[libsanitizer] add mach_override and enable libsanitizer on darwin

From-SVN: r193781

9 files changed, 1210 insertions, 7 deletions

diff --git a/libsanitizer/ChangeLog b/libsanitizer/ChangeLog
index 2c7c289a702..90053021bd5 100644
--- a/libsanitizer/ChangeLog
+++ b/libsanitizer/ChangeLog
@@ -1,3 +1,16 @@
+2012-11-24  Kostya Serebryany kcc@google.com
+	    Jack Howarth <howarth@bromo.med.uc.edu>
+
+	* interception/mach_override/mach_override.c: Migrate from llvm.
+	* interception/mach_override/mach_override.h: Likewise.
+	* interception/mach_override/LICENSE.txt: Likewise.
+	* configure.tgt: Add darwin to supported targets.
+	* configure.ac: Define USING_MACH_OVERRIDE when on darwin.
+	* interception/Makefile.am: Compile mach_override.c when
+	USING_MACH_OVERRIDE defined.
+	* configure: Regenerated.
+	* interception/Makefile.in: Likewise.
+
 2012-11-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR sanitizer/55450
diff --git a/libsanitizer/configure b/libsanitizer/configure
index 198a94d3272..48f984c7bbb 100755
--- a/libsanitizer/configure
+++ b/libsanitizer/configure
@@ -604,6 +604,8 @@ ac_subst_vars='am__EXEEXT_FALSE
 am__EXEEXT_TRUE
 LTLIBOBJS
 LIBOBJS
+USING_MACH_OVERRIDE_FALSE
+USING_MACH_OVERRIDE_TRUE
 TSAN_SUPPORTED_FALSE
 TSAN_SUPPORTED_TRUE
 enable_static
@@ -11078,7 +11080,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11081 "configure"
+#line 11083 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11184,7 +11186,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11187 "configure"
+#line 11189 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -14494,6 +14496,19 @@ else
 fi
 
 
+case "$host" in
+  *-*-darwin*) MACH_OVERRIDE=true ;;
+  *) MACH_OVERRIDE=false ;;
+esac
+ if $MACH_OVERRIDE; then
+  USING_MACH_OVERRIDE_TRUE=
+  USING_MACH_OVERRIDE_FALSE='#'
+else
+  USING_MACH_OVERRIDE_TRUE='#'
+  USING_MACH_OVERRIDE_FALSE=
+fi
+
+
 ac_config_files="$ac_config_files Makefile"
 
 
@@ -14670,6 +14685,10 @@ if test -z "${TSAN_SUPPORTED_TRUE}" && test -z "${TSAN_SUPPORTED_FALSE}"; then
   as_fn_error "conditional \"TSAN_SUPPORTED\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${USING_MACH_OVERRIDE_TRUE}" && test -z "${USING_MACH_OVERRIDE_FALSE}"; then
+  as_fn_error "conditional \"USING_MACH_OVERRIDE\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 
 : ${CONFIG_STATUS=./config.status}
 ac_write_fail=0
diff --git a/libsanitizer/configure.ac b/libsanitizer/configure.ac
index 45183db609f..2d62ec4ecc0 100644
--- a/libsanitizer/configure.ac
+++ b/libsanitizer/configure.ac
@@ -80,6 +80,12 @@ unset TSAN_SUPPORTED
 . ${srcdir}/configure.tgt
 AM_CONDITIONAL(TSAN_SUPPORTED, [test "x$TSAN_SUPPORTED" = "xyes"])
 
+case "$host" in
+  *-*-darwin*) MACH_OVERRIDE=true ;;
+  *) MACH_OVERRIDE=false ;;
+esac
+AM_CONDITIONAL(USING_MACH_OVERRIDE, $MACH_OVERRIDE)
+
 AC_CONFIG_FILES([Makefile])
 
 AC_CONFIG_FILES(AC_FOREACH([DIR], [interception sanitizer_common asan], [DIR/Makefile ]),
diff --git a/libsanitizer/configure.tgt b/libsanitizer/configure.tgt
index 1506a20dab1..26335391c4a 100644
--- a/libsanitizer/configure.tgt
+++ b/libsanitizer/configure.tgt
@@ -27,6 +27,9 @@ case "${target}" in
 	;;
   sparc*-*-linux*)
 	;;
+  x86_64-*-darwin* | i?86-*-darwin*)
+	TSAN_SUPPORTED=no
+	;;
   *)
 	UNSUPPORTED=1
 	;;
diff --git a/libsanitizer/interception/Makefile.am b/libsanitizer/interception/Makefile.am
index b92a18033f0..029417f46e5 100644
--- a/libsanitizer/interception/Makefile.am
+++ b/libsanitizer/interception/Makefile.am
@@ -14,7 +14,11 @@ interception_files = \
         interception_mac.cc \
         interception_win.cc
 
-libinterception_la_SOURCES = $(interception_files) 
+if USING_MACH_OVERRIDE
+libinterception_la_SOURCES = $(interception_files) mach_override/mach_override.c
+else
+libinterception_la_SOURCES = $(interception_files)
+endif
 
 # Work around what appears to be a GNU make bug handling MAKEFLAGS
 # values defined in terms of make variables, as is the case for CC and
diff --git a/libsanitizer/interception/Makefile.in b/libsanitizer/interception/Makefile.in
index b32e86ecdf2..bd58c4d47a0 100644
--- a/libsanitizer/interception/Makefile.in
+++ b/libsanitizer/interception/Makefile.in
@@ -53,14 +53,29 @@ CONFIG_CLEAN_FILES =
 CONFIG_CLEAN_VPATH_FILES =
 LTLIBRARIES = $(noinst_LTLIBRARIES)
 libinterception_la_LIBADD =
+am__libinterception_la_SOURCES_DIST = interception_linux.cc \
+	interception_mac.cc interception_win.cc \
+	mach_override/mach_override.c
 am__objects_1 = interception_linux.lo interception_mac.lo \
 	interception_win.lo
-am_libinterception_la_OBJECTS = $(am__objects_1)
+@USING_MACH_OVERRIDE_FALSE@am_libinterception_la_OBJECTS =  \
+@USING_MACH_OVERRIDE_FALSE@	$(am__objects_1)
+@USING_MACH_OVERRIDE_TRUE@am_libinterception_la_OBJECTS =  \
+@USING_MACH_OVERRIDE_TRUE@	$(am__objects_1) mach_override.lo
 libinterception_la_OBJECTS = $(am_libinterception_la_OBJECTS)
 DEFAULT_INCLUDES = -I.@am__isrc@
 depcomp = $(SHELL) $(top_srcdir)/../depcomp
 am__depfiles_maybe = depfiles
 am__mv = mv -f
+COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
+	$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
+LTCOMPILE = $(LIBTOOL) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+	--mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) \
+	$(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
+CCLD = $(CC)
+LINK = $(LIBTOOL) --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
+	--mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) \
+	$(LDFLAGS) -o $@
 CXXCOMPILE = $(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) \
 	$(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS)
 LTCXXCOMPILE = $(LIBTOOL) --tag=CXX $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
@@ -71,7 +86,7 @@ CXXLINK = $(LIBTOOL) --tag=CXX $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
 	--mode=link $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) $(AM_LDFLAGS) \
 	$(LDFLAGS) -o $@
 SOURCES = $(libinterception_la_SOURCES)
-DIST_SOURCES = $(libinterception_la_SOURCES)
+DIST_SOURCES = $(am__libinterception_la_SOURCES_DIST)
 ETAGS = etags
 CTAGS = ctags
 DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
@@ -215,7 +230,8 @@ interception_files = \
         interception_mac.cc \
         interception_win.cc
 
-libinterception_la_SOURCES = $(interception_files) 
+@USING_MACH_OVERRIDE_FALSE@libinterception_la_SOURCES = $(interception_files)
+@USING_MACH_OVERRIDE_TRUE@libinterception_la_SOURCES = $(interception_files) mach_override/mach_override.c
 
 # Work around what appears to be a GNU make bug handling MAKEFLAGS
 # values defined in terms of make variables, as is the case for CC and
@@ -261,7 +277,7 @@ MAKEOVERRIDES =
