unix - Homebrew UNIX operating system

Age	Commit message (Collapse)	Author
2020-03-07	Makefile now correctly calls i386 QEMU instead of x86_64	Jake Mannens
	Changed the type for block addresses from size_t to uint16_t. Added the '%c' conversion specifier to vsprintf(), so that it can now output individual characters passed as arguments. Added a an errno.h header containing a list of commonly used error codes, as well as a basic strerror() routine to fetch corresponding human-readable strings from a table. Implemented barebones floppy driver. Currently lacking many (essential) features, see TODO notes in floppy.c for more details. Buffer structs now have a b_present flag to indicate whether or not the data section is populated, as well as a b_wait element, as a queue for any tasks waiting on the buffer. All tasks waiting on a block wait in this queue, however, the task that originally called the driver to read, may wait in a separate queue maintained by the driver. This system may change in the future, and will likely depend on how head scheduling is implemented in the driver. The buffer_get_block() routine is now publically available in kernel/fs.h. It can be called to retrieve a block from the buffer cache (if readily available), or from the specified block device otherwise. This routine returns a pointer to the buffer containing the cache. The block_read() function now passes arguments and return values to the floppy driver regardless of the device specified. The block_write() function now indicates an error condition by setting b_device to zero in the allocated buffer structure, as no devices with write functionality currently exist. This behaviour will be updated in future, as more block devices are added. The mount_root() function has been modified to call buffer_get_block(), instead of calling block_read() directly. As of now, nothing should call block_read() or block_write() directly, as those functions are intended for use by the buffer subsystem only.
2018-08-26	Updated the style of the code in lib/string.c to conform to the rest of	Jake Mannens
	the project. Added the system call 'sys_panic' as well as the corresponding library function panic() whose prototype is defined in unistd.h. This is to allow userspace programs to deliberately crash the kernel for the purpose of debugging. Added the element 'write' as a function pointer in the tty_struct structure. The purpose of this function pointer is to provide a means for the TTY subsystem to notify the device driver of any newly added data to the write queue. Added the tty_write() function to the TTY subsystem. This function will copy data provided by the user into the specified TTY device's write queue, blocking if the queue's buffer is full. tty_write() will then call the driver's write() function to notify it of new data. Added the rsint_tx() function to the serial driver to handle transmit interrupts by re-supplying the UART's transmit FIFO.
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.