[src/trunk]: src/sys/kern Change the pattern of KMEM_REDZONE so that the firs...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f25c3745596a
branches:  trunk
changeset: 330294:f25c3745596a
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Jul 03 08:43:49 2014 +0000

description:
Change the pattern of KMEM_REDZONE so that the first byte is never '\0'.

>From me and lars@.

diffstat:

 sys/kern/subr_kmem.c |  50 +++++++++++++++++++++++++++++++-------------------
 1 files changed, 31 insertions(+), 19 deletions(-)

diffs (119 lines):

diff -r 034134a0c00c -r f25c3745596a sys/kern/subr_kmem.c
--- a/sys/kern/subr_kmem.c      Thu Jul 03 07:18:42 2014 +0000
+++ b/sys/kern/subr_kmem.c      Thu Jul 03 08:43:49 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_kmem.c,v 1.58 2014/07/02 15:00:28 maxv Exp $      */
+/*     $NetBSD: subr_kmem.c,v 1.59 2014/07/03 08:43:49 maxv Exp $      */
 
 /*-
  * Copyright (c) 2009 The NetBSD Foundation, Inc.
@@ -90,7 +90,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_kmem.c,v 1.58 2014/07/02 15:00:28 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_kmem.c,v 1.59 2014/07/03 08:43:49 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/callback.h>
@@ -482,16 +482,16 @@
 #else /* defined(_LP64) */
 #define PRIME 0x9e3779b1
 #endif /* defined(_LP64) */
-#endif /* defined(KMEM_POISON) || defined(KMEM_REDZONE) */
 
-#if defined(KMEM_POISON)
 static inline uint8_t
-kmem_poison_pattern(const void *p)
+kmem_pattern_generate(const void *p)
 {
        return (uint8_t)(((uintptr_t)p) * PRIME
           >> ((sizeof(uintptr_t) - sizeof(uint8_t))) * CHAR_BIT);
 }
+#endif /* defined(KMEM_POISON) || defined(KMEM_REDZONE) */
 
+#if defined(KMEM_POISON)
 static int
 kmem_poison_ctor(void *arg, void *obj, int flag)
 {
@@ -511,7 +511,7 @@
        cp = p;
        ep = cp + sz;
        while (cp < ep) {
-               *cp = kmem_poison_pattern(cp);
+               *cp = kmem_pattern_generate(cp);
                cp++;
        }
 }
@@ -525,7 +525,7 @@
        cp = p;
        ep = cp + sz;
        while (cp < ep) {
-               const uint8_t expected = kmem_poison_pattern(cp);
+               const uint8_t expected = kmem_pattern_generate(cp);
 
                if (*cp != expected) {
                        panic("%s: %p: 0x%02x != 0x%02x\n",
@@ -562,23 +562,27 @@
 #endif /* defined(KMEM_SIZE) */
 
 #if defined(KMEM_REDZONE)
-static inline uint8_t
-kmem_redzone_pattern(const void *p)
-{
-       return (uint8_t)(((uintptr_t)p) * PRIME
-          >> ((sizeof(uintptr_t) - sizeof(uint8_t))) * CHAR_BIT);
-}
-
+#define STATIC_BYTE    0xFE
+CTASSERT(REDZONE_SIZE > 1);
 static void
 kmem_redzone_fill(void *p, size_t sz)
 {
-       uint8_t *cp;
+       uint8_t *cp, pat;
        const uint8_t *ep;
 
        cp = (uint8_t *)p + sz;
        ep = cp + REDZONE_SIZE;
+
+       /*
+        * We really don't want the first byte of the red zone to be '\0';
+        * an off-by-one in a string may not be properly detected.
+        */
+       pat = kmem_pattern_generate(cp);
+       *cp = (pat == '\0') ? STATIC_BYTE: pat;
+       cp++;
+
        while (cp < ep) {
-               *cp = kmem_redzone_pattern(cp);
+               *cp = kmem_pattern_generate(cp);
                cp++;
        }
 }
@@ -586,14 +590,22 @@
 static void
 kmem_redzone_check(void *p, size_t sz)
 {
-       uint8_t *cp;
+       uint8_t *cp, pat, expected;
        const uint8_t *ep;
 
        cp = (uint8_t *)p + sz;
        ep = cp + REDZONE_SIZE;
+
+       pat = kmem_pattern_generate(cp);
+       expected = (pat == '\0') ? STATIC_BYTE: pat;
+       if (expected != *cp) {
+               panic("%s: %p: 0x%02x != 0x%02x\n",
+                  __func__, cp, *cp, expected);
+       }
+       cp++;
+
        while (cp < ep) {
-               const uint8_t expected = kmem_redzone_pattern(cp);
-
+               expected = kmem_pattern_generate(cp);
                if (*cp != expected) {
                        panic("%s: %p: 0x%02x != 0x%02x\n",
                           __func__, cp, *cp, expected);