It is too risky to rely on the compiler to not insert any operations using the
stack.
Having a stack-setting call in Rust using the cortex-a crate as the first action
in a Rust-only _start() function does not work if you're subsequently using the
stack, because the compiler often inserts the operations to make room on the
stack to prepare a function call BEFORE the call to set the stack, which crashes
the boot process.
Hence, keep on using a small piece of assembly boot code throughout.
- Don't wildcard-import from arch modules. Make it explicit.
- Put translation table code into its own module.
- Put boot code in boot.rs instead of cpu.rs
- Other minor changes, most memory subsystem.
We have to remove the `#[naked]` attribute from `_start` for now, since it emits
a warning now when used with non-asm statements in the function body. For now,
just hope for the compiler's mercy to not emit code using the stack pointer
before we've actually set up a stack.
register-rs 1.0.0 now uses UnsafeCell internally, which means we lost the Copy
derive on InMemoryRegister.
Therefore, a small set of changes was needed in the MMU driver to dance around
the static array init depending on a Copy type.
The RPi4 GPIO pull-up/pull down sequence is done differently than on the
RPi3. Switch to using the correct way.
Also, configure pull-ups for both UART pins.
Fixes#81
The GCC versions of `objdump` and `nm` seem to have better out-of-the-box
support (for AArch64). Demangling works better, and instructions in objdump are
presented as 4 bytes instead of 4 * 1 bytes, which helps a lot.
Hence, switch to the GCC versions for now until LLVM has caught up.
Andre Richter
Carl Fredrik Samson