Re: [PATCH] KVM: arm64: nVHE: gen-hyprel: Silent build warnings

[tianjia.zhang]

Hi Nick,

On 10/10/24 11:23 PM, Nick Desaulniers wrote:
> On Thu, Oct 10, 2024 at 1:13 AM tianjia.zhang
> <tianjia.zhang@xxxxxxxxxxxxxxxxx> wrote:
> > On 10/9/24 7:07 PM, Marc Zyngier wrote:
> > > On Wed, 09 Oct 2024 09:57:51 +0100,
> > > Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx> wrote:
> > > > This patch silent the some mismatch format build warnings
> > > > with clang, like:
> > > >
> > > >     arch/arm64/kvm/hyp/nvhe/gen-hyprel.c:233:2: warning: format specifies
> > > >     type 'unsigned long' but the argument has type 'Elf64_Off'
> > > >     (aka 'unsigned long long') [-Wformat]
> > > >       233 |         assert_ne(off, 0UL, "%lu");
> > > >           |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >           |                              %llu
> > > >     arch/arm64/kvm/hyp/nvhe/gen-hyprel.c:193:34: note: expanded from macro 'assert_ne'
> > > >       193 | #define assert_ne(lhs, rhs, fmt)        assert_op(lhs, rhs, fmt, !=)
> > > >           |                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >     arch/arm64/kvm/hyp/nvhe/gen-hyprel.c:188:19: note: expanded from macro 'assert_op'
> > > >       187 |                                 " failed (lhs=" fmt ", rhs=" fmt        \
> > > >           |                                                 ~~~
> > > >       188 |                                 ", line=%d)", _lhs, _rhs, __LINE__);    \
> > > >           |                                               ^~~~
> > > >     arch/arm64/kvm/hyp/nvhe/gen-hyprel.c:167:17: note: expanded from macro 'fatal_error'
> > > >       166 |                 fprintf(stderr, "error: %s: " fmt "\n",                 \
> > > >           |                                               ~~~
> > > >       167 |                         elf.path, ## __VA_ARGS__);                      \
> > > >           |                                      ^~~~~~~~~~~
> > > >
> > > > Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
> > >
> > > I don't see these warnings. What version of LLVM are you using?
> >
> > I compiled the kernel on Apple Silicon M3 Pro in macOS 15.0.1, Maybe this is
> > a special scenario that is rarely used.
>
> Right, so I had an initial patch set for building the kernel from a
> MacOS host.  I sent a v1, but didn't chase sending a v2 at the time
> because there didn't appear to be any interest.
>
> https://www.phoronix.com/news/Linux-Compile-On-macOS
>
> Since then, I saw a v2 or even a v3 fly by (I was cc'ed).
>
> One issue I recall building from MacOS was that MacOS does not have an
> <elf.h> (their object file format is not ELF, but Mach-O).  I had to
> install some dependency through homebrew for that header.
>
> Just a guess but:
> Perhaps it defines Elf64_Off as a `unsigned long` incorrectly, and
> should be defining it as an `unsigned long long`.  I'd check if that's
> the case and if so, Tianjia, you may want to report that issue on the
> thread where folks are reposting the MacOS host support.

Thanks for the information, great work, very useful attempt.

I have successfully compiled the latest 6.11 rc2 on macOS 15.0.1 Apple
Silicon M3 chip. It seems that compiling on this version of the kernel
is easier. I just added three header files, elf.h, byteswap.h and
endian.h, and add the missing definitions. In addition, I fixed
scriptsj/mod/file2alias.c as you did, and it compiled successfully
without encountering other exceptions. The dependent toolchains are
all installed through brew, include make, llvm and lld.

Cheers,
Tianjia