![]() The auto default could be buggy either due to gdbstub or bugs in GDB itself. You can use `set architecture i8086` to tell GDB that the x86 CPU is in real-mode. I wrote it as a separate Python tool which interacts with the Bochs command-line debugger, rather than modify Bochs's built-in debugger GUI, because I wanted a nicer-looking Qt GUI and I wanted it to be easy for me and anyone else to hack in new things. I need to do a lot more work on it for it to be truly usable and I don't know if I'll ever get to that, but if anyone else is interested in this I might do some more work on it. It's just some hacks but it has the main thing I wanted, which is the ability to load a listing file output by Ida Pro and then highlight the line corresponding to the current CS:IP. I wanted a more powerful and user-friendly interface on the Bochs debugger and didn't like any of the ones I could find so started writing my own at one point. The Bochs built-in debugger seemed better in this regard. Unfortunately when I tried using Bochs + gdb + Emacs, it seemed that the gdb interface didn't have things exposed to it properly - I don't think it knew whether the machine was in real or protected mode, for example, or maybe it did know it was in real mode but still presented linear addresses. I don't think anyone mentioned that both Bochs and Qemu have gdb stubs in them so you can use gdb to debug the virtual/emulated machine instead of the built-in Bochs and Qemu debuggers.Īs someone mentioned, there are some nicer interfaces that can sit on top of gdb, such as Emacs (some people might not consider that a nice interface but I do). Unfortunately, qemu doesn't come with a debugger, and we won't be testing your software with qemu by default.I guess for many purposes an adequate alternative is to use virtualization platforms and gdb (or whatever).Īs you said later, the line between emulator and virtualisation is blurry. Qemu is generally faster than bochs and may be more forgiving. d 1 for the first one you set) before you can start stepping through your program. One annoying feature of bochs as currently implemented appears to be that the step command will not step over a breakpoint! So you may need to delete your breakpoint (e.g. b 0x7c00 will set a breakpoint at the start of your bootloader). The most useful early on is probably the stock breakpoint command b, which lets you specify a physical memory address(e.g. There are several breakpoint commands in bochs-debug. If you just want to run your simulation, type c (for continue). Type help to get a list of commands or see for documentation. The bochs-debug program works exactly like stock bochs, except that it gives a gdb-style command prompt after initializing. Look for common/bin/bochs-debug in your user or group directory this should run on any recent Intel-architecture Linux machine (e.g., Zoo nodes). Luckily, if you are taking CS422 we have already compiled it for you. ![]() For CS422 assignments, we will generally supply you with a standard bochsrc file along with the assignment files.īochs runs in debugging mode if compiled with the appropriate files. Bochs will load options from a file with this name by default, or you can tell it to load from a different file with the -f option, e.g. Since having to edit options all the time is annoying, you can save your current options out to a bochsrc file once you have the setup you like. You can then run the emulator using Begin simulation from the main menu. bochsrc file in the current directory, you will probably need to specify at minimum a disk image file using Edit Options/Disk Options. This will pop up a text menu with several options. ![]() Type bochs in a terminal emulator window. ![]() These notes are to get you started with using bochs on the Zoo machines. Full documentation can be found through the Sourceforge project page. Bochs is a 386 PC emulator that runs on top of a variety of operating systems. ![]()
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