Add mechanism to declare variables as "low mem" and use for extra stack.

Add a mechanism (VARLOW declaration) to make a variable reside in the
low memory (e-segment) area.  This is useful for runtime variables
that need to be accessed from 16bit code and need to be modifiable
during runtime.

Move the 16bit "extra stack" from the EBDA to the low memory area
using this declaration mechanism.  Also increase the size of this
stack from 512 bytes to 2048 bytes.

This also reworks tools/layoutrom.py a bit.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/util.h b/src/util.h
index 04de66b..e0e98f0 100644
--- a/src/util.h
+++ b/src/util.h
@@ -230,6 +230,7 @@ int get_keystroke(int msec);
 
 // stacks.c
 u32 call32(void *func, u32 eax, u32 errret);
+extern u8 ExtraStack[];
 inline u32 stack_hop(u32 eax, u32 edx, void *func);
 extern struct thread_info MainThread;
 extern int CanPreempt;