# Linux Kernel Module Cheat

### 33.4. Baremetal command line arguments

QEMU and gem5 currently supports baremetal CLI arguments!

You can see them in action e.g. with:

    ./run --arch aarch64 --baremetal userland/c/command_line_arguments.c --cli-args 'aa bb cc'
    ./run --arch aarch64 --userland userland/c/command_line_arguments.c --cli-args 'aa bb cc'

both of which output the exact same thing:

    aa
    bb
    cc

This is implemented by parsing the command line arguments and placing them into memory where the code will find them.

This works by:

- fixing the `argc` and `argv` addresses in memory in the Baremetal linker script

- the Baremetal bootloaders pass those addresses correctly to the call of `main`

- our Python scripts write the desired binary memory values to a file

- QEMU loads those files into memory with `-device loader`: https://github.com/qemu/qemu/blob/60905286cb5150de854e08279bca7dfc4b549e91/docs/generic-loader.txt

It is worth noting that e.g. ARM has a Semihosting mechanism for loading CLI arguments through `SYS_GET_CMDLINE`, but our mechanism works in principle for any ISA.

- gem5 baremetal arm CLI args