[llvm-dev] Cross-compiling for ARM on x86 with llvm/Clang

Wed Nov 2 04:34:25 PDT 2016

A simpler way might be to get ELLCC (http://ellcc.org):

rich at dev:~$ ~/ellcc/bin/ecc -target arm64v8-linux hello.c
rich at dev:~$ file a.out
a.out: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), 
statically linked, not stripped
rich at dev:~$ ~/ellcc/bin/qemu-aarch64 a.out
hello world
rich at dev:~$

ELLCC includes all the stuff you need: libraries, linker, etc.

That was on an x86_64 system.

-Rich

  On 11/02/2016 02:49 AM, via llvm-dev wrote:
>
> Hello list
>
> I have some problems when using x86 cross-compile the arm progress.
>
> First I know a way to get aarch64 binary in x86 with llvm/clang.
>
> There need two things prepared for cross-compile.
>
> 1.GUN ARM toolchain à  apt-get install gcc-arm-linux-gnueabi
> 2.Clang/llvm compile àhttp://clang.llvm.org/get_started.html
> clang -emit-llvm -target aarch64 helloworld.c -I 
> /usr/aarch64-linux-gnu/include -c
> (can get helloworld.bc)
> llc helloworld.bc -o helloworld.s
> aarch64-linux-gnu-gcc helloworld.s -o helloworld
> From the cmd above, I can get the aarch64 binary which is function 
> well in aarch64 machine.
> But, Is there other way that I can get aarch64 without gcc.
> When I try to use below:
> clang -v -target arm-linux-gnueabi --sysroot=/usr/arm-linux-gnueabi/ 
> helloworld.c -o hello
> I get:
> Obfuscator-LLVM clang version 3.6.1 (tags/RELEASE_361/final) (based on 
> Obfuscator-LLVM 3.6.1)
> Target: arm--linux-gnueabi
> Thread model: posix
> "/usr/local/bin/clang-3.6" -cc1 -triple armv4t--linux-gnueabi 
> -emit-obj -mrelax-all -disable-free -disable-llvm-verifier 
> -main-file-name arm.c -mrelocation-model static -mthread-model posix 
> -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases 
> -target-cpu arm7tdmi -target-feature +soft-float-abi -target-abi 
> aapcs-linux -mfloat-abi soft -v -dwarf-column-info -resource-dir 
> /usr/local/bin/../lib/clang/3.6.1 -isysroot /usr/arm-linux-gnueabi/ 
> -internal-isystem /usr/arm-linux-gnueabi//usr/local/include 
> -internal-isystem /usr/local/bin/../lib/clang/3.6.1/include 
> -internal-externc-isystem /usr/arm-linux-gnueabi//include 
> -internal-externc-isystem /usr/arm-linux-gnueabi//usr/include 
> -fdebug-compilation-dir /home/zyj/Desktop -ferror-limit 19 
> -fmessage-length 80 -mstackrealign -fno-signed-char -fobjc-runtime=gcc 
> -fdiagnostics-show-option -fcolor-diagnostics -o 
> /tmp/helloworld-6b36a6.o -x c helloworld.c
> clang -cc1 version 3.6.1 based upon Obfuscator-LLVM 3.6.1 default 
> target i386-pc-linux-gnu
> ignoring nonexistent directory "/usr/arm-linux-gnueabi//usr/local/include"
> ignoring nonexistent directory "/usr/arm-linux-gnueabi//usr/include"
> #include "..." search starts here:
> #include <...> search starts here:
> /usr/local/bin/../lib/clang/3.6.1/include
> /usr/arm-linux-gnueabi//include
> End of search list.
> "/usr/local/bin/ld" --sysroot=/usr/arm-linux-gnueabi/ -z relro -X 
> --hash-style=gnu --build-id --eh-frame-hdr -m armelf_linux_eabi 
> -dynamic-linker /lib/ld-linux.so.3 -o hello 
> /usr/arm-linux-gnueabi//lib/../lib/crt1.o 
> /usr/arm-linux-gnueabi//lib/../lib/crti.o crtbegin.o 
> -L/usr/arm-linux-gnueabi//lib/../lib -L/usr/arm-linux-gnueabi//lib 
> /tmp/helloworld-6b36a6.o -lgcc --as-needed -lgcc_s --no-as-needed -lc 
> -lgcc --as-needed -lgcc_s --no-as-needed crtend.o 
> /usr/arm-linux-gnueabi//lib/../lib/crtn.o
> /usr/local/bin/ld: unrecognised emulation mode: armelf_linux_eabi
> Supported emulations: elf_i386 i386linux elf32_x86_64 elf_x86_64 
> elf_l1om elf_k1om i386pep i386pe
