lguest: example launcher to use guard pages, drop PROT_EXEC, fix limit logic
lguest: example launcher to use guard pages, drop PROT_EXEC, fix limit logic

PROT_EXEC seems to be completely unnecessary (as the lguest binary
never executes there), and will allow it to work with SELinux (and
more importantly, PaX :-) as they can/do forbid writable and
executable mappings.

Also, map PROT_NONE guard pages at start and end of guest memory for extra
paranoia.

I changed the length check to addr + size > guest_limit because >= is wrong
(addr of 0, size of getpagesize() with a guest_limit of getpagesize() would
false positive).

Signed-off-by: Rusty Russell <df9728c9e5104131c08c7adb03af425394842596@rustcorp.com.au>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs