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Master the fundamental concepts of arm assembly (aarch64) through this focused micro-challenge.
Apple M-series, every Android device, and AWS Graviton all run AArch64. Unlike x86's variable-length instructions, AArch64 uses fixed 32-bit encodings. It is a load/store architecture: arithmetic touches registers, not memory operands.
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Syscall 64 is write, 93 is exit. musl and glibc wrap the same svc #0 entry.
For this exercise, you will assemble a freestanding hello with GNU as and link without libc. This task asks you to print Hello, ARM!\n using only write and exit, because every arm64 container and iOS kernel extension ultimately bottoms out here.
Keep the relevant man page, ABI doc, or Rust reference chapter open while you work. When your output disagrees with the reference implementation on the same machine, the mismatch is usually an alignment rule, an off-by-one terminator, or a register slot you misread in GDB. Skim the official documentation for the tool or ABI named in the exercise; the prose changes, but register roles, syscall numbers, and ownership rules stay stable across releases.
Simulate the AArch64 svc #0 write(2) syscall setup for a hello message.
Input is one line: the message your .data section would hold (the classic buffer always ends with an embedded '\n', like db "Hello, ARM!", 10). Compute and print the exact register state the kernel would see (x8 = the arm64 write syscall number, x0 = fd for stdout, x1 = the simulated buffer address 0x400080, x2 = the byte count (message length + the newline)), then dump every buffer byte as uppercase hex, exactly what gdb's x/16x would show.
Requirements:
Three hints are available for this task, revealed one at a time inside the code workspace so you can struggle productively before seeing them.
Every task includes starter code, theory, and hidden tests so you can implement and verify locally in the browser.
How it works