--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/libsys/rand.c	Fri May 15 01:28:16 2020 +0000
@@ -0,0 +1,32 @@
+/*
+ * This version of rand() has been lifted from Ancient UNIX, and modified
+ * to match the version used in TI's TCS211 GSM firmware, as revealed by
+ * disassembly of rand.obj in the rts16le_flash.lib binary library used
+ * by that semi-src package.  TI's version (most likely from their compiler
+ * tools group, rather than the GSM fw group, but who knows) uses the
+ * same trivial implementation of rand() as the original Ancient UNIX libc,
+ * but with one change: TI's return value is right-shifted by 16 bits
+ * compared to what the Ancient UNIX rand() would have returned.
+ * The caller thus gets back only 15 pseudo-random bits rather than 31,
+ * but then the lower bits of the original rand() return value are
+ * known to be pretty bad.
+ *
+ * rand() is used by some FFS code in reclaim.c.  If we don't provide our
+ * own version of rand() and let the linker pull the version from newlib,
+ * the link fails because the latter uses malloc.  This ancient implementation
+ * of rand() is quite poor, but my plan is to look into possibly adopting
+ * some better PRNG after we get the basic TI GSM firmware reintegrated.
+ */
+
+static	long	randx = 1;
+
+srand(x)
+unsigned x;
+{
+	randx = x;
+}
+
+rand()
+{
+	return ((randx = randx * 1103515245 + 12345) & 0x7fffffff) >> 16;
+}