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From: Brian Feldman <green@FreeBSD.org>
Subject: PERFORCE change 8572 for review
To: Perforce Change Reviews <perforce@freebsd.org>
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http://people.freebsd.org/~peter/p4db/chv.cgi?CH=8572

Change 8572 by green@green_laptop_2 on 2002/03/28 09:02:01

	Re-add 0xdeadc0de-filling support to free(9).

Affected files ...

... //depot/projects/trustedbsd/mac/sys/kern/kern_malloc.c#4 edit

Differences ...

==== //depot/projects/trustedbsd/mac/sys/kern/kern_malloc.c#4 (text+ko) ====

@@ -116,6 +116,13 @@
 	{0, NULL},
 };
 
+/*
+ * The WEIRD_ADDR is used as known text to copy into free objects so
+ * that modifications after frees can be detected.
+ */
+#define	WEIRD_ADDR	0xdeadc0de
+#define	MAX_COPY	64
+
 static struct mtx malloc_mtx;
 
 u_int vm_kmem_size;
@@ -198,6 +205,24 @@
 }
 
 /*
+ * Copy in known text to make the memory look free.
+ */
+static __inline void
+trash_mem(void *addr, size_t size)
+{
+#ifdef INVARIANTS
+	uint32_t *ip;
+	
+	ip = (uint32_t *)addr;
+	size = size >= MAX_COPY ? MAX_COPY : size & ~sizeof(uint32_t);
+	while (size != 0) {
+		*ip++ = WEIRD_ADDR;
+		size -= sizeof(uint32_t);
+	}
+#endif
+}
+
+/*
  *	free:
  *
  *	Free a block of memory allocated by malloc.
@@ -230,9 +255,11 @@
 
 	if (!(slab->us_flags & UMA_SLAB_MALLOC)) {
 		size = slab->us_zone->uz_size;
+		trash_mem(addr, size);
 		uma_zfree_arg(slab->us_zone, addr, slab);
 	} else {
 		size = slab->us_size;
+		trash_mem(addr, size);
 		uma_large_free(slab);
 	}
 	/* mtx_lock(&malloc_mtx); XXX */

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