unix - Homebrew UNIX operating system

Age	Commit message (Collapse)	Author
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.
2018-07-07	Added '-g' flag for GCC to all makefiles to ensure debugging information	Jake Mannens
	is produced. This may change later. Added the new directory 'lib' to the source tree which build lib.a, an archive containing common library routines for both the kernel and userspace code to use. Added the file string.c to the lib directory (as well as the appropriate headers in /include) which provides some basic functions from the standard C string library. Added a physical memory manager which is now located in memory.c. This memory manager tracks free pages from 1MB-8MB with a simple table and allocates memory in blocks of 4KB pages. Multiple pages can be allocated in which they are returned as a linked list. Added a 'page window' in memory.c which allows the temporary mapping of a single page at a time into the current address space. Moved all paging routines that were previously located in page.s over to memory.c where they have been re-implemented as a mixture of C and inline assembly. Moved the primative userspace routines from usrspace.s over to the new sched.c. The only remaining routine, usrcall is now located in asm.s as 'switch_to' which takes two arguments, pointers to the task structure and task state structure of the new task which is being switched to. Pages for userspace are now allocated dynamically. The user binary is loaded in at 1GB upwards. The user stack is located at the end of the 4GB address space with the lower 1GB being reserved for the kernel. Updated the link.ld file for the userspace binary to include the new starting address 0x40000000 (1GB). Renamed the symbols for the user binary blob to make them shorter.
2018-06-24	Re-structured the source tree and modified makefiles accordingly.	Jake Mannens
	Hopefully further separation will help to keep the code readable and understandable.