Loading...
--- dyld/dyld-195.5/src/dyldInitialization.cpp
+++ dyld/dyld-95.3/src/dyldInitialization.cpp
@@ -1,6 +1,6 @@
/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
*
- * Copyright (c) 2004-2008 Apple Inc. All rights reserved.
+ * Copyright (c) 2004-2005 Apple Computer, Inc. All rights reserved.
*
* @APPLE_LICENSE_HEADER_START@
*
@@ -45,11 +45,13 @@
#if __LP64__
+ #define macho_header mach_header_64
#define LC_SEGMENT_COMMAND LC_SEGMENT_64
#define macho_segment_command segment_command_64
#define macho_section section_64
#define RELOC_SIZE 3
#else
+ #define macho_header mach_header
#define LC_SEGMENT_COMMAND LC_SEGMENT
#define macho_segment_command segment_command
#define macho_section section
@@ -112,28 +114,6 @@
}
}
-
-//
-// The kernel may have slid a Position Independent Executable
-//
-static uintptr_t slideOfMainExecutable(const struct macho_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;
- for (uint32_t i = 0; i < cmd_count; ++i) {
- if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
- const struct macho_segment_command* segCmd = (struct macho_segment_command*)cmd;
- if ( strcmp(segCmd->segname, "__TEXT") == 0 ) {
- return (uintptr_t)mh - segCmd->vmaddr;
- }
- }
- cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
- }
- return 0;
-}
-
-
//
// If the kernel does not load dyld at its preferred address, we need to apply
// fixups to various initialized parts of the __DATA segment
@@ -208,6 +188,126 @@
}
+//
+// For some reason the kernel loads dyld with __TEXT and __LINKEDIT writable
+// rdar://problem/3702311
+//
+static void segmentProtectDyld(const struct macho_header* mh, intptr_t slide)
+{
+ 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;
+ for (uint32_t i = 0; i < cmd_count; ++i) {
+ switch (cmd->cmd) {
+ case LC_SEGMENT_COMMAND:
+ {
+ const struct macho_segment_command* seg = (struct macho_segment_command*)cmd;
+ vm_address_t addr = seg->vmaddr + slide;
+ vm_size_t size = seg->vmsize;
+ const bool setCurrentPermissions = false;
+ vm_protect(mach_task_self(), addr, size, setCurrentPermissions, seg->initprot);
+ //dyld::log("dyld: segment %s, 0x%08X -> 0x%08X, set to %d\n", seg->segname, addr, addr+size-1, seg->initprot);
+ }
+ break;
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+
+}
+
+
+//
+// re-map the main executable to a new random address
+//
+static const struct mach_header* randomizeExecutableLoadAddress(const struct mach_header* orgMH, uintptr_t* appsSlide)
+{
+#if __ppc__
+ // don't slide PIE programs running under rosetta
+ if ( dyld::isRosetta() )
+ return orgMH;
+#endif
+ // count segments
+ uint32_t segCount = 0;
+ const uint32_t cmd_count = orgMH->ncmds;
+ const struct load_command* const cmds = (struct load_command*)(((char*)orgMH)+sizeof(macho_header));
+ const struct load_command* cmd = cmds;
+ for (uint32_t i = 0; i < cmd_count; ++i) {
+ if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
+ const struct macho_segment_command* segCmd = (struct macho_segment_command*)cmd;
+ // page-zero and custom stacks don't move
+ if ( (strcmp(segCmd->segname, "__PAGEZERO") != 0) && (strcmp(segCmd->segname, "__UNIXSTACK") != 0) )
+ ++segCount;
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+
+ // make copy of segment info
+ macho_segment_command segs[segCount];
+ uint32_t index = 0;
+ uintptr_t highestAddressUsed = 0;
+ uintptr_t lowestAddressUsed = UINTPTR_MAX;
+ cmd = cmds;
+ for (uint32_t i = 0; i < cmd_count; ++i) {
+ if ( cmd->cmd == LC_SEGMENT_COMMAND ) {
+ const struct macho_segment_command* segCmd = (struct macho_segment_command*)cmd;
+ if ( (strcmp(segCmd->segname, "__PAGEZERO") != 0) && (strcmp(segCmd->segname, "__UNIXSTACK") != 0) ) {
+ segs[index++] = *segCmd;
+ if ( (segCmd->vmaddr + segCmd->vmsize) > highestAddressUsed )
+ highestAddressUsed = ((segCmd->vmaddr + segCmd->vmsize) + 4095) & -4096;
+ if ( segCmd->vmaddr < lowestAddressUsed )
+ lowestAddressUsed = segCmd->vmaddr;
+ // do nothing if kernel has already randomized load address
