uts: Allow for address space randomisation.
Randomise the base addresses of shared objects, non-fixed mappings, the
stack and the heap.  Introduce a service, svc:/system/process-security,
and a tool psecflags(1) to control and observe it

@@ -57,10 +57,11 @@
 #include <sys/exechdr.h>
 #include <sys/debug.h>
 #include <sys/vmsystm.h>
 #include <sys/swap.h>
 #include <sys/dumphdr.h>
+#include <sys/random.h>
 
 #include <vm/hat.h>
 #include <vm/as.h>
 #include <vm/seg.h>
 #include <vm/seg_kp.h>

@@ -635,10 +636,17 @@
 {
         return (0);
 }
 
 /*
+ * The maximum amount a randomized mapping will be slewed.  We should perhaps
+ * arrange things so these tunables can be separate for mmap, mmapobj, and
+ * ld.so
+ */
+volatile size_t aslr_max_map_skew = 256 * 1024 * 1024; /* 256MB */
+
+/*
  * map_addr_proc() is the routine called when the system is to
  * choose an address for the user.  We will pick an address
  * range which is the highest available below userlimit.
  *
  * Every mapping will have a redzone of a single page on either side of

@@ -750,10 +758,11 @@
 
         ASSERT(ISP2(align_amount));
         ASSERT(align_amount == 0 || align_amount >= PAGESIZE);
 
         off = off & (align_amount - 1);
+
         /*
          * Look for a large enough hole starting below userlimit.
          * After finding it, use the upper part.
          */
         if (as_gap_aligned(as, len, &base, &slen, AH_HI, NULL, align_amount,

@@ -777,10 +786,27 @@
                 addr += (uintptr_t)off;
                 if (addr > as_addr) {
                         addr -= align_amount;
                 }
 
+                /*
+                 * If randomization is requested, slew the allocation
+                 * backwards, within the same gap, by a random amount.
+                 *
+                 * XXX: This will fall over in processes like Java, which
+                 * commonly have a great many small mappings.
+                 */
+                if (flags & _MAP_RANDOMIZE) {
+                        uint32_t slew;
+
+                        (void) random_get_pseudo_bytes((uint8_t *)&slew,
+                            sizeof (slew));
+
+                        slew = slew % MIN(aslr_max_map_skew, (addr - base));
+                        addr -= P2ALIGN(slew, align_amount);
+                }
+
                 ASSERT(addr > base);
                 ASSERT(addr + len < base + slen);
                 ASSERT(((uintptr_t)addr & (align_amount - 1)) ==
                     ((uintptr_t)(off)));
                 *addrp = addr;

@@ -3924,16 +3950,10 @@
  */
 void
 dcache_flushall()
 {}
 
-size_t
-exec_get_spslew(void)
-{
-        return (0);
-}
-
 /*
  * Allocate a memory page.  The argument 'seed' can be any pseudo-random
  * number to vary where the pages come from.  This is quite a hacked up
  * method -- it works for now, but really needs to be fixed up a bit.
  *