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+++ dyld/dyld-519.2.2/src/dyldInitialization.cpp
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+/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
+ *
+ * Copyright (c) 2004-2008 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#define __STDC_LIMIT_MACROS
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+#include <stdlib.h>
+#include <Availability.h>
+#include <mach/mach.h>
+#include <mach-o/loader.h>
+#include <mach-o/ldsyms.h>
+#include <mach-o/reloc.h>
+#if __x86_64__
+ #include <mach-o/x86_64/reloc.h>
+#endif
+#include "dyld.h"
+#include "dyldSyscallInterface.h"
+
+// from dyld_gdb.cpp
+extern void addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]);
+extern void syncProcessInfo();
+
+#ifndef MH_PIE
+ #define MH_PIE 0x200000
+#endif
+
+// currently dyld has no initializers, but if some come back, set this to non-zero
+#define DYLD_INITIALIZER_SUPPORT 0
+
+#if __LP64__
+ #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 LC_SEGMENT_COMMAND LC_SEGMENT
+ #define macho_segment_command segment_command
+ #define macho_section section
+ #define RELOC_SIZE 2
+#endif
+
+#if __x86_64__
+ #define POINTER_RELOC X86_64_RELOC_UNSIGNED
+#else
+ #define POINTER_RELOC GENERIC_RELOC_VANILLA
+#endif
+
+
+#if TARGET_IPHONE_SIMULATOR
+const dyld::SyscallHelpers* gSyscallHelpers = NULL;
+#endif
+
+
+//
+// Code to bootstrap dyld into a runnable state
+//
+//
+
+namespace dyldbootstrap {
+
+
+
+#if DYLD_INITIALIZER_SUPPORT
+
+typedef void (*Initializer)(int argc, const char* argv[], const char* envp[], const char* apple[]);
+
+extern const Initializer inits_start __asm("section$start$__DATA$__mod_init_func");
+extern const Initializer inits_end __asm("section$end$__DATA$__mod_init_func");
+
+//
+// For a regular executable, the crt code calls dyld to run the executables initializers.
+// For a static executable, crt directly runs the initializers.
+// dyld (should be static) but is a dynamic executable and needs this hack to run its own initializers.
+// We pass argc, argv, etc in case libc.a uses those arguments
+//
+static void runDyldInitializers(const struct macho_header* mh, intptr_t slide, int argc, const char* argv[], const char* envp[], const char* apple[])
+{
+ for (const Initializer* p = &inits_start; p < &inits_end; ++p) {
+ (*p)(argc, argv, envp, apple);
+ }
+}
+#endif // DYLD_INITIALIZER_SUPPORT
+
+
+//
+// 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 ( (segCmd->fileoff == 0) && (segCmd->filesize != 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
+//
+static void rebaseDyld(const struct macho_header* mh, intptr_t slide)
+{
+ // rebase non-lazy pointers (which all point internal to dyld, since dyld uses no shared libraries)
+ // and get interesting pointers into dyld
+ 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 macho_segment_command* linkEditSeg = NULL;
+#if __x86_64__
+ const struct macho_segment_command* firstWritableSeg = NULL;
+#endif
+ const struct dysymtab_command* dynamicSymbolTable = NULL;
+ 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;
+ if ( strcmp(seg->segname, "__LINKEDIT") == 0 )
+ linkEditSeg = seg;
+ const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command));
+ const struct macho_section* const sectionsEnd = §ionsStart[seg->nsects];
+ for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) {
+ const uint8_t type = sect->flags & SECTION_TYPE;
+ if ( type == S_NON_LAZY_SYMBOL_POINTERS ) {
+ // rebase non-lazy pointers (which all point internal to dyld, since dyld uses no shared libraries)
+ const uint32_t pointerCount = (uint32_t)(sect->size / sizeof(uintptr_t));
+ uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + slide);
+ for (uint32_t j=0; j < pointerCount; ++j) {
+ symbolPointers[j] += slide;
+ }
+ }
+ }
+#if __x86_64__
+ if ( (firstWritableSeg == NULL) && (seg->initprot & VM_PROT_WRITE) )
+ firstWritableSeg = seg;
+#endif
+ }
+ break;
+ case LC_DYSYMTAB:
+ dynamicSymbolTable = (struct dysymtab_command *)cmd;
+ break;
+ }
+ cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
+ }
+
+ // use reloc's to rebase all random data pointers
+#if __x86_64__
+ const uintptr_t relocBase = firstWritableSeg->vmaddr + slide;
+#else
+ const uintptr_t relocBase = (uintptr_t)mh;
+#endif
+ const relocation_info* const relocsStart = (struct relocation_info*)(linkEditSeg->vmaddr + slide + dynamicSymbolTable->locreloff - linkEditSeg->fileoff);
+ const relocation_info* const relocsEnd = &relocsStart[dynamicSymbolTable->nlocrel];
+ for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
+ if ( reloc->r_length != RELOC_SIZE )
+ throw "relocation in dyld has wrong size";
+
+ if ( reloc->r_type != POINTER_RELOC )
+ throw "relocation in dyld has wrong type";
+
+ // update pointer by amount dyld slid
+ *((uintptr_t*)(reloc->r_address + relocBase)) += slide;
+ }
+}
+
+
+extern "C" void mach_init();
+extern "C" void __guard_setup(const char* apple[]);
+
+
+//
+// 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* startGlue)
+{
+ // 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);
+ }
+
+ // allow dyld to use mach messaging
+ mach_init();
+
+ // kernel sets up env pointer to be just past end of agv array
+ const char** envp = &argv[argc+1];
+
+ // kernel sets up apple pointer to be just past end of envp array
+ const char** apple = envp;
+ while(*apple != NULL) { ++apple; }
+ ++apple;
+
+ // set up random value for stack canary
+ __guard_setup(apple);
+
+#if DYLD_INITIALIZER_SUPPORT
+ // run all C++ initializers inside dyld
+ runDyldInitializers(dyldsMachHeader, slide, argc, argv, envp, apple);
+#endif
+
+ // 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, startGlue);
+}
+
+
+#if TARGET_IPHONE_SIMULATOR
+
+extern "C" uintptr_t start_sim(int argc, const char* argv[], const char* envp[], const char* apple[],
+ const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide,
+ const dyld::SyscallHelpers*, uintptr_t* startGlue);
+
+
+uintptr_t start_sim(int argc, const char* argv[], const char* envp[], const char* apple[],
+ const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide,
+ const dyld::SyscallHelpers* sc, uintptr_t* startGlue)
+{
+ // if simulator dyld loaded slid, it needs to rebase itself
+ // we have to do this before using any global variables
+ if ( dyldSlide != 0 ) {
+ rebaseDyld(dyldMH, dyldSlide);
+ }
+
+ // save table of syscall pointers
+ gSyscallHelpers = sc;
+
+ // allow dyld to use mach messaging
+ mach_init();
+
+ // set up random value for stack canary
+ __guard_setup(apple);
+
+ // setup gProcessInfo to point to host dyld's struct
+ dyld::gProcessInfo = (struct dyld_all_image_infos*)(sc->getProcessInfo());
+ syncProcessInfo();
+
+ // now that we are done bootstrapping dyld, call dyld's main
+ uintptr_t appsSlide = slideOfMainExecutable(mainExecutableMH);
+ return dyld::_main(mainExecutableMH, appsSlide, argc, argv, envp, apple, startGlue);
+}
+#endif
+
+
+} // end of namespace
+
+
+
+