4/27/2023 0 Comments Bochs debuggerIf you're still stuck, download the Bochs source package and search for the message you received. The CPU will try to look up the descriptor in the LDT, but there's no LDT registered! In most cases, the error comes from some mispairing of push and pop on the stack, which lead to a non-selector value to be loaded in a segment register. This message usually means that your program tried to load a selector with some garbage value, which happened to have the 3rd bit (Table Indicator) set. I do not have an LDT and I read it wasn't mandatory!?". Go back to your chip's data sheet and double-check that your sizes are correct. Reading a byte from port 0x1234 is usually not the same thing as reading a 32-bit value. Your page tables do not point to the correct parts of memoryīochs performs some rather paranoid checks on I/O operand size.You have not loaded an IDT, or the IDT is corrupt interrupt(): gate descriptor is not valid sys seg.Some common messages that might be displayed: In several cases, there are other error messages prior to this one which can provide more details in the error. Push 0xf001 pop ds 0xf001 is no valid segment, mov ax, ~ let's see if we get the GPF Check your exception works with "illegal" asm instructions like idiv 0, or Sometimes (but less likely), it can also be due to a severe bug in your exception handler code. This is probably due to a bad IDT register content, or a bad IDT descriptor. The CPU didn't manage to invoke an exception handler and would normally triple fault. Make your code more clean, test pointers before you follow them, initialize every pointer (especially those who are on the stack) and enable *-Wall* in GCC. This means you either followed a NULL (or uninitialized) pointer, or you damaged the return address of your stack frame. You sent your code pointer (EIP) to some uninitialized memory area. 2 Differences between Bochs and real hardwareįrequent error messages Running in Bogus Memory.Apparently, the VMWare format for disks is popular because several emulators support it.They start small when the emulated disk is empty and expand as more data is written. Growing images are similar to sparse images.Journaling images keep track of changes made by each session, and they can be undone/redone in order.Useful if you want to remove any changes to a "good" disk. Any changes are stored in a new image that is layered on top. Stackable images allow a "base" read-only image.A sparse image does not store blank space, so you could emulate a 1 GB hard disk, but it would only take up 200 MB of space if it had 800 MB free space.The concatenated format allows several separate files to emulate one combined hard disk useful for partitions.A flat image offers no special features and takes up the full amount of disk space that it emulates.The emulators usually support only a flat image for a floppy and an ISO image file for CD-ROMs. This chart shows the file formats for an emulated hard disk. VBE, OpenGL virtualization, VGA (decent), BGA, VBoxVideo VBE, VGA (partial), Cirrus Logic GD54xx, (BGA?) VBE, VGA (partial), BGA, Cirrus Logic GD54xx Yes: ARM, SPARC, MIPS, MIPS64, m68k, PowerPC Maybe (yes for PowerPCs, no for Intel Macs) It can't hurt to use more than one emulator (or several), in order to test your OS on a variety of platforms without using real hardware. This comparison is just to point out their differences. None of them are necessarily "better" than the others. Bochs is by far the slowest, but that is because of its full emulation, which gives it the highest accuracy. Overall, VirtualBox offers the richest set of features, along with very fast performance. Virtualization, Emulation on legacy devices Web interface, non-free Windows client (VI3) Virtualization (on PC), Emulation (on Mac) Command line, script file, interactive menus
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |