Add MALLOC_DEBUG_MAXZONES debug malloc(9) option to use multiple uma

zones for each malloc bucket size.  The purpose is to isolate
different malloc types into hash classes, so that any buffer overruns
or use-after-free will usually only affect memory from malloc types in
that hash class.  This is purely a debugging tool; by varying the hash
function and tracking which hash class was corrupted, the intersection
of the hash classes from each instance will point to a single malloc
type that is being misused.  At this point inspection or memguard(9)
can be used to catch the offending code.

Add MALLOC_DEBUG_MAXZONES=8 to -current GENERIC configuration files.
The suggestion to have this on by default came from Kostik Belousov on
-arch.

This code is based on work by Ron Steinke at Isilon Systems.

Reviewed by:    -arch (mostly silence)
Reviewed by:    zml
Approved by:    zml (mentor)

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/sun4v/conf/GENERIC b/sys/sun4v/conf/GENERIC
index 26ec3af..f7a4e77 100644
--- a/sys/sun4v/conf/GENERIC
+++ b/sys/sun4v/conf/GENERIC
@@ -79,6 +79,7 @@ options 	DDB			# Support DDB.
 #options 	INVARIANT_SUPPORT	# Extra sanity checks of internal structures, required by INVARIANTS
 #options 	WITNESS			# Enable checks to detect deadlocks and cycles
 #options 	WITNESS_SKIPSPIN	# Don't run witness on spinlocks for speed
+#options 	MALLOC_DEBUG_MAXZONES=8	# Separate malloc(9) zones
 #options 	DEBUG_LOCKS
 #options 	DEBUG_VFS_LOCKS