 all: all-am
 
 .SUFFIXES:
-.SUFFIXES: .cc .lo .o .obj
+.SUFFIXES: .c .cc .lo .o .obj
 $(srcdir)/Makefile.in: @MAINTAINER_MODE_TRUE@ $(srcdir)/Makefile.am  $(am__configure_deps)
 	@for dep in $?; do \
 	  case '$(am__configure_deps)' in \
@@ -313,6 +329,35 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/interception_linux.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/interception_mac.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/interception_win.Plo@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/mach_override.Plo@am__quote@
+
+.c.o:
+@am__fastdepCC_TRUE@	$(COMPILE) -MT $@ -MD -MP -MF $(DEPDIR)/$*.Tpo -c -o $@ $<
+@am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/$*.Tpo $(DEPDIR)/$*.Po
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	source='$<' object='$@' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(COMPILE) -c $<
+
+.c.obj:
+@am__fastdepCC_TRUE@	$(COMPILE) -MT $@ -MD -MP -MF $(DEPDIR)/$*.Tpo -c -o $@ `$(CYGPATH_W) '$<'`
+@am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/$*.Tpo $(DEPDIR)/$*.Po
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	source='$<' object='$@' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(COMPILE) -c `$(CYGPATH_W) '$<'`
+
+.c.lo:
+@am__fastdepCC_TRUE@	$(LTCOMPILE) -MT $@ -MD -MP -MF $(DEPDIR)/$*.Tpo -c -o $@ $<
+@am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/$*.Tpo $(DEPDIR)/$*.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	source='$<' object='$@' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(LTCOMPILE) -c -o $@ $<
+
+mach_override.lo: mach_override/mach_override.c
+@am__fastdepCC_TRUE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -MT mach_override.lo -MD -MP -MF $(DEPDIR)/mach_override.Tpo -c -o mach_override.lo `test -f 'mach_override/mach_override.c' || echo '$(srcdir)/'`mach_override/mach_override.c
+@am__fastdepCC_TRUE@	$(am__mv) $(DEPDIR)/mach_override.Tpo $(DEPDIR)/mach_override.Plo
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	source='mach_override/mach_override.c' object='mach_override.lo' libtool=yes @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCC_FALSE@	DEPDIR=$(DEPDIR) $(CCDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCC_FALSE@	$(LIBTOOL)  --tag=CC $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) -c -o mach_override.lo `test -f 'mach_override/mach_override.c' || echo '$(srcdir)/'`mach_override/mach_override.c
 
 .cc.o:
 @am__fastdepCXX_TRUE@	$(CXXCOMPILE) -MT $@ -MD -MP -MF $(DEPDIR)/$*.Tpo -c -o $@ $<
diff --git a/libsanitizer/interception/mach_override/LICENSE.txt b/libsanitizer/interception/mach_override/LICENSE.txt
new file mode 100644
index 00000000000..9446965176c
--- /dev/null
+++ b/libsanitizer/interception/mach_override/LICENSE.txt
@@ -0,0 +1,3 @@
+Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
+Some rights reserved: <http://opensource.org/licenses/mit-license.php>
+
diff --git a/libsanitizer/interception/mach_override/mach_override.c b/libsanitizer/interception/mach_override/mach_override.c
new file mode 100644
index 00000000000..7511a7bebb8
--- /dev/null
+++ b/libsanitizer/interception/mach_override/mach_override.c
@@ -0,0 +1,970 @@
+/*******************************************************************************
+	mach_override.c
+		Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
+		Some rights reserved: <http://opensource.org/licenses/mit-license.php>
+
+	***************************************************************************/
+#ifdef __APPLE__
+
+#include "mach_override.h"
+
+#include <mach-o/dyld.h>
+#include <mach/mach_host.h>
+#include <mach/mach_init.h>
+#include <mach/vm_map.h>
+#include <sys/mman.h>
+
+#include <CoreServices/CoreServices.h>
+
+//#define DEBUG_DISASM 1
+#undef DEBUG_DISASM
+
+/**************************
+*	
+*	Constants
+*	
+**************************/
+#pragma mark	-
+#pragma mark	(Constants)
+
+#if defined(__ppc__) || defined(__POWERPC__)
+
+static
+long kIslandTemplate[] = {
+	0x9001FFFC,	//	stw		r0,-4(SP)
+	0x3C00DEAD,	//	lis		r0,0xDEAD
+	0x6000BEEF,	//	ori		r0,r0,0xBEEF
+	0x7C0903A6,	//	mtctr	r0
+	0x8001FFFC,	//	lwz		r0,-4(SP)
+	0x60000000,	//	nop		; optionally replaced
+	0x4E800420 	//	bctr
+};
+
+#define kAddressHi			3
+#define kAddressLo			5
+#define kInstructionHi		10
+#define kInstructionLo		11
+
+#elif defined(__i386__) 
+
+#define kOriginalInstructionsSize 16
+
+static
+unsigned char kIslandTemplate[] = {
+	// kOriginalInstructionsSize nop instructions so that we 
+	// should have enough space to host original instructions 
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
+	// Now the real jump instruction
+	0xE9, 0xEF, 0xBE, 0xAD, 0xDE
+};
+
+#define kInstructions	0
+#define kJumpAddress    kInstructions + kOriginalInstructionsSize + 1
+#elif defined(__x86_64__)
+
+#define kOriginalInstructionsSize 32
+
+#define kJumpAddress    kOriginalInstructionsSize + 6
+
+static
+unsigned char kIslandTemplate[] = {
+	// kOriginalInstructionsSize nop instructions so that we 
+	// should have enough space to host original instructions 
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 
+	0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
+	// Now the real jump instruction
+	0xFF, 0x25, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00
+};
+
+#endif
+
+#define	kAllocateHigh		1
+#define	kAllocateNormal		0
+
+/**************************
+*	
+*	Data Types
+*	
+**************************/
+#pragma mark	-
+#pragma mark	(Data Types)
+
+typedef	struct	{
+	char	instructions[sizeof(kIslandTemplate)];
+	int		allocatedHigh;
+}	BranchIsland;
+
+/**************************
+*	
+*	Funky Protos
+*	
+**************************/
+#pragma mark	-
+#pragma mark	(Funky Protos)
+
+
+	static mach_error_t
+allocateBranchIsland(
+		BranchIsland	**island,
+		int				allocateHigh,
+		void *originalFunctionAddress);
+
+	static mach_error_t
+freeBranchIsland(
+		BranchIsland	*island );
+
+	static mach_error_t
+defaultIslandMalloc(
+	  void **ptr, size_t unused_size, void *hint);
+
+	static mach_error_t
+defaultIslandFree(
+   	void *ptr);
+
+#if defined(__ppc__) || defined(__POWERPC__)
+	static mach_error_t
+setBranchIslandTarget(
+		BranchIsland	*island,
+		const void		*branchTo,
+		long			instruction );
+#endif 
+
+#if defined(__i386__) || defined(__x86_64__)
+static mach_error_t
+setBranchIslandTarget_i386(
+						   BranchIsland	*island,
+						   const void		*branchTo,
+						   char*			instructions );
+// Can't be made static because there's no C implementation for atomic_mov64
+// on i386.
