When we fill up the entire screen with text we'd like to move all the text one line up to make space for new lines. We'd need to shift all the bytes in vga::Writer's framebuffer using slice::copy_within.

This is where we want this to happen: https://github.com/grupacosmo/cosmos/blob/32eb080ee293a5011423adcd129b2748963555a0/kernel/src/logger.rs#L75-L77

• https://github.com/rust-osdev/bootloader/blob/main/common/src/framebuffer.rs
• https://os.phil-opp.com/vga-text-mode/ - Note that our bootloader sets vga to graphics mode, not text mode

closing #19

Double fault is raised when there is no handler setup for any other interrupt, so I added a bunch of handlers to find out what was causing the issue. It turns out it was general protection fault. I left the handlers in the PR as they will be useful in the future.

Then I found solution in this comment that seems to fix the issue, so I implemented it and explained it (i can only hope that my explanation is correct lol)

I diverged from the way tests are implemented in blog_os:

• Since we don't use bootimage, I had to implement our own runner. I based the implementation on bootloader's tests
• I didn't include any way to run unit tests. They obfuscate kernel's code and I don't think we need them.

The idea is simple. We have a test_kernel crate that communicates with qemu and allows us to freely customize everything (e.g panic handler for tests that should panic). Each test runs qemu with a different binary from test_kernel crate.

btw I discovered that breakpoint interrupt handling doesn't work, I made a new issue https://github.com/grupacosmo/cosmos/issues/19

We want to avoid triple that cause the system to reset. We will need to setup interrupt handlers as explained in:

1. https://os.phil-opp.com/cpu-exceptions/
2. https://os.phil-opp.com/double-fault-exceptions/

• [x] implementation
• [ ] tests

Resolves #17

The MemoryManager is useful when it comes to testing or abstracting operations that require both OffsetPageTable and BootInfoFrameAllocator.

But registering it as singleton hidden behind Once<Mutex<..>> may be not very convenient.

In future we will need MemoryManager inside alloc module or any other module that handles heap allocation.

Saying so there will be no reason to use MemoryManager outside of alloc module. So we can pass MemoryManager directly to that module and provide Once<Mutex<MemoryManager>> only for test purposes (by using #[cfg] attribute).

Feel free to provide your feedback.

• Add the ability to write "escape sequences" something similar to ANSI escape code. Each sequence/code should accessible as afunction and automatically processed in Logger::write_str.
• Create documentation for the escape sequences codes (or refer to ANSI escape code and document which sequences are available)

Something like

pub fn set_fg_color(&mut self, color: Color) { ... }
pub fn write_str(&mut self, s: &str) {
  if /* \eRED */ {
    self.set_color(Color::RED);
  }
  //...
}

I think we can implement the following:

• Set text color (from predefined list of colors) -> #22
• Set cursor position -> #21
• Move cursor (aka set relative position) -> #21 ??