AS_IS_LLVM=y v5.10.y patches

AS_IS_LLVM=y v5.10.y patches

[Nick Desaulniers]

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Dear Stable Kernel Maintainers,
Please consider applying the attached mbox file to v5.10.y.

For Android's T release in 2022, I'd like to verify whether clang's
integrated assembler was used. For the compiler and linker, they both
embed a string in object file that can be read via:

$ llvm-readelf -p .comment <object file>
String dump of section '.comment':
  [     0]  Linker: LLD 14.0.0
  [    13]  clang version 14.0.0 (git@github.com:llvm/llvm-project.git
2ff26d0e794ab7300d94051f91be7da274cc348e)

Unfortunately, the assembler version is not also embedded. Instead,
I'd like to check for the presence of AS_IS_LLVM in .config.  This
series helps move some toolchain version checking from build time to
configure time, though that's only a modest improvement and I don't
_have_ to check this config.

The mbox contains the following 7 commits:

1. commit 052c805a1851 ("kbuild: LD_VERSION redenomination")
2. commit aec6c60a01d3 ("kbuild: check the minimum compiler version in Kconfig")
3. commit 02aff8592204 ("kbuild: check the minimum linker version in Kconfig")
4. commit 1f09af062556 ("kbuild: Fix ld-version.sh script if LLD was
built with LLD_VENDOR")
5. commit bcbcf50f5218 ("kbuild: fix ld-version.sh to not be affected
by locale")
6. commit e24b3ffcf421 ("kbuild: collect minimum tool versions into
scripts/min-tool-version.sh")
7. commit ba64beb17493 ("kbuild: check the minimum assembler version
in Kconfig")

They landed respectively upstream in:
1. v5.12-rc1
2. v5.12-rc1
3. v5.12-rc1
4. v5.12-rc3
5. v5.12-rc3
6. v5.13-rc1
7. v5.13-rc1

I needed to manually resolve conflicts in the respective patches:
1. N/A
2. N/A
3. scripts/lld-version.sh due to df58fb431aa3
("scripts/lld-version.sh: Rewrite based on upstream ld-version.sh")
being 5.10 only. This file is removed regardless of what it looks
like.
4. N/A
5. N/A
6. N/A
7. arch/Kconfig due to missing dc5723b02e523 ("kbuild: add support for
Clang LTO") which landed in v5.12-rc1.

These conflicts are also noted in the commit messages of the commits
in the mbox.
-- 
Thanks,
~Nick Desaulniers

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Re: AS_IS_LLVM=y v5.10.y patches

[Greg KH]

On Wed, Dec 29, 2021 at 01:55:34PM -0800, Nick Desaulniers wrote:
> Dear Stable Kernel Maintainers,
> Please consider applying the attached mbox file to v5.10.y.
> 
> For Android's T release in 2022, I'd like to verify whether clang's
> integrated assembler was used. For the compiler and linker, they both
> embed a string in object file that can be read via:
> 
> $ llvm-readelf -p .comment <object file>
> String dump of section '.comment':
>   [     0]  Linker: LLD 14.0.0
>   [    13]  clang version 14.0.0 (git@github.com:llvm/llvm-project.git
> 2ff26d0e794ab7300d94051f91be7da274cc348e)
> 
> Unfortunately, the assembler version is not also embedded. Instead,
> I'd like to check for the presence of AS_IS_LLVM in .config.  This
> series helps move some toolchain version checking from build time to
> configure time, though that's only a modest improvement and I don't
> _have_ to check this config.
> 
> The mbox contains the following 7 commits:
> 
> 1. commit 052c805a1851 ("kbuild: LD_VERSION redenomination")
> 2. commit aec6c60a01d3 ("kbuild: check the minimum compiler version in Kconfig")
> 3. commit 02aff8592204 ("kbuild: check the minimum linker version in Kconfig")
> 4. commit 1f09af062556 ("kbuild: Fix ld-version.sh script if LLD was
> built with LLD_VENDOR")
> 5. commit bcbcf50f5218 ("kbuild: fix ld-version.sh to not be affected
> by locale")
> 6. commit e24b3ffcf421 ("kbuild: collect minimum tool versions into
> scripts/min-tool-version.sh")
> 7. commit ba64beb17493 ("kbuild: check the minimum assembler version
> in Kconfig")
> 
> They landed respectively upstream in:
> 1. v5.12-rc1
> 2. v5.12-rc1
> 3. v5.12-rc1
> 4. v5.12-rc3
> 5. v5.12-rc3
> 6. v5.13-rc1
> 7. v5.13-rc1
> 
> I needed to manually resolve conflicts in the respective patches:
> 1. N/A
> 2. N/A
> 3. scripts/lld-version.sh due to df58fb431aa3
> ("scripts/lld-version.sh: Rewrite based on upstream ld-version.sh")
> being 5.10 only. This file is removed regardless of what it looks
> like.
> 4. N/A
> 5. N/A
> 6. N/A
> 7. arch/Kconfig due to missing dc5723b02e523 ("kbuild: add support for
> Clang LTO") which landed in v5.12-rc1.

While I can appreciate your quest to make your Android kernel trees
smaller, this really looks like a "new feature".  What bug/issue is this
fixing that is currently present in 5.10 that people are hitting today?

thanks,

greg k-h

Re: AS_IS_LLVM=y v5.10.y patches

[Nick Desaulniers]

On Thu, Dec 30, 2021 at 2:37 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Dec 29, 2021 at 01:55:34PM -0800, Nick Desaulniers wrote:
> > Dear Stable Kernel Maintainers,
> > Please consider applying the attached mbox file to v5.10.y.
> >
> > For Android's T release in 2022, I'd like to verify whether clang's
> > integrated assembler was used.
>
> While I can appreciate your quest to make your Android kernel trees
> smaller, this really looks like a "new feature".  What bug/issue is this
> fixing that is currently present in 5.10 that people are hitting today?

Sure, not really a bug, I'll keep these downstream then.
-- 
Thanks,
~Nick Desaulniers