Re: [PATCH] 2-ptrace_multi

From: Daniel Jacobowitz
Date: Fri May 19 2006 - 09:09:25 EST

On Fri, May 19, 2006 at 11:07:26AM +0200, Renzo Davoli wrote:
> On Thu, May 18, 2006 at 07:23:13PM -0700, Ulrich Drepper wrote:
> > On 5/18/06, Renzo Davoli <renzo@xxxxxxxxxxx> wrote:
> > >e.g. To virtualize a write you'd have to call PTRACE_PEEKDATA for each
> > >word of the buffer, very many hundreds cycles lost.
> >
> > No, this is not how programs should do it. Just open /proc/PID/mem
> > and use pread() with an offset corresponding to the address. Now,
> > repeat your timings using this technique.
> That would be faster to access the memory but:
> - the manager has to keep one open file per controlled process

No, it doesn't. It can open it as needed. It can even maintain a
cache of open mem files.

GDB's been opening it as needed for years. It works very well and is
drastically faster than PTRACE_PEEKDATA.

Daniel Jacobowitz
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