TODO.md

TODO

Next Version

• Add SoftwareSpinLock that uses a hardware spin lock but there can be more than actual hardware spin locks. This is an active locking primitive that must only be used with interrupts disabled. It should be simple to add deadlock detection here.

• Add SoftwareMutex that uses a HardwareSpinLock internally. This is a passive locking primitive that must only be used with interrupts enabled.

• Add WaitingThreadQueue that keeps a list of threads that are waiting for some resource. This must only be used with interrupts disabled and uses a HardwareSpinLock internally.

• Verify that all of these locking primitives are functional.

• Protect all the resources with these locking primitives.

• Schedule on both cores.

Old

Next Version

• Group PageRanges together in PageAllocator::deallocate.

• Add passive locking primitives

• Add active locking primitives

Bugs

• We have a ton of memory leaks in the filesystem, e.g. VirtualFile::create_handle_impl.

• If we do stat /dev/tty we get invalid information, because ConsoleFileHandle always returns ConsoleFile instead of the actual file.

• Sometimes we seem to mess something up, this is visible when ConsoleFileHandle has an invalid this pointer. I reproduced this by running:

  Example.elf
  Example.elf
  Example.elf
  Example.elf
  Example.elf
  Example.elf
  Example.elf
  

Future features

• Keep track of 'used' page ranges. There is an excelent algorithm that can be used to store these bits in a very compact tree structure.

• Maybe I could port the Minix filesystem when I add an IDE driver?

• Keep documentation about interrupt safe functions and which functions can be called in which boot stage

• Add MemoryAllocator::allocate_eternal which doesn't create MTRACE logs

• Run inside QEMU

• Write userland applications in Zig

Future tweaks (Userland)

• Implement a proper malloc

Future tweaks (Kernel)

• Setup MPU for supervisor mode

• HardFault in usermode crashes kernel

• Stack smash protection with MPU

  • Build with -fstack-protector?

Future tweaks (Build)

• Alignment of .stack, .heap sections is lost in readelf

• C++20 modules

• Drop SDK entirely

  • Link libsup++ or add a custom downcast?

• Meson build

• Try using LLDB instead of GDB

• Don't leak includes from newlib libc

• Use LLVM/LLD for FileEmbed; Not sure what I meant with this, but LLVM surely has all the tools buildin that I need

• GDB apparently has a secret 'proc' command that makes it possible to debug multiple processes. This was mentioned in the DragonFlyBSD documentation, keyword: "inferiour"