This is a quick note on how to run x86 (32- or 64-bits) binaries on an Android phone (with an ARM64 CPU). I’m using Termux as my terminal. It has packages for QEMU user (qemu-user-i386 and qemu-user-x86-64 among others), which will run x86 binaries on an emulated x86 CPU. This alone is not enough though:

❯ lscpu | head -n2
Architecture:        aarch64
CPU op-mode(s):      32-bit, 64-bit

❯ readelf -h ./test | grep '\(Class\|Machine\):'
Class:                             ELF32
Machine:                           Intel 80386

❯ qemu-i386 ./test
qemu-i386: Could not open '/lib/ld-linux.so.2': No such file or directory

QEMU needs an x86 loader (as specified in the .interp section), which understandably isn’t available on Android:

❯ objdump -j .interp -s ./test

./test:     file format elf32-little

Contents of section .interp:
 8048154 2f6c6962 2f6c642d 6c696e75 782e736f  /lib/ld-linux.so
 8048164 2e3200                               .2.

Termux doesn’t package random loaders for foreign architectures, but it has PRoot, a chroot-like trick (based on LD_PRELOAD) that lets us install a basic Debian “container”:

❯ pkg install proot proot-distro
❯ proot-distro install debian
❯ cp ./test ~/../usr/var/lib/proot-distro/installed-rootfs/debian/home/
❯ proot-distro login debian
$ dpkg --add-architecture i386
$ apt update
$ apt install libc6:i386
$ qemu-i386 /home/test
Hello, World!

It works now! We can even debug the x86 program with GDB multiarch:

$ qemu-i386 -g 1234 /home/test

Now in a separate Termux session:

❯ proot-distro login debian
$ apt install gdb-multiarch
$ gdb-multiarch /home/test
(gdb)$ target remote localhost:1234
(gdb)$ # debug shit

It’s not much but not gonna lie, it feels great. :D