+void 
+atomic_mov64(
+		uint64_t *targetAddress,
+		uint64_t value ) __attribute__((visibility("hidden")));
+
+	static Boolean 
+eatKnownInstructions( 
+	unsigned char	*code, 
+	uint64_t		*newInstruction,
+	int				*howManyEaten, 
+	char			*originalInstructions,
+	int				*originalInstructionCount, 
+	uint8_t			*originalInstructionSizes );
+
+	static void
+fixupInstructions(
+    void		*originalFunction,
+    void		*escapeIsland,
+    void		*instructionsToFix,
+	int			instructionCount,
+	uint8_t		*instructionSizes );
+
+#ifdef DEBUG_DISASM
+	static void
+dump16Bytes(
+	void	*ptr);
+#endif  // DEBUG_DISASM
+#endif
+
+/*******************************************************************************
+*	
+*	Interface
+*	
+*******************************************************************************/
+#pragma mark	-
+#pragma mark	(Interface)
+
+#if defined(__i386__) || defined(__x86_64__)
+static mach_error_t makeIslandExecutable(void *address) {
+	mach_error_t err = err_none;
+    vm_size_t pageSize;
+    host_page_size( mach_host_self(), &pageSize );
+    uintptr_t page = (uintptr_t)address & ~(uintptr_t)(pageSize-1);
+    int e = err_none;
+    e |= mprotect((void *)page, pageSize, PROT_EXEC | PROT_READ | PROT_WRITE);
+    e |= msync((void *)page, pageSize, MS_INVALIDATE );
+    if (e) {
+        err = err_cannot_override;
+    }
+    return err;
+}
+#endif
+
+		static mach_error_t
+defaultIslandMalloc(
+	void **ptr, size_t unused_size, void *hint) {
+  return allocateBranchIsland( (BranchIsland**)ptr, kAllocateHigh, hint );
+}
+		static mach_error_t
+defaultIslandFree(
+	void *ptr) {
+	return freeBranchIsland(ptr);
+}
+
+    mach_error_t
+__asan_mach_override_ptr(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland )
+{
+  return __asan_mach_override_ptr_custom(originalFunctionAddress,
+		overrideFunctionAddress,
+		originalFunctionReentryIsland,
+		defaultIslandMalloc,
+		defaultIslandFree);
+}
+
+    mach_error_t
+__asan_mach_override_ptr_custom(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland,
+		island_malloc *alloc,
+		island_free *dealloc)
+{
+	assert( originalFunctionAddress );
+	assert( overrideFunctionAddress );
+	
+	// this addresses overriding such functions as AudioOutputUnitStart()
+	// test with modified DefaultOutputUnit project
+#if defined(__x86_64__)
+    for(;;){
+        if(*(uint16_t*)originalFunctionAddress==0x25FF)    // jmp qword near [rip+0x????????]
+            originalFunctionAddress=*(void**)((char*)originalFunctionAddress+6+*(int32_t *)((uint16_t*)originalFunctionAddress+1));
+        else break;
+    }
+#elif defined(__i386__)
+    for(;;){
+        if(*(uint16_t*)originalFunctionAddress==0x25FF)    // jmp *0x????????
+            originalFunctionAddress=**(void***)((uint16_t*)originalFunctionAddress+1);
+        else break;
+    }
+#endif
+#ifdef DEBUG_DISASM
+  {
+    fprintf(stderr, "Replacing function at %p\n", originalFunctionAddress);
+    fprintf(stderr, "First 16 bytes of the function: ");
+    unsigned char *orig = (unsigned char *)originalFunctionAddress;
+    int i;
+    for (i = 0; i < 16; i++) {
+       fprintf(stderr, "%x ", (unsigned int) orig[i]);
+    }
+    fprintf(stderr, "\n");
+    fprintf(stderr, 
+            "To disassemble, save the following function as disas.c"
+            " and run:\n  gcc -c disas.c && gobjdump -d disas.o\n"
+            "The first 16 bytes of the original function will start"
+            " after four nop instructions.\n");
+    fprintf(stderr, "\nvoid foo() {\n  asm volatile(\"nop;nop;nop;nop;\");\n");
+    int j = 0;
+    for (j = 0; j < 2; j++) {
+      fprintf(stderr, "  asm volatile(\".byte ");
+      for (i = 8 * j; i < 8 * (j+1) - 1; i++) {
+        fprintf(stderr, "0x%x, ", (unsigned int) orig[i]);
+      }
+      fprintf(stderr, "0x%x;\");\n", (unsigned int) orig[8 * (j+1) - 1]);
+    }
+    fprintf(stderr, "}\n\n");
+  }
+#endif
+
+	long	*originalFunctionPtr = (long*) originalFunctionAddress;
+	mach_error_t	err = err_none;
+	
+#if defined(__ppc__) || defined(__POWERPC__)
+	//	Ensure first instruction isn't 'mfctr'.
+	#define	kMFCTRMask			0xfc1fffff
+	#define	kMFCTRInstruction	0x7c0903a6
+	
+	long	originalInstruction = *originalFunctionPtr;
+	if( !err && ((originalInstruction & kMFCTRMask) == kMFCTRInstruction) )
+		err = err_cannot_override;
+#elif defined(__i386__) || defined(__x86_64__)
+	int eatenCount = 0;
+	int originalInstructionCount = 0;
+	char originalInstructions[kOriginalInstructionsSize];
+	uint8_t originalInstructionSizes[kOriginalInstructionsSize];
+	uint64_t jumpRelativeInstruction = 0; // JMP
+
+	Boolean overridePossible = eatKnownInstructions ((unsigned char *)originalFunctionPtr, 
+										&jumpRelativeInstruction, &eatenCount, 
+										originalInstructions, &originalInstructionCount, 
+										originalInstructionSizes );
+#ifdef DEBUG_DISASM
+  if (!overridePossible) fprintf(stderr, "overridePossible = false @%d\n", __LINE__);
+#endif
+	if (eatenCount > kOriginalInstructionsSize) {
+#ifdef DEBUG_DISASM
+		fprintf(stderr, "Too many instructions eaten\n");
+#endif    
+		overridePossible = false;
+	}
+	if (!overridePossible) err = err_cannot_override;
+	if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
+#endif
+	
+	//	Make the original function implementation writable.
