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[原创] 笔记 - 学习使用活跃变量分析来清除基本块内的垃圾指令
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发表于: 2025-1-19 15:28
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理论
判断是否为垃圾指令：(insn是指令)def[insn] ∩ out[insn] = ∅ <==> insn 是垃圾指令
代码演示
使用x86汇编代码做例子
代码使用了capstone反汇编库
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 | #include <iostream>#include <vector>#include <string>#include <algorithm>#include <capstone/capstone.h>#pragma comment(lib, "capstone.lib")#define max(a,b) (((a) > (b)) ? (a) : (b))#define min(a,b) (((a) < (b)) ? (a) : (b))// 差集运算template <typename T>std::vector<T> my_set_diff(std::vector<T> a, std::vector<T> b) { if (a.empty()) { return {}; } if (b.empty()) { return a; } std::vector<T> tem; tem.resize(max(a.size(), b.size())); std::sort(a.begin(), a.end()); std::sort(b.begin(), b.end()); auto temLast = set_difference(a.begin(), a.end(), b.begin(), b.end(), tem.begin()); std::vector<T> ret; for (auto it = tem.begin(); it != temLast; it++) { ret.push_back(*it); } return ret;}// 并集运算template <typename T>std::vector<T> my_set_union(std::vector<T> a, std::vector<T> b) { if (a.empty()) { return b; } if (b.empty()) { return a; } std::vector<T> tem; tem.resize(a.size() + b.size()); std::sort(a.begin(), a.end()); std::sort(b.begin(), b.end()); auto temLast = set_union(a.begin(), a.end(), b.begin(), b.end(), tem.begin()); std::vector<T> ret; for (auto it = tem.begin(); it != temLast; it++) { ret.push_back(*it); } return ret;}// 交集运算template <typename T>std::vector<T> my_set_intersection(std::vector<T> a, std::vector<T> b) { if (a.empty()) { return {}; } if (b.empty()) { return {}; } std::vector<T> tem; tem.resize(min(a.size(), b.size())); std::sort(a.begin(), a.end()); std::sort(b.begin(), b.end()); auto temLast = set_intersection(a.begin(), a.end(), b.begin(), b.end(), tem.begin()); std::vector<T> ret; for (auto it = tem.begin(); it != temLast; it++) { ret.push_back(*it); } return ret;}cs_err disasm(csh hCs, const uint8_t* codePtr, uint64_t virAddr, uint64_t codeSize, cs_insn* insn, cs_detail* detail) { cs_insn* _insn = 0; size_t err = 0; if ((err = cs_disasm(hCs, codePtr, codeSize, virAddr, 1, &_insn)) <= 0) { return cs_errno(hCs); } memcpy(insn, _insn, sizeof(cs_insn)); if (detail != NULL) { memcpy(detail, _insn->detail, sizeof(cs_detail)); } insn->detail = detail; cs_free(_insn, 1); return cs_errno(hCs);}cs_err disasm_iter(csh hCs, uint8_t*& codePtr, uint64_t& virAddr, uint64_t& codeSize, cs_insn* insn, cs_detail* detail) { cs_err status = CS_ERR_OK; if ((status = disasm(hCs, codePtr, virAddr, codeSize, insn, detail)) != CS_ERR_OK) { return status; } codePtr += insn->size; virAddr += insn->size; codeSize -= insn->size; return status;}using regs = std::vector<uint16_t>;struct accessRegs { regs reads; regs writes;};accessRegs get_regs_access(csh hCs, cs_insn* insn) { cs_regs read_regs{}; uint8_t read_num = 0; cs_regs write_regs{}; uint8_t write_num = 0; cs_regs_access(hCs, insn, read_regs, &read_num, write_regs, &write_num); regs reads = {}; regs writes = {}; for (uint8_t i = 0; i < read_num; i++) { reads.push_back(read_regs[i]); } for (uint8_t i = 0; i < write_num; i++) { writes.push_back(write_regs[i]); } return { reads, writes };}struct Insn { uint8_t addr[16]; size_t size; uint64_t viraddr; std::string opstr;};enum