Having a hard time compiling on Apple Silicon

[ikatson]

Hi, I'm not sure if Apple Silicon is even a configuration that is supposed to work, but libkrun's support of macos/arm64 indicated that is probably is. As it lists libkrunfw as a dependency, I'm trying to build libkrunfw on Apple M1, which makes it build the kernel on osx natively.

There's a myriad of issues I was facing so far, here are some of them:

1. ARCH variable is not exported, so kernel build system does not see ARCH=arm64. Worked around by exporting it.

2. Files in the root folder are called like *aarch64, but on M1 uname -m is arm64. Worked around by renaming all the files.

3. System linker /usr/bin/ld is incompatible with the kernel build system, spits out messages like ld: unknown option: --version. Worked around by symlinking ld.lld into my PATH as ld.

4. There's no elf.h on big sur. So far worked around (kind of) by using elf.h from libelf.

5. Maybe it is from the previous problem, but getting this output during the kernel build MKELF scripts/mod/elfconfig.h, Error: not ELF. Worked around by temporarily making mk_elfconfig.c always return 0.

6. uuid_t from OSX is incompatible with kernel one, here's the error

    scripts/mod/file2alias.c:47:3: error: typedef redefinition with different types ('struct uuid_t' vs '__darwin_uuid_t' (aka 'unsigned char [16]'))
    } uuid_t;
      ^
    /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_uuid_t.h:31:25: note: previous definition is here
    typedef __darwin_uuid_t uuid_t;
                            ^
    scripts/mod/file2alias.c:1329:42: error: array initializer must be an initializer list or string literal
            DEF_FIELD(symval, tee_client_device_id, uuid);
                                                    ^
    2 errors generated.
    make[2]: *** [scripts/Makefile.host:112: scripts/mod/file2alias.o] Error 1
    make[1]: *** [Makefile:1205: prepare0] Error 2
   

I have no idea how far will I go trying to overcome all this, but the main question stands - is it supposed to be possible, or it's not a configuration that was ever tested?

[slp]

Building a Linux kernel on macOS is not an easy feat. That's why libkrunfw includes https://github.com/containers/libkrunfw/blob/main/build_on_krunvm.sh, a script that allows you to build the kernel under Linux using krunvm on macOS.

Of course, that means that you need libkrunfw+libkrun+krunvm in your system to be able to build libkrunfw, which is kind of a chicken<->egg problem, but there are binaries (bottles) in the krunvm Homebrew repo, and this is significantly easier and less cumbersome than any other solution I could come up with.

[ikatson]

@slp thanks, that's perfect! Did not know about the homebrew repo, so it might be worth mentioning in libkrun/libkrunfw READMEs.

[slp]

@ikatson Yeah, I was waiting to have them in the official Homebrew repo, but we can probably point to the one we have and just update it in the future.