This treats a nasty bug where forking and exiting before the child
causes the kernel to panic, because the syscall -1 is run, which
just contains a trash value that happened to be 0.
The cause is still unknown. Might be the scheduler.
This won't help me sleep at night.
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 The noop kernel-thread has been replaced
by a simple user-space infinite-loop program 'idle'.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.
