Cross toolchain question about tc-build HOT 6 CLOSED

clang is multi-targeted by default unlike GCC, so it builds code for both the host and cross architectures through the --target flag.

from tc-build.

Yes, but Linux cross-compile cmdline looks like make -j8 O=out ARCH=arm64 CC=clang CROSS_COMPILE=aarch64-linux-gnu- CC=clang READELF=llvm-readelf OBJCOPY=llvm-objcopy AS=llvm-as LD=ld.lld NM=llvm-nm OBJDUMP=llvm-objdump STRIP=llvm-strip CROSS_COMPILE_ARM32=arm-linux-gnueabi- LLVM=1 without CROSS_COMPILE it won't build vDSO. Is aarch64-linux-gnu-* thing called binutils?

from tc-build.

Is aarch64-linux-gnu-* thing called binutils?

Yes.

CROSS_COMPILE has two meanings depending on the age of the kernel tree. It is used to prefix as, gcc, ld, etc but it is also used as the value for --target prior to commit ddc72c9659b5 ("kbuild: clang: do not use CROSS_COMPILE for target triple") (same with CROSS_COMPILE_ARM32 but for the 32-bit vDSO). Since you have specified all the make variables that would have been prefixed with CROSS_COMPILE, you would think that you could drop it, but it is still being used for --target. You don't need the aarch64-linux-gnu- tools as a result.

Two additional comments about your build command:

1. LLVM=1 is the same thing as AR=llvm-ar CC=clang LD=ld.lld NM=llvm-nm OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf STRIP=llvm-strip, you don't need to specify both.
2. AS=llvm-as is incorrect, as $(AS) does not exist after commit aa824e0c962b ("kbuild: remove AS variable") and even if it did, llvm-as is the LLVM IR to bitcode assembler. You are looking for LLVM_IAS=1 if you want to use the integrated assembler.

from tc-build.

I see, should I use build-binutils.py for that? Or there's another way for binutils?

CROSS_COMPILE has two meanings depending on the age of the kernel tree.

Kernel is really old (4.14), due vendor issues it won't be bumped to at least 4.19

You don't need the aarch64-linux-gnu- tools as a result.

Without that it probably uses x86 clang (message about broken assembly or smth)

Two additional comments about your build command

Thanks!

from tc-build.

Yes, that is why build-binutils.py exists, you can get the aarch64-linux-gnu tools via build-binutils.py -t aarch64 (see -h for more options if you need them).

from tc-build.

Thanks! For someone who will find that: I prefixed them with ./build-binutils.py -i target_dir -t aarch64 and binutils will be in target_dir/bin/

from tc-build.