class x86_flag : uint8_t { AF, CF, SF, ZF, PF, OF, TF, IF, DF, NT, RF };enum class x86_fpuflag : uint8_t { C0, C1, C2, C3 };// ----------------------------------std::vector<x86_flag> calc_eflags_use(csh hCs, const Insn& ins); // 计算指令针对EFlags中具体各个标志位的use集合std::vector<x86_flag> calc_eflags_def(csh hCs, const Insn& ins); // 计算指令针对EFlags中具体各个标志位的def集合std::vector<x86_fpuflag> calc_fpuflags_use(csh hCs, const Insn& ins); // 计算指令针对FPU Flags中具体各个标志位的use集合std::vector<x86_fpuflag> calc_fpuflags_def(csh hCs, const Insn& ins); // 计算指令针对FPU Flags中具体各个标志位的use集合void RemoveDeadCode(char* x86code, size_t codesize, bool is64, uint64_t virtualAddressBegin) { csh hCs = 0; if (!cs_support(CS_ARCH_X86)) { std::cout << "当前Capstone不支持X86架构" << std::endl; return; } if (cs_open(CS_ARCH_X86, ((is64) ? CS_MODE_64 : CS_MODE_32), &hCs) != CS_ERR_OK) { std::cout << "打开Capstone句柄失败" << std::endl; return; } if (cs_option(hCs, CS_OPT_DETAIL, CS_OPT_ON) != CS_ERR_OK) { std::cout << "无法开启Detail" << std::endl; return; } uint8_t* addr = (uint8_t*)x86code; size_t size = codesize; uint64_t virAddr = virtualAddressBegin; std::vector<Insn> bb; std::vector<std::vector<Insn>> bbs; while (size > 0 && (virAddr < (virtualAddressBegin + codesize))) { cs_insn cinsn{}; cs_detail cdetail{}; cs_err err = CS_ERR_OK; if ((err = disasm_iter(hCs, addr, virAddr, size, &cinsn, &cdetail)) != CS_ERR_OK) { std::cout << "反汇编发生错误: " << err << std::endl; break; } bool end_sign1 = (cs_insn_group(hCs, &cinsn, X86_GRP_JUMP) || cs_insn_group(hCs, &cinsn, X86_GRP_BRANCH_RELATIVE) || cs_insn_group(hCs, &cinsn, X86_GRP_CALL) && cinsn.id != X86_INS_CALL); bool end_sign2 = (cinsn.id == X86_INS_RET || cinsn.id == X86_INS_RETF || cinsn.id == X86_INS_RETFQ || cs_insn_group(hCs, &cinsn, X86_GRP_INT)); bool end_sign3 = cs_insn_group(hCs, &cinsn, X86_GRP_PRIVILEGE); if (end_sign1 || end_sign2 || end_sign3) { // 基本块终止，收集过的指令全部加入基本块 if (!bb.empty()) { bbs.push_back(bb); bb = {}; } } else { std::string opstr = cinsn.mnemonic; opstr += "\t"; opstr += cinsn.op_str; Insn ins = {}; ins.opstr = opstr; ins.size = cinsn.size; ins.viraddr = cinsn.address; memcpy(&ins.addr, cinsn.bytes, cinsn.size); bb.push_back(ins); } } if (!bb.empty()) { // 退出循环后，把剩下来的指令也加入到基本块中 bbs.push_back(bb); bb = {}; } std::cout << "\"---->\" 表示该指令可以被删除" << std::endl; bool changed = false; // 迭代标志 for (std::vector<Insn> mbb : bbs) { std::cout << "@@@-------------------------------------------------------"; std::cout << std::endl; std::vector<bool> delList; delList.resize(mbb.size()); do { changed = false; if (mbb.empty()) { continue; } std::vector<std::vector<uint16_t>> use; std::vector<std::vector<uint16_t>> def; std::vector<std::vector<x86_flag>> use_flags; std::vector<std::vector<x86_flag>> def_flags; std::vector<std::vector<x86_fpuflag>> use_fpuflags; std::vector<std::vector<x86_fpuflag>> def_fpuflags; for (size_t i = 0; i < mbb.size(); i++) { // use 和 def 可以直接从汇编代码中解析出来，所以算做已知量 cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, mbb[i].addr, mbb[i].viraddr, mbb[i].size, &cinsn, &cdetail); auto access = get_regs_access(hCs, &cinsn); // 获取指令对寄存器的读写列表 use.push_back(my_set_diff(access.reads, { X86_REG_EFLAGS })); // 指令的 use def.push_back(my_set_diff(access.writes, { X86_REG_EFLAGS })); // 指令的 def use_flags.push_back(calc_eflags_use(hCs, mbb[i])); // 针对指令中对具体标志位的 use