This commit got completely out of control.
Added the fork(), getpid(), getppid(), sleep(), usleep() system calls, and
aliases in the Maxsi:: namespace.
Fixed a bug where zero-byte allocation would fail.
Worked on the DescriptorTable class which now works and can fork.
Got rid of some massive print-registers statements and replaced them with
the portable InterruptRegisters::LogRegisters() function.
Removed the SysExecuteOld function and replaced it with Process::Execute().
Rewrote the boot sequence in kernel.cpp such that it now loads the system
idle process 'idle' as PID 0, and the initization process 'init' as PID 1.
Rewrote the SIGINT hack.
Processes now maintain a family-tree structure and keep track of their
threads. PIDs are now allocated using a simple hack. Virtual memory
per-process can now be allocated using a simple hack. Processes can now be
forked. Fixed the Process::Execute function such that it now resets the
stack pointer to where the stack actually is - not just a magic value.
Removed the old and ugly Process::_endcodesection hack.
Rewrote the scheduler into a much cleaner and faster version. Debug code is
now moved to designated functions. The noop kernel-thread has been replaced
by a simple user-space infinite-loop program 'idle'.
The Thread class has been seperated from the Scheduler except in Scheduler-
related code. Thread::{Save,Load}Registers has been improved and has been
moved to $(CPU)/thread.cpp. Threads can now be forked. A new CreateThread
function creates threads properly and portably.
Added a MicrosecondsSinceBoot() function.
Fixed a crucial bug in MemoryManagement::Fork().
Added an 'idle' user-space program that is a noop infinite loop, which is
used by the scheduler when there is nothing to do.
Rewrote the 'init' program such that it now forks off a shell, instead of
becoming the shell.
Added the $$ (current PID) and $PPID (parent PPID) variables to the shell.
1) The PML2 was not initialized to zeroes, thus leaving some bits behind that
caused the fork code to go crazy, forking the unforkable, and mapping addresses
that never, ever, should have been mapped, leaving behind a trail of page faults
and general protection faults on some computers, while other computers worked
because the uninitalized memory just wasn't uninitialized enough. Yep, this was
a schrödinbug!
2) Fixed a time bomb. The kernel heap was accidentally put such that whenever a
few megabytes were allocated, it would begin overwriting the physical page stack
causing unthinkable events to unfold and would probably be even more obscure to
debug than 1).
Oh, and some string errors fixed and removed RunApplication from kernel.cpp,
funny thing that even linked in the first place. Guess, the optimizer actually
did work for once. :)
Physical paging have been extended with Page::Insert() and Page::GetStats()
which allows the physical paging system to add new pages to the physical page
allocator, and still keep the "free/used pages" count accurate, and providing
this information to the kernel (and user-space at some point).
The virtual memory API has been extended with RemapKernel(), RemapUser(),
MapRangeKernel(), UnmapRangeKernel(), MapRangeUser(), and UnmapRangeUser().
This huge number of related functions have been created in the hope that it
hides the internal complexity of portable virtual memory management and avoid
bugs. It is crucial that the correct group of functions are used when solving
a problem and that they are not mixed in a manner not documented.
I probably overdocumented the code - hopefully it should help avoiding making
stupid or bothersome code.
Another problem is that code calling Page::Get() often should call something
like Page::AlwaysGetPageEvenIfYouHaveToSwap(). I'd be swell to have a function
that always gets a page under heavily-swapping conditions. Possibly Page::Get()
could become that?
uintptr_t is now replaced with addr_t when referring to physical memory
addresses in Sortix. Many bugs in the previous memory management code have been
fixed. The new interface is less flexible - but should prove more solid as the
nasty internals have been hidden away. The current interface design should also
make the code more 64-bit ready/friendly. And so on.
