From: Dave Hansen <[email protected]>
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.
Signed-off-by: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
--
Note: this applies on top of tip/x86/fpu, which is currently:
97ac46a x86/mpx: Allow 32-bit binaries on 64-bit kernels again
This was introduced by:
39f1acd x86/fpu/xstate: Don't assume the first zero xfeatures zero bit
means the end
---
b/arch/x86/kernel/fpu/xstate.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN arch/x86/kernel/fpu/xstate.c~x86-fpu-xstate-fix-double-leaf-increment
arch/x86/kernel/fpu/xstate.c
--- a/arch/x86/kernel/fpu/xstate.c~x86-fpu-xstate-fix-double-leaf-increment
2015-06-11 11:25:42.706604347 -0700
+++ b/arch/x86/kernel/fpu/xstate.c 2015-06-11 11:38:45.271899550 -0700
@@ -31,7 +31,8 @@ static const char *xfeature_names[] =
*/
u64 xfeatures_mask __read_mostly;
-static unsigned int xstate_offsets[XFEATURES_NR_MAX],
xstate_sizes[XFEATURES_NR_MAX];
+static unsigned int xstate_offsets[XFEATURES_NR_MAX] = { [ 0 ...
XFEATURES_NR_MAX - 1] = -1};
+static unsigned int xstate_sizes[XFEATURES_NR_MAX] = { [ 0 ...
XFEATURES_NR_MAX - 1] = -1};
static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
/* The number of supported xfeatures in xfeatures_mask: */
@@ -187,7 +188,6 @@ static void __init setup_xstate_features
xstate_sizes[leaf] = eax;
printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %04x,
xstate_sizes[%d]: %04x\n", leaf, ebx, leaf, eax);
- leaf++;
}
}
_
--
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