Re: [patch v4 13/13] btrace, x86: restrict to Atom

Mark Kettenis
2012-11-27T14:42:06Z

> From: "Metzger, Markus T" <markus.t.metzger@intel.com>
> Date: Tue, 27 Nov 2012 11:49:09 +0000
>
> > > From: <markus.t.metzger@intel.com>
> > > Date: Tue, 27 Nov 2012 11:49:11 +0100
> > >
> > > From: Markus Metzger <markus.t.metzger@intel.com>
> > >
> > > Restrict branch tracing support to Atom processors.
> > >
> > > 2012-11-27 Markus Metzger <markus.t.metzger@intel.com>
> > >
> > > * amd64-linux-nat.c (amd64_linux_supports_btrace): New.
> > > (_initialize_amd64_linux_nat): Change supports_btrace method.
> > > * i386-linux-nat.c (i386_linux_supports_btrace): New.
> > > (_initialize_i386_linux_nat): Change supports_btrace method.
> > >
> > > gdbserver/
> > > * linux-low.h (linux_target_ops): Add supports_btrace method.
> > > * linux-low.c (linux_low_supports_btrace): New.
> > > (linux_target_ops): Change supports_btrace method.
> > > * linux-x86-low.c (x86_supports_btrace): New.
> > > (the_low_target): Add supports_btrace method.
> >
> > This is still unacceptable. This needs to be fixed in the Linux kernel.
>
> We will still need this patch in gdb so we handle kernels that do
> not contain the fix correctly.

Frankly I don't see why. I just consider this to be a bug in a
recently introduced new kernel feature. People should just upgrade to
a kernel that has this bug fixed. We can't add workarounds for every
Linux kernel bug. And in this case it is especially bad since you're
restricting GDB to supporting this feature on specific CPU models even
on systems that support the feature on other CPU types. I feel
(rather strongly) that this is bad.