def_flags.push_back(calc_eflags_def(hCs, mbb[i])); // 针对指令中对具体标志位的 def use_fpuflags.push_back(calc_fpuflags_use(hCs, mbb[i])); // 针对指令中对具体fpu标志位的 use def_fpuflags.push_back(calc_fpuflags_def(hCs, mbb[i])); // 针对指令中对具体fpu标志位的 def } std::vector<std::vector<uint16_t>> in; std::vector<std::vector<uint16_t>> out; std::vector<std::vector<x86_flag>> in_flags; std::vector<std::vector<x86_flag>> out_flags; std::vector<std::vector<x86_fpuflag>> in_fpuflags; std::vector<std::vector<x86_fpuflag>> out_fpuflags; in.resize(mbb.size()); out.resize(mbb.size()); in_flags.resize(mbb.size()); out_flags.resize(mbb.size()); in_fpuflags.resize(mbb.size()); out_fpuflags.resize(mbb.size()); // 给基本块最后一个指令的out集合赋值的意义是：如果这个基本块退出，有哪些寄存器是会被下一个函数入口所继续使用的 // 为了保证最大兼容性，索性直接把x86里的所有寄存器都加了进来 out.back() = { X86_REG_AH, X86_REG_AL, X86_REG_AX, X86_REG_BH, X86_REG_BL, X86_REG_BP, X86_REG_BPL, X86_REG_BX, X86_REG_CH, X86_REG_CL, X86_REG_CS, X86_REG_CX, X86_REG_DH, X86_REG_DI, X86_REG_DIL, X86_REG_DL, X86_REG_DS, X86_REG_DX, X86_REG_EAX, X86_REG_EBP, X86_REG_EBX, X86_REG_ECX, X86_REG_EDI, X86_REG_EDX, X86_REG_EIP, X86_REG_EIZ, X86_REG_ES, X86_REG_ESI, X86_REG_ESP, X86_REG_FPSW, X86_REG_FS, X86_REG_GS, X86_REG_IP, X86_REG_RAX, X86_REG_RBP, X86_REG_RBX, X86_REG_RCX, X86_REG_RDI, X86_REG_RDX, X86_REG_RIP, X86_REG_RIZ, X86_REG_RSI, X86_REG_RSP, X86_REG_SI, X86_REG_SIL, X86_REG_SP, X86_REG_SPL, X86_REG_SS, X86_REG_CR0, X86_REG_CR1, X86_REG_CR2, X86_REG_CR3, X86_REG_CR4, X86_REG_CR5, X86_REG_CR6, X86_REG_CR7, X86_REG_CR8, X86_REG_CR9, X86_REG_CR10, X86_REG_CR11, X86_REG_CR12, X86_REG_CR13, X86_REG_CR14, X86_REG_CR15, X86_REG_DR0, X86_REG_DR1, X86_REG_DR2, X86_REG_DR3, X86_REG_DR4, X86_REG_DR5, X86_REG_DR6, X86_REG_DR7, X86_REG_DR8, X86_REG_DR9, X86_REG_DR10, X86_REG_DR11, X86_REG_DR12, X86_REG_DR13, X86_REG_DR14, X86_REG_DR15, X86_REG_FP0, X86_REG_FP1, X86_REG_FP2, X86_REG_FP3, X86_REG_FP4, X86_REG_FP5, X86_REG_FP6, X86_REG_FP7, X86_REG_K0, X86_REG_K1, X86_REG_K2, X86_REG_K3, X86_REG_K4, X86_REG_K5, X86_REG_K6, X86_REG_K7, X86_REG_MM0, X86_REG_MM1, X86_REG_MM2, X86_REG_MM3, X86_REG_MM4, X86_REG_MM5, X86_REG_MM6, X86_REG_MM7, X86_REG_R8, X86_REG_R9, X86_REG_R10, X86_REG_R11, X86_REG_R12, X86_REG_R13, X86_REG_R14, X86_REG_R15, X86_REG_ST0, X86_REG_ST1, X86_REG_ST2, X86_REG_ST3, X86_REG_ST4, X86_REG_ST5, X86_REG_ST6, X86_REG_ST7, X86_REG_XMM0, X86_REG_XMM1, X86_REG_XMM2, X86_REG_XMM3, X86_REG_XMM4, X86_REG_XMM5, X86_REG_XMM6, X86_REG_XMM7, X86_REG_XMM8, X86_REG_XMM9, X86_REG_XMM10, X86_REG_XMM11, X86_REG_XMM12, X86_REG_XMM13, X86_REG_XMM14, X86_REG_XMM15, X86_REG_XMM16, X86_REG_XMM17, X86_REG_XMM18, X86_REG_XMM19, X86_REG_XMM20, X86_REG_XMM21, X86_REG_XMM22, X86_REG_XMM23, X86_REG_XMM24, X86_REG_XMM25, X86_REG_XMM26, X86_REG_XMM27, X86_REG_XMM28, X86_REG_XMM29, X86_REG_XMM30, X86_REG_XMM31, X86_REG_YMM0, X86_REG_YMM1, X86_REG_YMM2, X86_REG_YMM3, X86_REG_YMM4, X86_REG_YMM5, X86_REG_YMM6, X86_REG_YMM7, X86_REG_YMM8, X86_REG_YMM9, X86_REG_YMM10, X86_REG_YMM11, X86_REG_YMM12, X86_REG_YMM13, X86_REG_YMM14, X86_REG_YMM15, X86_REG_YMM16, X86_REG_YMM17, X86_REG_YMM18, X86_REG_YMM19, X86_REG_YMM20, X86_REG_YMM21, X86_REG_YMM22, X86_REG_YMM23, X86_REG_YMM24, X86_REG_YMM25, X86_REG_YMM26, X86_REG_YMM27, X86_REG_YMM28, X86_REG_YMM29, X86_REG_YMM30, X86_REG_YMM31, X86_REG_ZMM0, X86_REG_ZMM1, X86_REG_ZMM2, X86_REG_ZMM3, X86_REG_ZMM4, X86_REG_ZMM5, X86_REG_ZMM6, X86_REG_ZMM7, X86_REG_ZMM8, X86_REG_ZMM9, X86_REG_ZMM10, X86_REG_ZMM11, X86_REG_ZMM12, X86_REG_ZMM13, X86_REG_ZMM14, X86_REG_ZMM15, X86_REG_ZMM16, X86_REG_ZMM17, X86_REG_ZMM18, X86_REG_ZMM19, X86_REG_ZMM20, X86_REG_ZMM21, X86_REG_ZMM22, X86_REG_ZMM23, X86_REG_ZMM24, X86_REG_ZMM25, X86_REG_ZMM26, X86_REG_ZMM27, X86_REG_ZMM28, X86_REG_ZMM29, X86_REG_ZMM30, X86_REG_ZMM31, X86_REG_R8B, X86_REG_R9B, X86_REG_R10B, X86_REG_R11B, X86_REG_R12B, X86_REG_R13B, X86_REG_R14B, X86_REG_R15B, X86_REG_R8D, X86_REG_R9D, X86_REG_R10D, X86_REG_R11D, X86_REG_R12D, X86_REG_R13D, X86_REG_R14D, X86_REG_R15D, X86_REG_R8W, X86_REG_R9W, X86_REG_R10W, X86_REG_R11W, X86_REG_R12W, X86_REG_R13W, X86_REG_R14W, X86_REG_R15W, X86_REG_BND0, X86_REG_BND1, X86_REG_BND2, X86_REG_BND3, }; out_flags.back() = { x86_flag::AF, x86_flag::CF, x86_flag::SF, x86_flag::ZF, x86_flag::PF, x86_flag::OF, x86_flag::TF, x86_flag::IF, x86_flag::DF, x86_flag::NT, x86_flag::RF }; out_fpuflags.back() = { x86_fpuflag::C0, x86_fpuflag::C1, x86_fpuflag::C2, x86_fpuflag::C3 }; // in 和 out 需要根据 use 和 def，使用 活跃变量数据流方程 进行求解 for (size_t i = 0; i < mbb.size(); i++) { size_t j = (mbb.size() - 1) - i; // 倒序索引 (因为活性变量分析本身就是从后往前分析的) std::vector<uint16_t> tem = my_set_diff(out[j], def[j]); in[j] = my_set_union(use[j], tem); // 计算 in std::vector<x86_flag> tem_flag = my_set_diff(out_flags[j], def_flags[j]); in_flags[j] = my_set_union(use_flags[j], tem_flag); // 计算 in_flags std::vector<x86_fpuflag> tem_fpuflag = my_set_diff(out_fpuflags[j], def_fpuflags[j]); in_fpuflags[j] = my_set_union(use_fpuflags[j], tem_fpuflag); // 计算 in_fpuflags if (j != 0) { out[j - 1] = in[j]; // 计算 out out_flags[j - 1] = in_flags[j]; // 计算 out_flags out_fpuflags[j - 1] = in_fpuflags[j]; // 计算 out_fpuflags } } for (size_t i = 0; i < mbb.size(); i++) { if (def[i].empty() && def_flags[i].empty() && def_fpuflags[i].empty()) { // 如果def为空集，则直接跳过 continue; } if (delList[i]) { // 如果此前已经被标记过垃圾指令，则跳过 continue; } if (my_set_intersection(def[i], out[i]).empty() && my_set_intersection(def_flags[i], out_flags[i]).empty() && my_set_intersection(def_fpuflags[i], out_fpuflags[i]).empty()) { // 判断 mbb[i] 是否为垃圾指令 changed = true; // 准备进行新一轮迭代 delList[i] = true; // 标记垃圾指令 } } } while (changed); // 最终优化展示 for (size_t i = 0; i < mbb.size(); i++) { if (delList[i]) { std::cout << "| ---->"; // 可被删除的 } else { std::cout << "| "; } std::cout << std::hex << std::uppercase; std::cout << "\t0x" << mbb[i].viraddr << "\t\t" << mbb[i].opstr << std::endl; } std::cout << "--------------------------------------------------------@@@"; std::cout << std::endl << std::endl; } cs_close(&hCs);}int main() { /* mov eax, 5 * mov ebx, 10 * add eax, ebx * mov ecx, 20 * mov edx, 30 * add eax, ebx * mov edx, 10 * int3 --------------> int3只是方便拿来划分基本块用的 * stc * clc * cld * std */ char x86code[] = "\xB8\x05\x00\x00\x00\xBB\x10\x00\x00\x00\x01\xD8\xB9\x20\x00\x00\x00\xBA\x30\x00\x00\x00\x01\xD8\xBA\x10\x00\x00\x00\xCC\xF9\xF8\xFC\xFD"; bool is64 = false; uint64_t virtualAddressBegin = 0x00000000; RemoveDeadCode(x86code, sizeof(x86code) - 1, is64, virtualAddressBegin); return 0;}std::vector<x86_flag> calc_eflags_use(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t eflags = cdetail.x86.eflags; std::vector<x86_flag> ret = {}; // TEST: Instruction tests flag std::vector<uint64_t> useChecks = { X86_EFLAGS_TEST_OF, X86_EFLAGS_TEST_SF, X86_EFLAGS_TEST_ZF, X86_EFLAGS_TEST_PF, X86_EFLAGS_TEST_CF, X86_EFLAGS_TEST_NT, X86_EFLAGS_TEST_DF, X86_EFLAGS_TEST_RF, X86_EFLAGS_TEST_IF, X86_EFLAGS_TEST_TF, X86_EFLAGS_TEST_AF }; for (uint64_t check : useChecks) { if (eflags & check) { x86_flag ret_flag; switch (check){ case X86_EFLAGS_TEST_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_TEST_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_TEST_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_TEST_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_TEST_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_TEST_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_TEST_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_TEST_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_TEST_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_TEST_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_TEST_AF: ret_flag = x86_flag::AF; break; } ret.push_back(ret_flag); } } return ret;}std::vector<x86_flag> calc_eflags_def(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t eflags = cdetail.x86.eflags; std::vector<x86_flag> ret = {}; // MODIFY: Instruction modifies flag (either sets or resets depending on operands). // PRIOR: Instruction restores prior value of flag // SET: Instruction sets flag // RESET: Instruction resets flag std::vector<uint64_t> defChecks = { X86_EFLAGS_PRIOR_OF, X86_EFLAGS_PRIOR_SF, X86_EFLAGS_PRIOR_ZF, X86_EFLAGS_PRIOR_AF, X86_EFLAGS_PRIOR_PF, X86_EFLAGS_PRIOR_CF, X86_EFLAGS_PRIOR_TF, X86_EFLAGS_PRIOR_IF, X86_EFLAGS_PRIOR_DF, X86_EFLAGS_PRIOR_NT, X86_EFLAGS_MODIFY_AF, X86_EFLAGS_MODIFY_CF, X86_EFLAGS_MODIFY_SF, X86_EFLAGS_MODIFY_ZF, X86_EFLAGS_MODIFY_PF, X86_EFLAGS_MODIFY_OF, X86_EFLAGS_MODIFY_TF, X86_EFLAGS_MODIFY_IF, X86_EFLAGS_MODIFY_DF, X86_EFLAGS_MODIFY_NT, X86_EFLAGS_MODIFY_RF, X86_EFLAGS_SET_CF, X86_EFLAGS_SET_DF, X86_EFLAGS_SET_IF, X86_EFLAGS_SET_OF, X86_EFLAGS_SET_SF, X86_EFLAGS_SET_ZF, X86_EFLAGS_SET_AF, X86_EFLAGS_SET_PF, X86_EFLAGS_RESET_OF, X86_EFLAGS_RESET_CF, X86_EFLAGS_RESET_DF, X86_EFLAGS_RESET_IF, X86_EFLAGS_RESET_SF, X86_EFLAGS_RESET_AF, X86_EFLAGS_RESET_TF, X86_EFLAGS_RESET_NT, X86_EFLAGS_RESET_PF, X86_EFLAGS_RESET_RF, X86_EFLAGS_RESET_ZF }; for (uint64_t check : defChecks) { if (eflags & check) { x86_flag ret_flag; switch (check) { case X86_EFLAGS_MODIFY_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_MODIFY_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_MODIFY_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_MODIFY_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_MODIFY_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_MODIFY_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_MODIFY_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_MODIFY_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_MODIFY_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_MODIFY_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_MODIFY_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_PRIOR_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_PRIOR_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_PRIOR_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_PRIOR_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_PRIOR_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_PRIOR_