From: Julian Seward <jseward@acm.org>
Date: Sun, 4 Dec 2005 23:27:14 +0000 (+0000)
Subject: Defensive hacks to detect cases where V corrupts its own heap and/or
X-Git-Tag: svn/VALGRIND_3_2_0~541
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=07f008c0f2bc54be917d5a1ca5779f88bfad976f;p=thirdparty%2Fvalgrind.git

Defensive hacks to detect cases where V corrupts its own heap and/or
uses memory after freeing.  Check the redzones for all non-client
frees, and fill all non-client freed areas with garbage.  Unroll
VG_(memset) as a precautionary measure against performance lossage.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@5283
---

diff --git a/coregrind/m_libcbase.c b/coregrind/m_libcbase.c
index b420b68713..4a53095227 100644
--- a/coregrind/m_libcbase.c
+++ b/coregrind/m_libcbase.c
@@ -372,10 +372,19 @@ void* VG_(memcpy) ( void *dest, const void *src, SizeT sz )
 void* VG_(memset) ( void *dest, Int c, SizeT sz )
 {
    Char *d = (Char *)dest;
-
-   while (sz--)
-      *d++ = c;
-
+   while (sz >= 4) {
+      d[0] = c;
+      d[1] = c;
+      d[2] = c;
+      d[3] = c;
+      d += 4;
+      sz -= 4;
+   }
+   while (sz > 0) {
+      d[0] = c;
+      d++;
+      sz--;
+   }
    return dest;
 }
 
diff --git a/coregrind/m_mallocfree.c b/coregrind/m_mallocfree.c
index a5916ae4c6..d975f0879d 100644
--- a/coregrind/m_mallocfree.c
+++ b/coregrind/m_mallocfree.c
@@ -1058,9 +1058,10 @@ void VG_(arena_free) ( ArenaId aid, void* ptr )
       
    b = get_payload_block(a, ptr);
 
-#  ifdef DEBUG_MALLOC
-   vg_assert(blockSane(a, b));
-#  endif
+   /* If this is one of V's areas, check carefully the block we're
+      getting back.  This picks up simple block-end overruns. */
+   if (aid != VG_AR_CLIENT)
+      vg_assert(blockSane(a, b));
 
    b_bszB   = get_bszB(b);
    b_pszB   = bszB_to_pszB(a, b_bszB);
@@ -1070,6 +1071,15 @@ void VG_(arena_free) ( ArenaId aid, void* ptr )
 
    a->bytes_on_loan -= b_pszB;
 
+   /* If this is one of V's areas, fill it up with junk to enhance the
+      chances of catching any later reads of it.  Note, 0xDD is
+      carefully chosen junk :-), in that: (1) 0xDDDDDDDD is an invalid
+      and non-word-aligned address on most systems, and (2) 0xDD is a
+      value which is unlikely to be generated by the new compressed
+      Vbits representation for memcheck. */
+   if (aid != VG_AR_CLIENT)
+      VG_(memset)(ptr, 0xDD, (SizeT)b_pszB);
+
    // Put this chunk back on a list somewhere.
    b_listno = pszB_to_listNo(b_pszB);
    mkFreeBlock( a, b, b_bszB, b_listno );