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src/ImageLoaderMachO.cpp dyld-732.8 dyld-239.4
--- dyld/dyld-732.8/src/ImageLoaderMachO.cpp
+++ dyld/dyld-239.4/src/ImageLoaderMachO.cpp
@@ -39,7 +39,6 @@
 #include <mach/thread_status.h>
 #include <mach-o/loader.h> 
 #include <mach-o/nlist.h> 
-#include <mach-o/dyld_images.h>
 #include <sys/sysctl.h>
 #include <sys/syscall.h>
 #include <libkern/OSAtomic.h>
@@ -47,26 +46,18 @@
 #include <stdint.h>
 #include <System/sys/codesign.h>
 
-#if __has_feature(ptrauth_calls)
-#include <ptrauth.h>
-#endif
-
 #include "ImageLoaderMachO.h"
 #include "ImageLoaderMachOCompressed.h"
 #if SUPPORT_CLASSIC_MACHO
 #include "ImageLoaderMachOClassic.h"
 #endif
-#include "Tracing.h"
-#include "dyld2.h"
+#include "mach-o/dyld_images.h"
 
 // <rdar://problem/8718137> use stack guard random value to add padding between dylibs
 extern "C" long __stack_chk_guard;
 
-#define LIBSYSTEM_DYLIB_PATH 		  	  "/usr/lib/libSystem.B.dylib"
-#define LIBDYLD_DYLIB_PATH 		  	  "/usr/lib/system/libdyld.dylib"
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-  #define DRIVERKIT_LIBSYSTEM_DYLIB_PATH  "/System/DriverKit/usr/lib/libSystem.dylib"
-  #define DRIVERKIT_LIBDYLD_DYLIB_PATH 	  "/System/DriverKit/usr/lib/system/libdyld.dylib"
+#ifndef LC_LOAD_UPWARD_DYLIB
+	#define	LC_LOAD_UPWARD_DYLIB (0x23|LC_REQ_DYLD)	/* load of dylib whose initializers run later */
 #endif
 
 // relocation_info.r_length field has value 3 for 64-bit executables and value 2 for 32-bit executables
@@ -87,24 +78,23 @@
 #endif
 
 uint32_t ImageLoaderMachO::fgSymbolTableBinarySearchs = 0;
+uint32_t ImageLoaderMachO::fgSymbolTrieSearchs = 0;
 
 
 ImageLoaderMachO::ImageLoaderMachO(const macho_header* mh, const char* path, unsigned int segCount, 
 																uint32_t segOffsets[], unsigned int libCount)
- : ImageLoader(path, libCount), fCoveredCodeLength(0), fMachOData((uint8_t*)mh), fLinkEditBase(NULL), fSlide(0),
+ : ImageLoader(path, libCount), fMachOData((uint8_t*)mh), fLinkEditBase(NULL), fSlide(0), 
 	fEHFrameSectionOffset(0), fUnwindInfoSectionOffset(0), fDylibIDOffset(0), 
-fSegmentsCount(segCount), fIsSplitSeg(false), fInSharedCache(false),
+	fSegmentsCount(segCount), fIsSplitSeg(false), fInSharedCache(false),  
 #if TEXT_RELOC_SUPPORT
 	fTextSegmentRebases(false),
 	fTextSegmentBinds(false),
-#else
-    fReadOnlyDataSegment(false),
 #endif
 #if __i386__
 	fReadOnlyImportSegment(false),
 #endif
 	fHasSubLibraries(false), fHasSubUmbrella(false), fInUmbrella(false), fHasDOFSections(false), fHasDashInit(false),
-	fHasInitializers(false), fHasTerminators(false), fNotifyObjC(false), fRetainForObjC(false), fRegisteredAsRequiresCoalescing(false), fOverrideOfCacheImageNum(0)
+	fHasInitializers(false), fHasTerminators(false), fRegisteredAsRequiresCoalescing(false)
 {
 	fIsSplitSeg = ((mh->flags & MH_SPLIT_SEGS) != 0);        
 
@@ -119,7 +109,7 @@
 			// ignore zero-sized segments
 			if ( segCmd->vmsize != 0 ) {
 				// record offset of load command
-				segOffsets[segIndex++] = (uint32_t)((uint8_t*)segCmd - fMachOData);
+				segOffsets[segIndex++] = (uint8_t*)segCmd - fMachOData;
 			}
 		}
 		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
@@ -127,175 +117,49 @@
 
 }
 
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-static uintptr_t pageAlign(uintptr_t value)
-{
-	return (value + 4095) & (-4096);
-}
-#endif
 
 // determine if this mach-o file has classic or compressed LINKEDIT and number of segments it has
-void ImageLoaderMachO::sniffLoadCommands(const macho_header* mh, const char* path, bool inCache, bool* compressed,
+void ImageLoaderMachO::sniffLoadCommands(const macho_header* mh, const char* path, bool* compressed, 
 											unsigned int* segCount, unsigned int* libCount, const LinkContext& context,
-											const linkedit_data_command** codeSigCmd,
-											const encryption_info_command** encryptCmd)
+											const linkedit_data_command** codeSigCmd)
 {
 	*compressed = false;
 	*segCount = 0;
 	*libCount = 0;
 	*codeSigCmd = NULL;
-	*encryptCmd = NULL;
+	struct macho_segment_command* segCmd;
+	bool foundLoadCommandSegment = false;
+	uint32_t loadCommandSegmentIndex = 0xFFFFFFFF;
+	uintptr_t loadCommandSegmentVMStart = 0;
+	uintptr_t loadCommandSegmentVMEnd = 0;
 
