Mac: Let chrome coexist with the Chinese Handwriting IME.

The renderer sandbox breaks the Chinese Handwriting shortcut while Chrome
is running, even when Chrome is not active: In a nutshell, Carbon tries to load
the IME in every process, and if that fails, it uninstalls the toggle shorcut. It
fails in the renderer process due to the sandbox. See the bug for details.

Prewarming (patch set 1) doesn't work because that opens up clipboard
access to the renderer – the IME doesn't load correctly if it doesn't have
clipboard access.

dyld __interpose based interposing (patch set 2) doesn't work because
TISCreateInputSourceList and its broken caller are in the same
framework (HIToolbox).

Hence, use binary rewriting to return an arbitrary array with size > 0 to make
HIToolbox believe that the IME loads correctly, so that it doesn't uninstall the
global handwriting keyboard shortcut.

BUG=31225
TEST=Enable Chinese in the input menu. Make sure Chrome's not running.
Note that ctrl-shift-space opens and dismisses the Handwriting IME
(you need a multitouch trackpad for that). Open Chrome, note that the
IME still works.
(If you run Chrome without this patch, the IME will be broken until you do
  ps aux | grep Chinese
and then
  kill $CHINESE_HANDWRITING_PID
and then toggle the IME once through the Menu Extra menu.)
It is a good idea to have a Terminal open during testing, because killing
the task is the only way to dismiss the IME with the keyboard without this
CL.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=81308

Review URL: http://codereview.chromium.org/6801056

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@81332 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 682 insertions, 0 deletions

