Tolvanen (1):
> >       pgo: Add Clang's Profile Guided Optimization infrastructure
> > 
> >  Documentation/dev-tools/index.rst     |   1 +
> >  Documentation/dev-tools/pgo.rst       | 127 +++++++++++
> >  MAINTAINERS                           |  25 ++
> >  Makefile                              |   3 +
> >  arch/Kconfig                          |   8 +
> >  arch/arm64/Kconfig                    |   1 +
> >  arch/arm64/include/asm/compiler.h     |  16 ++
> >  arch/arm64/include/asm/memory.h       |  16 --
> >  arch/s390/Kconfig                     |   1 +
> >  arch/x86/Kconfig                      |   6 +-
> >  arch/x86/boot/Makefile                |   1 +
> >  arch/x86/boot/compressed/Makefile     |   1 +
> >  arch/x86/crypto/Makefile              |   3 +
> >  arch/x86/entry/vdso/Makefile          |   1 +
> >  arch/x86/kernel/Makefile              |   3 +
> >  arch/x86/kernel/vmlinux.lds.S         |   2 +
> >  arch/x86/platform/efi/Makefile        |   1 +
> >  arch/x86/purgatory/Makefile           |   1 +
> >  arch/x86/realmode/rm/Makefile         |   1 +
> >  arch/x86/um/vdso/Makefile             |   1 +
> >  drivers/firmware/efi/libstub/Makefile |   1 +
> >  include/asm-generic/vmlinux.lds.h     |  32 +++
> >  include/linux/compiler.h              |  10 +
> >  include/linux/compiler_attributes.h   |  19 +-
> >  include/linux/compiler_types.h        |   2 +-
> >  include/linux/mm.h                    |  10 -
> >  init/Kconfig                          |   3 +
> >  kernel/Makefile                       |   1 +
> >  kernel/gcov/Kconfig                   |   1 +
> >  kernel/pgo/Kconfig                    |  37 +++
> >  kernel/pgo/Makefile                   |   5 +
> >  kernel/pgo/fs.c                       | 413 ++++++++++++++++++++++++++++++++++
> >  kernel/pgo/instrument.c               | 188 ++++++++++++++++
> >  kernel/pgo/pgo.h                      | 211 +++++++++++++++++
> >  scripts/Makefile.lib                  |  10 +
> >  35 files changed, 1130 insertions(+), 32 deletions(-)
> >  create mode 100644 Documentation/dev-tools/pgo.rst
> >  create mode 100644 kernel/pgo/Kconfig
> >  create mode 100644 kernel/pgo/Makefile
> >  create mode 100644 kernel/pgo/fs.c
> >  create mode 100644 kernel/pgo/instrument.c
> >  create mode 100644 kernel/pgo/pgo.h
> > 
> > -- 
> > Kees Cook
> 
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-- 
Kees Cook