 	const uint32_t cmd_count = mh->ncmds;
-	const uint32_t sizeofcmds = mh->sizeofcmds;
-	if ( sizeofcmds > (MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE-sizeof(macho_header)) )
-		dyld::throwf("malformed mach-o: load commands size (%u) > %u", sizeofcmds, MAX_MACH_O_HEADER_AND_LOAD_COMMANDS_SIZE);
-	if ( cmd_count > (sizeofcmds/sizeof(load_command)) )
-		dyld::throwf("malformed mach-o: ncmds (%u) too large to fit in sizeofcmds (%u)", cmd_count, sizeofcmds);
-	const struct load_command* const startCmds = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header));
-	const struct load_command* const endCmds = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header) + sizeofcmds);
+	const struct load_command* const startCmds    = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header));
+	const struct load_command* const endCmds = (struct load_command*)(((uint8_t*)mh) + sizeof(macho_header) + mh->sizeofcmds);
 	const struct load_command* cmd = startCmds;
-	bool foundLoadCommandSegment = false;
-	const macho_segment_command* linkeditSegCmd = NULL;
-	const macho_segment_command* startOfFileSegCmd = NULL;
-	const dyld_info_command* dyldInfoCmd = NULL;
-	const linkedit_data_command* chainedFixupsCmd = NULL;
-	const linkedit_data_command* exportsTrieCmd = NULL;
-	const symtab_command* symTabCmd = NULL;
-	const dysymtab_command*	dynSymbTabCmd = NULL;
 	for (uint32_t i = 0; i < cmd_count; ++i) {
-		uint32_t cmdLength = cmd->cmdsize;
-		const macho_segment_command* segCmd;
-		const dylib_command* dylibCmd;
-		if ( cmdLength < 8 ) {
-			dyld::throwf("malformed mach-o image: load command #%d length (%u) too small in %s",
-											   i, cmdLength, path);
-		}
-		const struct load_command* const nextCmd = (const struct load_command*)(((char*)cmd)+cmdLength);
-		if ( (nextCmd > endCmds) || (nextCmd < cmd) ) {
-			dyld::throwf("malformed mach-o image: load command #%d length (%u) would exceed sizeofcmds (%u) in %s",
-											   i, cmdLength, mh->sizeofcmds, path);
-		}
 		switch (cmd->cmd) {
 			case LC_DYLD_INFO:
 			case LC_DYLD_INFO_ONLY:
-				if ( cmd->cmdsize != sizeof(dyld_info_command) )
-					throw "malformed mach-o image: LC_DYLD_INFO size wrong";
-				dyldInfoCmd = (struct dyld_info_command*)cmd;
 				*compressed = true;
-				break;
-			case LC_DYLD_CHAINED_FIXUPS:
-				if ( cmd->cmdsize != sizeof(linkedit_data_command) )
-					throw "malformed mach-o image: LC_DYLD_CHAINED_FIXUPS size wrong";
-				chainedFixupsCmd = (struct linkedit_data_command*)cmd;
-				*compressed = true;
-				break;
-			case LC_DYLD_EXPORTS_TRIE:
-				if ( cmd->cmdsize != sizeof(linkedit_data_command) )
-					throw "malformed mach-o image: LC_DYLD_EXPORTS_TRIE size wrong";
-				exportsTrieCmd = (struct linkedit_data_command*)cmd;
 				break;
 			case LC_SEGMENT_COMMAND:
 				segCmd = (struct macho_segment_command*)cmd;
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-				// rdar://problem/19617624 allow unmapped segments on OSX (but not iOS)
-				if ( ((segCmd->filesize) > pageAlign(segCmd->vmsize)) && (segCmd->vmsize != 0) )
-#else
-				// <rdar://problem/19986776> dyld should support non-allocatable __LLVM segment
-				if ( (segCmd->filesize > segCmd->vmsize) && ((segCmd->vmsize != 0) || ((segCmd->flags & SG_NORELOC) == 0)) )
-#endif
-				    dyld::throwf("malformed mach-o image: segment load command %s filesize (0x%0lX) is larger than vmsize (0x%0lX)", segCmd->segname, (long)segCmd->filesize , (long)segCmd->vmsize );
-				if ( cmd->cmdsize < sizeof(macho_segment_command) )
-					throw "malformed mach-o image: LC_SEGMENT size too small";
-				if ( cmd->cmdsize != (sizeof(macho_segment_command) + segCmd->nsects * sizeof(macho_section)) )
-					throw "malformed mach-o image: LC_SEGMENT size wrong for number of sections";
 				// ignore zero-sized segments
 				if ( segCmd->vmsize != 0 )
 					*segCount += 1;
-				if ( strcmp(segCmd->segname, "__LINKEDIT") == 0 ) {
-		#if TARGET_OS_SIMULATOR
-					// Note: should check on all platforms that __LINKEDIT is read-only, but <rdar://problem/22637626&22525618>
-					if ( segCmd->initprot != VM_PROT_READ )
-						throw "malformed mach-o image: __LINKEDIT segment does not have read-only permissions";
-		#endif
-					if ( segCmd->fileoff ==  0 )
-						throw "malformed mach-o image: __LINKEDIT has fileoff==0 which overlaps mach_header";
-					if ( linkeditSegCmd != NULL )
-						throw "malformed mach-o image: multiple __LINKEDIT segments";
-					linkeditSegCmd = segCmd;
-				}
-				else {
-					if ( segCmd->initprot & 0xFFFFFFF8 )
-						dyld::throwf("malformed mach-o image: %s segment has invalid permission bits (0x%X) in initprot", segCmd->segname, segCmd->initprot);
-					if ( segCmd->maxprot & 0xFFFFFFF8 )
-						dyld::throwf("malformed mach-o image: %s segment has invalid permission bits (0x%X) in maxprot", segCmd->segname, segCmd->maxprot);
-					if ( (segCmd->initprot != 0) && ((segCmd->initprot & VM_PROT_READ) == 0) )
-						dyld::throwf("malformed mach-o image: %s segment is not mapped readable", segCmd->segname);
-				}
-                if ( (segCmd->fileoff == 0) && (segCmd->filesize != 0) ) {
-					if ( (segCmd->initprot & VM_PROT_READ) == 0 )
-						dyld::throwf("malformed mach-o image: %s segment maps start of file but is not readable", segCmd->segname);
-					if ( (segCmd->initprot & VM_PROT_WRITE) == VM_PROT_WRITE ) {
-						if ( context.strictMachORequired )
-							dyld::throwf("malformed mach-o image: %s segment maps start of file but is writable", segCmd->segname);
-					}
-					if ( segCmd->filesize < (sizeof(macho_header) + mh->sizeofcmds) )
-						dyld::throwf("malformed mach-o image: %s segment does not map all of load commands", segCmd->segname);
-					if ( startOfFileSegCmd != NULL )
-						dyld::throwf("malformed mach-o image: multiple segments map start of file: %s %s", startOfFileSegCmd->segname, segCmd->segname);
-					startOfFileSegCmd = segCmd;
-				}
-				if ( context.strictMachORequired ) {
-					uintptr_t vmStart   = segCmd->vmaddr;
-					uintptr_t vmSize    = segCmd->vmsize;
-					uintptr_t vmEnd     = vmStart + vmSize;
-					uintptr_t fileStart = segCmd->fileoff;
-					uintptr_t fileSize  = segCmd->filesize;
-					if ( (intptr_t)(vmSize) < 0 )
-						dyld::throwf("malformed mach-o image: segment load command %s vmsize too large in %s", segCmd->segname, path);
-					if ( vmStart > vmEnd )
-						dyld::throwf("malformed mach-o image: segment load command %s wraps around address space", segCmd->segname);
-					if ( vmSize != fileSize ) {
-						if ( segCmd->initprot == 0 ) {
-							// allow: fileSize == 0 && initprot == 0		e.g. __PAGEZERO
-							// allow: vmSize == 0 && initprot == 0			e.g. __LLVM
-							if ( (fileSize != 0) && (vmSize != 0) )
-								dyld::throwf("malformed mach-o image: unaccessable segment %s has non-zero filesize and vmsize", segCmd->segname);
-						}
-						else {
-							// allow: vmSize > fileSize && initprot != X  e.g. __DATA
-							if ( vmSize < fileSize ) {
-								dyld::throwf("malformed mach-o image: segment %s has vmsize < filesize", segCmd->segname);
-							}
-							if ( segCmd->initprot & VM_PROT_EXECUTE ) {
-								dyld::throwf("malformed mach-o image: segment %s has vmsize != filesize and is executable", segCmd->segname);
-							}
-						}
-					}
-					if ( inCache ) {
-						if ( (fileSize != 0) && (segCmd->initprot == (VM_PROT_READ | VM_PROT_EXECUTE)) ) {
-							if ( foundLoadCommandSegment )
-								throw "load commands in multiple segments";
-							foundLoadCommandSegment = true;
-						}
-					}
-					else if ( (fileStart < mh->sizeofcmds) && (fileSize != 0) ) {
-						// <rdar://problem/7942521> all load commands must be in an executable segment
-						if ( (fileStart != 0) || (fileSize < (mh->sizeofcmds+sizeof(macho_header))) )
-							dyld::throwf("malformed mach-o image: segment %s does not span all load commands", segCmd->segname); 
-						if ( segCmd->initprot != (VM_PROT_READ | VM_PROT_EXECUTE) ) 
-							dyld::throwf("malformed mach-o image: load commands found in segment %s with wrong permissions", segCmd->segname); 
-						if ( foundLoadCommandSegment )
-							throw "load commands in multiple segments";
-						foundLoadCommandSegment = true;
-					}
-
-					const struct macho_section* const sectionsStart = (struct macho_section*)((char*)segCmd + sizeof(struct macho_segment_command));
-					const struct macho_section* const sectionsEnd = &sectionsStart[segCmd->nsects];
-					for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
-						if (!inCache && sect->offset != 0 && ((sect->offset + sect->size) > (segCmd->fileoff + segCmd->filesize)))
-							dyld::throwf("malformed mach-o image: section %s,%s of '%s' exceeds segment %s booundary", sect->segname, sect->sectname, path, segCmd->segname);
-					}
+				// <rdar://problem/7942521> all load commands must be in an executable segment
+				if ( context.codeSigningEnforced && (segCmd->fileoff < mh->sizeofcmds) && (segCmd->filesize != 0) ) {
+					if ( (segCmd->fileoff != 0) || (segCmd->filesize < (mh->sizeofcmds+sizeof(macho_header))) ) 
+						dyld::throwf("malformed mach-o image: segment %s does not span all load commands", segCmd->segname); 
+					if ( segCmd->initprot != (VM_PROT_READ | VM_PROT_EXECUTE) ) 
+						dyld::throwf("malformed mach-o image: load commands found in segment %s with wrong permissions", segCmd->segname); 
+					if ( foundLoadCommandSegment )
+						throw "load commands in multiple segments";
+					foundLoadCommandSegment = true;
+					loadCommandSegmentIndex = i;
+					loadCommandSegmentVMStart = segCmd->vmaddr;
+					loadCommandSegmentVMEnd   = segCmd->vmaddr + segCmd->vmsize;
 				}
 				break;
 			case LC_SEGMENT_COMMAND_WRONG:
@@ -306,250 +170,45 @@
 			case LC_REEXPORT_DYLIB:
 			case LC_LOAD_UPWARD_DYLIB:
 				*libCount += 1;
-				// fall thru
-				[[clang::fallthrough]];
-			case LC_ID_DYLIB:
-				dylibCmd = (dylib_command*)cmd;
-				if ( dylibCmd->dylib.name.offset > cmdLength )
-					dyld::throwf("malformed mach-o image: dylib load command #%d has offset (%u) outside its size (%u)", i, dylibCmd->dylib.name.offset, cmdLength);
-				if ( (dylibCmd->dylib.name.offset + strlen((char*)dylibCmd + dylibCmd->dylib.name.offset) + 1) > cmdLength )
-					dyld::throwf("malformed mach-o image: dylib load command #%d string extends beyond end of load command", i);
 				break;
 			case LC_CODE_SIGNATURE:
-				if ( cmd->cmdsize != sizeof(linkedit_data_command) )
-					throw "malformed mach-o image: LC_CODE_SIGNATURE size wrong";
-				// <rdar://problem/22799652> only support one LC_CODE_SIGNATURE per image
-				if ( *codeSigCmd != NULL )
-					throw "malformed mach-o image: multiple LC_CODE_SIGNATURE load commands";
-				*codeSigCmd = (struct linkedit_data_command*)cmd;
-				break;
-			case LC_ENCRYPTION_INFO:
-				if ( cmd->cmdsize != sizeof(encryption_info_command) )
-					throw "malformed mach-o image: LC_ENCRYPTION_INFO size wrong";
-				// <rdar://problem/22799652> only support one LC_ENCRYPTION_INFO per image
-				if ( *encryptCmd != NULL )
-					throw "malformed mach-o image: multiple LC_ENCRYPTION_INFO load commands";
-				*encryptCmd = (encryption_info_command*)cmd;
-				break;
-			case LC_ENCRYPTION_INFO_64:
-				if ( cmd->cmdsize != sizeof(encryption_info_command_64) )
-					throw "malformed mach-o image: LC_ENCRYPTION_INFO_64 size wrong";
-				// <rdar://problem/22799652> only support one LC_ENCRYPTION_INFO_64 per image
-				if ( *encryptCmd != NULL )
-					throw "malformed mach-o image: multiple LC_ENCRYPTION_INFO_64 load commands";
-				*encryptCmd = (encryption_info_command*)cmd;
-				break;
-			case LC_SYMTAB:
-				if ( cmd->cmdsize != sizeof(symtab_command) )
-					throw "malformed mach-o image: LC_SYMTAB size wrong";
-				symTabCmd = (symtab_command*)cmd;
-				break;
-			case LC_DYSYMTAB:
-				if ( cmd->cmdsize != sizeof(dysymtab_command) )
-					throw "malformed mach-o image: LC_DYSYMTAB size wrong";
-				dynSymbTabCmd = (dysymtab_command*)cmd;
-				break;
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-			// <rdar://problem/26797345> error when loading iOS Simulator mach-o binary into macOS process
-			case LC_VERSION_MIN_WATCHOS:
-			case LC_VERSION_MIN_TVOS:
-			case LC_VERSION_MIN_IPHONEOS:
-				if ( !context.iOSonMac )
-					throw "mach-o, but built for simulator (not macOS)";
-				break;
-#endif
-		}
-		cmd = nextCmd;
-	}
-
-	if ( context.strictMachORequired && !foundLoadCommandSegment )
+				*codeSigCmd = (struct linkedit_data_command*)cmd; // only support one LC_CODE_SIGNATURE per image
+				break;
+		}
+		uint32_t cmdLength = cmd->cmdsize;
+		cmd = (const struct load_command*)(((char*)cmd)+cmdLength);
+		if ( (cmd > endCmds) || (cmd < startCmds) ) {
+			dyld::throwf("malformed mach-o image: load command #%d length (%u) would exceed sizeofcmds (%u) in %s", 
+							i, cmdLength, mh->sizeofcmds, path);
+		}
+	}
+	
+	if ( context.codeSigningEnforced && !foundLoadCommandSegment )
 		throw "load commands not in a segment";
-	if ( linkeditSegCmd == NULL )
-		throw "malformed mach-o image: missing __LINKEDIT segment";
-	if ( !inCache && (startOfFileSegCmd == NULL) )
-		throw "malformed mach-o image: missing __TEXT segment that maps start of file";
-	// <rdar://problem/13145644> verify every segment does not overlap another segment
-	if ( context.strictMachORequired ) {
-		uintptr_t lastFileStart = 0;
-		uintptr_t linkeditFileStart = 0;
-		const struct load_command* cmd1 = startCmds;
+	// <rdar://problem/13145644> verify another segment does not over-map load commands
+	cmd = startCmds;
+	if ( context.codeSigningEnforced ) {
 		for (uint32_t i = 0; i < cmd_count; ++i) {
-			if ( cmd1->cmd == LC_SEGMENT_COMMAND ) {
-				struct macho_segment_command* segCmd1 = (struct macho_segment_command*)cmd1;
-				uintptr_t vmStart1   = segCmd1->vmaddr;
-				uintptr_t vmEnd1     = segCmd1->vmaddr + segCmd1->vmsize;
-				uintptr_t fileStart1 = segCmd1->fileoff;
-				uintptr_t fileEnd1   = segCmd1->fileoff + segCmd1->filesize;
-
-				if (fileStart1 > lastFileStart)
-					lastFileStart = fileStart1;
-
-				if ( strcmp(&segCmd1->segname[0], "__LINKEDIT") == 0 ) {
-					linkeditFileStart = fileStart1;
-				}
-
-				const struct load_command* cmd2 = startCmds;
-				for (uint32_t j = 0; j < cmd_count; ++j) {
-					if ( cmd2 == cmd1 )
-						continue;
-					if ( cmd2->cmd == LC_SEGMENT_COMMAND ) {
-						struct macho_segment_command* segCmd2 = (struct macho_segment_command*)cmd2;
-						uintptr_t vmStart2   = segCmd2->vmaddr;
-						uintptr_t vmEnd2     = segCmd2->vmaddr + segCmd2->vmsize;
-						uintptr_t fileStart2 = segCmd2->fileoff;
-						uintptr_t fileEnd2   = segCmd2->fileoff + segCmd2->filesize;
-						if ( ((vmStart2 <= vmStart1) && (vmEnd2 > vmStart1) && (vmEnd1 > vmStart1)) 
-						|| ((vmStart2 >= vmStart1) && (vmStart2 < vmEnd1) && (vmEnd2 > vmStart2)) )
-							dyld::throwf("malformed mach-o image: segment %s vm overlaps segment %s", segCmd1->segname, segCmd2->segname);
-						if ( ((fileStart2 <= fileStart1) && (fileEnd2 > fileStart1) && (fileEnd1 > fileStart1))
-						  || ((fileStart2 >= fileStart1) && (fileStart2 < fileEnd1) && (fileEnd2 > fileStart2)) )
-							dyld::throwf("malformed mach-o image: segment %s file content overlaps segment %s", segCmd1->segname, segCmd2->segname); 
+			switch (cmd->cmd) {
+				case LC_SEGMENT_COMMAND:
+					if ( i != loadCommandSegmentIndex ) {
+						segCmd = (struct macho_segment_command*)cmd;
+						uintptr_t start = segCmd->vmaddr;
+						uintptr_t end = segCmd->vmaddr + segCmd->vmsize;
+						if ( ((start <= loadCommandSegmentVMStart) && (end > loadCommandSegmentVMStart)) 
+						   || ((start >= loadCommandSegmentVMStart) && (start < loadCommandSegmentVMEnd)) )
+							dyld::throwf("malformed mach-o image: segment %s overlaps load commands", segCmd->segname); 
 					}
-					cmd2 = (const struct load_command*)(((char*)cmd2)+cmd2->cmdsize);
-				}
+					break;
 			}
-			cmd1 = (const struct load_command*)(((char*)cmd1)+cmd1->cmdsize);
-		}
-
-		if (lastFileStart != linkeditFileStart)
-			dyld::throwf("malformed mach-o image: __LINKEDIT must be last segment");
-	}
-
-	// validate linkedit content
-	if  ( (dyldInfoCmd == NULL) && (chainedFixupsCmd == NULL) && (symTabCmd == NULL) )
-		throw "malformed mach-o image: missing LC_SYMTAB, LC_DYLD_INFO, or LC_DYLD_CHAINED_FIXUPS";
-	if  ( dynSymbTabCmd == NULL )
-		throw "malformed mach-o image: missing LC_DYSYMTAB";
-
-	uint32_t  linkeditFileOffsetStart = (uint32_t)linkeditSegCmd->fileoff;
-	uint32_t  linkeditFileOffsetEnd = (uint32_t)linkeditSegCmd->fileoff + (uint32_t)linkeditSegCmd->filesize;
-
-	if ( !inCache && (dyldInfoCmd != NULL) && context.strictMachORequired ) {
-		// validate all LC_DYLD_INFO chunks fit in LINKEDIT and don't overlap
-		uint32_t offset = linkeditFileOffsetStart;
-		if ( dyldInfoCmd->rebase_size != 0 ) {
-			if ( dyldInfoCmd->rebase_size & 0x80000000 )
-				throw "malformed mach-o image: dyld rebase info size overflow";
-			if ( dyldInfoCmd->rebase_off < offset )
-				throw "malformed mach-o image: dyld rebase info underruns __LINKEDIT";
-			offset = dyldInfoCmd->rebase_off + dyldInfoCmd->rebase_size;
-			if ( offset > linkeditFileOffsetEnd )
-				throw "malformed mach-o image: dyld rebase info overruns __LINKEDIT";
-		}
-		if ( dyldInfoCmd->bind_size != 0 ) {
-			if ( dyldInfoCmd->bind_size & 0x80000000 )
-				throw "malformed mach-o image: dyld bind info size overflow";
-			if ( dyldInfoCmd->bind_off < offset )
-				throw "malformed mach-o image: dyld bind info overlaps rebase info";
-			offset = dyldInfoCmd->bind_off + dyldInfoCmd->bind_size;
-			if ( offset > linkeditFileOffsetEnd )
-				throw "malformed mach-o image: dyld bind info overruns __LINKEDIT";
-		}
-		if ( dyldInfoCmd->weak_bind_size != 0 ) {
-			if ( dyldInfoCmd->weak_bind_size & 0x80000000 )
-				throw "malformed mach-o image: dyld weak bind info size overflow";
-			if ( dyldInfoCmd->weak_bind_off < offset )
-				throw "malformed mach-o image: dyld weak bind info overlaps bind info";
-			offset = dyldInfoCmd->weak_bind_off + dyldInfoCmd->weak_bind_size;
-			if ( offset > linkeditFileOffsetEnd )
-				throw "malformed mach-o image: dyld weak bind info overruns __LINKEDIT";
-		}
-		if ( dyldInfoCmd->lazy_bind_size != 0 ) {
-			if ( dyldInfoCmd->lazy_bind_size & 0x80000000 )
-				throw "malformed mach-o image: dyld lazy bind info size overflow";
-			if ( dyldInfoCmd->lazy_bind_off < offset )
-				throw "malformed mach-o image: dyld lazy bind info overlaps weak bind info";
-			offset = dyldInfoCmd->lazy_bind_off + dyldInfoCmd->lazy_bind_size;
-			if ( offset > linkeditFileOffsetEnd )
-				throw "malformed mach-o image: dyld lazy bind info overruns __LINKEDIT";
-		}
-		if ( dyldInfoCmd->export_size != 0 ) {
-			if ( dyldInfoCmd->export_size & 0x80000000 )
-				throw "malformed mach-o image: dyld export info size overflow";
-			if ( dyldInfoCmd->export_off < offset )
-				throw "malformed mach-o image: dyld export info overlaps lazy bind info";
-			offset = dyldInfoCmd->export_off + dyldInfoCmd->export_size;
-			if ( offset > linkeditFileOffsetEnd )
-				throw "malformed mach-o image: dyld export info overruns __LINKEDIT";
-		}
-	}
-
-	if ( !inCache && (chainedFixupsCmd != NULL) && context.strictMachORequired ) {
-		// validate all LC_DYLD_CHAINED_FIXUPS chunks fit in LINKEDIT and don't overlap
-		if ( chainedFixupsCmd->dataoff < linkeditFileOffsetStart )
-			throw "malformed mach-o image: dyld chained fixups info underruns __LINKEDIT";
-		if ( (chainedFixupsCmd->dataoff + chainedFixupsCmd->datasize) > linkeditFileOffsetEnd )
-			throw "malformed mach-o image: dyld chained fixups info overruns __LINKEDIT";
-	}
-
-	if ( !inCache && (exportsTrieCmd != NULL) && context.strictMachORequired ) {
-		// validate all LC_DYLD_EXPORTS_TRIE chunks fit in LINKEDIT and don't overlap
-		if ( exportsTrieCmd->dataoff < linkeditFileOffsetStart )
-			throw "malformed mach-o image: dyld chained fixups info underruns __LINKEDIT";
-		if ( (exportsTrieCmd->dataoff + exportsTrieCmd->datasize) > linkeditFileOffsetEnd )
-			throw "malformed mach-o image: dyld chained fixups info overruns __LINKEDIT";
-	}
-
-	if ( symTabCmd != NULL ) {
-		// validate symbol table fits in LINKEDIT
-		if ( (symTabCmd->nsyms > 0) && (symTabCmd->symoff < linkeditFileOffsetStart) )
-			throw "malformed mach-o image: symbol table underruns __LINKEDIT";
-		if ( symTabCmd->nsyms > 0x10000000 )
-			throw "malformed mach-o image: symbol table too large";
-		uint32_t symbolsSize = symTabCmd->nsyms * sizeof(macho_nlist);
-		if ( symbolsSize > linkeditSegCmd->filesize )
-			throw "malformed mach-o image: symbol table overruns __LINKEDIT";
-		if ( symTabCmd->symoff + symbolsSize < symTabCmd->symoff )
-			throw "malformed mach-o image: symbol table size wraps";
-		if ( symTabCmd->symoff + symbolsSize > symTabCmd->stroff )
-			throw "malformed mach-o image: symbol table overlaps symbol strings";
-		if ( symTabCmd->stroff + symTabCmd->strsize < symTabCmd->stroff )
-			throw "malformed mach-o image: symbol string size wraps";
-		if ( symTabCmd->stroff + symTabCmd->strsize > linkeditFileOffsetEnd ) {
-			// <rdar://problem/24220313> let old apps overflow as long as it stays within mapped page
-			if ( context.strictMachORequired || (symTabCmd->stroff + symTabCmd->strsize > ((linkeditFileOffsetEnd + 4095) & (-4096))) )
-				throw "malformed mach-o image: symbol strings overrun __LINKEDIT";
-		}
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-		if ( (symTabCmd->symoff % sizeof(void*)) != 0 ) {
-			// <rdar://53723577> allow old malformed plugins in new app
-			if ( sdkVersion((mach_header*)mh) >= DYLD_PACKED_VERSION(10,15,0) )
-				throw "malformed mach-o image: mis-aligned symbol table __LINKEDIT";
-		}
-#endif
-		// validate indirect symbol table
-		if ( dynSymbTabCmd->nindirectsyms != 0 ) {
-			if ( dynSymbTabCmd->indirectsymoff < linkeditFileOffsetStart )
-				throw "malformed mach-o image: indirect symbol table underruns __LINKEDIT";
-			if ( dynSymbTabCmd->nindirectsyms > 0x10000000 )
-				throw "malformed mach-o image: indirect symbol table too large";
-			uint32_t indirectTableSize = dynSymbTabCmd->nindirectsyms * sizeof(uint32_t);
-			if ( indirectTableSize > linkeditSegCmd->filesize )
-				throw "malformed mach-o image: indirect symbol table overruns __LINKEDIT";
-			if ( dynSymbTabCmd->indirectsymoff + indirectTableSize < dynSymbTabCmd->indirectsymoff )
-				throw "malformed mach-o image: indirect symbol table size wraps";
-			if ( context.strictMachORequired && (dynSymbTabCmd->indirectsymoff + indirectTableSize > symTabCmd->stroff)  )
-				throw "malformed mach-o image: indirect symbol table overruns string pool";
-		}
-		if ( (dynSymbTabCmd->nlocalsym > symTabCmd->nsyms) || (dynSymbTabCmd->ilocalsym > symTabCmd->nsyms) )
-			throw "malformed mach-o image: indirect symbol table local symbol count exceeds total symbols";
-		if ( dynSymbTabCmd->ilocalsym + dynSymbTabCmd->nlocalsym < dynSymbTabCmd->ilocalsym  )
-			throw "malformed mach-o image: indirect symbol table local symbol count wraps";
-		if ( (dynSymbTabCmd->nextdefsym > symTabCmd->nsyms) || (dynSymbTabCmd->iextdefsym > symTabCmd->nsyms) )
-			throw "malformed mach-o image: indirect symbol table extern symbol count exceeds total symbols";
-		if ( dynSymbTabCmd->iextdefsym + dynSymbTabCmd->nextdefsym < dynSymbTabCmd->iextdefsym  )
-			throw "malformed mach-o image: indirect symbol table extern symbol count wraps";
-		if ( (dynSymbTabCmd->nundefsym > symTabCmd->nsyms) || (dynSymbTabCmd->iundefsym > symTabCmd->nsyms) )
-			throw "malformed mach-o image: indirect symbol table undefined symbol count exceeds total symbols";
-		if ( dynSymbTabCmd->iundefsym + dynSymbTabCmd->nundefsym < dynSymbTabCmd->iundefsym  )
-			throw "malformed mach-o image: indirect symbol table undefined symbol count wraps";
-	}
-
-
+			cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+		}
+	}
+	
 	// fSegmentsArrayCount is only 8-bits
 	if ( *segCount > 255 )
 		dyld::throwf("malformed mach-o image: more than 255 segments in %s", path);
-
+		
 	// fSegmentsArrayCount is only 8-bits
 	if ( *libCount > 4095 )
 		dyld::throwf("malformed mach-o image: more than 4095 dependent libraries in %s", path);
@@ -569,8 +228,7 @@
 	unsigned int segCount;
 	unsigned int libCount;
 	const linkedit_data_command* codeSigCmd;
-	const encryption_info_command* encryptCmd;
-	sniffLoadCommands(mh, path, false, &compressed, &segCount, &libCount, context, &codeSigCmd, &encryptCmd);
+	sniffLoadCommands(mh, path, &compressed, &segCount, &libCount, context, &codeSigCmd);
 	// instantiate concrete class based on content of load commands
 	if ( compressed ) 
 		return ImageLoaderMachOCompressed::instantiateMainExecutable(mh, slide, path, segCount, libCount, context);
@@ -584,21 +242,31 @@
 
 
 // create image by mapping in a mach-o file
-ImageLoader* ImageLoaderMachO::instantiateFromFile(const char* path, int fd, const uint8_t firstPages[], size_t firstPagesSize, uint64_t offsetInFat,
+ImageLoader* ImageLoaderMachO::instantiateFromFile(const char* path, int fd, const uint8_t firstPage[4096], uint64_t offsetInFat, 
 									uint64_t lenInFat, const struct stat& info, const LinkContext& context)
 {
+	// get load commands
+	const unsigned int dataSize = sizeof(macho_header) + ((macho_header*)firstPage)->sizeofcmds;
+	uint8_t buffer[dataSize];
+	const uint8_t* fileData = firstPage;
+	if ( dataSize > 4096 ) {
+		// only read more if cmds take up more space than first page
+		fileData = buffer;
+		memcpy(buffer, firstPage, 4096);
+		pread(fd, &buffer[4096], dataSize-4096, offsetInFat+4096);
+	}
+
 	bool compressed;
 	unsigned int segCount;
 	unsigned int libCount;
 	const linkedit_data_command* codeSigCmd;
-	const encryption_info_command* encryptCmd;
-	sniffLoadCommands((const macho_header*)firstPages, path, false, &compressed, &segCount, &libCount, context, &codeSigCmd, &encryptCmd);
+	sniffLoadCommands((const macho_header*)fileData, path, &compressed, &segCount, &libCount, context, &codeSigCmd);
 	// instantiate concrete class based on content of load commands
 	if ( compressed ) 
-		return ImageLoaderMachOCompressed::instantiateFromFile(path, fd, firstPages, firstPagesSize, offsetInFat, lenInFat, info, segCount, libCount, codeSigCmd, encryptCmd, context);
+		return ImageLoaderMachOCompressed::instantiateFromFile(path, fd, fileData, offsetInFat, lenInFat, info, segCount, libCount, codeSigCmd, context);
 	else
 #if SUPPORT_CLASSIC_MACHO
-		return ImageLoaderMachOClassic::instantiateFromFile(path, fd, firstPages, firstPagesSize, offsetInFat, lenInFat, info, segCount, libCount, codeSigCmd, context);
+		return ImageLoaderMachOClassic::instantiateFromFile(path, fd, fileData, offsetInFat, lenInFat, info, segCount, libCount, codeSigCmd, context);
 #else
 		throw "missing LC_DYLD_INFO load command";
 #endif
@@ -612,8 +280,7 @@
 	unsigned int segCount;
 	unsigned int libCount;
 	const linkedit_data_command* codeSigCmd;
-	const encryption_info_command* encryptCmd;
-	sniffLoadCommands(mh, path, true, &compressed, &segCount, &libCount, context, &codeSigCmd, &encryptCmd);
+	sniffLoadCommands(mh, path, &compressed, &segCount, &libCount, context, &codeSigCmd);
 	// instantiate concrete class based on content of load commands
 	if ( compressed ) 
 		return ImageLoaderMachOCompressed::instantiateFromCache(mh, path, slide, info, segCount, libCount, context);
@@ -632,8 +299,7 @@
 	unsigned int segCount;
 	unsigned int libCount;
 	const linkedit_data_command* sigcmd;
-	const encryption_info_command* encryptCmd;
-	sniffLoadCommands(mh, moduleName, false, &compressed, &segCount, &libCount, context, &sigcmd, &encryptCmd);
+	sniffLoadCommands(mh, moduleName, &compressed, &segCount, &libCount, context, &sigcmd);
 	// instantiate concrete class based on content of load commands
 	if ( compressed ) 
 		return ImageLoaderMachOCompressed::instantiateFromMemory(moduleName, mh, len, segCount, libCount, context);
@@ -662,30 +328,21 @@
 }
 
 
-void ImageLoaderMachO::parseLoadCmds(const LinkContext& context)
+void ImageLoaderMachO::parseLoadCmds()
 {
 	// now that segments are mapped in, get real fMachOData, fLinkEditBase, and fSlide
 	for(unsigned int i=0; i < fSegmentsCount; ++i) {
 		// set up pointer to __LINKEDIT segment
-		if ( strcmp(segName(i),"__LINKEDIT") == 0 ) {
-	#if !__MAC_OS_X_VERSION_MIN_REQUIRED
-			// <rdar://problem/42419336> historically, macOS never did this check
-			if ( segFileOffset(i) > fCoveredCodeLength )
-				dyld::throwf("cannot load '%s' (segment outside of code signature)", this->getShortName());
-	#endif
+		if ( strcmp(segName(i),"__LINKEDIT") == 0 ) 
 			fLinkEditBase = (uint8_t*)(segActualLoadAddress(i) - segFileOffset(i));
-		}
 #if TEXT_RELOC_SUPPORT
 		// __TEXT segment always starts at beginning of file and contains mach_header and load commands
-		if ( segExecutable(i) ) {
+		if ( strcmp(segName(i),"__TEXT") == 0 ) {
 			if ( segHasRebaseFixUps(i) && (fSlide != 0) )
 				fTextSegmentRebases = true;
 			if ( segHasBindFixUps(i) )
 				fTextSegmentBinds = true;
 		}
-#else
-		if ( segIsReadOnlyData(i) )
-			fReadOnlyDataSegment = true;
 #endif
 #if __i386__
 		if ( segIsReadOnlyImport(i) )
@@ -711,8 +368,6 @@
 
 	// walk load commands (mapped in at start of __TEXT segment)
 	const dyld_info_command* dyldInfo = NULL;
-	const linkedit_data_command* chainedFixupsCmd = NULL;
-	const linkedit_data_command* exportsTrieCmd = NULL;
 	const macho_nlist* symbolTable = NULL;
 	const char* symbolTableStrings = NULL;
 	const struct load_command* firstUnknownCmd = NULL;
@@ -749,65 +404,24 @@
 			case LC_DYLD_INFO_ONLY:
 				dyldInfo = (struct dyld_info_command*)cmd;
 				break;
-			case LC_DYLD_CHAINED_FIXUPS:
-				chainedFixupsCmd = (struct linkedit_data_command*)cmd;
-				break;
-			case LC_DYLD_EXPORTS_TRIE:
-				exportsTrieCmd = (struct linkedit_data_command*)cmd;
-				break;
 			case LC_SEGMENT_COMMAND:
 				{
 					const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
 					const bool isTextSeg = (strcmp(seg->segname, "__TEXT") == 0);
-		#if __i386__ && __MAC_OS_X_VERSION_MIN_REQUIRED
-					const bool isObjCSeg = (strcmp(seg->segname, "__OBJC") == 0);
-					if ( isObjCSeg )
-						fNotifyObjC = true;
-		#else
-					const bool isDataSeg = (strncmp(seg->segname, "__DATA", 6) == 0);
-		#endif
 					const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
 					const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
 					for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 						const uint8_t type = sect->flags & SECTION_TYPE;
 						if ( type == S_MOD_INIT_FUNC_POINTERS )
 							fHasInitializers = true;
-						else if ( type == S_INIT_FUNC_OFFSETS )
-							fHasInitializers = true;
 						else if ( type == S_MOD_TERM_FUNC_POINTERS )
 							fHasTerminators = true;
 						else if ( type == S_DTRACE_DOF )
 							fHasDOFSections = true;
 						else if ( isTextSeg && (strcmp(sect->sectname, "__eh_frame") == 0) )
-							fEHFrameSectionOffset = (uint32_t)((uint8_t*)sect - fMachOData);
+							fEHFrameSectionOffset = (uint8_t*)sect - fMachOData;
 						else if ( isTextSeg && (strcmp(sect->sectname, "__unwind_info") == 0) )
-							fUnwindInfoSectionOffset = (uint32_t)((uint8_t*)sect - fMachOData);
-
-		#if __i386__ && __MAC_OS_X_VERSION_MIN_REQUIRED
-						else if ( isObjCSeg ) {
-							if ( strcmp(sect->sectname, "__image_info") == 0 ) {
-								const uint32_t* imageInfo = (uint32_t*)(sect->addr + fSlide);
-								uint32_t flags = imageInfo[1];
-								if ( (flags & 4) && (((macho_header*)fMachOData)->filetype != MH_EXECUTE) )
-									dyld::throwf("cannot load '%s' because Objective-C garbage collection is not supported", getPath());
-							}
-							else if ( ((macho_header*)fMachOData)->filetype == MH_DYLIB ) {
-								fRetainForObjC = true;
-							}
-						}
-		#else
-						else if ( isDataSeg && (strncmp(sect->sectname, "__objc_imageinfo", 16) == 0) ) {
-			#if __MAC_OS_X_VERSION_MIN_REQUIRED
-							const uint32_t* imageInfo = (uint32_t*)(sect->addr + fSlide);
-							uint32_t flags = imageInfo[1];
-							if ( (flags & 4) && (((macho_header*)fMachOData)->filetype != MH_EXECUTE) )
-								dyld::throwf("cannot load '%s' because Objective-C garbage collection is not supported", getPath());
-			#endif
-							fNotifyObjC = true;
-						}
-						else if ( isDataSeg && (strncmp(sect->sectname, "__objc_", 7) == 0) && (((macho_header*)fMachOData)->filetype == MH_DYLIB) )
-							fRetainForObjC = true;
-		#endif
+							fUnwindInfoSectionOffset = (uint8_t*)sect - fMachOData;;
 					}
 				}
 				break;
@@ -816,7 +430,7 @@
 				break;
 			case LC_ID_DYLIB:
 				{
-					fDylibIDOffset = (uint32_t)((uint8_t*)cmd - fMachOData);
+					fDylibIDOffset = (uint8_t*)cmd - fMachOData;
 				}
 				break;
 			case LC_RPATH:
@@ -824,11 +438,10 @@
 		    case LC_REEXPORT_DYLIB:
 			case LC_LOAD_UPWARD_DYLIB:
 			case LC_MAIN:
+				// do nothing, just prevent LC_REQ_DYLD exception from occuring
 				break;
 			case LC_VERSION_MIN_MACOSX:
 			case LC_VERSION_MIN_IPHONEOS:
-			case LC_VERSION_MIN_TVOS:
-			case LC_VERSION_MIN_WATCHOS:
 				minOSVersionCmd = (version_min_command*)cmd;
 				break;
 			default:
@@ -855,13 +468,9 @@
 	
 	if ( dyldInfo != NULL )
 		this->setDyldInfo(dyldInfo);
-	if ( chainedFixupsCmd != NULL )
-		this->setChainedFixups(chainedFixupsCmd);
-	if ( exportsTrieCmd != NULL )
-		this->setExportsTrie(exportsTrieCmd);
-
 	if ( symbolTable != NULL)
 		this->setSymbolTableInfo(symbolTable, symbolTableStrings, dynSymbolTable);
+	
 }
 
 // don't do this work in destructor because we need object to be full subclass
@@ -973,7 +582,6 @@
 
 bool ImageLoaderMachO::segHasRebaseFixUps(unsigned int segIndex) const
 {
-#if TEXT_RELOC_SUPPORT
 	// scan sections for fix-up bit
 	const macho_segment_command* segCmd = segLoadCommand(segIndex);
 	const struct macho_section* const sectionsStart = (struct macho_section*)((char*)segCmd + sizeof(struct macho_segment_command));
@@ -982,13 +590,11 @@
 		if ( (sect->flags & S_ATTR_LOC_RELOC) != 0 )
 			return true;
 	}
-#endif
 	return false;
 }
 
 bool ImageLoaderMachO::segHasBindFixUps(unsigned int segIndex) const
 {
-#if TEXT_RELOC_SUPPORT
 	// scan sections for fix-up bit
 	const macho_segment_command* segCmd = segLoadCommand(segIndex);
 	const struct macho_section* const sectionsStart = (struct macho_section*)((char*)segCmd + sizeof(struct macho_segment_command));
@@ -997,7 +603,6 @@
 		if ( (sect->flags & S_ATTR_EXT_RELOC) != 0 )
 			return true;
 	}
-#endif
 	return false;
 }
 
@@ -1011,13 +616,6 @@
 }
 #endif
 
-bool ImageLoaderMachO::segIsReadOnlyData(unsigned int segIndex) const
-{
-	const macho_segment_command* segCmd = segLoadCommand(segIndex);
-	return (    (segCmd->initprot & VM_PROT_WRITE)
-			&& ((segCmd->initprot & VM_PROT_EXECUTE) == 0)
-			&& (segCmd->flags & SG_READ_ONLY) );
-}
 
 void ImageLoaderMachO::UnmapSegments()
 {
@@ -1027,7 +625,7 @@
 		unsigned int textSegmentIndex = 0;
 		for(unsigned int i=0; i < fSegmentsCount; ++i) {
 			//dyld::log("unmap %s at 0x%08lX\n", seg->getName(), seg->getActualLoadAddress(this));
-			if ( (segFileOffset(i) == 0) && (segFileSize(i) != 0) ) {
+			if ( strcmp(segName(i), "__TEXT") == 0 ) {
 				textSegmentIndex = i;
 			}
 			else {
@@ -1045,6 +643,32 @@
 }
 
 
+// prefetch __DATA/__OBJC pages during launch, but not for dynamically loaded code
+void ImageLoaderMachO::preFetchDATA(int fd, uint64_t offsetInFat, const LinkContext& context)
+{
+	if ( context.linkingMainExecutable ) {
+		for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
+			if ( segWriteable(i) && (segFileSize(i) > 0) ) {
+				// prefetch writable segment that have mmap'ed regions
+				radvisory advice;
+				advice.ra_offset = offsetInFat + segFileOffset(i);
+				advice.ra_count = segFileSize(i);
+				// limit prefetch to 1MB (256 pages)
+				if ( advice.ra_count > 1024*1024 )
+					advice.ra_count = 1024*1024;
+				// don't prefetch single pages, let them fault in
+				fgTotalBytesPreFetched += advice.ra_count;
+				fcntl(fd, F_RDADVISE, &advice);
+				if ( context.verboseMapping ) {
+					dyld::log("%18s prefetching 0x%0lX -> 0x%0lX\n", 
+						segName(i), segActualLoadAddress(i), segActualLoadAddress(i)+advice.ra_count-1);
+				}
+			}
+		}
+	}
+}
+
+
 bool ImageLoaderMachO::segmentsMustSlideTogether() const 
 {
 	return true;
@@ -1129,87 +753,53 @@
 
 void ImageLoaderMachO::loadCodeSignature(const struct linkedit_data_command* codeSigCmd, int fd,  uint64_t offsetInFatFile, const LinkContext& context)
 {
-	dyld3::ScopedTimer(DBG_DYLD_TIMING_ATTACH_CODESIGNATURE, 0, 0, 0);
 	// if dylib being loaded has no code signature load command
-	if ( codeSigCmd == NULL) {
-		disableCoverageCheck();
+	if ( codeSigCmd == NULL ) {
+#if __MAC_OS_X_VERSION_MIN_REQUIRED
+		bool codeSigningEnforced = context.codeSigningEnforced;
+		if ( context.mainExecutableCodeSigned && !codeSigningEnforced ) {
+			static bool codeSignEnforcementDynamicallyEnabled = false;
+			if ( !codeSignEnforcementDynamicallyEnabled ) {
+				uint32_t flags;
+				if ( csops(0, CS_OPS_STATUS, &flags, sizeof(flags)) != -1 ) {
+					if ( flags & CS_ENFORCEMENT ) {
+						codeSignEnforcementDynamicallyEnabled = true;
+					}
+				}
+			}
+			codeSigningEnforced = codeSignEnforcementDynamicallyEnabled;
+		}
+		// if we require dylibs to be code signed
+		if ( codeSigningEnforced  ) {
+			// if there is a non-load command based code signature, use it
+			off_t offset = (off_t)offsetInFatFile;
+			if ( fcntl(fd, F_FINDSIGS, &offset, sizeof(offset)) != -1 )
+				return;
+			// otherwise gracefully return from dlopen()
+			dyld::throwf("required code signature missing for '%s'\n", this->getPath());
+		}
+#endif
 	}
 	else {
 #if __MAC_OS_X_VERSION_MIN_REQUIRED
 		// <rdar://problem/13622786> ignore code signatures in binaries built with pre-10.9 tools
-		if ( this->sdkVersion() < DYLD_PACKED_VERSION(10,9,0) ) {
-			disableCoverageCheck();
+		if ( this->sdkVersion() < DYLD_MACOSX_VERSION_10_9 ) {
 			return;
 		}
 #endif
-
 		fsignatures_t siginfo;
-		siginfo.fs_file_start=offsetInFatFile;				// start of mach-o slice in fat file
+		siginfo.fs_file_start=offsetInFatFile;				// start of mach-o slice in fat file 
 		siginfo.fs_blob_start=(void*)(long)(codeSigCmd->dataoff);	// start of CD in mach-o file
 		siginfo.fs_blob_size=codeSigCmd->datasize;			// size of CD
-		int result = fcntl(fd, F_ADDFILESIGS_RETURN, &siginfo);
-
-#if TARGET_OS_SIMULATOR
-		// rdar://problem/18759224> check range covered by the code directory after loading
-		// Attempt to fallback only if we are in the simulator
-
-		if ( result == -1 ) {
-			result = fcntl(fd, F_ADDFILESIGS, &siginfo);
-			siginfo.fs_file_start = codeSigCmd->dataoff;
-		}
-#endif
-
+		int result = fcntl(fd, F_ADDFILESIGS, &siginfo);
 		if ( result == -1 ) {
 			if ( (errno == EPERM) || (errno == EBADEXEC) )
 				dyld::throwf("code signature invalid for '%s'\n", this->getPath());
-			if ( context.verboseCodeSignatures )
+			if ( context.verboseCodeSignatures ) 
 				dyld::log("dyld: Failed registering code signature for %s, errno=%d\n", this->getPath(), errno);
-			siginfo.fs_file_start = UINT64_MAX;
-		} else if ( context.verboseCodeSignatures )  {
-			dyld::log("dyld: Registered code signature for %s\n", this->getPath());
-		}
-		fCoveredCodeLength = siginfo.fs_file_start;
-	}
-
-	{
-		fchecklv checkInfo;
-		char  messageBuffer[512];
-		messageBuffer[0] = '\0';
-		checkInfo.lv_file_start = offsetInFatFile;
-		checkInfo.lv_error_message_size = sizeof(messageBuffer);
-		checkInfo.lv_error_message = messageBuffer;
-		int res = fcntl(fd, F_CHECK_LV, &checkInfo);
-		if ( res == -1 ) {
-			dyld::throwf("code signature in (%s) not valid for use in process using Library Validation: %s", this->getPath(), messageBuffer);
-		}
-	}
-}
-
-void ImageLoaderMachO::validateFirstPages(const struct linkedit_data_command* codeSigCmd, int fd, const uint8_t *fileData, size_t lenFileData, off_t offsetInFat, const LinkContext& context)
-{
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-	// rdar://problem/21839703> 15A226d: dyld crashes in mageLoaderMachO::validateFirstPages during dlopen() after encountering an mmap failure
-	// We need to ignore older code signatures because they will be bad.
-	if ( this->sdkVersion() < DYLD_PACKED_VERSION(10,9,0) ) {
-		return;
-	}
-#endif
-	if (codeSigCmd != NULL) {
-		void *fdata = xmmap(NULL, lenFileData, PROT_READ, MAP_SHARED, fd, offsetInFat);
-		if ( fdata == MAP_FAILED ) {
-			int errnoCopy = errno;
-			if ( errnoCopy == EPERM ) {
-				if ( dyld::sandboxBlockedMmap(getPath()) )
-					dyld::throwf("file system sandbox blocked mmap() of '%s'", getPath());
-				else
-					dyld::throwf("code signing blocked mmap() of '%s'", getPath());
-			}
 			else
-				dyld::throwf("mmap() errno=%d validating first page of '%s'", errnoCopy, getPath());
-		}
-		if ( memcmp(fdata, fileData, lenFileData) != 0 )
-			dyld::throwf("mmap() page compare failed for '%s'", getPath());
-		munmap(fdata, lenFileData);
+				dyld::log("dyld: Registered code signature for %s\n", this->getPath());
+		}
 	}
 }
 
@@ -1223,7 +813,7 @@
 	return NULL;
 }
 
-void ImageLoaderMachO::registerInterposing(const LinkContext& context)
+void ImageLoaderMachO::registerInterposing()
 {
 	// mach-o files advertise interposing by having a __DATA __interpose section
 	struct InterposeData { uintptr_t replacement; uintptr_t replacee; };
@@ -1239,23 +829,15 @@
 					const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
 					for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 						if ( ((sect->flags & SECTION_TYPE) == S_INTERPOSING) || ((strcmp(sect->sectname, "__interpose") == 0) && (strcmp(seg->segname, "__DATA") == 0)) ) {
-							// <rdar://problem/23929217> Ensure section is within segment
-							if ( (sect->addr < seg->vmaddr) || (sect->addr+sect->size > seg->vmaddr+seg->vmsize) || (sect->addr+sect->size < sect->addr) )
-								dyld::throwf("interpose section has malformed address range for %s\n", this->getPath());
 							const InterposeData* interposeArray = (InterposeData*)(sect->addr + fSlide);
-							const size_t count = sect->size / sizeof(InterposeData);
-							for (size_t j=0; j < count; ++j) {
+							const unsigned int count = sect->size / sizeof(InterposeData);
+							for (uint32_t i=0; i < count; ++i) {
 								ImageLoader::InterposeTuple tuple;
-								tuple.replacement		= interposeArray[j].replacement;
-								tuple.neverImage		= this;
-								tuple.onlyImage		    = NULL;
-								tuple.replacee			= interposeArray[j].replacee;
-								// <rdar://problem/25686570> ignore interposing on a weak function that does not exist
-								if ( tuple.replacee == 0 )
-									continue;
+								tuple.replacement		= interposeArray[i].replacement;
+								tuple.replacementImage	= this;
+								tuple.replacee			= interposeArray[i].replacee;
 								// <rdar://problem/7937695> verify that replacement is in this image
 								if ( this->containsAddress((void*)tuple.replacement) ) {
-									// chain to any existing interpositions
 									for (std::vector<InterposeTuple>::iterator it=fgInterposingTuples.begin(); it != fgInterposingTuples.end(); it++) {
 										if ( it->replacee == tuple.replacee ) {
 											tuple.replacee = it->replacement;
@@ -1273,66 +855,25 @@
 	}
 }
 
