Troubleshooting

QEMU shows no output

• Confirm you used -nographic and -bios none.
• Ensure the program writes to UART at 0x10000000.
• Verify the ELF is RV32 (readelf -h shows ELF32 + RISC-V).

GDB connects but breakpoints do not hit

• Start QEMU with -S so the CPU is halted.
• Make sure your ELF has symbols (-g).
• Set set arch riscv:rv32 in GDB.

Linker errors: missing _start

• Confirm src/start.s is included on the command line.
• Check src/link.ld uses ENTRY(_start).

QEMU exits immediately

• If main returns, _start should loop or execute wfi.
• Check that your _start function is present and not optimized away.

Exercises

1. Intentionally remove -T src/link.ld and observe the error.
2. Remove src/start.s and identify the missing symbol.
3. Change -march to rv32i and see if any examples break.

Summary

Most issues are caused by missing the startup file, using the wrong ELF, or forgetting QEMU flags. The fixes are deterministic and easy to confirm with readelf and GDB.