diff --git a/third_party/mach_override/mach_override.c b/third_party/mach_override/mach_override.c
new file mode 100644
index 0000000..30b6afd
--- /dev/null
+++ b/third_party/mach_override/mach_override.c
@@ -0,0 +1,682 @@
+/*******************************************************************************
+	mach_override.c
+		Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
+		Some rights reserved: <http://opensource.org/licenses/mit-license.php>
+
+	***************************************************************************/
+
+#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>
+
+/**************************
+*	
+*	Constants
+*	
+**************************/
+#pragma mark	-
+#pragma mark	(Constants)
+
+#if defined(__ppc__) || defined(__POWERPC__)
+
+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
+
+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
+
+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)
+
+	mach_error_t
+allocateBranchIsland(
+		BranchIsland	**island,
+		int				allocateHigh,
+		void *originalFunctionAddress);
+
+	mach_error_t
+freeBranchIsland(
+		BranchIsland	*island );
+
+#if defined(__ppc__) || defined(__POWERPC__)
+	mach_error_t
+setBranchIslandTarget(
+		BranchIsland	*island,
+		const void		*branchTo,
+		long			instruction );
+#endif 
+
+#if defined(__i386__) || defined(__x86_64__)
+mach_error_t
+setBranchIslandTarget_i386(
+						   BranchIsland	*island,
+						   const void		*branchTo,
+						   char*			instructions );
+void 
+atomic_mov64(
+		uint64_t *targetAddress,
+		uint64_t value );
+
+	static Boolean 
+eatKnownInstructions( 
+	unsigned char	*code, 
+	uint64_t		*newInstruction,
+	int				*howManyEaten, 
+	char			*originalInstructions );
+#endif
+
+/*******************************************************************************
+*	
+*	Interface
+*	
+*******************************************************************************/
+#pragma mark	-
+#pragma mark	(Interface)
+
+#if defined(__x86_64__)
+mach_error_t makeIslandExecutable(void *address) {
+	mach_error_t err = err_none;
+    vm_size_t pageSize;
+    host_page_size( mach_host_self(), &pageSize );
+    uint64_t page = (uint64_t)address & ~(uint64_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
+
+    mach_error_t
+mach_override_ptr(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland )
+{
+	assert( originalFunctionAddress );
+	assert( overrideFunctionAddress );
+	
+	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;
+	char originalInstructions[kOriginalInstructionsSize];
+	uint64_t jumpRelativeInstruction = 0; // JMP
+
+	Boolean overridePossible = eatKnownInstructions ((unsigned char *)originalFunctionPtr, 
+										&jumpRelativeInstruction, &eatenCount, originalInstructions);
+	if (eatenCount > kOriginalInstructionsSize) {
+		//printf ("Too many instructions eaten\n");
+		overridePossible = false;
+	}
+	if (!overridePossible) err = err_cannot_override;
+	if (err) printf("err = %x %d\n", err, __LINE__);
+#endif
+	
+	//	Make the original function implementation writable.
+	if( !err ) {
+		err = vm_protect( mach_task_self(),
+				(vm_address_t) originalFunctionPtr,
+				sizeof(long), false, (VM_PROT_ALL | VM_PROT_COPY) );
+		if( err )
+			err = vm_protect( mach_task_self(),
+					(vm_address_t) originalFunctionPtr, sizeof(long), false,
+					(VM_PROT_DEFAULT | VM_PROT_COPY) );
+	}
+	if (err) printf("err = %x %d\n", err, __LINE__);
+	
+	//	Allocate and target the escape island to the overriding function.
+	BranchIsland	*escapeIsland = NULL;
+	if( !err )	
+		err = allocateBranchIsland( &escapeIsland, kAllocateHigh, originalFunctionAddress );
+		if (err) printf("err = %x %d\n", err, __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) printf("err = %x %d\n", err, __LINE__);
+
+	if( !err )
+		err = setBranchIslandTarget_i386( escapeIsland, overrideFunctionAddress, 0 );
+ 
+	if (err) printf("err = %x %d\n", err, __LINE__);
+	// Build the jump relative instruction to the escape island
+#endif
+
+
+#if defined(__i386__) || defined(__x86_64__)
+	if (!err) {
+		uint32_t addressOffset = ((void*)escapeIsland - (void*)originalFunctionPtr - 5);
+		addressOffset = OSSwapInt32(addressOffset);
+		
+		jumpRelativeInstruction |= 0xE900000000000000LL; 
+		jumpRelativeInstruction |= ((uint64_t)addressOffset & 0xffffffff) << 24;
+		jumpRelativeInstruction = OSSwapInt64(jumpRelativeInstruction);		
+	}
+#endif
+	
+	//	Optionally allocate & return the reentry island.
+	BranchIsland	*reentryIsland = NULL;
+	if( !err && originalFunctionReentryIsland ) {
+		err = allocateBranchIsland( &reentryIsland, kAllocateNormal, NULL);
+		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 ) {
+		if( reentryIsland )
+			err = setBranchIslandTarget_i386( reentryIsland,
+										 (void*) ((char *)originalFunctionPtr+eatenCount), originalInstructions );
+		if ( !err )
+			atomic_mov64((uint64_t *)originalFunctionPtr, jumpRelativeInstruction);
+	}
+#endif
+	
+	//	Clean up on error.
+	if( err ) {
+		if( reentryIsland )
+			freeBranchIsland( reentryIsland );
+		if( escapeIsland )
+			freeBranchIsland( escapeIsland );
+	}
+
+#if defined(__x86_64__)
+        err = makeIslandExecutable(escapeIsland);
+        err = makeIslandExecutable(reentryIsland);
+#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
+
+	***************************************************************************/
+
+	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(__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 = 0xfeffffff;
+			vm_address_t last = 0xfe000000 + pageSize;
+#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 = (void*) 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
+
+	***************************************************************************/
+
+	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__)
+	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__)
+	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__)
+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[] = {
+	{ 0x1, {0xFF}, {0x90} },							// nop
+	{ 0x1, {0xFF}, {0x55} },							// push %esp
+	{ 0x2, {0xFF, 0xFF}, {0x89, 0xE5} },				                // mov %esp,%ebp
+	{ 0x1, {0xFF}, {0x53} },							// push %ebx
+	{ 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
+	{ 0x1, {0xFF}, {0x57} },							// push %edi
+	{ 0x1, {0xFF}, {0x56} },							// push %esi
+	{ 0x2, {0xFF, 0xFF}, {0x31, 0xC0} },						// xor %eax, %eax
+	{ 0x0 }
+};
+#elif defined(__x86_64__)
+static AsmInstructionMatch possibleInstructions[] = {
+	{ 0x1, {0xFF}, {0x90} },							// nop
+	{ 0x1, {0xF8}, {0x50} },							// push %rX
+	{ 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, 0x00, 0x00}, {0x48, 0x89, 0x00, 0x00} },	                // move onto rbp
+	{ 0x2, {0xFF, 0x00}, {0x41, 0x00} },						// push %rXX
+	{ 0x2, {0xFF, 0x00}, {0x85, 0x00} },						// test %rX,%rX
+	{ 0x0 }
+};
+#endif
+
+static Boolean codeMatchesInstruction(unsigned char *code, AsmInstructionMatch* instruction) 
+{
+	Boolean match = true;
+	
+	size_t i;
+	for (i=0; i<instruction->length; i++) {
+		unsigned char mask = instruction->mask[i];
+		unsigned char constraint = instruction->constraint[i];
+		unsigned char codeValue = code[i];
+				
+		match = ((codeValue & mask) == constraint);
+		if (!match) break;
+	}
+	
+	return match;
+}
+
+#if defined(__i386__) || defined(__x86_64__)
+	static Boolean 
+eatKnownInstructions( 
+	unsigned char *code, 
+	uint64_t* newInstruction,
+	int* howManyEaten, 
+	char* originalInstructions )
+{
+	Boolean allInstructionsKnown = true;
+	int totalEaten = 0;
+	unsigned char* ptr = code;
+	int remainsToEat = 5; // a JMP instruction takes 5 bytes
+	
+	if (howManyEaten) *howManyEaten = 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;
+			break;
+		}
+		
+		// At this point, we've matched curInstr
+		int eaten = curInstr->length;
+		ptr += eaten;
+		remainsToEat -= eaten;
+		totalEaten += eaten;
+	}
+
+
+	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 {
+			// printf ("Not enough space in island to store original instructions. Adapt the island definition and kOriginalInstructionsSize\n");
+			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;
+}
+#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