Messages in this thread | | | Date | Mon, 23 Apr 2018 10:42:24 -0700 | From | Matthias Kaehlcke <> | Subject | Re: Clang patch stacks for LTS kernels (v4.4 and v4.9) and status update |
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Hi Sedat,
On Mon, Apr 23, 2018 at 03:56:41PM +0200, Sedat Dilek wrote: > [ CC Nick ] > [ CC Arnd ] > [ CC JF ]
> I wrote some early documentation (wiki) and tested/booted a > clang-compiled kernel on x86-64 bare metal. > The project was called "lll-project" these days. > The followup - LLVMlinux project - seems to be somehow dead?
Yes, I think it stalled in 2014 or so. There is still a mailing list with very occasional traffic.
> After reading your posting, I got really excited and had a quick look > over the Linux v4.9.y-LTS patch-stack with additional stuff: > > $ git fetch https://chromium.googlesource.com/chromiumos/third_party/kernel > refs/sandbox/mka/llvm/v4.9_ext > $ git checkout -b llvm_v4.9_ext FETCH_HEAD > > I like your commit subjects and messages. > > Before starting to compile I have some questions, I hope you can answer them. > > [ CLANG-VERSION ] > > Here on Debian/testing (will get Version 10 with codename "buster") > AMD64 I have the choice of installing CLANG v4.0.1, v5.0.1 and v6.0.0. > As you point out LLVM/CLANG v5.0 or higher are a good and faster > choice than v4.0. > Using CLANG >= 5.0 makes the *CLANG* patch-series obsolete?
Correct, preferably use clang v6 or newer.
> [ REFRESH PATCH-STACK ] > > What about the *FROMGIT* and *CUSTOM* patch-series? > Are they in upstream in the meantime?
CUSTOM patches address issues in older kernels that have been fixed upstream in a different, not easily backportable way. They will never land in upstream.
FROMGIT patches should eventually land upstream, since they were taken from a maintainer tree.
The commit message includes the upstream git hash, so you can easily check if it has landed (though in some cases the hash changes ...)
> If yes, will you refresh this v4.9.y-LTS patch-stack?
I eventually will, the two FROMGIT patches are relatively recent, and respinning the trees just to update the tags isn't one of my priorities.
> [ ASM-GOTO ] > > Foremore, I have seen you have a "refs/sandbox/mka/llvm/v4.14" Git branch. > Linux v4.14 is also an LTS release.
Yes, there is also a follow up post: https://lkml.org/lkml/2017/11/22/943
> After Linux v4.9 "asm-goto" support was added which is GCC specific.
asm-goto was optional until a few weeks ago, when x86 maintainers decided to make it mandatory, and thus break clang builds for x86:
https://lkml.org/lkml/2018/4/2/486
> Is there a workaround to compile Linux-kernel with any CLANG > version?
You could revert the patch that makes asm-goto mandatory.
> You happen to know the status in LLVM upstream?
I know people are actively working on this, but don't know an ETA.
> [ X86-EFLAGS/IF ] > > AFAICS, I remember an EFLAGS/IF problem on X86 and interrupt handling. > You happen to know if this is fixed in LLVM upstream? > Some LLVM developers were interested in fixing this. > Can you comment on this, JF (we had some email conversation in private in 2016)?
Yes, this has been fixed recently: https://bugs.llvm.org/show_bug.cgi?id=36028
Cheers
Matthias
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