Build issues on an AArch32 userspace when running an AArch64 kernel

[lgeek]

Trying to build on a system running Linux 3.18.0 (AArch64) in an AArch32 chroot (Arch Linux ARM, gcc 6.3.1, cmake 3.7.2). The first error I get is:

[ 11%] Building ASM object dynamorio/core/CMakeFiles/drhelper.dir/arch/asm_shared.asm.o
In file included from /home/cosmin/drmemory/dynamorio/core/arch/asm_shared.asm:37:0:
/home/cosmin/drmemory/dynamorio/core/arch/asm_defines.asm:65:3: error: #error ARM is only 32-bit; AARCH64 is 64-bit
 # error ARM is only 32-bit; AARCH64 is 64-bit
   ^~~~~

I guessed that the architecture reported by the kernel is used at some point in the build process, so I've then enabled the PER_LINUX32 personality by prepending linux32 to the cmake and make commands (on a clean build). This changes the output of uname, /proc/cpuinfo, etc to be compatible with that on AArch32 kernels. The build then completed.

DynamoRIO 266b8a3c8b on its own also fails to build without PER_LINUX32, but with a different error, so I think both the DR and Dr. Memory build systems misbehave.

[  8%] Building CXX object clients/drcachesim/CMakeFiles/drcachesim_ops.dir/common/options.cpp.o
c++: error: unrecognized command line option '-mpreferred-stack-boundary=2'; did you mean '-mstructure-size-boundary='?

I've generally found the output of $(CC) -dumpmachine to be a more robust way of detecting the target architecture, but I'm not sure how well that would work with your build system.

[egrimley]

This might be a CMake bug rather than a DynamoRIO/DrMemory bug. Personally I always (except when I forget) use linux32 when entering the chroot, thus:

chroot debian-armhf-stretch linux32 /bin/su -

Some interesting comments on -dumpmachine here:
https://stackoverflow.com/questions/28505562/is-there-a-gcc-option-to-print-the-target-triplet-when-cross-compiling

Asking the C compiler does make sense, because you could be on a system that is capable of running lots of different kinds of binary. For example, with one kernel I built:

$ arch-test 
arm64
arm64ilp32
armel
armhf

(See https://packages.debian.org/sid/admin/arch-test. It's unlikely that DynamoRIO will ever be ported to arm64ilp32 but thinking about how it would be handled might contribute to a better understanding of what we mean by "architecture".)