# Re: \[PATCH 3/3\] isystem: delete global -isystem compile option

- From: Nathan Chancellor \<nathan@kernel.org\>
- Date: 2021-08-02 20:38:16 
- List: linux-arch
- Page: https://ratatoskr.run/linux-arch/2021/08/1465749
- Thread: https://ratatoskr.run/linux-arch/2021/08/1464433/t.md

```text
On 8/2/2021 1:32 PM, Alexey Dobriyan wrote:
> On Mon, Aug 02, 2021 at 11:18:32AM -0700, Nathan Chancellor wrote:
>> On Sun, Aug 01, 2021 at 11:13:36PM +0300, Alexey Dobriyan wrote:
>>> In theory, it enables "leakage" of userspace headers into kernel which
>>> may present licensing problem.
>>>
>>> In practice, only stdarg.h was used, stdbool.h is trivial and SIMD
>>> intrinsics are contained to a few architectures and aren't global
>>> problem.
>>>
>>> In general, kernel is very self contained code and -isystem removal
>>> will further isolate it from Ring Threeland influence.
>>>
>>> nds32 keeps -isystem globally due to intrisics used in entrenched header.
>>>
>>> -isystem is selectively reenabled for some files.
>>>
>>> Not compile tested on hexagon.
>>
>> With this series on top of v5.14-rc4 and a tangential patch to fix
>> another issue, ARCH=hexagon defconfig and allmodconfig show no issues.
>>
>> Tested-by: Nathan Chancellor <redacted> # build (hexagon)
>
> Oh wow, small miracle. Thank you!
>
> Where can I find a cross-compiler? This link doesn't seem to have one
> https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/11.1.0/

Hexagon only builds with LLVM now because of the bump to require gcc 4.9: https://lore.kernel.org/r/20210623141854.GA32155@lst.de/

Brian Cain has a link in that thread to an LLVM toolchain that works well for defconfig (allmodconfig requires LLVM 13/14 from git). Otherwise, https://apt.llvm.org or LLVM from your package manager should be sufficient for the same targets.

$ make -skj"$(nproc)" ARCH=hexagon CROSS_COMPILE=hexagon-linux-musl- LLVM=1 LLVM_IAS=1 defconfig all

should work fine as long as the bin folder for whatever toolchain you download is in your PATH.

Cheers,
Nathan
```