Re: Getting a process' EIP address (and other registers)

[suthambhara nagaraj]

Why don't you use the pt_regs structure to restore the EIP
value stored during SAVE_ALL. Add a line in sys_ioctl to access the SAVE_ALL
stored values (EIP).This would then be simple pointer arithmetic.

I hope I havae answered you.

Regards 
Suthambhara





On Tue, 12 Oct 2004 21:10:13 -0700, Hanson, Jonathan M
<jonathan.m.hanson@xxxxxxxxx> wrote:
>        I have written a 2.4 kernel module that is triggered upon an
> IOCTL from a user application. Once triggered the kernel module dumps
> out the contents of the system memory and the x86 CPU architecture state
> to separate files.
>        I'm writing to the list because my method for getting registers
> from the user process before it entered the kernel is producing
> incorrect results. I've looked all through the kernel code and searched
> all over the web for an answer to this specific question and found
> nothing relevant.
>        In my research how to do this I've found that the stack pointer
> for the user process before it entered the kernel is stored in
> current->thread.esp0. From there the registers for the user process are
> stored at offsets from that location (for example, EIP is supposed to be
> 0x28 unsigned char bytes from esp0). I have code to get the EIP as
> follows:
> 
> unsigned char *stack_address, *eip;
> 
> stack_address = (unsigned char *)(current->thread.esp0);
> eip = stack_address + 0x28;
> printk("eip = %08lx\n", *(unsigned long *)eip);
> 
> Like I mentioned this is producing incorrect results. How do I access
> the user process' general purpose registers contents as they were before
> the kernel was entered (or correct my code above if I'm accessing
> something wrong)?
>        Thanks in advance for any help offered.
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