+	if( !err ) {
+		err = vm_protect( mach_task_self(),
+				(vm_address_t) originalFunctionPtr, 8, false,
+				(VM_PROT_ALL | VM_PROT_COPY) );
+		if( err )
+			err = vm_protect( mach_task_self(),
+					(vm_address_t) originalFunctionPtr, 8, false,
+					(VM_PROT_DEFAULT | VM_PROT_COPY) );
+	}
+	if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
+	
+	//	Allocate and target the escape island to the overriding function.
+	BranchIsland	*escapeIsland = NULL;
+	if( !err )
+		err = alloc( (void**)&escapeIsland, sizeof(BranchIsland), originalFunctionAddress );
+	if ( err ) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
+	
+#if defined(__ppc__) || defined(__POWERPC__)
+	if( !err )
+		err = setBranchIslandTarget( escapeIsland, overrideFunctionAddress, 0 );
+	
+	//	Build the branch absolute instruction to the escape island.
+	long	branchAbsoluteInstruction = 0; // Set to 0 just to silence warning.
+	if( !err ) {
+		long escapeIslandAddress = ((long) escapeIsland) & 0x3FFFFFF;
+		branchAbsoluteInstruction = 0x48000002 | escapeIslandAddress;
+	}
+#elif defined(__i386__) || defined(__x86_64__)
+        if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
+
+	if( !err )
+		err = setBranchIslandTarget_i386( escapeIsland, overrideFunctionAddress, 0 );
+ 
+	if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
+	// Build the jump relative instruction to the escape island
+#endif
+
+
+#if defined(__i386__) || defined(__x86_64__)
+	if (!err) {
+		uint32_t addressOffset = ((char*)escapeIsland - (char*)originalFunctionPtr - 5);
+		addressOffset = OSSwapInt32(addressOffset);
+		
+		jumpRelativeInstruction |= 0xE900000000000000LL; 
+		jumpRelativeInstruction |= ((uint64_t)addressOffset & 0xffffffff) << 24;
+		jumpRelativeInstruction = OSSwapInt64(jumpRelativeInstruction);		
+	}
+#endif
+	
+	//	Optionally allocate & return the reentry island. This may contain relocated
+	//  jmp instructions and so has all the same addressing reachability requirements
+	//  the escape island has to the original function, except the escape island is
+	//  technically our original function.
+	BranchIsland	*reentryIsland = NULL;
+	if( !err && originalFunctionReentryIsland ) {
+		err = alloc( (void**)&reentryIsland, sizeof(BranchIsland), escapeIsland);
+		if( !err )
+			*originalFunctionReentryIsland = reentryIsland;
+	}
+	
+#if defined(__ppc__) || defined(__POWERPC__)	
+	//	Atomically:
+	//	o If the reentry island was allocated:
+	//		o Insert the original instruction into the reentry island.
+	//		o Target the reentry island at the 2nd instruction of the
+	//		  original function.
+	//	o Replace the original instruction with the branch absolute.
+	if( !err ) {
+		int escapeIslandEngaged = false;
+		do {
+			if( reentryIsland )
+				err = setBranchIslandTarget( reentryIsland,
+						(void*) (originalFunctionPtr+1), originalInstruction );
+			if( !err ) {
+				escapeIslandEngaged = CompareAndSwap( originalInstruction,
+										branchAbsoluteInstruction,
+										(UInt32*)originalFunctionPtr );
+				if( !escapeIslandEngaged ) {
+					//	Someone replaced the instruction out from under us,
+					//	re-read the instruction, make sure it's still not
+					//	'mfctr' and try again.
+					originalInstruction = *originalFunctionPtr;
+					if( (originalInstruction & kMFCTRMask) == kMFCTRInstruction)
+						err = err_cannot_override;
+				}
+			}
+		} while( !err && !escapeIslandEngaged );
+	}
+#elif defined(__i386__) || defined(__x86_64__)
+	// Atomically:
+	//	o If the reentry island was allocated:
+	//		o Insert the original instructions into the reentry island.
+	//		o Target the reentry island at the first non-replaced 
+	//        instruction of the original function.
+	//	o Replace the original first instructions with the jump relative.
+	//
+	// Note that on i386, we do not support someone else changing the code under our feet
+	if ( !err ) {
+		fixupInstructions(originalFunctionPtr, reentryIsland, originalInstructions,
+					originalInstructionCount, originalInstructionSizes );
+	
+		if( reentryIsland )
+			err = setBranchIslandTarget_i386( reentryIsland,
+										 (void*) ((char *)originalFunctionPtr+eatenCount), originalInstructions );
+		// try making islands executable before planting the jmp
+#if defined(__x86_64__) || defined(__i386__)
+        if( !err )
+            err = makeIslandExecutable(escapeIsland);
+        if( !err && reentryIsland )
+            err = makeIslandExecutable(reentryIsland);
+#endif
+		if ( !err )
+			atomic_mov64((uint64_t *)originalFunctionPtr, jumpRelativeInstruction);
+	}
+#endif
+	
+	//	Clean up on error.
+	if( err ) {
+		if( reentryIsland )
+			dealloc( reentryIsland );
+		if( escapeIsland )
+			dealloc( escapeIsland );
+	}
+
+#ifdef DEBUG_DISASM
+  {
+    fprintf(stderr, "First 16 bytes of the function after slicing: ");
+    unsigned char *orig = (unsigned char *)originalFunctionAddress;
+    int i;
+    for (i = 0; i < 16; i++) {
+       fprintf(stderr, "%x ", (unsigned int) orig[i]);
+    }
+    fprintf(stderr, "\n");
+  }
+#endif
+	return err;
+}
+
+/*******************************************************************************
+*	
+*	Implementation
+*	
+*******************************************************************************/
+#pragma mark	-
+#pragma mark	(Implementation)
+
+/***************************************************************************//**
+	Implementation: Allocates memory for a branch island.
+	
+	@param	island			<-	The allocated island.
+	@param	allocateHigh	->	Whether to allocate the island at the end of the
+								address space (for use with the branch absolute
+								instruction).
+	@result					<-	mach_error_t
+
+	***************************************************************************/
+
+	static mach_error_t
+allocateBranchIsland(
+		BranchIsland	**island,
+		int				allocateHigh,
+		void *originalFunctionAddress)
+{
+	assert( island );
+	
+	mach_error_t	err = err_none;
+	
+	if( allocateHigh ) {
+		vm_size_t pageSize;
+		err = host_page_size( mach_host_self(), &pageSize );
+		if( !err ) {
+			assert( sizeof( BranchIsland ) <= pageSize );
+#if defined(__ppc__) || defined(__POWERPC__)
+			vm_address_t first = 0xfeffffff;
+			vm_address_t last = 0xfe000000 + pageSize;
+#elif defined(__x86_64__)
+			vm_address_t first = ((uint64_t)originalFunctionAddress & ~(uint64_t)(((uint64_t)1 << 31) - 1)) | ((uint64_t)1 << 31); // start in the middle of the page?