-uint32_t ImageLoaderMachO::sdkVersion(const mach_header* mh)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const struct load_command* const cmds = (struct load_command*)(((char*)mh) + sizeof(macho_header));
+uint32_t ImageLoaderMachO::sdkVersion() const
+{
+	const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
+	const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
 	const struct load_command* cmd = cmds;
 	const struct version_min_command* versCmd;
-	const struct build_version_command* buildVersCmd;
 	for (uint32_t i = 0; i < cmd_count; ++i) {
 		switch ( cmd->cmd ) {
 			case LC_VERSION_MIN_MACOSX:
 			case LC_VERSION_MIN_IPHONEOS:
-			case LC_VERSION_MIN_TVOS:
-			case LC_VERSION_MIN_WATCHOS:
 				versCmd = (version_min_command*)cmd;
 				return versCmd->sdk;
-			case LC_BUILD_VERSION:
-				buildVersCmd = (build_version_command*)cmd;
-				return buildVersCmd->sdk;
 		}
 		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 	}
 	return 0;
 }
 
-uint32_t ImageLoaderMachO::sdkVersion() const
-{
-	return ImageLoaderMachO::sdkVersion(machHeader());
-}
-
-uint32_t ImageLoaderMachO::minOSVersion(const mach_header* mh)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const struct load_command* const cmds = (struct load_command*)(((char*)mh) + sizeof(macho_header));
-	const struct load_command* cmd = cmds;
-	const struct version_min_command* versCmd;
-	const struct build_version_command* buildVersCmd;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		switch ( cmd->cmd ) {
-			case LC_VERSION_MIN_MACOSX:
-			case LC_VERSION_MIN_IPHONEOS:
-			case LC_VERSION_MIN_TVOS:
-			case LC_VERSION_MIN_WATCHOS:
-				versCmd = (version_min_command*)cmd;
-				return versCmd->version;
-			case LC_BUILD_VERSION:
-				buildVersCmd = (build_version_command*)cmd;
-				return buildVersCmd->minos;
-		}
-		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	return 0;
-}
-
-uint32_t ImageLoaderMachO::minOSVersion() const
-{
-	return ImageLoaderMachO::minOSVersion(machHeader());
-}
-
-
-void* ImageLoaderMachO::getEntryFromLC_MAIN() const
+void* ImageLoaderMachO::getThreadPC() const
 {
 	const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
 	const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
@@ -1353,33 +894,33 @@
 }
 
 
-void* ImageLoaderMachO::getEntryFromLC_UNIXTHREAD() const
+void* ImageLoaderMachO::getMain() const
 {
 	const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
 	const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
 	const struct load_command* cmd = cmds;
 	for (uint32_t i = 0; i < cmd_count; ++i) {
-		if ( cmd->cmd == LC_UNIXTHREAD ) {
-	#if __i386__
-			const i386_thread_state_t* registers = (i386_thread_state_t*)(((char*)cmd) + 16);
-			void* entry = (void*)(registers->eip + fSlide);
-			// <rdar://problem/8543820&9228031> verify entry point is in image
-			if ( this->containsAddress(entry) )
-				return entry;
-	#elif __x86_64__
-			const x86_thread_state64_t* registers = (x86_thread_state64_t*)(((char*)cmd) + 16);
-			void* entry = (void*)(registers->rip + fSlide);
-			// <rdar://problem/8543820&9228031> verify entry point is in image
-			if ( this->containsAddress(entry) )
-				return entry;
-	#elif __arm64__ && !__arm64e__
-			// temp support until <rdar://39514191> is fixed
-			const uint64_t* regs64 = (uint64_t*)(((char*)cmd) + 16);
-			void* entry = (void*)(regs64[32] + fSlide); // arm_thread_state64_t.__pc
-			// <rdar://problem/8543820&9228031> verify entry point is in image
-			if ( this->containsAddress(entry) )
-				return entry;
-	#endif
+		switch (cmd->cmd) {
+			case LC_UNIXTHREAD:
+			{
+			#if __i386__
+				const i386_thread_state_t* registers = (i386_thread_state_t*)(((char*)cmd) + 16);
+				void* entry = (void*)(registers->eip + fSlide);
+			#elif __x86_64__
+				const x86_thread_state64_t* registers = (x86_thread_state64_t*)(((char*)cmd) + 16);
+				void* entry = (void*)(registers->rip + fSlide);
+			#elif __arm__
+				const arm_thread_state_t* registers = (arm_thread_state_t*)(((char*)cmd) + 16);
+				void* entry = (void*)(registers->__pc + fSlide);
+			#else
+				#warning need processor specific code
+			#endif
+				// <rdar://problem/8543820&9228031> verify entry point is in image
+				if ( this->containsAddress(entry) ) {
+					return entry;
+				}
+			}
+			break;
 		}
 		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 	}
@@ -1414,8 +955,7 @@
 				// It is OK for OS dylibs (libSystem or libmath or Rosetta shims) to have no dependents
 				// but all other dylibs must depend on libSystem for initialization to initialize libSystem first
 				// <rdar://problem/6497528> rosetta circular dependency spew
-				isNonOSdylib = ( (strncmp(installPath, "/usr/lib/", 9) != 0) && (strncmp(installPath, "/System/DriverKit/usr/lib/", 26) != 0) && (strncmp(installPath, "/usr/libexec/oah/Shims", 9) != 0) );
-				// if (isNonOSdylib) dyld::log("ImageLoaderMachO::needsAddedLibSystemDepency(%s)\n", installPath);
+				isNonOSdylib = ( (strncmp(installPath, "/usr/lib/", 9) != 0) && (strncmp(installPath, "/usr/libexec/oah/Shims", 9) != 0) );
 				}
 				break;
 		}
@@ -1429,7 +969,7 @@
 {
 	if ( needsAddedLibSystemDepency(libraryCount(), (macho_header*)fMachOData) ) {
 		DependentLibraryInfo* lib = &libs[0];
-		lib->name = LIBSYSTEM_DYLIB_PATH;
+		lib->name = "/usr/lib/libSystem.B.dylib";
 		lib->info.checksum = 0;
 		lib->info.minVersion = 0;
 		lib->info.maxVersion = 0;
@@ -1467,7 +1007,7 @@
 	}
 }
 
-ImageLoader::LibraryInfo ImageLoaderMachO::doGetLibraryInfo(const LibraryInfo&)
+ImageLoader::LibraryInfo ImageLoaderMachO::doGetLibraryInfo()
 {
 	LibraryInfo info;
 	if ( fDylibIDOffset != 0 ) {
@@ -1494,9 +1034,9 @@
 			case LC_RPATH:
 				const char* pathToAdd = NULL;
 				const char* path = (char*)cmd + ((struct rpath_command*)cmd)->path.offset;
-				if ( (strncmp(path, "@loader_path", 12) == 0) && ((path[12] == '/') || (path[12] == '\0')) ) {
-					if ( !context.allowAtPaths && (context.mainExecutable == this) ) {
-						dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @loader_path (Codesign main executable with Library Validation to allow @ paths)\n", path, this->getPath());
+				if ( strncmp(path, "@loader_path/", 13) == 0 ) {
+					if ( context.processIsRestricted  && (context.mainExecutable == this) ) {
+						dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @loader_path\n", path, this->getPath());
 						break;
 					}
 					char resolvedPath[PATH_MAX];
@@ -1504,15 +1044,16 @@
 						char newRealPath[strlen(resolvedPath) + strlen(path)];
 						strcpy(newRealPath, resolvedPath);
 						char* addPoint = strrchr(newRealPath,'/');
-						if ( addPoint != NULL ) {
-							strcpy(addPoint, &path[12]);
-							pathToAdd = strdup(newRealPath);
-						}
+						if ( addPoint != NULL )
+							strcpy(&addPoint[1], &path[13]);
+						else
+							strcpy(newRealPath, &path[13]);
+						pathToAdd = strdup(newRealPath);
 					}
 				}
-				else if ( (strncmp(path, "@executable_path", 16) == 0) && ((path[16] == '/') || (path[16] == '\0')) ) {
-					if ( !context.allowAtPaths) {
-						dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @executable_path (Codesign main executable with Library Validation to allow @ paths)\n", path, this->getPath());
+				else if ( strncmp(path, "@executable_path/", 17) == 0 ) {
+					if ( context.processIsRestricted ) {
+						dyld::warn("LC_RPATH %s in %s being ignored in restricted program because of @executable_path\n", path, this->getPath());
 						break;
 					}
 					char resolvedPath[PATH_MAX];
@@ -1520,44 +1061,39 @@
 						char newRealPath[strlen(resolvedPath) + strlen(path)];
 						strcpy(newRealPath, resolvedPath);
 						char* addPoint = strrchr(newRealPath,'/');
-						if ( addPoint != NULL ) {
-							strcpy(addPoint, &path[16]);
-							pathToAdd = strdup(newRealPath);
-						}
+						if ( addPoint != NULL )
+							strcpy(&addPoint[1], &path[17]);
+						else
+							strcpy(newRealPath, &path[17]);
+						pathToAdd = strdup(newRealPath);
 					}
 				}
-				else if ( (path[0] != '/') && !context.allowAtPaths) {
+				else if ( (path[0] != '/') && context.processIsRestricted ) {
 					dyld::warn("LC_RPATH %s in %s being ignored in restricted program because it is a relative path\n", path, this->getPath());
 					break;
 				}
-#if SUPPORT_ROOT_PATH
 				else if ( (path[0] == '/') && (context.rootPaths != NULL) ) {
 					// <rdar://problem/5869973> DYLD_ROOT_PATH should apply to LC_RPATH rpaths
-					// <rdar://problem/49576123> Even if DYLD_ROOT_PATH exists, LC_RPATH should add raw path to rpaths
 					// DYLD_ROOT_PATH can be a list of paths, but at this point we can only support one, so use first combination that exists
-					for (const char** rp = context.rootPaths; *rp != NULL; ++rp) {
+					bool found = false;
+					for(const char** rp = context.rootPaths; *rp != NULL; ++rp) {
 						char newPath[PATH_MAX];
 						strlcpy(newPath, *rp, PATH_MAX);
 						strlcat(newPath, path, PATH_MAX);
 						struct stat stat_buf;
 						if ( stat(newPath, &stat_buf) != -1 ) {
-							// dyld::log("combined DYLD_ROOT_PATH and LC_RPATH: %s\n", newPath);
-							paths.push_back(strdup(newPath));
+							//dyld::log("combined DYLD_ROOT_PATH and LC_RPATH: %s\n", newPath);
+							pathToAdd = strdup(newPath);
+							found = true;
+							break;
 						}
 					}
-					// add in raw absolute path without root prefix
-					pathToAdd = strdup(path);
-				}
-#endif
+					if ( ! found ) {
+						// make copy so that all elements of 'paths' can be freed
+						pathToAdd = strdup(path);
+					}
+				}
 				else {
-					// realpath() is slow, and /usr/lib/swift is a real path, so don't realpath it
-					if ( strcmp(path, "/usr/lib/swift") != 0 ) {
-						char resolvedPath[PATH_MAX];
-						if ( (realpath(path, resolvedPath) != NULL) && (strcmp(path, resolvedPath) != 0) ) {
-							// <rdar://problem/45470293> support LC_RPATH symlinks to directories of things in the dyld cache
-							path = resolvedPath;
-						}
-					}
 					// make copy so that all elements of 'paths' can be freed
 					pathToAdd = strdup(path);
 				}
@@ -1568,7 +1104,6 @@
 		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 	}
 }
-
 
 bool ImageLoaderMachO::getUUID(uuid_t uuid) const
 {
@@ -1590,14 +1125,6 @@
 
 void ImageLoaderMachO::doRebase(const LinkContext& context)
 {
-	// <rdar://problem/25329861> Delay calling setNeverUnload() until we know this is not for dlopen_preflight()
-	if ( fRetainForObjC )
-		this->setNeverUnload();
-
-    // dylibs with thread local variables cannot be unloaded because there is no way to clean up all threads
-    if ( !this->inSharedCache() && (this->machHeader()->flags & MH_HAS_TLV_DESCRIPTORS) )
-        this->setNeverUnload();
-
 	// if prebound and loaded at prebound address, then no need to rebase
 	if ( this->usablePrebinding(context) ) {
 		// skip rebasing because prebinding is valid
@@ -1634,7 +1161,7 @@
 #endif
 
 	// if loaded at preferred address, no rebasing necessary
-	if ( this->fSlide == 0 )
+	if ( this->fSlide == 0 ) 
 		return;
 
 #if TEXT_RELOC_SUPPORT
@@ -1644,7 +1171,7 @@
 #endif
 
 	// do actual rebasing
-	this->rebase(context, fSlide);
+	this->rebase(context);
 			
 #if TEXT_RELOC_SUPPORT
 	// if there were __TEXT fixups, restore write protection
@@ -1657,28 +1184,31 @@
 #if TEXT_RELOC_SUPPORT
 void ImageLoaderMachO::makeTextSegmentWritable(const LinkContext& context, bool writeable)
 {
+	int textSegmentIndex = 0;
 	for(unsigned int i=0; i < fSegmentsCount; ++i) {
-		if ( segExecutable(i) ) {
-			if ( writeable ) {
-				segMakeWritable(i, context);
-			}
-			else {
-			#if !__i386__ && !__x86_64__
-				// some processors require range to be invalidated before it is made executable
-				sys_icache_invalidate((void*)segActualLoadAddress(i), segSize(textSegmentIndex));
-			#endif
-				segProtect(i, context);
-			}
-		}
-	}
-
+		if ( strcmp(segName(i), "__TEXT") == 0 ) {
+			textSegmentIndex = i;
+			break;
+		}
+	}
+
+	if ( writeable ) {
+		segMakeWritable(textSegmentIndex, context);
+	}
+	else {
+	#if !__i386__ && !__x86_64__
+		// some processors require range to be invalidated before it is made executable
+		sys_icache_invalidate((void*)segActualLoadAddress(textSegmentIndex), segSize(textSegmentIndex));
+	#endif
+		segProtect(textSegmentIndex, context);
+	}
 }
 #endif
 
-const ImageLoader::Symbol* ImageLoaderMachO::findExportedSymbol(const char* name, bool searchReExports, const char* thisPath, const ImageLoader** foundIn) const
+const ImageLoader::Symbol* ImageLoaderMachO::findExportedSymbol(const char* name, bool searchReExports, const ImageLoader** foundIn) const
 {
 	// look in this image first
-	const ImageLoader::Symbol* result = this->findShallowExportedSymbol(name, foundIn);
+	const ImageLoader::Symbol* result = this->findExportedSymbol(name, foundIn);
 	if ( result != NULL )
 		return result;
 	