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_PRIOR_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_PRIOR_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_PRIOR_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_PRIOR_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_SET_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_SET_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_SET_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_SET_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_SET_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_SET_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_SET_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_SET_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_RESET_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_RESET_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_RESET_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_RESET_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_RESET_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_RESET_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_RESET_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_RESET_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_RESET_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_RESET_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_RESET_ZF: ret_flag = x86_flag::ZF; break; } ret.push_back(ret_flag); } } return ret;}std::vector<x86_fpuflag> calc_fpuflags_use(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t fpuflags = cdetail.x86.fpu_flags; std::vector<x86_fpuflag> ret = {}; std::vector<uint32_t> useChecks = { X86_FPU_FLAGS_TEST_C0, X86_FPU_FLAGS_TEST_C1, X86_FPU_FLAGS_TEST_C2, X86_FPU_FLAGS_TEST_C3 }; for (uint32_t check : useChecks) { if (fpuflags & check) { x86_fpuflag ret_flag; switch (check) { case X86_FPU_FLAGS_TEST_C0: ret_flag = x86_fpuflag::C0; break; case X86_FPU_FLAGS_TEST_C1: ret_flag = x86_fpuflag::C1; break; case X86_FPU_FLAGS_TEST_C2: ret_flag = x86_fpuflag::C2; break; case X86_FPU_FLAGS_TEST_C3: ret_flag = x86_fpuflag::C3; break; } ret.push_back(ret_flag); } } return ret;}std::vector<x86_fpuflag> calc_fpuflags_def(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t fpuflags = cdetail.x86.fpu_flags; std::vector<x86_fpuflag> ret = {}; std::vector<uint32_t> defChecks = { X86_FPU_FLAGS_MODIFY_C0, X86_FPU_FLAGS_MODIFY_C1, X86_FPU_FLAGS_MODIFY_C2, X86_FPU_FLAGS_MODIFY_C3, X86_FPU_FLAGS_RESET_C0, X86_FPU_FLAGS_RESET_C1, X86_FPU_FLAGS_RESET_C2, X86_FPU_FLAGS_RESET_C3, X86_FPU_FLAGS_SET_C0, X86_FPU_FLAGS_SET_C1, X86_FPU_FLAGS_SET_C2, X86_FPU_FLAGS_SET_C3 }; for (uint32_t check : defChecks) { if (fpuflags & check) { x86_fpuflag ret_flag; switch (check) { case X86_FPU_FLAGS_MODIFY_C0: ret_flag = x86_fpuflag::C0; break; case X86_FPU_FLAGS_MODIFY_C1: ret_flag = x86_fpuflag::C1; break; case X86_FPU_FLAGS_MODIFY_C2: ret_flag = x86_fpuflag::C2; break; case X86_FPU_FLAGS_MODIFY_C3: ret_flag = x86_fpuflag::C3; break; case X86_FPU_FLAGS_RESET_C0: ret_flag = x86_fpuflag::C0; break; case X86_FPU_FLAGS_RESET_C1: ret_flag = x86_fpuflag::C1; break; case X86_FPU_FLAGS_RESET_C2: ret_flag = x86_fpuflag::C2; break; case X86_FPU_FLAGS_RESET_C3: ret_flag = x86_fpuflag::C3; break; case X86_FPU_FLAGS_SET_C0: ret_flag = x86_fpuflag::C0; break; case X86_FPU_FLAGS_SET_C1: ret_flag = x86_fpuflag::C1; break; case X86_FPU_FLAGS_SET_C2: ret_flag = x86_fpuflag::C2; break; case X86_FPU_FLAGS_SET_C3: ret_flag = x86_fpuflag::C3; break; } ret.push_back(ret_flag); } } return ret;} |
