114 lines
3.8 KiB
C++
114 lines
3.8 KiB
C++
// ObjectFileGenerator.cpp
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#include "ObjectFileGenerator.h"
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#include <fstream>
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#include <cstring>
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#include <mach-o/loader.h>
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#include <mach-o/nlist.h>
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#include <mach/vm_prot.h>
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#include <iostream>
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bool ObjectFileGenerator::writeObject(const std::string &filename,
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const std::vector<uint32_t> &code) {
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std::cout << "Code size: " << code.size() << std::endl;
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for (auto instr : code) {
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std::cout << std::hex << instr << std::endl; // 打印机器码
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}
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// 1) 计算各部分大小/偏移
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const uint32_t segcmd_sz = sizeof(segment_command_64) + sizeof(section_64);
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const uint32_t symcmd_sz = sizeof(symtab_command);
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const uint32_t ncmds = 2; // __TEXT + SYMTAB
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const uint32_t sizeofcmds = segcmd_sz + symcmd_sz;
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const uint32_t fileoff_code = sizeof(mach_header_64) + sizeofcmds;
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const uint32_t codesize = uint32_t(code.size() * 4);
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// 字符串表： "\0_main\0"
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std::vector<char> strtab = {'\0','_','m','a','i','n','\0'};
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const uint32_t nsyms = 1;
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const uint32_t symoff = fileoff_code + codesize;
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std::cout << "Symbol offset: " << symoff << std::endl;
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const uint32_t stroff = symoff + nsyms * sizeof(nlist_64);
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const uint32_t strsize = uint32_t(strtab.size());
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// 2) Mach-O Header
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mach_header_64 mh{};
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mh.magic = MH_MAGIC_64;
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mh.cputype = CPU_TYPE_ARM64;
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mh.cpusubtype = CPU_SUBTYPE_ARM64_ALL;
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mh.filetype = MH_OBJECT;
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mh.ncmds = ncmds;
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mh.sizeofcmds = sizeofcmds;
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mh.flags = 0;
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mh.reserved = 0;
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// 3) LC_SEGMENT_64 for __TEXT/__text
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segment_command_64 sc{};
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sc.cmd = LC_SEGMENT_64;
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sc.cmdsize = segcmd_sz;
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std::strncpy(sc.segname, "__TEXT", sizeof(sc.segname));
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sc.vmaddr = 0;
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sc.vmsize = codesize;
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sc.fileoff = fileoff_code;
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sc.filesize = codesize;
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sc.maxprot = VM_PROT_READ | VM_PROT_WRITE;
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sc.initprot = VM_PROT_READ | VM_PROT_WRITE;
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sc.nsects = 1;
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sc.flags = 0;
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section_64 sect{};
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std::strncpy(sect.sectname, "__text", sizeof(sect.sectname));
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std::strncpy(sect.segname, "__TEXT", sizeof(sect.segname));
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sect.addr = 0;
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sect.size = codesize;
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sect.offset = fileoff_code;
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sect.align = 2; // 4-byte align
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sect.reloff = 0;
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sect.nreloc = 0;
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sect.flags = 0;
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sect.reserved1 = sect.reserved2 = sect.reserved3 = 0;
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// 4) LC_SYMTAB
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symtab_command stc{};
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stc.cmd = LC_SYMTAB;
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stc.cmdsize = symcmd_sz;
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stc.symoff = symoff;
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stc.nsyms = nsyms;
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stc.stroff = stroff;
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stc.strsize = strsize;
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// 5) 写入 header + load commands + section
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std::ofstream ofs(filename, std::ios::binary);
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if (!ofs) return false;
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ofs.write(reinterpret_cast<char*>(&mh), sizeof(mh));
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ofs.write(reinterpret_cast<char*>(&sc), sizeof(segment_command_64));
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ofs.write(reinterpret_cast<char*>(§), sizeof(section_64));
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ofs.write(reinterpret_cast<char*>(&stc), sizeof(stc));
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// 6) 写入机器码
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ofs.seekp(fileoff_code, std::ios::beg);
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for (auto instr : code) {
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ofs.put(char(instr & 0xFF));
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ofs.put(char((instr >> 8) & 0xFF));
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ofs.put(char((instr >> 16) & 0xFF));
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ofs.put(char((instr >> 24) & 0xFF));
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}
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// 7) 写入符号表 (_main)
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ofs.seekp(symoff, std::ios::beg);
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nlist_64 nl{};
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nl.n_un.n_strx = 1; // "_main" 在 strtab 的偏移
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nl.n_type = N_SECT | N_EXT; // 定义在 section、对外可见
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nl.n_sect = 1; // 第一节 __text
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nl.n_desc = 0;
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nl.n_value = 0; // 从节首开始
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ofs.write(reinterpret_cast<char*>(&nl), sizeof(nl));
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// 8) 写入字符串表
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ofs.seekp(stroff, std::ios::beg);
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ofs.write(strtab.data(), strtab.size());
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return true;
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}
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