Brokenthorn's Known Bugs

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Brokenthorn's tutorials are some of the better OSDev tutorials out there. They teach better coding practices, and go very in depth. Like all tutorials, there are a few bugs in it. Here are the most prevalent:


Wrong description of CR0.PE

In OSDev8, CR0.PE (bit 0) is incorrectly described as setting the processor to 32-bit mode. Setting bit 0 of CR0 does not put the processor in 32-bit mode. Performing a far jump to a 32-bit code segment puts the processor in 32-bit mode. The far jump itself will still be executed in 16-bit mode.

iret using inline ASM

In OSDev15, the provided ISR handler uses inline asm to iretd from a C function:

void int_handler_5 () {
	_asm add esp, 12
	_asm pushad
	// do whatever...
	_asm popad
	_asm iretd

This makes assumptions about the calling conventions used, and isn't a good idea in general. Better options may be found here.

Missing semicolon

In OSDevPE, there is a missing semicolon in the IMAGE_THUNK_DATA structure

Issues with paging code

In OSDev18, the paging code has some issues. It directly accesses physical memory without mapping it. You can use it as a base, but implement recursive paging.

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