+;;; * For FreeBSD, the requirement of user and kernel space are
+;;; getting larger, and users tend to extend them.
+;;; If MAXDSIZ is extended from 512MB to 1GB, we can't use up to
+;;; around 0x50000000.
+;;; And if KVA_PAGES is extended from 1GB to 1.5GB, we can't use
+;;; down to around 0xA0000000.
+;;; So we use 0x58000000--0x98000000 for dynamic space.
+;;; * OpenBSD address space changes for W^X as well as malloc()
+;;; randomization made the old addresses unsafe.
+;;; ** By default (linked without -Z option):
+;;; The executable's text segment starts at #x1c000000 and the
+;;; data segment MAXDSIZ bytes higher, at #x3c000000. Shared
+;;; library text segments start randomly between #x00002000 and
+;;; #x10002000, with the data segment MAXDSIZ bytes after that.
+;;; ** If the -Z linker option is used:
+;;; The executable's text and data segments simply start at
+;;; #x08048000, data immediately following text. Shared library
+;;; text and data is placed as if allocated by malloc().
+;;; ** In both cases, the randomized range for malloc() starts
+;;; MAXDSIZ bytes after the end of the data segment (#x48048000
+;;; with -Z, #x7c000000 without), and extends 256 MB.
+;;; ** The read only, static, and linkage table spaces should be
+;;; safe with and without -Z if they are located just before
+;;; #x1c000000.
+;;; ** Ideally the dynamic space should be at #x94000000, 64 MB
+;;; after the end of the highest random malloc() address.
+;;; Unfortunately the dynamic space must be in the lower half
+;;; of the address space, where there are no large areas which
+;;; are unused both with and without -Z. So we break -Z by
+;;; starting at #x40000000. By only using 512 - 64 MB we can
+;;; run under the default 512 MB data size resource limit.