+			vm_address_t last = 0x0;
+#else
+			vm_address_t first = 0xffc00000;
+			vm_address_t last = 0xfffe0000;
+#endif
+
+			vm_address_t page = first;
+			int allocated = 0;
+			vm_map_t task_self = mach_task_self();
+			
+			while( !err && !allocated && page != last ) {
+
+				err = vm_allocate( task_self, &page, pageSize, 0 );
+				if( err == err_none )
+					allocated = 1;
+				else if( err == KERN_NO_SPACE ) {
+#if defined(__x86_64__)
+					page -= pageSize;
+#else
+					page += pageSize;
+#endif
+					err = err_none;
+				}
+			}
+			if( allocated )
+				*island = (BranchIsland*) page;
+			else if( !allocated && !err )
+				err = KERN_NO_SPACE;
+		}
+	} else {
+		void *block = malloc( sizeof( BranchIsland ) );
+		if( block )
+			*island = block;
+		else
+			err = KERN_NO_SPACE;
+	}
+	if( !err )
+		(**island).allocatedHigh = allocateHigh;
+	
+	return err;
+}
+
+/***************************************************************************//**
+	Implementation: Deallocates memory for a branch island.
+	
+	@param	island	->	The island to deallocate.
+	@result			<-	mach_error_t
+
+	***************************************************************************/
+
+	static mach_error_t
+freeBranchIsland(
+		BranchIsland	*island )
+{
+	assert( island );
+	assert( (*(long*)&island->instructions[0]) == kIslandTemplate[0] );
+	assert( island->allocatedHigh );
+	
+	mach_error_t	err = err_none;
+	
+	if( island->allocatedHigh ) {
+		vm_size_t pageSize;
+		err = host_page_size( mach_host_self(), &pageSize );
+		if( !err ) {
+			assert( sizeof( BranchIsland ) <= pageSize );
+			err = vm_deallocate(
+					mach_task_self(),
+					(vm_address_t) island, pageSize );
+		}
+	} else {
+		free( island );
+	}
+	
+	return err;
+}
+
+/***************************************************************************//**
+	Implementation: Sets the branch island's target, with an optional
+	instruction.
+	
+	@param	island		->	The branch island to insert target into.
+	@param	branchTo	->	The address of the target.
+	@param	instruction	->	Optional instruction to execute prior to branch. Set
+							to zero for nop.
+	@result				<-	mach_error_t
+
+	***************************************************************************/
+#if defined(__ppc__) || defined(__POWERPC__)
+	static mach_error_t
+setBranchIslandTarget(
+		BranchIsland	*island,
+		const void		*branchTo,
+		long			instruction )
+{
+	//	Copy over the template code.
+    bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) );
+    
+    //	Fill in the address.
+    ((short*)island->instructions)[kAddressLo] = ((long) branchTo) & 0x0000FFFF;
+    ((short*)island->instructions)[kAddressHi]
+    	= (((long) branchTo) >> 16) & 0x0000FFFF;
+    
+    //	Fill in the (optional) instuction.
+    if( instruction != 0 ) {
+        ((short*)island->instructions)[kInstructionLo]
+        	= instruction & 0x0000FFFF;
+        ((short*)island->instructions)[kInstructionHi]
+        	= (instruction >> 16) & 0x0000FFFF;
+    }
+    
+    //MakeDataExecutable( island->instructions, sizeof( kIslandTemplate ) );
+	msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE );
+    
+    return err_none;
+}
+#endif 
+
+#if defined(__i386__)
+	static mach_error_t
+setBranchIslandTarget_i386(
+	BranchIsland	*island,
+	const void		*branchTo,
+	char*			instructions )
+{
+
+	//	Copy over the template code.
+    bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) );
+
+	// copy original instructions
+	if (instructions) {
+		bcopy (instructions, island->instructions + kInstructions, kOriginalInstructionsSize);
+	}
+	
+    // Fill in the address.
+    int32_t addressOffset = (char *)branchTo - (island->instructions + kJumpAddress + 4);
+    *((int32_t *)(island->instructions + kJumpAddress)) = addressOffset; 
+
+    msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE );
+    return err_none;
+}
+
+#elif defined(__x86_64__)
+static mach_error_t
+setBranchIslandTarget_i386(
+        BranchIsland	*island,
+        const void		*branchTo,
+        char*			instructions )
+{
+    // Copy over the template code.
+    bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) );
+
+    // Copy original instructions.
+    if (instructions) {
+        bcopy (instructions, island->instructions, kOriginalInstructionsSize);
+    }
+
+    //	Fill in the address.
+    *((uint64_t *)(island->instructions + kJumpAddress)) = (uint64_t)branchTo; 
+    msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE );
+
+    return err_none;
+}
+#endif
+
+
+#if defined(__i386__) || defined(__x86_64__)
+// simplistic instruction matching
+typedef struct {
+	unsigned int length; // max 15
+	unsigned char mask[15]; // sequence of bytes in memory order
+	unsigned char constraint[15]; // sequence of bytes in memory order
+}	AsmInstructionMatch;
+
+#if defined(__i386__)
+static AsmInstructionMatch possibleInstructions[] = {
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE9, 0x00, 0x00, 0x00, 0x00} },	// jmp 0x????????
+	{ 0x5, {0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, {0x55, 0x89, 0xe5, 0xc9, 0xc3} },	// push %esp; mov %esp,%ebp; leave; ret
+	{ 0x1, {0xFF}, {0x90} },							// nop
+	{ 0x1, {0xF8}, {0x50} },							// push %reg
+	{ 0x2, {0xFF, 0xFF}, {0x89, 0xE5} },				                // mov %esp,%ebp
+	{ 0x3, {0xFF, 0xFF, 0xFF}, {0x89, 0x1C, 0x24} },				                // mov %ebx,(%esp)
+	{ 0x3, {0xFF, 0xFF, 0x00}, {0x83, 0xEC, 0x00} },	                        // sub 0x??, %esp
+	{ 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0x81, 0xEC, 0x00, 0x00, 0x00, 0x00} },	// sub 0x??, %esp with 32bit immediate
+	{ 0x2, {0xFF, 0xFF}, {0x31, 0xC0} },						// xor %eax, %eax
+	{ 0x3, {0xFF, 0x4F, 0x00}, {0x8B, 0x45, 0x00} },  // mov $imm(%ebp), %reg
+	{ 0x3, {0xFF, 0x4C, 0x00}, {0x8B, 0x40, 0x00} },  // mov $imm(%eax-%edx), %reg
+	{ 0x3, {0xFF, 0xCF, 0x00}, {0x8B, 0x4D, 0x00} },  // mov $imm(%rpb), %reg
+	{ 0x3, {0xFF, 0x4F, 0x00}, {0x8A, 0x4D, 0x00} },  // mov $imm(%ebp), %cl
+	{ 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x8B, 0x4C, 0x24, 0x00} },  			// mov $imm(%esp), %ecx
+	{ 0x4, {0xFF, 0x00, 0x00, 0x00}, {0x8B, 0x00, 0x00, 0x00} },  			// mov r16,r/m16 or r32,r/m32
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xB9, 0x00, 0x00, 0x00, 0x00} }, 	// mov $imm, %ecx
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xB8, 0x00, 0x00, 0x00, 0x00} }, 	// mov $imm, %eax
+	{ 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x66, 0x0F, 0xEF, 0x00} },             	// pxor xmm2/128, xmm1
+	{ 0x2, {0xFF, 0xFF}, {0xDB, 0xE3} }, 						// fninit
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE8, 0x00, 0x00, 0x00, 0x00} },	// call $imm
+	{ 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x0F, 0xBE, 0x55, 0x00} },                    // movsbl $imm(%ebp), %edx
+	{ 0x0, {0x00}, {0x00} }
+};
+#elif defined(__x86_64__)
+// TODO(glider): disassembling the "0x48, 0x89" sequences is trickier than it's done below.
