# Linux Kernel Module Cheat

### 33.2. Baremetal bootloaders

As can be seen from Baremetal GDB step debug, all examples under baremetal/, with the exception of `baremetal/arch/<arch>/no_bootloader`, start from our tiny bootloaders:

- baremetal/lib/arm.S

- baremetal/lib/aarch64.S

Out simplistic bootloaders basically setup up just enough system state to allow calling:

- C functions such as `exit` from the assembly examples

- the `main` of C examples itself

The most important things that we setup in the bootloaders are:

- the stack pointer

- NEON: Section 33.11.2, “aarch64 baremetal NEON setup”

- TODO: we don’t do this currently but maybe we should setup BSS

The C functions that become available as a result are:

- Newlib functions implemented at baremetal/lib/syscalls.c

- `lkmc_` non-Newlib functions implemented at lkmc.c

It is not possible to call those C functions from the examples that don’t use a bootloader.

For this reason, we tend to create examples with bootloaders, as it is easier to write them portably.