> clang-3.6: error: linker command failed with exit code 1 (use -v to 
> see invocation)
> This seems that linker is wrong, so I change the ld point to 
> /usr/arm-linux-gnueabi/bin/ld
> (using: ln -s /usr/arm-linux-gnueabi/bin/ld ld)
> But I get anther question
> Obfuscator-LLVM clang version 3.6.1 (tags/RELEASE_361/final) (based on 
> Obfuscator-LLVM 3.6.1)
> Target: arm--linux-gnueabi
> Thread model: posix
> "/usr/local/bin/clang-3.6" -cc1 -triple armv4t--linux-gnueabi 
> -emit-obj -mrelax-all -disable-free -disable-llvm-verifier 
> -main-file-name arm.c -mrelocation-model static -mthread-model posix 
> -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases 
> -target-cpu arm7tdmi -target-feature +soft-float-abi -target-abi 
> aapcs-linux -mfloat-abi soft -v -dwarf-column-info -resource-dir 
> /usr/local/bin/../lib/clang/3.6.1 -isysroot /usr/arm-linux-gnueabi/ 
> -internal-isystem /usr/arm-linux-gnueabi//usr/local/include 
> -internal-isystem /usr/local/bin/../lib/clang/3.6.1/include 
> -internal-externc-isystem /usr/arm-linux-gnueabi//include 
> -internal-externc-isystem /usr/arm-linux-gnueabi//usr/include 
> -fdebug-compilation-dir /home/zyj/Desktop -ferror-limit 19 
> -fmessage-length 80 -mstackrealign -fno-signed-char -fobjc-runtime=gcc 
> -fdiagnostics-show-option -fcolor-diagnostics -o 
> /tmp/helloworld-fa5b7f.o -x c helloworld.c
> clang -cc1 version 3.6.1 based upon Obfuscator-LLVM 3.6.1 default 
> target i386-pc-linux-gnu
> ignoring nonexistent directory "/usr/arm-linux-gnueabi//usr/local/include"
> ignoring nonexistent directory "/usr/arm-linux-gnueabi//usr/include"
> #include "..." search starts here:
> #include <...> search starts here:
> /usr/local/bin/../lib/clang/3.6.1/include
> /usr/arm-linux-gnueabi//include
> End of search list.
> "/usr/local/bin/ld" --sysroot=/usr/arm-linux-gnueabi/ -z relro -X 
> --hash-style=gnu --build-id --eh-frame-hdr -m armelf_linux_eabi 
> -dynamic-linker /lib/ld-linux.so.3 -o hello 
> /usr/arm-linux-gnueabi//lib/../lib/crt1.o 
> /usr/arm-linux-gnueabi//lib/../lib/crti.o crtbegin.o 
> -L/usr/arm-linux-gnueabi//lib/../lib -L/usr/arm-linux-gnueabi//lib 
> /tmp/helloworld-fa5b7f.o -lgcc --as-needed -lgcc_s --no-as-needed -lc 
> -lgcc --as-needed -lgcc_s --no-as-needed crtend.o 
> /usr/arm-linux-gnueabi//lib/../lib/crtn.o
> /usr/local/bin/ld: cannot find crtbegin.o: No such file or directory
> /usr/local/bin/ld: cannot find -lgcc
> /usr/local/bin/ld: cannot find -lgcc_s
> /usr/local/bin/ld: cannot find /usr/arm-linux-gnueabi/lib/libc.so.6 
> inside /usr/arm-linux-gnueabi/
> /usr/local/bin/ld: cannot find 
> /usr/arm-linux-gnueabi/lib/libc_nonshared.a inside /usr/arm-linux-gnueabi/
> /usr/local/bin/ld: cannot find 
> /usr/arm-linux-gnueabi/lib/ld-linux.so.3 inside /usr/arm-linux-gnueabi/
> clang-3.6: error: linker command failed with exit code 1 (use -v to 
> see invocation)
> From above message I am confused about the:
> /usr/local/bin/ld: cannot find crtbegin.o: No such file or directory
> /usr/local/bin/ld: cannot find -lgcc
> /usr/local/bin/ld: cannot find -lgcc_s
> /usr/local/bin/ld: cannot find /usr/arm-linux-gnueabi/lib/libc.so.6 
> inside /usr/arm-linux-gnueabi/
> /usr/local/bin/ld: cannot find 
> /usr/arm-linux-gnueabi/lib/libc_nonshared.a inside /usr/arm-linux-gnueabi/
> /usr/local/bin/ld: cannot find 
> /usr/arm-linux-gnueabi/lib/ld-linux.so.3 inside /usr/arm-linux-gnueabi/
> While all these lib is at the right location, why error says ld cannot 
> find them.
> If you need more imformation from me, please let me know.
> Thanks
>
>
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