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2018-07-08Added a printf() function to the library under stdio.c which uses theJake 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.
2018-06-25Added the header asm/interrupt.h which includes a prototype for theJake Mannens
assembly function register_isr making it usable within the C portions of the source. Added a new file panic.s with the function panic that will print a panic message, disable interrupts and halt the system. Created the skeleton framework for paging in the new file page.s. The new function paging_init (called in kboot) will setup a simple page directory with two tables covering all addresses 0-8MB. It will also mark pages from 0-1MB as 'supervisor-only' to protect the kernel. NOTE: The function paging_init must be called before initialising the IDT as it does not disable interrupts! Modified the page fault handler to print the offending linear address along with the supplied error code. Following that, the handler will initiate a kernel panic. This function (along with panic) assumes console I/O to be operational. Modified the userspace test code to deliberately intiate a page fault by accessing an unmapped page.
2018-06-24Re-structured the source tree and modified makefiles accordingly.Jake Mannens
Hopefully further separation will help to keep the code readable and understandable.