@@ -1687,8 +1217,7 @@
 			if ( libReExported(i) ) {
 				ImageLoader* image = libImage(i);
 				if ( image != NULL ) {
-					const char* reExPath = libPath(i);
-					result = image->findExportedSymbol(name, searchReExports, reExPath, foundIn);
+					const Symbol* result = image->findExportedSymbol(name, searchReExports, foundIn);
 					if ( result != NULL )
 						return result;
 				}
@@ -1703,7 +1232,7 @@
 
 
 uintptr_t ImageLoaderMachO::getExportedSymbolAddress(const Symbol* sym, const LinkContext& context, 
-											const ImageLoader* requestor, bool runResolver, const char* symbolName) const
+											const ImageLoader* requestor, bool runResolver) const
 {
 	return this->getSymbolAddress(sym, requestor, context, runResolver);
 }
@@ -1713,7 +1242,16 @@
 {
 	uintptr_t result = exportedSymbolAddress(context, sym, requestor, runResolver);
 	// check for interposing overrides
-	result = interposedAddress(context, result, requestor);
+	for (std::vector<InterposeTuple>::iterator it=fgInterposingTuples.begin(); it != fgInterposingTuples.end(); it++) {
+		// replace all references to 'replacee' with 'replacement'
+		if ( (result == it->replacee) && (requestor != it->replacementImage) ) {
+			if ( context.verboseInterposing ) {
+				dyld::log("dyld interposing: replace 0x%lX with 0x%lX in %s\n", 
+					it->replacee, it->replacement, this->getPath());
+			}
+			result = it->replacement;
+		}
+	}
 	return result;
 }
 
@@ -1815,51 +1353,8 @@
 	}
 }
 
-intptr_t ImageLoaderMachO::computeSlide(const mach_header* mh)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const load_command* const cmds = (load_command*)((char*)mh + sizeof(macho_header));
-	const load_command* cmd = cmds;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
-			const macho_segment_command* seg = (macho_segment_command*)cmd;
-			if ( strcmp(seg->segname, "__TEXT") == 0 )
-				return (char*)mh - (char*)(seg->vmaddr);
-		}
-		cmd = (const load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	return 0;
-}
-
-bool ImageLoaderMachO::findSection(const mach_header* mh, const char* segmentName, const char* sectionName, void** sectAddress, size_t* sectSize)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const load_command* const cmds = (load_command*)((char*)mh + sizeof(macho_header));
-	const load_command* cmd = cmds;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		switch (cmd->cmd) {
-			case LC_SEGMENT_COMMAND:
-				{
-					const macho_segment_command* seg = (macho_segment_command*)cmd;
-					const macho_section* const sectionsStart = (macho_section*)((char*)seg + sizeof(macho_segment_command));
-					const macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
-					for (const macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
-						if ( (strcmp(sect->segname, segmentName) == 0) && (strcmp(sect->sectname, sectionName) == 0) ) {
-							*sectAddress = (void*)(sect->addr + computeSlide(mh));
-							*sectSize = sect->size;
-							return true;
-						}
-					}
-				}
-				break;
-		}
-		cmd = (const load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	return false;
-}
-
-
-const macho_section* ImageLoaderMachO::findSection(const void* imageInterior) const
+
+bool ImageLoaderMachO::findSection(const void* imageInterior, const char** segmentName, const char** sectionName, size_t* sectionOffset)
 {
 	const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
 	const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
@@ -1875,7 +1370,13 @@
 						const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
 						for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 							if ((sect->addr <= unslidInteriorAddress) && (unslidInteriorAddress < (sect->addr+sect->size))) {
-								return sect;
+								if ( segmentName != NULL )
+									*segmentName = sect->segname;
+								if ( sectionName != NULL )
+									*sectionName = sect->sectname;
+								if ( sectionOffset != NULL )
+									*sectionOffset = unslidInteriorAddress - sect->addr;
+								return true;
 							}
 						}
 					}
@@ -1884,64 +1385,16 @@
 		}
 		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 	}
-	return nullptr;
-}
-
-
-bool ImageLoaderMachO::findSection(const void* imageInterior, const char** segmentName, const char** sectionName, size_t* sectionOffset)
-{
-	if (const struct macho_section* sect = findSection(imageInterior)) {
-		const uintptr_t unslidInteriorAddress = (uintptr_t)imageInterior - this->getSlide();
-		if ( segmentName != NULL )
-			*segmentName = sect->segname;
-		if ( sectionName != NULL )
-			*sectionName = sect->sectname;
-		if ( sectionOffset != NULL )
-			*sectionOffset = unslidInteriorAddress - sect->addr;
-		return true;
-	}
 	return false;
 }
 
-const char* ImageLoaderMachO::libPath(unsigned int index) const
-{
-	const uint32_t cmd_count = ((macho_header*)fMachOData)->ncmds;
-	const struct load_command* const cmds = (struct load_command*)&fMachOData[sizeof(macho_header)];
-	const struct load_command* cmd = cmds;
-	unsigned count = 0;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		switch ( cmd->cmd ) {
-			case LC_LOAD_DYLIB:
-			case LC_LOAD_WEAK_DYLIB:
-			case LC_REEXPORT_DYLIB:
-			case LC_LOAD_UPWARD_DYLIB:
-				if ( index == count ) {
-					const struct dylib_command*  dylibCmd = (struct dylib_command*)cmd;
-					return (char*)cmd + dylibCmd->dylib.name.offset;
-				}
-				++count;
-				break;
-		}
-		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-
-	// <rdar://problem/24256354> if image linked with nothing and we implicitly added libSystem.dylib, return that
-	if ( needsAddedLibSystemDepency(libraryCount(), (macho_header*)fMachOData) ) {
-		return LIBSYSTEM_DYLIB_PATH;
-	}
-
-	return NULL;
-}
-
 
 void __attribute__((noreturn)) ImageLoaderMachO::throwSymbolNotFound(const LinkContext& context, const char* symbol, 
-																	const char* referencedFrom, const char* fromVersMismatch,
-																	const char* expectedIn)
+																	const char* referencedFrom, const char* expectedIn)
 {
 	// record values for possible use by CrashReporter or Finder
-	(*context.setErrorStrings)(DYLD_EXIT_REASON_SYMBOL_MISSING, referencedFrom, expectedIn, symbol);
-	dyld::throwf("Symbol not found: %s\n  Referenced from: %s%s\n  Expected in: %s\n",
-					symbol, referencedFrom, fromVersMismatch, expectedIn);
+	(*context.setErrorStrings)(dyld_error_kind_symbol_missing, referencedFrom, expectedIn, symbol);
+	dyld::throwf("Symbol not found: %s\n  Referenced from: %s\n  Expected in: %s\n", symbol, referencedFrom, expectedIn); 
 }
 
 const mach_header* ImageLoaderMachO::machHeader() const
@@ -1968,29 +1421,24 @@
 	return (const void*)lastAddress;
 }
 
-uintptr_t ImageLoaderMachO::bindLocation(const LinkContext& context, uintptr_t baseVMAddress,
-                                         uintptr_t location, uintptr_t value,
-                                         uint8_t type, const char* symbolName,
-                                         intptr_t addend, const char* inPath, const char* toPath, const char* msg,
-                                         ExtraBindData *extraBindData, uintptr_t slide)
-{
-    auto logBind = [&]() {
-        if ( !context.verboseBind )
-            return;
-        if ( addend != 0 ) {
-            dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX + %ld\n",
-                      msg, shortName(inPath), (uintptr_t)location,
-                      ((toPath != NULL) ? shortName(toPath) : "<missing weak_import>"),
-                      symbolName, (uintptr_t)location, value, addend);
-        } else {
-            dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX\n",
-                      msg, shortName(inPath), (uintptr_t)location,
-                      ((toPath != NULL) ? shortName(toPath) : "<missing weak_import>"),
-                      symbolName, (uintptr_t)location, value);
-        }
-    };
-
-
+
+uintptr_t ImageLoaderMachO::bindLocation(const LinkContext& context, uintptr_t location, uintptr_t value, 
+										const ImageLoader* targetImage, uint8_t type, const char* symbolName, 
+										intptr_t addend, const char* msg)
+{
+	// log
+	if ( context.verboseBind ) {
+		if ( addend != 0 )
+			dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX + %ld\n",
+						msg, this->getShortName(), (uintptr_t)location,
+						((targetImage != NULL) ? targetImage->getShortName() : "<weak_import-missing>"),
+						symbolName, (uintptr_t)location, value, addend);
+		else
+			dyld::log("dyld: %sbind: %s:0x%08lX = %s:%s, *0x%08lX = 0x%08lX\n",
+						msg, this->getShortName(), (uintptr_t)location,
+						((targetImage != NULL) ? targetImage->getShortName() : "<weak>import-missing>"),
+						 symbolName, (uintptr_t)location, value);
+	}
 #if LOG_BINDINGS
 //	dyld::logBindings("%s: %s\n", targetImage->getShortName(), symbolName);
 #endif
@@ -2002,45 +1450,22 @@
 	uint32_t value32;
 	switch (type) {
 		case BIND_TYPE_POINTER:
-            logBind();
 			// test first so we don't needless dirty pages
 			if ( *locationToFix != newValue )
 				*locationToFix = newValue;
 			break;
-        case BIND_TYPE_TEXT_ABSOLUTE32:
-            logBind();
+		case BIND_TYPE_TEXT_ABSOLUTE32:
 			loc32 = (uint32_t*)locationToFix;
 			value32 = (uint32_t)newValue;
 			if ( *loc32 != value32 )
 				*loc32 = value32;
 			break;
-        case BIND_TYPE_TEXT_PCREL32:
-            logBind();
+		case BIND_TYPE_TEXT_PCREL32:
 			loc32 = (uint32_t*)locationToFix;
-			value32 = (uint32_t)(newValue - (((uintptr_t)locationToFix) + 4));
+			value32 = (uint32_t)newValue - (((uintptr_t)locationToFix) + 4);
 			if ( *loc32 != value32 )
 				*loc32 = value32;
-            break;
-        case BIND_TYPE_THREADED_BIND:
-            logBind();
-            // test first so we don't needless dirty pages
-            if ( *locationToFix != newValue )
-                *locationToFix = newValue;
-            break;
-        case BIND_TYPE_THREADED_REBASE: {
-            // Regular pointer which needs to fit in 51-bits of value.
-            // C++ RTTI uses the top bit, so we'll allow the whole top-byte
-            // and the signed-extended bottom 43-bits to be fit in to 51-bits.
-            uint64_t top8Bits = *locationToFix & 0x0007F80000000000ULL;
-            uint64_t bottom43Bits = *locationToFix & 0x000007FFFFFFFFFFULL;
-            uint64_t targetValue = ( top8Bits << 13 ) | (((intptr_t)(bottom43Bits << 21) >> 21) & 0x00FFFFFFFFFFFFFF);
-            newValue = (uintptr_t)(targetValue + slide);
-            if ( context.verboseRebase ) {
-                dyld::log("dyld: rebase: %s:*0x%08lX += 0x%08lX = 0x%08lX\n", shortName(inPath), (uintptr_t)locationToFix, slide, newValue);
-            }
-            *locationToFix = newValue;
 			break;
-        }
 		default:
 			dyld::throwf("bad bind type %d", type);
 	}
@@ -2063,7 +1488,7 @@
 #endif
 
 struct DATAdyld {
-	void*			dyldLazyBinder;		// filled in at launch by dyld to point into dyld to &stub_binding_helper
+	void*			dyldLazyBinder;		// filled in at launch by dyld to point into dyld to &stub_binding_helper_interface
 	void*			dyldFuncLookup;		// filled in at launch by dyld to point into dyld to &_dyld_func_lookup
 	// the following only exist in main executables built for 10.5 or later
 	ProgramVars		vars;
@@ -2071,17 +1496,8 @@
 
 // These are defined in dyldStartup.s
 extern "C" void stub_binding_helper();
-extern "C" int _dyld_func_lookup(const char* name, void** address);
-
-static const char* libDyldPath(const ImageLoader::LinkContext& context)
-{
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-	if ( context.driverKit )
-		return DRIVERKIT_LIBDYLD_DYLIB_PATH;
-	else
-#endif
-	return LIBDYLD_DYLIB_PATH;
-}
+extern "C" bool dyld_func_lookup(const char* name, uintptr_t* address);
+
 
 void ImageLoaderMachO::setupLazyPointerHandler(const LinkContext& context)
 {
@@ -2097,39 +1513,19 @@
 		for (uint32_t i = 0; i < cmd_count; ++i) {
 			if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
 				const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
-				if ( strncmp(seg->segname, "__DATA", 6) == 0 ) {
+				if ( strcmp(seg->segname, "__DATA") == 0 ) {
 					const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
 					const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
 					for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 						if ( strcmp(sect->sectname, "__dyld" ) == 0 ) {
 							struct DATAdyld* dd = (struct DATAdyld*)(sect->addr + fSlide);
-				#if !__arm64__ && !__ARM_ARCH_7K__
 							if ( sect->size > offsetof(DATAdyld, dyldLazyBinder) ) {
 								if ( dd->dyldLazyBinder != (void*)&stub_binding_helper )
 									dd->dyldLazyBinder = (void*)&stub_binding_helper;
 							}
-				#endif // !__arm64__
-							// <rdar://problem/40352925> Add work around for existing apps that have deprecated __dyld section
-							const char* installNm = this->getInstallPath();
-							if ( (mh->filetype != MH_DYLIB) || (installNm == NULL) || (strcmp(installNm, libDyldPath(context)) != 0) ) {
-						#if TARGET_OS_OSX
-								// don't allow macOS apps build with 10.14 or later SDK and targeting 10.8 or later to have a __dyld section
-								if ( (minOSVersion() >= 0x000a0800) && (sdkVersion() >= 0x000a0e00) )
-									dyld::throwf("__dyld section not supported in %s", this->getPath());
-						#endif
-						#if TARGET_OS_IOS || TARGET_OS_TV
-								// don't allow iOS apps build with 12.0 or later SDK to have a __dyld section
-								if ( sdkVersion() >= 0x000c0000 )
-									dyld::throwf("__dyld section not supported in %s", this->getPath());
-						#endif
-						#if TARGET_OS_WATCH
-								if ( sdkVersion() >= 0x00050000 )
-									dyld::throwf("__dyld section not supported in %s", this->getPath());
-						#endif
-							}
 							if ( sect->size > offsetof(DATAdyld, dyldFuncLookup) ) {
-								if ( dd->dyldFuncLookup != (void*)&_dyld_func_lookup )
-									dd->dyldFuncLookup = (void*)&_dyld_func_lookup;
+								if ( dd->dyldFuncLookup != (void*)&dyld_func_lookup )
+									dd->dyldFuncLookup = (void*)&dyld_func_lookup;
 							}
 							if ( mh->filetype == MH_EXECUTE ) {
 								// there are two ways to get the program variables
@@ -2146,7 +1542,7 @@
 									// match what crt1.o supplies, then the program has a custom entry point.
 									// This means it might be doing something that needs to be executed before 
 									// initializers are run. 
-									if ( memcmp(this->getEntryFromLC_UNIXTHREAD(), sStandardEntryPointInstructions, 16) != 0 ) {
+									if ( memcmp(this->getMain(), sStandardEntryPointInstructions, 16) != 0 ) {
 										if ( context.verboseInit )
 											dyld::log("dyld: program uses non-standard entry point so delaying running of initializers\n");
 										context.setRunInitialzersOldWay();
@@ -2156,7 +1552,7 @@
 							}
 							else if ( mh->filetype == MH_DYLIB ) {
 								const char* installPath = this->getInstallPath();
-								if ( (installPath != NULL) && ((strncmp(installPath, "/usr/lib/", 9) == 0) || (strncmp(installPath, "/System/DriverKit/usr/lib/", 26) == 0)) ) {
+								if ( (installPath != NULL) && (strncmp(installPath, "/usr/lib/", 9) == 0) ) {
 									if ( sect->size > offsetof(DATAdyld, vars) ) {
 										// use ProgramVars from libdyld.dylib but tweak mh field to correct value
 										dd->vars.mh = context.mainExecutable->machHeader();
@@ -2188,24 +1584,24 @@
 	vars.mh = (macho_header*)fMachOData;
 	
