x86/fpu: Fix double-increment in setup_xstate_features()
authorDave Hansen <dave.hansen@linux.intel.com>
Thu, 11 Jun 2015 19:34:00 +0000 (12:34 -0700)
committerIngo Molnar <mingo@kernel.org>
Fri, 12 Jun 2015 08:48:12 +0000 (10:48 +0200)
commita8424003679e90b9952e20adcd1ff1560d9dd3e9
tree23353c4cd86e4c77f6f3b1f01c5f410b63dc9917
parent97ac46a5087eaf87fd76ff7bb31ec9c896010442
x86/fpu: Fix double-increment in setup_xstate_features()

I noticed that my MPX tracepoints were producing garbage for the
lower and upper bounds:

mpx_bounds_register_exception: address referenced: 0x00007fffffffccb7 bounds: lower: 0x0 ~upper: 0xffffffffffffffff
mpx_bounds_register_exception: address referenced: 0x00007fffffffccbf bounds: lower: 0x0 ~upper: 0xffffffffffffffff

This is, of course, bogus because 0x00007fffffffccbf is *within*
the bounds.  I assumed that my instruction decoder was bad and
went looking at it.  But I eventually realized that I was
getting a '0' offset back from xstate_offsets[BNDREGS].

It was being skipped in the initialization, which is obviously
bogus, so remove the extra leaf++.

This also goes an initializes xstate_offsets/sizes[] to -1 so
so that bugs like this will oops instead of silently failing
in interesting ways.

This was introduced by:

39f1acd ("x86/fpu/xstate: Don't assume the first zero xfeatures zero bit means the end")

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@sr71.net
Link: http://lkml.kernel.org/r/20150611193400.2E0B00DB@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/kernel/fpu/xstate.c