mem: Add magic field to detect memory corruption

Very little checking is performed on the validity of freelist
metadata. Add a magic field to struct arena_header which can be used
to detect memory corruption or whether a user tries to free something
that isn't a malloc pointer.

This feature can be enabled with -DDEBUG_MALLOC. Turn it on for
development in mk/devel.mk.

Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 0 insertions, 4 deletions

diff --git a/dos/free.c b/dos/free.c
index 020dc157..b0b72ef7 100644
--- a/dos/free.c
+++ b/dos/free.c
@@ -67,10 +67,6 @@ void free(void *ptr)
     ah = (struct free_arena_header *)
 	((struct arena_header *)ptr - 1);
 
-#ifdef DEBUG_MALLOC
-    assert(ah->a.type == ARENA_TYPE_USED);
-#endif
-
     __free_block(ah);
 
     /* Here we could insert code to return memory to the system. */