How to implement/set a data breakpoint?

Requirements:

I need to generate an interrupt, when a memory location changes or is written to. From an ISR, I can trigger a blue screen which gives me a nice stack trace with method names.

Approaches:

• Testing the value in the timer ISR. Obviously this doesn't give satisfying results.
• I discovered the bochs virtual machine. It has a basic builtin debugger that can set data breakpoints and stop the program. But I can't seem to generate an interrupt at that point.
• bochs allows one to connect a gdb to it. I haven't been able to build it with gdb support though.

Other thoughts:

• A kind of "preview instruction" interrupt that triggers for every instruction before executing it. The set of used memory-writing instructions should be pretty manageable, but it would still be a PITA to extract the adress I think. And I think there is no such interrupt.
• A kind of "preview memory access" interrupt. Again, I don't think its there.
• Abuse paging. Mark the page of interest as not present and test the address in the page fault handler. One would still have to distinguish read and write operations and I think, the page fault handler doesn't get to know the exact address, just the page number.

See chapter 16 in Intel's Software Developer's Manual Volume 3A. It gives information about using the debug registers, which provide support for causing the debugger exception when accessing a certain address, among other things. The interrupt will be triggered after the instruction which caused it. Specifically, you will have to set one of dr0-dr3 to the address you want to watch, and dr7 with the proper values to tell the processor what types of accesses should cause the interrupt.