From: "Hua Zhong" <hzhong@cisco.com>
To: "'Hanson, Jonathan M'" <jonathan.m.hanson@intel.com>,
<linux-kernel@vger.kernel.org>
Subject: RE: Getting a process' EIP address (and other registers)
Date: Tue, 12 Oct 2004 21:20:23 -0700 [thread overview]
Message-ID: <015501c4b0db$f5e6b340$ca41cb3f@amer.cisco.com> (raw)
In-Reply-To: <C863B68032DED14E8EBA9F71EB8FE4C204FB456A@azsmsx406>
The EIP is not on the user space stack. It's a system call, not a function
call, and the EIP is where the system call is made.
Upon entering kernel all registeres are saved on the kernel stack. You can
get it by the following:
struct pt_regs *regs = *(((struct pt_regs *)(THREAD_SIZE + (unsigned
long)current)) - 1);
> 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.
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
next prev parent reply other threads:[~2004-10-13 4:20 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-13 4:10 Getting a process' EIP address (and other registers) Hanson, Jonathan M
2004-10-13 4:20 ` Hua Zhong [this message]
2004-10-13 4:56 ` suthambhara nagaraj
-- strict thread matches above, loose matches on Subject: below --
2004-10-13 18:15 Hanson, Jonathan M
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='015501c4b0db$f5e6b340$ca41cb3f@amer.cisco.com' \
--to=hzhong@cisco.com \
--cc=jonathan.m.hanson@intel.com \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox