Re: [RFC PATCH v3 3/6] uretprobes: generalize xol_get_insn_slot()

From: Oleg Nesterov
Date: Thu Feb 28 2013 - 15:03:11 EST


Anton, I'll try to read this series asap. Just one note,

On 02/28, Anton Arapov wrote:
>
> Generalize xol_take_insn_slot() to enable more consumers of the
> function, e.g. trampoline implementation for return probes.

Yes, this is can work too.

But I guess you misunderstood me, or I missed something...

Why do you need xol_area->rp_trampoline_vaddr at all? From the very
beginning I am trying to suggest to use the first slot for trampoline:

Or. Perhaps even better, do not add this helper at all. xol_alloc_area()
could reserve the first slot/bit for trampoline. And note that in this
case we do not need xol_area->rp_trampoline_vaddr, it is always equal
to xol_area->vaddr.

Doesn't this look simpler?

Oleg.

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