Re: [PATCH v5 3.1.0-rc4-tip 5/26] Uprobes: copy of the originalinstruction.

[Oleg Nesterov]

On 10/05, Srikar Dronamraju wrote:
>
> * Oleg Nesterov <oleg@xxxxxxxxxx> [2011-10-03 18:29:05]:
>
> > But I am starting to think I simply do not understand this change.
> > To the point, I do not underestand why do we need copy_insn() at all.
> > We are going to replace this page, can't we save/analyze ->insn later
> > when we copy the content of the old page? Most probably I missed
> > something simple...
> >
>
> Copying the instruction at the time we replace the original instruction
> would have been ideal. However there are a few irritants to handle.
>
> ...
>    How do we distinguish if the
>    breakpoint instruction was around in the text or somebody inserted a
>    breakpoint in that address-space? Since we read from the page-cache,
>    we can easily resolve this.

Ah. I see.

> -  On archs like x86, with variable size instructions, the original
>    instruction can be across 2 pages.

Heh. Indeed ;)

Thanks Srikar.

Oleg.

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