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SubjectRe: [Question] How get instruction pointer of user space ???
On 8/31/05, liyu@WAN <liyu@ccoss.com.cn> wrote:
> Hi everyone:
>
> I am implemnting one ioctl() in one character device.
>
> That need know instruction pointer of user space. I am on i386
> platform.
> I can sure I am in process context. and enter kernel by system call way.
>
> As I known, in default case, each task have one kernel stack, its length
> is THREAD_SIZE(2 pages), and current_thread_info() is at its top. the
> struct pt_regs is at bottom of this stack.
>
> so I write the code like here:
>
> pt_regs = ((struct pt_regs *)(THREAD_SIZE + current_thread_info()))+1;

try doing the following, I amnot sure of it, just try it.

pt_regs = (struct pt_regs *) (((int *)(THREAD_SIZE + current)) -
(sizeof(pt_regs) + 1));

> return pt_regs->eip;
>
> but it do not work! even, I get segment fault and kernel Oops at
> sometime.
>
> Also, I am sure current_thread_info() return right value of current
> user task.
>
> Any idea on here?
>
> thanks
>
>
> sailor.
>
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