Re: [PATCH 03/23] perf: Add ability to attach user level registers dump to sample

[Jiri Olsa <jolsa@redhat.com>]

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

jirka