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.
2018-06-24	Modified makefiles to use the more appropriate variable $(MAKE) when	Jake Mannens
	invoking the tool recursively. Disabled GCC's position-independent-code generation in makefiles. Modified makefile for kernel/usrbin so that it now compiles and links C code into the userspace test. Created errno.h and populated it with standard error definitions. Replaced the va_list based system call handlers with a system call table defined in the header kernel/sys.h. NOTE: This header is included in kmain.c and should ONLY be included there! Do NOT include this header in sys.c. Rather than fetching the user's stack pointer and using it to initialize a va_list, parameters are now passed to the call handlers via the general purpose registers EAX, EBX, ECX and EDX where EAX contains the requested call number and conveys the return value. Setup macros in unistd.h to aid to making system calls from userspace. Implemented two basic system calls; sys_print and sys_dummy. The former takes a single char* argument and displays it on screen whilst the latter is used to populate otherwise empty entries of the system call table. sys_dummy returns the error ENOSYS whenever it is called.