6502: add warning about ordering of stash_zp

diff --git a/Kernel/lowlevel-6502.s b/Kernel/lowlevel-6502.s
index 771d557..ab8eba6 100644 (file)
--- a/Kernel/lowlevel-6502.s
+++ b/Kernel/lowlevel-6502.s
@@ -82,6 +82,11 @@ _doexec:
 ;      The C world here is fairly ugly. We have to stash various bits of
 ;      zero page magic because its not re-entrant.
 ;
+;      stash_zp must bappen *before* we change mapping so the zp stash
+;      must be in common. The map routines are allowed to use _tmp1 and
+;      _ptr1 which will upset userspace terribly if they are not saved and
+;      properly restored!
+;
 interrupt_handler:
        jsr stash_zp                    ; Save zero page bits
        jsr map_save