Add more linker protections around variables accessed from 16bit mode.

Rename VAR16 to VAR16_32 -- that macro supports accesses from both
    16bit and 32bit mode.
Introduce a new macro VAR16 that must be present on all global
    variables accessed from 16bit mode.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/rombios16.lds.S b/src/rombios16.lds.S
index 009eb89..2966ce6 100644
--- a/src/rombios16.lds.S
+++ b/src/rombios16.lds.S
@@ -16,10 +16,7 @@ SECTIONS
                 *(.text)
                 code16_rodata = . ;
                 *(.rodata*)
-                *(.data)
-                code16_bss = . ;
-                *(.bss)
-                *(COMMON)
+                *(.data.var16)
                 }
         freespace1_start = . ;
         code16_end = . ;
@@ -31,4 +28,8 @@ SECTIONS
                 *(.text.fixed.addr)
                 }
         code16_fixed_end = . ;
+
+        // Discard regular data sections to force a link error if
+        // 16bit code attempts to access data not marked with VAR16.
+        /DISCARD/ : { *(.data) *(.bss) *(COMMON) }
 }