7029 want per-process exploit mitigation features (secflags)
7030 want basic address space layout randomization (aslr)
7031 noexec_user_stack should be a secflag
7032 want a means to forbid mappings around NULL.

*** 50,59 ****
--- 50,60 ----
  #include <sys/machsystm.h>
  #include <vm/seg_kmem.h>
  #include <sys/stack.h>
  #include <sys/atomic.h>
  #include <sys/promif.h>
+ #include <sys/random.h>
  
  uint_t page_colors = 0;
  uint_t page_colors_mask = 0;
  uint_t page_coloring_shift = 0;
  int consistent_coloring;
*** 166,175 ****
--- 167,183 ----
  /* Boot-time allocated buffer to pre-populate the contig_mem_arena */
  static size_t contig_mem_prealloc_size;
  static void *contig_mem_prealloc_buf;
  
  /*
+  * 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
+  */
+ 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 just below the current stack limit.  The
   * algorithm used for cache consistency on machines with virtual
   * address caches is such that offset 0 in the vnode is always
*** 318,327 ****
--- 326,349 ----
                  addr += (long)off;
                  if (addr > as_addr) {
                          addr -= align_amount;
                  }
  
+                 /*
+                  * If randomization is requested, slew the allocation
+                  * backwards, within the same gap, by a random amount.
+                  */
+                 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 - 1l)) ==
                      ((uintptr_t)(off)));
                  *addrp = addr;
*** 773,788 ****
          }
          alloc_base += contig_mem_prealloc_size;
  
          return (alloc_base);
  }
- 
- static uint_t sp_color_stride = 16;
- static uint_t sp_color_mask = 0x1f;
- static uint_t sp_current_color = (uint_t)-1;
- 
- size_t
- exec_get_spslew(void)
- {
-         uint_t spcolor = atomic_inc_32_nv(&sp_current_color);
-         return ((size_t)((spcolor & sp_color_mask) * SA(sp_color_stride)));
- }
--- 795,799 ----