tree b4bca57aa7aaf315092c21ecd66e56b7ee413655
parent 0011c7ec81b12ef641edf535288459b8f83c6611
author Dave Hansen <dave.hansen@intel.com> 1447118019 -0800
committer Dave Hansen <dave.hansen@intel.com> 1447118019 -0800

x86, mpx: fix 32-bit address space calculation

From: Dave Hansen <dave.hansen@linux.intel.com>

I received a bug report that running 32-bit MPX binaries on
64-bit kernels was broken.  I traced it down to this little code
snippet.  We were switching our "number of bounds directory
entries" calculation correctly.  But, we didn't switch the other
side of the calculation: the virtual space size.

This meant that we were calculating an absurd size for
bd_entry_virt_space() on 32-bit because we used the 64-bit
virt_space.

This was _also_ broken for 32-bit kernels running on 64-bit
hardware since boot_cpu_data.x86_virt_bits=48 even when running
in 32-bit mode.

Correct that and properly handle all 3 possible cases:

 1. 32-bit binary on 64-bit kernel
 2. 64-bit binary on 64-bit kernel
 3. 32-bit binary on 32-bit kernel

This manifested in having bounds tables not properly unmapped.
It "leaked" memory but had no functional impact otherwise.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>