From be04ca8babcbc795992b22c0df0790ff671841d5 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Sun, 19 Sep 2004 20:14:14 +0000 Subject: [PATCH] Add instructions for compiling and modifying Bochs. --- doc/debug.texi | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/doc/debug.texi b/doc/debug.texi index e9bb413..9b0cd5a 100644 --- a/doc/debug.texi +++ b/doc/debug.texi @@ -177,3 +177,30 @@ that the third is less likely, but it is also possible. @node Modifying Bochs @section Modifying Bochs +An advanced debugging technique is to modify and recompile the +simulator. This proves useful when the simulated hardware has more +information than it makes available to the OS. For example, page +faults have a long list of potential causes, but the hardware does not +report to the OS exactly which one is the particular cause. +Furthermore, a bug in the kernel's handling of page faults can easily +lead to recursive faults, but a ``triple fault'' will cause the CPU to +reset itself, which is hardly conducive to debugging. + +In a case like this, you might appreciate being able to make Bochs +print out more debug information, such as the exact type of fault that +occurred. It's not very hard. You start by retrieving the source +code for Bochs 2.1.1 from @uref{http://bochs.sourceforge.net} and +extracting it into a directory. Then read +@file{pintos/src/misc/bochs-2.1.1.patch} and apply the patches needed. +Then run @file{./configure}, supplying the options you want (some +suggestions are in the patch file). Finally, run @command{make}. +This will compile Bochs and eventually produce a new binary +@file{bochs}. To use your @file{bochs} binary with @command{pintos}, +put it in your @env{PATH}, and make sure that it is earlier than +@file{/usr/class/cs140/i386/bochs}. + +Of course, to get any good out of this you'll have to actually modify +Bochs. Instructions for doing this are firmly out of the scope of +this document. However, if you want to debug page faults as suggested +above, a good place to start adding @code{printf()}s is +@code{BX_CPU_C::dtranslate_linear()} in @file{cpu/paging.cc}. -- 2.30.2