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SubjectRe: [PATCH 03/23] perf: Add ability to attach user level registers dump to sample
On Fri, Jun 29, 2012 at 01:30:12PM +0200, Jiri Olsa wrote:
> On Fri, Jun 29, 2012 at 01:23:51PM +0200, Frederic Weisbecker wrote:
>
> SNIP
>
> > >
> > > well, thats basically what we have now..
> > >
> > > when the kernel is compiled for 32 bits, the bitmask allows to store:
> > >
> > > ax, bx, cx, dx, si, di, bp, sp, ip, flags, cs, ds, es, fs, gs, ss
> > >
> > > and when kernel is compiled for 64 bits, the bitmask adds 64bit stuff:
> > >
> > > ax, bx, cx, dx, si, di, bp, sp, ip, flags, cs, ds, es, fs, gs, ss
> > > r8, r9, r10, r11, r12, r13, r14, r15
> > >
> > >
> > > - 32 bits kernel is straightforward
> > >
> > > - for 64 bits kernel we store whatever bitmask instructs to,
> > > regardless if we are in compat task or native 64,
> > > user space will deal with that in post processing
> >
> > I can think of the crazy scenario where perf itself is compat and there
> > are 64 bits apps that will be profiled by perf. It means perf must check
> > if the kernel is 32 or 64 and depending on this, request r8-r15 or not.
> >
> > May be that's just too unlikely to matter.
>
> hopefully ;) anyway the kernel interface stays the same in this case as well
>
> we can add this check later when/if we deal with compat tasks

Right!


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