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

[Nathan Chancellor]

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 <nathan at kernel> # 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