@@ -1,6 +1,8 @@
 #include <k/core.h>
 #include <k/def.h>
+#include <k/type.h>
+#include <posix.h>
 /* heapa.c - kmheapa() "heap alloc"
  * ~ lexi hale <lexi@hale.su>
  * kmheapa() allocates a pointer on the heap à la libc malloc()
  * see also: kmheapf() "heap free"
@@ -10,51 +12,52 @@
  * whether or not they're for the correct
  * platform - only the ones actually called
  * by the generated code will be linked,
  * linker errors are our friend here! */
-extern void* kmem_posix_mmap(void* addr,
+extern void* kmem_platform_mmap(void* addr,
 		unsigned long sz, unsigned long prot, unsigned long flags,
 		unsigned long fd, unsigned long off);
 
-enum posix_prot {
-	posix_prot_none  = 0,
-	posix_prot_read  = 1 << 0,
-	posix_prot_write = 1 << 1,
-	posix_prot_exec  = 1 << 2
-};
-
-enum posix_map {
-	posix_map_shared  = 1,
-	posix_map_private = 2
-};
-
-enum posix_flag {
-	posix_flag_fixed     = 0x10,
-	posix_flag_anonymous = 0x20,
-
-	/* platform flags */
-	posix_flag_linux_hugetlb = 0x40000
-};
-
 void* kmheapa(sz len) {
 	/* allocate an object on the heap and return
 	 * a pointer, or NULL if the allocation failed. */
 	void* val;
 
 #	ifdef KFenv_posix
- 	   /* posix APIs - we've got it easy */
-		val = kmem_posix_mmap(null, len, posix_prot_read | posix_prot_write,
-				posix_flag_anonymous, -1, 0);
+ 	   /* posix APIs - we've got it easy. currently for nonlinear
+		* heap allocation kmheapa simply uses m(un)map and lets the 
+		* kernel worry about it. it may ultimately be worth replacing
+		* this with a more sophisticated implementation, most likely
+		* an existing allocator like jemalloc, though i'm wary of
+		* including outside code - it creates a licensing mess and
+		* i'd prefer libk to be AGPLv3 across the board. possibility:
+		* include hooks for multiple allocators, allowing the user
+		* to select & link in her preferred allocator at compile time? */
+
+		/* because munmap needs to be informed of the size of
+		 * the region it is going to unmap, we need to store
+		 * that information in the allocated region itself.
+		 * the user will be given a pointer that can be
+		 * adjusted to point a field of type size_t that
+		 * contains the size of the allocate space.*/
+
+		sz     const region_total = len + sizeof len;
+		ubyte* const region = kmem_platform_mmap(null, region_total,
+				posix_prot_read | posix_prot_write,
+				posix_flag_anonymous | posix_map_shared, -1, 0);
 		/* impl note: while per manpage fd is "ignored"
 		 * for MAP_ANONYMOUS, "some implementations" require
 		 * a value of -1 */
 
-		if (val == (void*) -1) return null;
+		if (region == (void*) -1) return null;
 		/* worth retrieving errno? discuss */
 
+		*((sz*)region) = len;
+		val = region + sizeof len;
+
 #	else
  	   Knoimpl(kmheapa,KVos);
 #		error missing implementation
 #	endif
 
 	return val;
 }