On 8/2/2021 1:32 PM, Alexey Dobriyan wrote:

On Mon, Aug 02, 2021 at 11:18:32AM -0700, Nathan Chancellor wrote:

quoted

On Sun, Aug 01, 2021 at 11:13:36PM +0300, Alexey Dobriyan wrote:

quoted

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/ (local)

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