+// If it stops working, refer to http://ref.x86asm.net/geek.html#modrm_byte_32_64 to do it
+// more accurately.
+// Note: 0x48 is in fact the REX.W prefix, but it might be wrong to treat it as a separate
+// instruction.
+static AsmInstructionMatch possibleInstructions[] = {
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE9, 0x00, 0x00, 0x00, 0x00} },	// jmp 0x????????
+	{ 0x1, {0xFF}, {0x90} },							// nop
+	{ 0x1, {0xF8}, {0x50} },							// push %rX
+	{ 0x1, {0xFF}, {0x65} },							// GS prefix
+	{ 0x3, {0xFF, 0xFF, 0xFF}, {0x48, 0x89, 0xE5} },				// mov %rsp,%rbp
+	{ 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x48, 0x83, 0xEC, 0x00} },	                // sub 0x??, %rsp
+	{ 0x4, {0xFB, 0xFF, 0x07, 0x00}, {0x48, 0x89, 0x05, 0x00} },	                // move onto rbp
+	{ 0x3, {0xFB, 0xFF, 0x00}, {0x48, 0x89, 0x00} },	                            // mov %reg, %reg
+	{ 0x3, {0xFB, 0xFF, 0x00}, {0x49, 0x89, 0x00} },	                            // mov %reg, %reg (REX.WB)
+	{ 0x2, {0xFF, 0x00}, {0x41, 0x00} },						// push %rXX
+	{ 0x2, {0xFF, 0x00}, {0x84, 0x00} },						// test %rX8,%rX8
+	{ 0x2, {0xFF, 0x00}, {0x85, 0x00} },						// test %rX,%rX
+	{ 0x2, {0xFF, 0x00}, {0x77, 0x00} },						// ja $i8
+	{ 0x2, {0xFF, 0x00}, {0x74, 0x00} },						// je $i8
+	{ 0x5, {0xF8, 0x00, 0x00, 0x00, 0x00}, {0xB8, 0x00, 0x00, 0x00, 0x00} },	// mov $imm, %reg
+	{ 0x3, {0xFF, 0xFF, 0x00}, {0xFF, 0x77, 0x00} },				// pushq $imm(%rdi)
+	{ 0x2, {0xFF, 0xFF}, {0x31, 0xC0} },						// xor %eax, %eax
+	{ 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0x25, 0x00, 0x00, 0x00, 0x00} },	// and $imm, %eax
+	{ 0x3, {0xFF, 0xFF, 0xFF}, {0x80, 0x3F, 0x00} },				// cmpb $imm, (%rdi)
+
+  { 0x8, {0xFF, 0xFF, 0xCF, 0xFF, 0x00, 0x00, 0x00, 0x00},
+         {0x48, 0x8B, 0x04, 0x25, 0x00, 0x00, 0x00, 0x00}, },                     // mov $imm, %{rax,rdx,rsp,rsi}
+  { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x48, 0x83, 0xFA, 0x00}, },   // cmp $i8, %rdx
+	{ 0x4, {0xFF, 0xFF, 0x00, 0x00}, {0x83, 0x7f, 0x00, 0x00}, },			// cmpl $imm, $imm(%rdi)
+	{ 0xa, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+               {0x48, 0xB8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00} },    // mov $imm, %rax
+        { 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00},
+               {0x81, 0xE6, 0x00, 0x00, 0x00, 0x00} },                            // and $imm, %esi
+        { 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00},
+               {0xFF, 0x25, 0x00, 0x00, 0x00, 0x00} },                            // jmpq *(%rip)
+        { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x66, 0x0F, 0xEF, 0x00} },              // pxor xmm2/128, xmm1
+        { 0x2, {0xFF, 0x00}, {0x89, 0x00} },                               // mov r/m32,r32 or r/m16,r16
+        { 0x3, {0xFF, 0xFF, 0xFF}, {0x49, 0x89, 0xF8} },                   // mov %rdi,%r8
+        { 0x4, {0xFF, 0xFF, 0xFF, 0xFF}, {0x40, 0x0F, 0xBE, 0xCE} },       // movsbl %sil,%ecx
+        { 0x7, {0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00},
+               {0x48, 0x8D, 0x05, 0x00, 0x00, 0x00, 0x00} },  // lea $imm(%rip),%rax
+        { 0x3, {0xFF, 0xFF, 0xFF}, {0x0F, 0xBE, 0xCE} },  // movsbl, %dh, %ecx
+        { 0x3, {0xFF, 0xFF, 0x00}, {0xFF, 0x77, 0x00} },  // pushq $imm(%rdi)
+        { 0x2, {0xFF, 0xFF}, {0xDB, 0xE3} }, // fninit
+        { 0x3, {0xFF, 0xFF, 0xFF}, {0x48, 0x85, 0xD2} },  // test %rdx,%rdx
+	{ 0x0, {0x00}, {0x00} }
+};
+#endif
+
+static Boolean codeMatchesInstruction(unsigned char *code, AsmInstructionMatch* instruction) 
+{
+	Boolean match = true;
+	
+	size_t i;
+  assert(instruction);
+#ifdef DEBUG_DISASM
+	fprintf(stderr, "Matching: ");
+#endif  
+	for (i=0; i<instruction->length; i++) {
+		unsigned char mask = instruction->mask[i];
+		unsigned char constraint = instruction->constraint[i];
+		unsigned char codeValue = code[i];
+#ifdef DEBUG_DISASM
+		fprintf(stderr, "%x ", (unsigned)codeValue);
+#endif    
+		match = ((codeValue & mask) == constraint);
+		if (!match) break;
+	}
+#ifdef DEBUG_DISASM
+	if (match) {
+		fprintf(stderr, " OK\n");
+	} else {
+		fprintf(stderr, " FAIL\n");
+	}
+#endif  
+	return match;
+}
+
+#if defined(__i386__) || defined(__x86_64__)
+	static Boolean 
+eatKnownInstructions( 
+	unsigned char	*code, 
+	uint64_t		*newInstruction,
+	int				*howManyEaten, 
+	char			*originalInstructions,
+	int				*originalInstructionCount, 
+	uint8_t			*originalInstructionSizes )
+{
+	Boolean allInstructionsKnown = true;
+	int totalEaten = 0;
+	unsigned char* ptr = code;
+	int remainsToEat = 5; // a JMP instruction takes 5 bytes
+	int instructionIndex = 0;
+	
+	if (howManyEaten) *howManyEaten = 0;
+	if (originalInstructionCount) *originalInstructionCount = 0;
+	while (remainsToEat > 0) {
+		Boolean curInstructionKnown = false;
+		
+		// See if instruction matches one  we know
+		AsmInstructionMatch* curInstr = possibleInstructions;
+		do { 
+			if ((curInstructionKnown = codeMatchesInstruction(ptr, curInstr))) break;
+			curInstr++;
+		} while (curInstr->length > 0);
+		
+		// if all instruction matches failed, we don't know current instruction then, stop here
