unix - Homebrew UNIX operating system

Age	Commit message (Collapse)	Author
2018-07-30	Fixed a bug where the tick_handler() and sigret() functions did not pass	Jake Mannens
	a pointer to the saved state information to check_signals(). This bug would have only manifested itself if multiple signals were to be processed (sigret) or if a signal had been set during the handling of a timer interrupt (tick_handler) and ONLY if switching to the user's own handler since the state information is not needed to invoke the kernel's default signal handler. Implemented alarms for userspace processes. This required significant modification of the scheduler algorithm. When idling waiting for a process that can run, the scheduler now continually checks the alarms and signals of each process and updates their state accordingly. Implemented the sys_alarm system call to set the new 'alarm' field for the calling process. Created the sys_pause system call which changes the state of the calling process to TSTATE_INTERRUPTIBLE, effectively removing it from the scheduler's run queue, putting it to sleep until a signal arrives.
2018-07-08	Added a printf() function to the library under stdio.c which uses the	Jake Mannens
	vsprintf() function to render formatted strings and then the puts system call to output them. Moved the vsprintf() function from the kernel to the library. Furthermore, the prototype for the function has been moved from the kernel's headers, to the new header file stdio.h. Renamed the kernel's internal printf() function to printk() in order to avoid confusion with the library provided function. Renamed the sys_print system call to the more appropriate name, sys_puts. Added a new system call sys_time, which returns the system's uptime in seconds. This is mainly for testing the userspace binary and will not be permanent. Added the file time.c to the library which contains the caller for sys_time and a helper routine sleep() which delays execution for the specified number of seconds. The new header file time.h contains prototypes for both these functions as well as the definition for the type time_t. Fixed a bug in which the value of EAX was not properly passed to the system call handler, resulting in the wrong system call being executed. This was caused by the code in the SAVE macro not properly preserving the value. Fixed a bug in which the value of EAX was not preserved during a return from system call, but rather restored with the original EAX value prior to the call. As a result, system call return codes were not properly passed. This has been corrected by introducing a new macro RESTORE_SYS which carries out the same restore operations, but maintains EAX prior to the return.