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When building zig natively from source on an RK3588 SoC board, the
generated stage3 compiler will use unsupported 'sha256h.4s' instructions
due to mis-identified CPU features. This happens when trying to
compile a new project generated with "zig init"
$ ~/devel/zig/build/stage3/bin/zig build
thread 919 panic: Illegal instruction at address 0x1fdc0c4
/home/dliviu/devel/zig/lib/std/crypto/sha2.zig:223:29: 0x1fdc0c4 in round (zig)
asm volatile (
^
/home/dliviu/devel/zig/lib/std/crypto/sha2.zig:168:20: 0x1fdca87 in final (zig)
d.round(&d.buf);
^
/home/dliviu/devel/zig/lib/std/crypto/sha2.zig:180:20: 0x1c8bb33 in finalResult (zig)
d.final(&result);
^
/mnt/home/dliviu/devel/zig/src/Package/Fetch.zig:754:49: 0x1a3a8eb in relativePathDigest (zig)
return Manifest.hexDigest(hasher.finalResult());
^
/mnt/home/dliviu/devel/zig/src/main.zig:5128:53: 0x1a37413 in cmdBuild (zig)
Package.Fetch.relativePathDigest(build_mod.root, global_cache_directory),
^
???:?:?: 0xff09ffffffffffff in ??? (???)
Unwind information for `???:0xff09ffffffffffff` was not available, trace may be incomplete
???:?:?: 0x3f7f137 in ??? (???)
Aborted (core dumped)
system/linux.zig parses "/proc/cpuinfo" to determine the CPU features, but it
seems to generate the wrong set of features from:
$ cat /proc/cpuinfo
processor : 0
BogoMIPS : 48.00
Features : fp asimd evtstrm crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop asimddp
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x2
CPU part : 0xd05
CPU revision : 0
.....
processor : 4
BogoMIPS : 48.00
Features : fp asimd evtstrm crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop asimddp
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x4
CPU part : 0xd0b
CPU revision : 0
.....
To fix this, use the Linux kernel way of reading the feature registers as documented
here: https://www.kernel.org/doc/html/latest/arch/arm64/cpu-feature-registers.html
arm.zig already has the code to parse the feature register values, we just need to
collect them in an array and pass them for identification.
Signed-off-by: Liviu Dudau <liviu@dudau.co.uk>