/* -*- 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 <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"

#ifndef MH_PIE
	#define MH_PIE 0x200000 
#endif


#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

// from dyld.cpp
namespace dyld { extern bool isRosetta(); };


//
//  Code to bootstrap dyld into a runnable state
//
//

namespace dyldbootstrap {


typedef void (*Initializer)(int argc, const char* argv[], const char* envp[], const char* apple[]);

//
// 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[])
{
	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;
					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 ){
							Initializer* inits = (Initializer*)(sect->addr + slide);
							const uint32_t count = sect->size / sizeof(uintptr_t);
							for (uint32_t i=0; i < count; ++i) {
								Initializer func = inits[i];
								func(argc, argv, envp, apple);
							}
						}
					}
				}
				break;
		}
		cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize);
	}
}


//
//  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
//
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 = &sectionsStart[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 = 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();

//
// _pthread_keys is partitioned in a lower part that dyld will use; libSystem
// will use the upper part.  We set __pthread_tsd_first to 1 as the start of
// the lower part.  Libc will take #1 and c++ exceptions will take #2.  There
// is one free key=3 left.
//
extern "C" {
	extern int __pthread_tsd_first;
	extern void _pthread_keys_init();
}


//
//  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);
	}

#if __IPHONE_OS_VERSION_MIN_REQUIRED		
	// set pthread keys to dyld range
	__pthread_tsd_first = 1;
	_pthread_keys_init();
#endif

	// 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;

	// run all C++ initializers inside dyld
	runDyldInitializers(dyldsMachHeader, slide, argc, argv, envp, apple);
		
	// 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);
}




} // end of namespace