The student is using arm-linux-gnueabi-gcc to assemble and link two ARM assembly files (memory.s and io.s) for a university course. Everything works in the default little-endian mode, but adding -mbig-endian — purely so that .data values display in big-endian order — breaks the link with:

libgcc_s.so.1: error adding symbols: file in wrong format

Why this is interesting: it exposes a misunderstanding that even experienced engineers occasionally hit. The -mbig-endian flag is not a cosmetic toggle on the data section — it switches the entire ABI/EABI variant the compiler targets. ARM EABI has two distinct, incompatible variants (armeb and arm), each with their own ELF EI_DATA byte, instruction encoding endianness for fetched words, and — critically — their own prebuilt system libraries. The toolchain prefix arm-linux-gnueabi- ships only the little-endian libgcc_s.so.1. When you flip to big-endian, the linker dutifully tries to pull in the same multilib path's libgcc and gets back an ELF whose e_ident[EI_DATA] says little-endian. Mixing endiannesses in one executable is forbidden, so ld rejects it with the famously cryptic "wrong format" error.

Direction toward a solution:

• Use a toolchain that actually ships big-endian multilibs, e.g. arm-linux-gnueabihf built with --with-multilib-list=... including be, or the dedicated armeb-linux-gnueabi- cross compiler.
• If they don't actually need libc/libgcc (pure assembly that doesn't call into runtime helpers), link with -nostdlib -nostartfiles and provide their own _start. This sidesteps the libgcc dependency entirely.
• If the goal really is just to view big-endian-ordered bytes in the data section for learning, they can keep little-endian compilation and use .byte directives to lay bytes out manually, or post-process with objcopy --reverse-bytes=4 on the section.

Gotchas:

• ARM also supports BE-8 vs BE-32 (data-only vs word-invariant big-endian). Modern ARMv7 essentially mandates BE-8; mixing modes silently corrupts instruction fetch.
• Even with a proper big-endian toolchain, QEMU user-mode emulation needs qemu-armeb, not qemu-arm.
• The -mbig-endian flag must be passed to both compile and link steps; passing it only to one produces this same error.