[PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont

[Zack Weinberg]

On Fri, Dec 11, 2015 at 3:44 PM, Zack Weinberg <zackw@panix.com> wrote:
> Digging into the kernel a little, it appears that MAP_32BIT (in
> 4.3) selects a page-aligned address at random from within a 1GB (not
> 2GB) space

Correction: the page-aligned address is selected at random from, if
I'm reading this correctly (and I'm not sure I am), the range
0x4000_0000 to 0x4200_0000.  That is *not* a 1GB space; it is only a
32MB space.  However, 'thirteen bits of randomness' is accurate.  I'm
looking at
http://lxr.free-electrons.com/source/arch/x86/kernel/sys_x86_64.c#L100
and I cannot tell whether this means each mmap() gets its own 13 bits
of randomness or what.

zw