Can old ARM32 binary files be run on AARCH64 kernel?

Question

I am curious about the feasibility of running old ARM32-Linux programs on AARCH64-Linux machines and I conducted some experiments:

1. write a program "Hello, World!" and compile it statically with arm-none-linux-gnueabi-gcc and aarch64-linux-gnu-gcc.
2. statically build and create a ramdisk using busybox and aarch64 compiler.
3. put the 2 "Hello, World!" programs (in ARM32 and AARCH64) to the ramdisk.
4. build a simple AARCH64-Linux kernel with vexpress_defconfig and aarch64 compiler.
5. run the kernel and ramdisk using qemu-system-aarch64.

(All binary files including busybox in the ramdisk are statically compiled.)

Result:

1. "Hello, World!" program in AARCH64 was successfully executed.
2. "Hello, World!" program in ARM32 cannot be run but shows the messages:

line 1: syntax error: unexpected word (expecting ")")

Is there suggestion or expertise to solve the issue above?

Answer 1

Thank you moonbutt74. You had provided an useful clue for me to seek the solution to that issue.

To enable the support of running ARM32-Linux programs on AARCH64 kernel, the option in the kernel should be selected:

1. run make menuconfig ARCH=arm64
2. go to the option and select it:

Userspace binary formats ---> Kernel support for 32-bit EL0

3. recompile the kernel by running make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-

4. run the recompiled kernel with ramdisk and qemu-system-aarch64.

5. the "Hello, World!" programs in (ARM32 and AARCH64) can be executed successfully !!