 	// lookup _NXArgc
-	sym = this->findShallowExportedSymbol("_NXArgc", NULL);
+	sym = this->findExportedSymbol("_NXArgc", false, NULL);
 	if ( sym != NULL )
-		vars.NXArgcPtr = (int*)this->getExportedSymbolAddress(sym, context, this, false, NULL);
+		vars.NXArgcPtr = (int*)this->getExportedSymbolAddress(sym, context, this, false);
 		
 	// lookup _NXArgv
-	sym = this->findShallowExportedSymbol("_NXArgv", NULL);
+	sym = this->findExportedSymbol("_NXArgv", false, NULL);
 	if ( sym != NULL )
-		vars.NXArgvPtr = (const char***)this->getExportedSymbolAddress(sym, context, this, false, NULL);
+		vars.NXArgvPtr = (const char***)this->getExportedSymbolAddress(sym, context, this, false);
 		
 	// lookup _environ
-	sym = this->findShallowExportedSymbol("_environ", NULL);
+	sym = this->findExportedSymbol("_environ", false, NULL);
 	if ( sym != NULL )
-		vars.environPtr = (const char***)this->getExportedSymbolAddress(sym, context, this, false, NULL);
+		vars.environPtr = (const char***)this->getExportedSymbolAddress(sym, context, this, false);
 		
 	// lookup __progname
-	sym = this->findShallowExportedSymbol("___progname", NULL);
+	sym = this->findExportedSymbol("___progname", false, NULL);
 	if ( sym != NULL )
-		vars.__prognamePtr = (const char**)this->getExportedSymbolAddress(sym, context, this, false, NULL);
+		vars.__prognamePtr = (const char**)this->getExportedSymbolAddress(sym, context, this, false);
 		
 	context.setNewProgramVars(vars);
 }
@@ -2213,9 +1609,10 @@
 
 bool ImageLoaderMachO::usablePrebinding(const LinkContext& context) const
 {
-	// dylibs in dyld cache do not need to be rebased or bound
-	// for chained fixups always pretend dylib is up to date, patch tables will be used later
-	if ( fInSharedCache && (this->allDependentLibrariesAsWhenPreBound() || context.dyldCache->header.builtFromChainedFixups) ) {
+	// if prebound and loaded at prebound address, and all libraries are same as when this was prebound, then no need to bind
+	if ( ((this->isPrebindable() && (this->getSlide() == 0)) || fInSharedCache)
+		&& this->usesTwoLevelNameSpace()
+		&& this->allDependentLibrariesAsWhenPreBound() ) {
 		// allow environment variables to disable prebinding
 		if ( context.bindFlat )
 			return false;
@@ -2233,14 +1630,6 @@
 	return false;
 }
 
-static void *stripPointer(void *ptr) {
-#if __has_feature(ptrauth_calls)
-    return __builtin_ptrauth_strip(ptr, ptrauth_key_asia);
-#else
-    return ptr;
-#endif
-}
-
 
 void ImageLoaderMachO::doImageInit(const LinkContext& context)
 {
@@ -2252,41 +1641,19 @@
 			switch (cmd->cmd) {
 				case LC_ROUTINES_COMMAND:
 					Initializer func = (Initializer)(((struct macho_routines_command*)cmd)->init_address + fSlide);
-#if __has_feature(ptrauth_calls)
-					func = (Initializer)__builtin_ptrauth_sign_unauthenticated((void*)func, ptrauth_key_asia, 0);
-#endif
 					// <rdar://problem/8543820&9228031> verify initializers are in image
-					if ( ! this->containsAddress(stripPointer((void*)func)) ) {
+					if ( ! this->containsAddress((void*)func) ) {
 						dyld::throwf("initializer function %p not in mapped image for %s\n", func, this->getPath());
-					}
-					if ( ! dyld::gProcessInfo->libSystemInitialized ) {
-						// <rdar://problem/17973316> libSystem initializer must run first
-						dyld::throwf("-init function in image (%s) that does not link with libSystem.dylib\n", this->getPath());
 					}
 					if ( context.verboseInit )
 						dyld::log("dyld: calling -init function %p in %s\n", func, this->getPath());
-					{
-						dyld3::ScopedTimer(DBG_DYLD_TIMING_STATIC_INITIALIZER, (uint64_t)fMachOData, (uint64_t)func, 0);
-						func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
-					}
+					func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
 					break;
 			}
 			cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 		}
 	}
 }
-
-static const char* libSystemPath(const ImageLoader::LinkContext& context)
-{
-#if __MAC_OS_X_VERSION_MIN_REQUIRED
-	if ( context.driverKit )
-		return DRIVERKIT_LIBSYSTEM_DYLIB_PATH;
-	else
-#endif
-	return LIBSYSTEM_DYLIB_PATH;
-}
-
-
 
 void ImageLoaderMachO::doModInitFunctions(const LinkContext& context)
 {
@@ -2303,77 +1670,27 @@
 					const uint8_t type = sect->flags & SECTION_TYPE;
 					if ( type == S_MOD_INIT_FUNC_POINTERS ) {
 						Initializer* inits = (Initializer*)(sect->addr + fSlide);
-						const size_t count = sect->size / sizeof(uintptr_t);
-						// <rdar://problem/23929217> Ensure __mod_init_func section is within segment
-						if ( (sect->addr < seg->vmaddr) || (sect->addr+sect->size > seg->vmaddr+seg->vmsize) || (sect->addr+sect->size < sect->addr) )
-							dyld::throwf("__mod_init_funcs section has malformed address range for %s\n", this->getPath());
-						for (size_t j=0; j < count; ++j) {
-							Initializer func = inits[j];
+						const uint32_t count = sect->size / sizeof(uintptr_t);
+						for (uint32_t i=0; i < count; ++i) {
+							Initializer func = inits[i];
 							// <rdar://problem/8543820&9228031> verify initializers are in image
-							if ( ! this->containsAddress(stripPointer((void*)func)) ) {
+							if ( ! this->containsAddress((void*)func) ) {
 								dyld::throwf("initializer function %p not in mapped image for %s\n", func, this->getPath());
-							}
-							if ( ! dyld::gProcessInfo->libSystemInitialized ) {
-								// <rdar://problem/17973316> libSystem initializer must run first
-								const char* installPath = getInstallPath();
-								if ( (installPath == NULL) || (strcmp(installPath, libSystemPath(context)) != 0) )
-									dyld::throwf("initializer in image (%s) that does not link with libSystem.dylib\n", this->getPath());
 							}
 							if ( context.verboseInit )
 								dyld::log("dyld: calling initializer function %p in %s\n", func, this->getPath());
-							bool haveLibSystemHelpersBefore = (dyld::gLibSystemHelpers != NULL);
-							{
-								dyld3::ScopedTimer(DBG_DYLD_TIMING_STATIC_INITIALIZER, (uint64_t)fMachOData, (uint64_t)func, 0);
-								func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
-							}
-							bool haveLibSystemHelpersAfter = (dyld::gLibSystemHelpers != NULL);
-							if ( !haveLibSystemHelpersBefore && haveLibSystemHelpersAfter ) {
-								// now safe to use malloc() and other calls in libSystem.dylib
-								dyld::gProcessInfo->libSystemInitialized = true;
-							}
+							func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
 						}
 					}
-					else if ( type == S_INIT_FUNC_OFFSETS ) {
-						const uint32_t* inits = (uint32_t*)(sect->addr + fSlide);
-						const size_t count = sect->size / sizeof(uint32_t);
-						// Ensure section is within segment
-						if ( (sect->addr < seg->vmaddr) || (sect->addr+sect->size > seg->vmaddr+seg->vmsize) || (sect->addr+sect->size < sect->addr) )
-							dyld::throwf("__init_offsets section has malformed address range for %s\n", this->getPath());
-						if ( seg->initprot & VM_PROT_WRITE )
-							dyld::throwf("__init_offsets section is not in read-only segment %s\n", this->getPath());
-						for (size_t j=0; j < count; ++j) {
-							uint32_t funcOffset = inits[j];
-							// verify initializers are in TEXT segment
-							if ( funcOffset > seg->filesize ) {
-								dyld::throwf("initializer function offset 0x%08X not in mapped image for %s\n", funcOffset, this->getPath());
-							}
-							if ( ! dyld::gProcessInfo->libSystemInitialized ) {
-								// <rdar://problem/17973316> libSystem initializer must run first
-								const char* installPath = getInstallPath();
-								if ( (installPath == NULL) || (strcmp(installPath, libSystemPath(context)) != 0) )
-									dyld::throwf("initializer in image (%s) that does not link with libSystem.dylib\n", this->getPath());
-							}
-                            Initializer func = (Initializer)((uint8_t*)this->machHeader() + funcOffset);
-							if ( context.verboseInit )
-								dyld::log("dyld: calling initializer function %p in %s\n", func, this->getPath());
-							bool haveLibSystemHelpersBefore = (dyld::gLibSystemHelpers != NULL);
-							{
-								dyld3::ScopedTimer(DBG_DYLD_TIMING_STATIC_INITIALIZER, (uint64_t)fMachOData, (uint64_t)func, 0);
-                                func(context.argc, context.argv, context.envp, context.apple, &context.programVars);
-                            }
-							bool haveLibSystemHelpersAfter = (dyld::gLibSystemHelpers != NULL);
-							if ( !haveLibSystemHelpersBefore && haveLibSystemHelpersAfter ) {
-								// now safe to use malloc() and other calls in libSystem.dylib
-								dyld::gProcessInfo->libSystemInitialized = true;
-							}
-						}
-					}
 				}
 			}
 			cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
 		}
 	}
 }
+
+
+
 
 
 
@@ -2393,9 +1710,6 @@
 						const struct macho_section* const sectionsEnd = &sectionsStart[seg->nsects];
 						for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 							if ( (sect->flags & SECTION_TYPE) == S_DTRACE_DOF ) {
-								// <rdar://problem/23929217> Ensure section is within segment
-								if ( (sect->addr < seg->vmaddr) || (sect->addr+sect->size > seg->vmaddr+seg->vmsize) || (sect->addr+sect->size < sect->addr) )
-									dyld::throwf("DOF section has malformed address range for %s\n", this->getPath());
 								ImageLoader::DOFInfo info;
 								info.dof			= (void*)(sect->addr + fSlide);
 								info.imageHeader	= this->machHeader();
@@ -2451,18 +1765,12 @@
 				for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
 					const uint8_t type = sect->flags & SECTION_TYPE;
 					if ( type == S_MOD_TERM_FUNC_POINTERS ) {
-						// <rdar://problem/23929217> Ensure section is within segment
-						if ( (sect->addr < seg->vmaddr) || (sect->addr+sect->size > seg->vmaddr+seg->vmsize) || (sect->addr+sect->size < sect->addr) )
-							dyld::throwf("DOF section has malformed address range for %s\n", this->getPath());
 						Terminator* terms = (Terminator*)(sect->addr + fSlide);
-						const size_t count = sect->size / sizeof(uintptr_t);
-						for (size_t j=count; j > 0; --j) {
-							Terminator func = terms[j-1];
-#if __has_feature(ptrauth_calls)
-							func = (Terminator)__builtin_ptrauth_sign_unauthenticated((void*)func, ptrauth_key_asia, 0);
-#endif
+						const uint32_t count = sect->size / sizeof(uintptr_t);
+						for (uint32_t i=count; i > 0; --i) {
+							Terminator func = terms[i-1];
 							// <rdar://problem/8543820&9228031> verify terminators are in image
-							if ( ! this->containsAddress(stripPointer((void*)func)) ) {
+							if ( ! this->containsAddress((void*)func) ) {
 								dyld::throwf("termination function %p not in mapped image for %s\n", func, this->getPath());
 							}
 							if ( context.verboseInit )
@@ -2478,9 +1786,9 @@
 }
 
