Re: [PATCH 2/5] uprobes: introduce uprobe_switch_to()

[Peter Zijlstra]

On Mon, 2011-11-28 at 20:06 +0100, Oleg Nesterov wrote:
> +void uprobe_switch_to(struct task_struct *curr)
> +{
> +       struct uprobe_task *utask = curr->utask;
> +       struct pt_regs *regs = task_pt_regs(curr);
> +
> +       if (!utask || utask->state != UTASK_SSTEP)
> +               return;
> +
> +       if (!(regs->flags & X86_EFLAGS_TF))
> +               return;
> +
> +       set_xol_ip(regs);
> +} 

> void __weak set_xol_ip(struct pt_regs *regs)
>  {
> +       int cpu = smp_processor_id();
> +       struct uprobe_task *utask = current->utask;
> +       struct uprobe *uprobe = utask->active_uprobe;
> +
> +       memcpy(uprobe_xol_slots[cpu], uprobe->insn, MAX_UINSN_BYTES);
> +
> +       utask->xol_vaddr = fix_to_virt(UPROBE_XOL_FIRST_PAGE)
> +                               + UPROBES_XOL_SLOT_BYTES * cpu;
> +       set_instruction_pointer(regs, utask->xol_vaddr);
>  }

So uprobe_switch_to() will always reset the IP to the start of the slot?
That sounds wrong, things like the RIP relative stuff needs multiple
instructions.


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