运行结果图：
关于 EFlags
对于eflags，capstone是写了一堆宏，然后让我们自行与detail->x86.eflags来判断，所以...只好自己写了各个标志位的enum
1 | enum class x86_flag : uint8_t { AF, CF, SF, ZF, PF, OF, TF, IF, DF, NT, RF }; |
然后intel规定一条指令对eflags的影响有7种形式，分别是：（来自Volume 1 -> Appendix A EFLAGES Cross-Reference）
- T Instruction tests flag.
- M Instruction modifies flag (either sets or resets depending on operands).
- 0 Instruction resets flag.
- 1 Instruction sets flag.
- — Instruction's effect on flag is undefined.
- R Instruction restores prior value of flag.
- Blank Instruction does not affect flag.
按照其内容，我将T归为了 use
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | std::vector<x86_flag> calc_eflags_use(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t eflags = cdetail.x86.eflags; std::vector<x86_flag> ret = {}; // TEST: Instruction tests flag std::vector<uint64_t> useChecks = { X86_EFLAGS_TEST_OF, X86_EFLAGS_TEST_SF, X86_EFLAGS_TEST_ZF, X86_EFLAGS_TEST_PF, X86_EFLAGS_TEST_CF, X86_EFLAGS_TEST_NT, X86_EFLAGS_TEST_DF, X86_EFLAGS_TEST_RF, X86_EFLAGS_TEST_IF, X86_EFLAGS_TEST_TF, X86_EFLAGS_TEST_AF }; for (uint64_t check : useChecks) { if (eflags & check) { x86_flag ret_flag; switch (check){ case X86_EFLAGS_TEST_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_TEST_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_TEST_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_TEST_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_TEST_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_TEST_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_TEST_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_TEST_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_TEST_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_TEST_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_TEST_AF: ret_flag = x86_flag::AF; break; } ret.push_back(ret_flag); } } return ret;} |
而对于M、R、1、0，我则将它们 归为了 def
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | std::vector<x86_flag> calc_eflags_def(csh hCs, const Insn& ins) { cs_insn cinsn{}; cs_detail cdetail{}; disasm(hCs, ins.addr, ins.viraddr, ins.size, &cinsn, &cdetail); uint64_t eflags = cdetail.x86.eflags; std::vector<x86_flag> ret = {}; // MODIFY: Instruction modifies flag (either sets or resets depending on operands). // PRIOR: Instruction restores prior value of flag // SET: Instruction sets flag // RESET: Instruction resets flag std::vector<uint64_t> defChecks = { X86_EFLAGS_PRIOR_OF, X86_EFLAGS_PRIOR_SF, X86_EFLAGS_PRIOR_ZF, X86_EFLAGS_PRIOR_AF, X86_EFLAGS_PRIOR_PF, X86_EFLAGS_PRIOR_CF, X86_EFLAGS_PRIOR_TF, X86_EFLAGS_PRIOR_IF, X86_EFLAGS_PRIOR_DF, X86_EFLAGS_PRIOR_NT, X86_EFLAGS_MODIFY_AF, X86_EFLAGS_MODIFY_CF, X86_EFLAGS_MODIFY_SF, X86_EFLAGS_MODIFY_ZF, X86_EFLAGS_MODIFY_PF, X86_EFLAGS_MODIFY_OF, X86_EFLAGS_MODIFY_TF, X86_EFLAGS_MODIFY_IF, X86_EFLAGS_MODIFY_DF, X86_EFLAGS_MODIFY_NT, X86_EFLAGS_MODIFY_RF, X86_EFLAGS_SET_CF, X86_EFLAGS_SET_DF, X86_EFLAGS_SET_IF, X86_EFLAGS_SET_OF, X86_EFLAGS_SET_SF, X86_EFLAGS_SET_ZF, X86_EFLAGS_SET_AF, X86_EFLAGS_SET_PF, X86_EFLAGS_RESET_OF, X86_EFLAGS_RESET_CF, X86_EFLAGS_RESET_DF, X86_EFLAGS_RESET_IF, X86_EFLAGS_RESET_SF, X86_EFLAGS_RESET_AF, X86_EFLAGS_RESET_TF, X86_EFLAGS_RESET_NT, X86_EFLAGS_RESET_PF, X86_EFLAGS_RESET_RF, X86_EFLAGS_RESET_ZF }; for (uint64_t check : defChecks) { if (eflags & check) { x86_flag ret_flag; switch (check) { case X86_EFLAGS_MODIFY_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_MODIFY_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_MODIFY_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_MODIFY_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_MODIFY_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_MODIFY_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_MODIFY_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_MODIFY_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_MODIFY_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_MODIFY_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_MODIFY_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_PRIOR_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_PRIOR_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_PRIOR_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_PRIOR_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_PRIOR_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_PRIOR_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_PRIOR_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_PRIOR_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_PRIOR_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_PRIOR_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_SET_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_SET_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_SET_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_SET_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_SET_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_SET_ZF: ret_flag = x86_flag::ZF; break; case X86_EFLAGS_SET_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_SET_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_RESET_OF: ret_flag = x86_flag::OF; break; case X86_EFLAGS_RESET_CF: ret_flag = x86_flag::CF; break; case X86_EFLAGS_RESET_DF: ret_flag = x86_flag::DF; break; case X86_EFLAGS_RESET_IF: ret_flag = x86_flag::IF; break; case X86_EFLAGS_RESET_SF: ret_flag = x86_flag::SF; break; case X86_EFLAGS_RESET_AF: ret_flag = x86_flag::AF; break; case X86_EFLAGS_RESET_TF: ret_flag = x86_flag::TF; break; case X86_EFLAGS_RESET_NT: ret_flag = x86_flag::NT; break; case X86_EFLAGS_RESET_PF: ret_flag = x86_flag::PF; break; case X86_EFLAGS_RESET_RF: ret_flag = x86_flag::RF; break; case X86_EFLAGS_RESET_ZF: ret_flag = x86_flag::ZF; break; } ret.push_back(ret_flag); } } return ret;} |
紧接类似地，用这些去创建eflags的use、def、in、out集合，和寄存器一样的流程去解析它们的use、def，去计算它们的in、out；最后再和寄存器的def/out的交集结果用&&连起来判断就可以了
1 2 3 4 5 6 | if (my_set_intersection(def[i], out[i]).empty() && my_set_intersection(def_flags[i], out_flags[i]).empty() && my_set_intersection(def_fpuflags[i], out_fpuflags[i]).empty()) { // 判断 mbb[i] 是否为垃圾指令 changed = true; // 准备进行新一轮迭代 delList[i] = true; // 标记垃圾指令} |
关于 fpu flags
这是只是我顺手写的，为了保证最大兼容性，写一下这个应该也无妨
参考
【利用活跃变量分析来去掉vmp的大部分垃圾指令】 https://bbs.kanxue.com/thread-265950.htm
【C++利用活跃变量分析清除基本块中的垃圾指令】
https://bbs.kanxue.com/thread-277825.htm
【中南大学 编译原理 - 课时42: 数据流分析(2) 】
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最后于 2025-1-20 08:51
被LingMo0412编辑
，原因：
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