 
-void ImageLoaderMachO::printStatisticsDetails(unsigned int imageCount, const InitializerTimingList& timingInfo)
-{
-	ImageLoader::printStatisticsDetails(imageCount, timingInfo);
+void ImageLoaderMachO::printStatistics(unsigned int imageCount, const InitializerTimingList& timingInfo)
+{
+	ImageLoader::printStatistics(imageCount, timingInfo);
 	dyld::log("total symbol trie searches:    %d\n", fgSymbolTrieSearchs);
 	dyld::log("total symbol table binary searches:    %d\n", fgSymbolTableBinarySearchs);
 	dyld::log("total images defining weak symbols:  %u\n", fgImagesHasWeakDefinitions);
@@ -2500,13 +1808,7 @@
 		uintptr_t highAddr = 0;
 		for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
 			const uintptr_t segLow = segPreferredLoadAddress(i);
-			const uintptr_t segHigh = dyld_page_round(segLow + segSize(i));
-			if ( segLow < highAddr ) {
-				if ( dyld_page_size > 4096 )
-					dyld::throwf("can't map segments into 16KB pages");
-				else
-					dyld::throwf("overlapping segments");
-			}
+			const uintptr_t segHigh = (segLow + segSize(i) + 4095) & -4096;
 			if ( segLow < lowAddr )
 				lowAddr = segLow;
 			if ( segHigh > highAddr )
@@ -2523,7 +1825,7 @@
 	} 
 	else if ( ! this->segmentsCanSlide() ) {
 		for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
-			if ( (strcmp(segName(i), "__PAGEZERO") == 0) && (segFileSize(i) == 0) && (segPreferredLoadAddress(i) == 0) )
+			if ( strcmp(segName(i), "__PAGEZERO") == 0 )
 				continue;
 			if ( !reserveAddressRange(segPreferredLoadAddress(i), segSize(i)) )
 				dyld::throwf("can't map unslidable segment %s to 0x%lX with size 0x%lX", segName(i), segPreferredLoadAddress(i), segSize(i));
@@ -2543,7 +1845,7 @@
 	// in PIE programs, load initial dylibs after main executable so they don't have fixed addresses either
 	if ( fgNextPIEDylibAddress != 0 ) {
 		 // add small (0-3 pages) random padding between dylibs
-		addr = fgNextPIEDylibAddress + (__stack_chk_guard/fgNextPIEDylibAddress & (sizeof(long)-1))*dyld_page_size;
+		addr = fgNextPIEDylibAddress + (__stack_chk_guard/fgNextPIEDylibAddress & (sizeof(long)-1))*4096;
 		//dyld::log("padding 0x%08llX, guard=0x%08llX\n", (long long)(addr - fgNextPIEDylibAddress), (long long)(__stack_chk_guard));
 		kern_return_t r = vm_alloc(&addr, size, VM_FLAGS_FIXED | VM_MAKE_TAG(VM_MEMORY_DYLIB));
 		if ( r == KERN_SUCCESS ) {
@@ -2575,39 +1877,24 @@
 {
 	// find address range for image
 	intptr_t slide = this->assignSegmentAddresses(context);
-	if ( context.verboseMapping ) {
-		if ( offsetInFat != 0 )
-			dyld::log("dyld: Mapping %s (slice offset=%llu)\n", this->getPath(), (unsigned long long)offsetInFat);
-		else
-			dyld::log("dyld: Mapping %s\n", this->getPath());
-	}
-
-	// <rdar://problem/47163421> speculatively read whole slice
-	fspecread_t specread = {} ;
-	specread.fsr_offset = offsetInFat;
-	specread.fsr_length = lenInFat;
-	specread.fsr_flags  = 0;
-	fcntl(fd, F_SPECULATIVE_READ, &specread);
 	if ( context.verboseMapping )
-		dyld::log("dyld: Speculatively read offset=0x%08llX, len=0x%08llX, path=%s\n", offsetInFat, lenInFat, this->getPath());
-
+		dyld::log("dyld: Mapping %s\n", this->getPath());
 	// map in all segments
 	for(unsigned int i=0, e=segmentCount(); i < e; ++i) {
-		vm_offset_t fileOffset = (vm_offset_t)(segFileOffset(i) + offsetInFat);
+		vm_offset_t fileOffset = segFileOffset(i) + offsetInFat;
 		vm_size_t size = segFileSize(i);
 		uintptr_t requestedLoadAddress = segPreferredLoadAddress(i) + slide;
 		int protection = 0;
 		if ( !segUnaccessible(i) ) {
-			if ( segExecutable(i) )
+			// If has text-relocs, don't set x-bit initially.
+			// Instead set it later after text-relocs have been done.
+			// The iPhone OS does not like it when you make executable code writable.
+			if ( segExecutable(i) && !(segHasRebaseFixUps(i) && (slide != 0)) )
 				protection   |= PROT_EXEC;
 			if ( segReadable(i) )
 				protection   |= PROT_READ;
-			if ( segWriteable(i) ) {
+			if ( segWriteable(i) )
 				protection   |= PROT_WRITE;
-				// rdar://problem/22525618 force __LINKEDIT to always be mapped read-only
-				if ( strcmp(segName(i), "__LINKEDIT") == 0 )
-					protection = PROT_READ;
-			}
 		}
 	#if __i386__
 		// initially map __IMPORT segments R/W so dyld can update them
@@ -2622,16 +1909,8 @@
 			}
 			void* loadAddress = xmmap((void*)requestedLoadAddress, size, protection, MAP_FIXED | MAP_PRIVATE, fd, fileOffset);
 			if ( loadAddress == ((void*)(-1)) ) {
-				int mmapErr = errno;
-				if ( mmapErr == EPERM ) {
-					if ( dyld::sandboxBlockedMmap(getPath()) )
-						dyld::throwf("file system sandbox blocked mmap() of '%s'", this->getPath());
-					else
-						dyld::throwf("code signing blocked mmap() of '%s'", this->getPath());
-				}
-				else
-					dyld::throwf("mmap() errno=%d at address=0x%08lX, size=0x%08lX segment=%s in Segment::map() mapping %s",
-						mmapErr, requestedLoadAddress, (uintptr_t)size, segName(i), getPath());
+				dyld::throwf("mmap() error %d at address=0x%08lX, size=0x%08lX segment=%s in Segment::map() mapping %s", 
+					errno, requestedLoadAddress, (uintptr_t)size, segName(i), getPath());
 			}
 		}
 		// update stats
@@ -2697,13 +1976,12 @@
 	}
 }	
 
-#if TEXT_RELOC_SUPPORT
 void ImageLoaderMachO::segMakeWritable(unsigned int segIndex, const ImageLoader::LinkContext& context)
 {
 	vm_address_t addr = segActualLoadAddress(segIndex);
 	vm_size_t size = segSize(segIndex);
 	const bool setCurrentPermissions = false;
-	vm_prot_t protection = VM_PROT_WRITE | VM_PROT_READ | VM_PROT_COPY;
+	vm_prot_t protection = VM_PROT_WRITE | VM_PROT_READ;
 	if ( segExecutable(segIndex) && !segHasRebaseFixUps(segIndex) )
 		protection |= VM_PROT_EXECUTE;
 	kern_return_t r = vm_protect(mach_task_self(), addr, size, setCurrentPermissions, protection);
@@ -2716,198 +1994,5 @@
 			(protection & PROT_READ) ? 'r' : '.',  (protection & PROT_WRITE) ? 'w' : '.',  (protection & PROT_EXEC) ? 'x' : '.' );
 	}
 }
-#endif
-
-const char* ImageLoaderMachO::findClosestSymbol(const mach_header* mh, const void* addr, const void** closestAddr)
-{
-	// called by dladdr()
-	// only works with compressed LINKEDIT if classic symbol table is also present
-	const dysymtab_command* dynSymbolTable = NULL;
-	const symtab_command* symtab = NULL;
-	const macho_segment_command* seg;
-	const uint8_t* unslidLinkEditBase = NULL;
-	bool linkEditBaseFound = false;
-	intptr_t slide = 0;
-	const uint32_t cmd_count = mh->ncmds;
-	const load_command* const cmds = (load_command*)((char*)mh + sizeof(macho_header));
-	const load_command* cmd = cmds;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		switch (cmd->cmd) {
-			case LC_SEGMENT_COMMAND:
-				seg = (macho_segment_command*)cmd;
-				if ( strcmp(seg->segname, "__LINKEDIT") == 0 ) {
-					unslidLinkEditBase = (uint8_t*)(seg->vmaddr - seg->fileoff);
-					linkEditBaseFound = true;
-				}
-				else if ( strcmp(seg->segname, "__TEXT") == 0 ) {
-					slide = (uintptr_t)mh - seg->vmaddr;
-                }
-				break;
-			case LC_SYMTAB:
-				symtab = (symtab_command*)cmd;
-				break;
-			case LC_DYSYMTAB:
-				dynSymbolTable = (dysymtab_command*)cmd;
-				break;
-		}
-		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	// no symbol table => no lookup by address
-	if ( (symtab == NULL) || (dynSymbolTable == NULL) || !linkEditBaseFound )
-		return NULL;
-
-	const uint8_t* linkEditBase = unslidLinkEditBase + slide;
-	const char* symbolTableStrings = (const char*)&linkEditBase[symtab->stroff];
-	const macho_nlist* symbolTable = (macho_nlist*)(&linkEditBase[symtab->symoff]);
-
-	uintptr_t targetAddress = (uintptr_t)addr - slide;
-	const struct macho_nlist* bestSymbol = NULL;
-	// first walk all global symbols
-	const struct macho_nlist* const globalsStart = &symbolTable[dynSymbolTable->iextdefsym];
-	const struct macho_nlist* const globalsEnd= &globalsStart[dynSymbolTable->nextdefsym];
-	for (const struct macho_nlist* s = globalsStart; s < globalsEnd; ++s) {
- 		if ( (s->n_type & N_TYPE) == N_SECT ) {
-			if ( bestSymbol == NULL ) {
-				if ( s->n_value <= targetAddress )
-					bestSymbol = s;
-			}
-			else if ( (s->n_value <= targetAddress) && (bestSymbol->n_value < s->n_value) ) {
-				bestSymbol = s;
-			}
-		}
-	}
-	// next walk all local symbols
-	const struct macho_nlist* const localsStart = &symbolTable[dynSymbolTable->ilocalsym];
-	const struct macho_nlist* const localsEnd= &localsStart[dynSymbolTable->nlocalsym];
-	for (const struct macho_nlist* s = localsStart; s < localsEnd; ++s) {
- 		if ( ((s->n_type & N_TYPE) == N_SECT) && ((s->n_type & N_STAB) == 0) ) {
-			if ( bestSymbol == NULL ) {
-				if ( s->n_value <= targetAddress )
-					bestSymbol = s;
-			}
-			else if ( (s->n_value <= targetAddress) && (bestSymbol->n_value < s->n_value) ) {
-				bestSymbol = s;
-			}
-		}
-	}
-	if ( bestSymbol != NULL ) {
-#if __arm__
-		if (bestSymbol->n_desc & N_ARM_THUMB_DEF)
-			*closestAddr = (void*)((bestSymbol->n_value | 1) + slide);
-		else
-			*closestAddr = (void*)(bestSymbol->n_value + slide);
-#else
-		*closestAddr = (void*)(bestSymbol->n_value + slide);
-#endif
-		return &symbolTableStrings[bestSymbol->n_un.n_strx];
-	}
-	return NULL;
-}
-
-bool ImageLoaderMachO::getLazyBindingInfo(uint32_t& lazyBindingInfoOffset, const uint8_t* lazyInfoStart, const uint8_t* lazyInfoEnd,
-													uint8_t* segIndex, uintptr_t* segOffset, int* ordinal, const char** symbolName, bool* doneAfterBind)
-{
-	if ( lazyBindingInfoOffset > (lazyInfoEnd-lazyInfoStart) )
-		return false;
-	bool done = false;
-	const uint8_t* p = &lazyInfoStart[lazyBindingInfoOffset];
-	while ( !done && (p < lazyInfoEnd) ) {
-		uint8_t immediate = *p & BIND_IMMEDIATE_MASK;
-		uint8_t opcode = *p & BIND_OPCODE_MASK;
-		++p;
-		switch (opcode) {
-			case BIND_OPCODE_DONE:
-				*doneAfterBind = false;
-				return true;
-				break;
-			case BIND_OPCODE_SET_DYLIB_ORDINAL_IMM:
-				*ordinal = immediate;
-				break;
-			case BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB:
-				*ordinal = (int)read_uleb128(p, lazyInfoEnd);
-				break;
-			case BIND_OPCODE_SET_DYLIB_SPECIAL_IMM:
-				// the special ordinals are negative numbers
-				if ( immediate == 0 )
-					*ordinal = 0;
-				else {
-					int8_t signExtended = BIND_OPCODE_MASK | immediate;
-					*ordinal = signExtended;
-				}
-				break;
-			case BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM:
-				*symbolName = (char*)p;
-				while (*p != '\0')
-					++p;
-				++p;
-				break;
-			case BIND_OPCODE_SET_TYPE_IMM:
-				break;
-			case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB:
-				*segIndex  = immediate;
-				*segOffset = read_uleb128(p, lazyInfoEnd);
-				break;
-			case BIND_OPCODE_DO_BIND:
-				*doneAfterBind = ((*p & BIND_OPCODE_MASK) == BIND_OPCODE_DONE);
-				lazyBindingInfoOffset += p - &lazyInfoStart[lazyBindingInfoOffset];
-				return true;
-				break;
-			case BIND_OPCODE_SET_ADDEND_SLEB:
-			case BIND_OPCODE_ADD_ADDR_ULEB:
-			case BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB:
-			case BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED:
-			case BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB:
-			default:
-				return false;
-		}
-	}	
-	return false;
-}
-
-const dyld_info_command* ImageLoaderMachO::findDyldInfoLoadCommand(const mach_header* mh)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const load_command* const cmds = (load_command*)((char*)mh + sizeof(macho_header));
-	const load_command* cmd = cmds;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		switch (cmd->cmd) {
-			case LC_DYLD_INFO:
-			case LC_DYLD_INFO_ONLY:
-				return (dyld_info_command*)cmd;
-		}
-		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	return NULL;
-}
-
-
-uintptr_t ImageLoaderMachO::segPreferredAddress(const mach_header* mh, unsigned segIndex)
-{
-	const uint32_t cmd_count = mh->ncmds;
-	const load_command* const cmds = (load_command*)((char*)mh + sizeof(macho_header));
-	const load_command* cmd = cmds;
-	unsigned curSegIndex = 0;
-	for (uint32_t i = 0; i < cmd_count; ++i) {
-		if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
-			if ( segIndex == curSegIndex ) {
-				const macho_segment_command* segCmd = (macho_segment_command*)cmd;
-				return segCmd->vmaddr;
-			}
-			++curSegIndex;
-		}
-		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
-	}
-	return 0;
-}
-
-
-
-uintptr_t ImageLoaderMachO::imageBaseAddress() const {
-    //printf("imageBaseAddress: %s %d->%d\n", getPath(), 0, segmentCount());
-    for (unsigned int i = 0, e = segmentCount(); i != e; ++i) {
-        if ( (segFileOffset(i) == 0) && (segFileSize(i) != 0) )
-            return segPreferredLoadAddress(i);
-    }
-    return 0;
-}
-
+
+