+		if (!curInstructionKnown) { 
+			allInstructionsKnown = false;
+			fprintf(stderr, "mach_override: some instructions unknown! Need to update mach_override.c\n");
+			break;
+		}
+		
+		// At this point, we've matched curInstr
+		int eaten = curInstr->length;
+		ptr += eaten;
+		remainsToEat -= eaten;
+		totalEaten += eaten;
+		
+		if (originalInstructionSizes) originalInstructionSizes[instructionIndex] = eaten;
+		instructionIndex += 1;
+		if (originalInstructionCount) *originalInstructionCount = instructionIndex;
+	}
+
+
+	if (howManyEaten) *howManyEaten = totalEaten;
+
+	if (originalInstructions) {
+		Boolean enoughSpaceForOriginalInstructions = (totalEaten < kOriginalInstructionsSize);
+		
+		if (enoughSpaceForOriginalInstructions) {
+			memset(originalInstructions, 0x90 /* NOP */, kOriginalInstructionsSize); // fill instructions with NOP
+			bcopy(code, originalInstructions, totalEaten);
+		} else {
+#ifdef DEBUG_DISASM
+			fprintf(stderr, "Not enough space in island to store original instructions. Adapt the island definition and kOriginalInstructionsSize\n");
+#endif      
+			return false;
+		}
+	}
+	
+	if (allInstructionsKnown) {
+		// save last 3 bytes of first 64bits of codre we'll replace
+		uint64_t currentFirst64BitsOfCode = *((uint64_t *)code);
+		currentFirst64BitsOfCode = OSSwapInt64(currentFirst64BitsOfCode); // back to memory representation
+		currentFirst64BitsOfCode &= 0x0000000000FFFFFFLL; 
+		
+		// keep only last 3 instructions bytes, first 5 will be replaced by JMP instr
+		*newInstruction &= 0xFFFFFFFFFF000000LL; // clear last 3 bytes
+		*newInstruction |= (currentFirst64BitsOfCode & 0x0000000000FFFFFFLL); // set last 3 bytes
+	}
+
+	return allInstructionsKnown;
+}
+
+	static void
+fixupInstructions(
+    void		*originalFunction,
+    void		*escapeIsland,
+    void		*instructionsToFix,
+	int			instructionCount,
+	uint8_t		*instructionSizes )
+{
+	void *initialOriginalFunction = originalFunction;
+	int	index, fixed_size, code_size = 0;
+	for (index = 0;index < instructionCount;index += 1)
+		code_size += instructionSizes[index];
+
+#ifdef DEBUG_DISASM
+	void *initialInstructionsToFix = instructionsToFix;
+	fprintf(stderr, "BEFORE FIXING:\n");
+	dump16Bytes(initialOriginalFunction);
+	dump16Bytes(initialInstructionsToFix);
+#endif  // DEBUG_DISASM
+
+	for (index = 0;index < instructionCount;index += 1)
+	{
+                fixed_size = instructionSizes[index];
+		if ((*(uint8_t*)instructionsToFix == 0xE9) || // 32-bit jump relative
+		    (*(uint8_t*)instructionsToFix == 0xE8))   // 32-bit call relative
+		{
+			uint32_t offset = (uintptr_t)originalFunction - (uintptr_t)escapeIsland;
+			uint32_t *jumpOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 1);
+			*jumpOffsetPtr += offset;
+		}
+		if ((*(uint8_t*)instructionsToFix == 0x74) ||  // Near jump if equal (je), 2 bytes.
+		    (*(uint8_t*)instructionsToFix == 0x77))    // Near jump if above (ja), 2 bytes.
+		{
+			// We replace a near je/ja instruction, "7P JJ", with a 32-bit je/ja, "0F 8P WW XX YY ZZ".
+			// This is critical, otherwise a near jump will likely fall outside the original function.
+			uint32_t offset = (uintptr_t)initialOriginalFunction - (uintptr_t)escapeIsland;
+			uint32_t jumpOffset = *(uint8_t*)((uintptr_t)instructionsToFix + 1);
+			*((uint8_t*)instructionsToFix + 1) = *(uint8_t*)instructionsToFix + 0x10;
+			*(uint8_t*)instructionsToFix = 0x0F;
+			uint32_t *jumpOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 2 );
+			*jumpOffsetPtr = offset + jumpOffset;
+			fixed_size = 6;
+                }
+		
+		originalFunction = (void*)((uintptr_t)originalFunction + instructionSizes[index]);
+		escapeIsland = (void*)((uintptr_t)escapeIsland + instructionSizes[index]);
+		instructionsToFix = (void*)((uintptr_t)instructionsToFix + fixed_size);
+
+		// Expanding short instructions into longer ones may overwrite the next instructions,
+		// so we must restore them.
+		code_size -= fixed_size;
+		if ((code_size > 0) && (fixed_size != instructionSizes[index])) {
+			bcopy(originalFunction, instructionsToFix, code_size);
+		}
+	}
+#ifdef DEBUG_DISASM
+	fprintf(stderr, "AFTER_FIXING:\n");
+	dump16Bytes(initialOriginalFunction);
+	dump16Bytes(initialInstructionsToFix);
+#endif  // DEBUG_DISASM
+}
+
+#ifdef DEBUG_DISASM
+#define HEX_DIGIT(x) ((((x) % 16) < 10) ? ('0' + ((x) % 16)) : ('A' + ((x) % 16 - 10)))
+
+	static void
+dump16Bytes(
+	void 	*ptr) {
+	int i;
+	char buf[3];
+	uint8_t *bytes = (uint8_t*)ptr;
+	for (i = 0; i < 16; i++) {
+		buf[0] = HEX_DIGIT(bytes[i] / 16);
+		buf[1] = HEX_DIGIT(bytes[i] % 16);
+		buf[2] = ' ';
+		write(2, buf, 3);
+	}
+	write(2, "\n", 1);
+}
+#endif  // DEBUG_DISASM
+#endif
+
+#if defined(__i386__)
+__asm(
+			".text;"
+			".align 2, 0x90;"
+			"_atomic_mov64:;"
+			"	pushl %ebp;"
+			"	movl %esp, %ebp;"
+			"	pushl %esi;"
+			"	pushl %ebx;"
+			"	pushl %ecx;"
+			"	pushl %eax;"
+			"	pushl %edx;"
+	
+			// atomic push of value to an address
+			// we use cmpxchg8b, which compares content of an address with 
+			// edx:eax. If they are equal, it atomically puts 64bit value 
+			// ecx:ebx in address. 
