bank8K: document assumptions better

diff --git a/Kernel/bank8k.c b/Kernel/bank8k.c
index b88a2fa..809fced 100644 (file)
--- a/Kernel/bank8k.c
+++ b/Kernel/bank8k.c
@@ -26,6 +26,10 @@
  *     Page numbers must not include 0 (0 is taken as swapped)
  *
  *     FIXME: currently requires that PROGTOP aligns to an 8K boundary
+ *     if using swap.
+ *
+ *     Also we kind of assume that program space starts at 0x0000. That
+ *     needs fixing.
  */
 #include <kernel.h>
 #include <kdata.h>
@@ -109,11 +113,20 @@ void pagemap_free(ptptr p)
        }
 }
 
-static int maps_needed(uint16_t top)
+/*
+ *     We are passed the number of bytes that are needed for this
+ *     process. On top of that we require the extra space between
+ *     the top of space and PROGTOP which is reserved for the common
+ *     space and udata. If you have no need for this then it'll come out
+ *     as size - 1, which is correct.
+ *
+ *     The code assumes that the program base is within the first bank
+ */
+static int maps_needed(uint16_t size)
 {
        /* On many platforms if you touch this or PROGTOP you must
           touch tricks.s */
-       uint16_t needed = top + 0xFFFF - PROGTOP;
+       uint16_t needed = size + 0xFFFF - PROGTOP;
        /* Usually we have 0x1000 common - 1 for shift and inc */
        needed >>= 13;          /* in banks */
        needed++;               /* rounded */