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Re: Translate memory addresses


Mark Kettenis wrote:
Date: Tue, 08 Mar 2011 08:47:53 -0800
From: Michael Eager <eager@eagerm.com>

Tom Tromey wrote:
"Michael" == Michael Eager <eager@eagerm.com> writes:
Michael> I'm working with a target which needs to translate
Michael> a virtual memory addresses to a physical address
Michael> before accessing the target's memory or the core file.

Michael> Core_ops is defined in corelow.c, and there doesn't appear
Michael> to be an obvious hook for the target code to modify it to
Michael> add the translation routine.

Michael> Any suggestions on the best way to add a hook or how to specify
Michael> a target routine to do address translations for core files?

I am not an expert in this area, but couldn't you make a new
arch_stratum target that does the translation?

With this approach maybe you don't even need a hook -- just do the
translation and call the target beneath.
Interesting idea. I didn't think of adding a stratum for translation.

I took a clue from the way that sol-thread.c prevents corelow.c
from calling add_target to install core_ops.  I added the following
to corelow.c:

CORE_ADDR (*target_translate_address) (struct target_ops *, CORE_ADDR addr);

and in init_core_ops():

core_ops.to_translate_address = target_translate_address;

The target code contains a definition for target_translate_address
which is initialized to point to the translation routine.  For other
targets, this will be zero.

It's inelegant, what can I say, but functional.

Did you look at how the BSD kvm target does things? It does a physical to virtual address translation (by using the system-provided libkvm), and seems to get away with this without having such a hook.

How would this help? The kernel isn't running when debugging a hardware target and you can't execute target code when debugging a core file.


-- Michael Eager eager@eagercon.com 1960 Park Blvd., Palo Alto, CA 94306 650-325-8077


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