+ if ( (strcmp(segCmd->segname, "__TEXT") == 0) && (segCmd->vmaddr != (uintptr_t)orgMH) )
+ return orgMH;
+ }
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+
+ // choose a random new base address
+#if __LP64__
+ uintptr_t highestAddressPossible = highestAddressUsed + 0x100000000ULL;
+#else
+ uintptr_t highestAddressPossible = 0x80000000;
+#endif
+ uintptr_t sizeNeeded = highestAddressUsed-lowestAddressUsed;
+ if ( (highestAddressPossible-sizeNeeded) < highestAddressUsed ) {
+ // new and old segments will overlap
+ // need better algorithm for remapping
+ // punt and don't re-map
+ return orgMH;
+ }
+ uintptr_t possibleRange = (highestAddressPossible-sizeNeeded) - highestAddressUsed;
+ uintptr_t newBaseAddress = highestAddressUsed + ((arc4random() % possibleRange) & -4096);
+
+ vm_address_t addr = newBaseAddress;
+ // reserve new address range
+ if ( vm_allocate(mach_task_self(), &addr, sizeNeeded, VM_FLAGS_FIXED) == KERN_SUCCESS ) {
+ // copy each segment to new address
+ for (uint32_t i = 0; i < segCount; ++i) {
+ uintptr_t newSegAddress = segs[i].vmaddr - lowestAddressUsed + newBaseAddress;
+ if ( (vm_copy(mach_task_self(), segs[i].vmaddr, segs[i].vmsize, newSegAddress) != KERN_SUCCESS)
+ || (vm_protect(mach_task_self(), newSegAddress, segs[i].vmsize, true, segs[i].maxprot) != KERN_SUCCESS)
+ || (vm_protect(mach_task_self(), newSegAddress, segs[i].vmsize, false, segs[i].initprot) != KERN_SUCCESS) ) {
+ // can't copy so dealloc new region and run with original base address
+ vm_deallocate(mach_task_self(), newBaseAddress, sizeNeeded);
+ dyld::warn("could not relocate position independent exectable\n");
+ return orgMH;
+ }
+ }
+ // unmap original segments
+ vm_deallocate(mach_task_self(), lowestAddressUsed, highestAddressUsed-lowestAddressUsed);
+
+ // run with newly mapped executable
+ *appsSlide = newBaseAddress - lowestAddressUsed;
+ return (const struct mach_header*)newBaseAddress;
+ }
+
+ // can't get new range, so don't slide to random address
+ return orgMH;
+}
+
+
extern "C" void dyld_exceptions_init(const struct macho_header*, uintptr_t slide); // in dyldExceptions.cpp
extern "C" void mach_init();
@@ -227,27 +327,32 @@
// This is code to bootstrap dyld. This work in normally done for a program by dyld and crt.
// In dyld we have to do this manually.
//
-uintptr_t start(const struct macho_header* appsMachHeader, int argc, const char* argv[],
- intptr_t slide, const struct macho_header* dyldsMachHeader)
-{
+uintptr_t start(const struct mach_header* appsMachHeader, int argc, const char* argv[], intptr_t slide)
+{
+ // _mh_dylinker_header is magic symbol defined by static linker (ld), see <mach-o/ldsyms.h>
+ const struct macho_header* dyldsMachHeader = (const struct macho_header*)(((char*)&_mh_dylinker_header)+slide);
+
// if kernel had to slide dyld, we need to fix up load sensitive locations
// we have to do this before using any global variables
if ( slide != 0 ) {
rebaseDyld(dyldsMachHeader, slide);
}
-
-#if __IPHONE_OS_VERSION_MIN_REQUIRED
+
+ uintptr_t appsSlide = 0;
+
// set pthread keys to dyld range
__pthread_tsd_first = 1;
_pthread_keys_init();
-#endif
-
+
// enable C++ exceptions to work inside dyld
dyld_exceptions_init(dyldsMachHeader, slide);
// allow dyld to use mach messaging
mach_init();
+ // set protection on segments (has to be done after mach_init)
+ segmentProtectDyld(dyldsMachHeader, slide);
+
// kernel sets up env pointer to be just past end of agv array
const char** envp = &argv[argc+1];
@@ -258,9 +363,12 @@
// run all C++ initializers inside dyld
runDyldInitializers(dyldsMachHeader, slide, argc, argv, envp, apple);
-
+
+ // if main executable was linked -pie, then randomize its load address
+ if ( appsMachHeader->flags & MH_PIE )
+ appsMachHeader = randomizeExecutableLoadAddress(appsMachHeader, &appsSlide);
+
// now that we are done bootstrapping dyld, call dyld's main
- uintptr_t appsSlide = slideOfMainExecutable(appsMachHeader);
return dyld::_main(appsMachHeader, appsSlide, argc, argv, envp, apple);
}