Re: Accessing x86 general-purpose registers

[Daniel Jacobowitz <drow@false.org>]

On Mon, Oct 18, 2004 at 01:03:42PM -0700, Hanson, Jonathan M wrote:
> 	My question really isn't about GDB per se but I was hoping some
> of the developers on this list would be able to help with what I'm
> trying to do.
> 	I have written a kernel module that, when triggered by an event,
> dumps out the contents of memory and the architectural state of the
> system to two files. The problem I'm running into is that the general
> purpose registers (EAX, EBX, EIP, etc.) I'm storing are incorrect. To
> investigate this problem I've downloaded the source to GDB and I've been
> looking at how GDB accomplishes this.
> 	In include/asm-i386/user.h is a structure called struct user
> with a member struct user_pt_regs, which is where GDB gets the general
> purpose register information for a program being debugged. I can see
> nowhere else in the kernel where this structure is written to. How is
> this information populated? Is there a way I can access this structure
> from the kernel itself?

I am inferring from context that you are talking about Linux.  You may
have better luck on a Linux development list; GDB uses ptrace, and the
kernel takes care of connecting the registers to that.

-- 
Daniel Jacobowitz