+			// We thus put contents of address in edx:eax to force ecx:ebx
+			// in address
+			"	mov		8(%ebp), %esi;"  // esi contains target address
+			"	mov		12(%ebp), %ebx;"
+			"	mov		16(%ebp), %ecx;" // ecx:ebx now contains value to put in target address
+			"	mov		(%esi), %eax;"
+			"	mov		4(%esi), %edx;"  // edx:eax now contains value currently contained in target address
+			"	lock; cmpxchg8b	(%esi);" // atomic move.
+			
+			// restore registers
+			"	popl %edx;"
+			"	popl %eax;"
+			"	popl %ecx;"
+			"	popl %ebx;"
+			"	popl %esi;"
+			"	popl %ebp;"
+			"	ret"
+);
+#elif defined(__x86_64__)
+void atomic_mov64(
+		uint64_t *targetAddress,
+		uint64_t value )
+{
+    *targetAddress = value;
+}
+#endif
+#endif
+#endif  // __APPLE__
diff --git a/libsanitizer/interception/mach_override/mach_override.h b/libsanitizer/interception/mach_override/mach_override.h
new file mode 100644
index 00000000000..7e60cdcd619
--- /dev/null
+++ b/libsanitizer/interception/mach_override/mach_override.h
@@ -0,0 +1,140 @@
+/*******************************************************************************
+	mach_override.h
+		Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
+		Some rights reserved: <http://opensource.org/licenses/mit-license.php>
+
+	***************************************************************************/
+
+/***************************************************************************//**
+	@mainpage	mach_override
+	@author		Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
+	
+	This package, coded in C to the Mach API, allows you to override ("patch")
+	program- and system-supplied functions at runtime. You can fully replace
+	functions with your implementations, or merely head- or tail-patch the
+	original implementations.
+	
+	Use it by #include'ing mach_override.h from your .c, .m or .mm file(s).
+	
+	@todo	Discontinue use of Carbon's MakeDataExecutable() and
+			CompareAndSwap() calls and start using the Mach equivalents, if they
+			exist. If they don't, write them and roll them in. That way, this
+			code will be pure Mach, which will make it easier to use everywhere.
+			Update: MakeDataExecutable() has been replaced by
+			msync(MS_INVALIDATE). There is an OSCompareAndSwap in libkern, but
+			I'm currently unsure if I can link against it. May have to roll in
+			my own version...
+	@todo	Stop using an entire 4K high-allocated VM page per 28-byte escape
+			branch island. Done right, this will dramatically speed up escape
+			island allocations when they number over 250. Then again, if you're
+			overriding more than 250 functions, maybe speed isn't your main
+			concern...
+	@todo	Add detection of: b, bl, bla, bc, bcl, bcla, bcctrl, bclrl
+			first-instructions. Initially, we should refuse to override
+			functions beginning with these instructions. Eventually, we should
+			dynamically rewrite them to make them position-independent.
+	@todo	Write mach_unoverride(), which would remove an override placed on a
+			function. Must be multiple-override aware, which means an almost
+			complete rewrite under the covers, because the target address can't
+			be spread across two load instructions like it is now since it will
+			need to be atomically updatable.
+	@todo	Add non-rentry variants of overrides to test_mach_override.
+
+	***************************************************************************/
+
+#ifdef __APPLE__
+
+#ifndef		_mach_override_
+#define		_mach_override_
+
+#include <sys/types.h>
+#include <mach/error.h>
+
+#ifdef	__cplusplus
+	extern	"C"	{
+#endif
+
+/**
+	Returned if the function to be overrided begins with a 'mfctr' instruction.
+*/
+#define	err_cannot_override	(err_local|1)
+
+/************************************************************************************//**
+	Dynamically overrides the function implementation referenced by
+	originalFunctionAddress with the implentation pointed to by overrideFunctionAddress.
+	Optionally returns a pointer to a "reentry island" which, if jumped to, will resume
+	the original implementation.
+	
+	@param	originalFunctionAddress			->	Required address of the function to
+												override (with overrideFunctionAddress).
+	@param	overrideFunctionAddress			->	Required address to the overriding
+												function.
+	@param	originalFunctionReentryIsland	<-	Optional pointer to pointer to the
+												reentry island. Can be NULL.
+	@result									<-	err_cannot_override if the original
+												function's implementation begins with
+												the 'mfctr' instruction.
+
+	************************************************************************************/
+
+// We're prefixing mach_override_ptr() with "__asan_" to avoid name conflicts with other
+// mach_override_ptr() implementations that may appear in the client program.
+    mach_error_t
+__asan_mach_override_ptr(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland );
+
+// Allow to use custom allocation and deallocation routines with mach_override_ptr().
+// This should help to speed up the things on x86_64.
+typedef mach_error_t island_malloc( void **ptr, size_t size, void *hint );
+typedef mach_error_t island_free( void *ptr );
+
+    mach_error_t
+__asan_mach_override_ptr_custom(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland,
+    island_malloc *alloc,
+    island_free *dealloc );
+
+/************************************************************************************//**
+	
+
+	************************************************************************************/
+ 
+#ifdef	__cplusplus
+
+#define MACH_OVERRIDE( ORIGINAL_FUNCTION_RETURN_TYPE, ORIGINAL_FUNCTION_NAME, ORIGINAL_FUNCTION_ARGS, ERR )			\
+	{																												\
+		static ORIGINAL_FUNCTION_RETURN_TYPE (*ORIGINAL_FUNCTION_NAME##_reenter)ORIGINAL_FUNCTION_ARGS;				\
+		static bool ORIGINAL_FUNCTION_NAME##_overriden = false;														\
+		class mach_override_class__##ORIGINAL_FUNCTION_NAME {														\
+		public:																										\
+			static kern_return_t override(void *originalFunctionPtr) {												\
+				kern_return_t result = err_none;																	\
+				if (!ORIGINAL_FUNCTION_NAME##_overriden) {															\
+					ORIGINAL_FUNCTION_NAME##_overriden = true;														\
+					result = mach_override_ptr( (void*)originalFunctionPtr,											\
+												(void*)mach_override_class__##ORIGINAL_FUNCTION_NAME::replacement,	\
+												(void**)&ORIGINAL_FUNCTION_NAME##_reenter );						\
+				}																									\
+				return result;																						\
+			}																										\
+			static ORIGINAL_FUNCTION_RETURN_TYPE replacement ORIGINAL_FUNCTION_ARGS {
+
+#define END_MACH_OVERRIDE( ORIGINAL_FUNCTION_NAME )																	\
+			}																										\
+		};																											\
+																													\
+		err = mach_override_class__##ORIGINAL_FUNCTION_NAME::override((void*)ORIGINAL_FUNCTION_NAME);				\
+	}
+ 
+#endif
+
+#ifdef	__cplusplus
+	}
+#endif
+#endif	//	_mach_override_
+
+#endif  // __APPLE__