Merge pull request #38 from espindola/master

Speed up allocateBranchIsland

1 files changed, 56 insertions, 80 deletions

diff --git a/mach_override/mach_override.c b/mach_override/mach_override.c
index 64dd0ab..f2a4fea 100644
--- a/mach_override/mach_override.c
+++ b/mach_override/mach_override.c
@@ -23,6 +23,7 @@
 #pragma mark	-
 #pragma mark	(Constants)
 
+#define kPageSize 4096
 #if defined(__ppc__) || defined(__POWERPC__)
 
 long kIslandTemplate[] = {
@@ -76,9 +77,6 @@ char kIslandTemplate[] = {
 
 #endif
 
-#define	kAllocateHigh		1
-#define	kAllocateNormal		0
-
 /**************************
 *	
 *	Data Types
@@ -89,7 +87,6 @@ char kIslandTemplate[] = {
 
 typedef	struct	{
 	char	instructions[sizeof(kIslandTemplate)];
-	int		allocatedHigh;
 }	BranchIsland;
 
 /**************************
@@ -103,7 +100,6 @@ typedef	struct	{
 	mach_error_t
 allocateBranchIsland(
 		BranchIsland	**island,
-		int				allocateHigh,
 		void *originalFunctionAddress);
 
 	mach_error_t
@@ -158,12 +154,10 @@ fixupInstructions(
 #if defined(__i386__) || 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 );
-    uintptr_t page = (uintptr_t)address & ~(uintptr_t)(pageSize-1);
+    uintptr_t page = (uintptr_t)address & ~(uintptr_t)(kPageSize-1);
     int e = err_none;
-    e |= mprotect((void *)page, pageSize, PROT_EXEC | PROT_READ | PROT_WRITE);
-    e |= msync((void *)page, pageSize, MS_INVALIDATE );
+    e |= mprotect((void *)page, kPageSize, PROT_EXEC | PROT_READ | PROT_WRITE);
+    e |= msync((void *)page, kPageSize, MS_INVALIDATE );
     if (e) {
         err = err_cannot_override;
     }
@@ -241,7 +235,7 @@ mach_override_ptr(
 	//	Allocate and target the escape island to the overriding function.
 	BranchIsland	*escapeIsland = NULL;
 	if( !err )	
-		err = allocateBranchIsland( &escapeIsland, kAllocateHigh, originalFunctionAddress );
+		err = allocateBranchIsland( &escapeIsland, originalFunctionAddress );
 		if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
 
 	
@@ -283,7 +277,7 @@ mach_override_ptr(
 	//  technically our original function.
 	BranchIsland	*reentryIsland = NULL;
 	if( !err && originalFunctionReentryIsland ) {
-		err = allocateBranchIsland( &reentryIsland, kAllocateHigh, escapeIsland);
+		err = allocateBranchIsland( &reentryIsland, escapeIsland);
 		if( !err )
 			*originalFunctionReentryIsland = reentryIsland;
 	}
@@ -367,9 +361,6 @@ mach_override_ptr(
 	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
 
 	***************************************************************************/
@@ -377,63 +368,63 @@ mach_override_ptr(
 	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;
+	assert( sizeof( BranchIsland ) <= kPageSize );
+
+	vm_map_t task_self = mach_task_self();
+	vm_address_t original_address = (vm_address_t) originalFunctionAddress;
+	static vm_address_t last_allocated = 0;
+	vm_address_t address =
+		last_allocated ? last_allocated : original_address;
+
+	for (;;) {
+		vm_size_t vmsize = 0;
+		memory_object_name_t object = 0;
+		kern_return_t kr = 0;
+		vm_region_flavor_t flavor = VM_REGION_BASIC_INFO;
+		// Find the page the address is in.
+#if __WORDSIZE == 32
+		vm_region_basic_info_data_t info;
+		mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT;
+		kr = vm_region(task_self, &address, &vmsize, flavor,
+			       (vm_region_info_t)&info, &info_count, &object);
 #else
-			vm_address_t first = 0xffc00000;
-			vm_address_t last = 0xfffe0000;
+		vm_region_basic_info_data_64_t info;
+		mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT_64;
+		kr = vm_region_64(task_self, &address, &vmsize, flavor,
+				  (vm_region_info_t)&info, &info_count, &object);
 #endif
+		if (kr != KERN_SUCCESS)
+			return kr;
 
-			vm_address_t page = first;
-			int allocated = 0;
-			vm_map_t task_self = mach_task_self();
-			
-			while( !err && !allocated && page != last ) {
+		// Don't underflow. This could be made to work, but this is a
+		// convenient place to give up.
+		assert((address & (kPageSize - 1)) == 0);
+		if (address == 0)
+			break;
 
-				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;
+		// Go back one page.
+		vm_address_t new_address = address - kPageSize;
+#if __WORDSIZE == 64
+		if(original_address - new_address - 5 > INT32_MAX)
+			break;
 #endif
-					err = err_none;
-				}
-			}
-			if( allocated )
-				*island = (BranchIsland*) page;
-			else if( !allocated && !err )
-				err = KERN_NO_SPACE;
+		address = new_address;
+
+		// Try to allocate this page.
+		kr = vm_allocate(task_self, &address, kPageSize, 0);
+		if (kr == KERN_SUCCESS) {
+			*island = (BranchIsland*) address;
+			last_allocated = address;
+			return err_none;
 		}
-	} else {
-		void *block = malloc( sizeof( BranchIsland ) );
-		if( block )
-			*island = block;
-		else
-			err = KERN_NO_SPACE;
+		if (kr != KERN_NO_SPACE)
+			return kr;
 	}
-	if( !err )
-		(**island).allocatedHigh = allocateHigh;
-	
-	return err;
+
+	return KERN_NO_SPACE;
 }
 
 /***************************************************************************//**
@@ -450,24 +441,9 @@ freeBranchIsland(
 {
 	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;
+	assert( sizeof( BranchIsland ) <= kPageSize );
+	return vm_deallocate( mach_task_self(), (vm_address_t) island,
+			      kPageSize );
 }
 
 /***************************************************************************//**