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商硕/afl-gcc.c

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+/*
+  Copyright 2013 Google LLC All rights reserved.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at:
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+*/
+
+// 这部分是版权声明和许可证信息，说明这个文件是在Apache License 2.0下发布的。
+
+/*
+   american fuzzy lop - wrapper for GCC and clang
+   ----------------------------------------------
+
+   Written and maintained by Michal Zalewski <lcamtuf@google.com>
+
+   This program is a drop-in replacement for GCC or clang. The most common way
+   of using it is to pass the path to afl-gcc or afl-clang via CC when invoking
+   ./configure.
+
+   (Of course, use CXX and point it to afl-g++ / afl-clang++ for C++ code.)
+
+   The wrapper needs to know the path to afl-as (renamed to 'as'). The default
+   is /usr/local/lib/afl/. A convenient way to specify alternative directories
+   would be to set AFL_PATH.
+
+   If AFL_HARDEN is set, the wrapper will compile the target app with various
+   hardening options that may help detect memory management issues more
+   reliably. You can also specify AFL_USE_ASAN to enable ASAN.
+
+   If you want to call a non-default compiler as a next step of the chain,
+   specify its location via AFL_CC or AFL_CXX.
+
+*/
+// 这部分是注释，提供了关于这个程序的概述和使用说明。
+#define AFL_MAIN
+
+#include "config.h"
+#include "types.h"
+#include "debug.h"
+#include "alloc-inl.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+// 这些是包含的头文件，其中一些是AFL自己的头文件，其他的是C标准库的头文件
+
+static u8*  as_path;                /* Path to the AFL 'as' wrapper      */
+static u8** cc_params;              /* Parameters passed to the real CC  */
+static u32  cc_par_cnt = 1;         /* Param count, including argv0      */
+static u8   be_quiet,               /* Quiet mode                        */
+            clang_mode;             /* Invoked as afl-clang*?            */
+
+
+// 这些是全局变量声明。`as_path`存储AFL汇编器的路径，`cc_params`存储传递给实际编译器的参数，`cc_par_cnt`是参数计数器，`be_quiet`用于控制
+// 是否静默模式，`clang_mode`指示是否以`afl-clang`或`afl-clang++`模式调用。
+
+/* Try to find our "fake" GNU assembler in AFL_PATH or at the location derived
+   from argv[0]. If that fails, abort. */
+
+static void find_as(u8* argv0) {
+// 这个函数尝试在AFL_PATH环境变量指定的路径或从argv[0]派生的路径中找到AFL的“假”GNU汇编器。如果找不到，程序将终止。
+  u8 *afl_path = getenv("AFL_PATH");
+  u8 *slash, *tmp;
+
+  if (afl_path) {
+
+    tmp = alloc_printf("%s/as", afl_path);
+
+    if (!access(tmp, X_OK)) {
+      as_path = afl_path;
+      ck_free(tmp);
+      return;
+    }
+
+    ck_free(tmp);
+
+  }
+
+  slash = strrchr(argv0, '/');
+
+  if (slash) {
+
+    u8 *dir;
+
+    *slash = 0;
+    dir = ck_strdup(argv0);
+    *slash = '/';
+
+    tmp = alloc_printf("%s/afl-as", dir);
+
+    if (!access(tmp, X_OK)) {
+      as_path = dir;
+      ck_free(tmp);
+      return;
+    }
+
+    ck_free(tmp);
+    ck_free(dir);
+
+  }
+
+  if (!access(AFL_PATH "/as", X_OK)) {
+    as_path = AFL_PATH;
+    return;
+  }
+
+  FATAL("Unable to find AFL wrapper binary for 'as'. Please set AFL_PATH");
+ 
+}
+
+
+/* Copy argv to cc_params, making the necessary edits. */
+
+static void edit_params(u32 argc, char** argv) {
+  //定义了一个函数edit_params，它接受两个参数：argc是参数的数量，argv是参数的数组。
+
+  u8 fortify_set = 0, asan_set = 0;//声明两个变量fortify_set和asan_set，用于跟踪是否已经设置了FORTIFY_SOURCE和address sanitizer（ASan）标志
+  u8 *name;//用于存储程序的名称
+
+#if defined(__FreeBSD__) && defined(__x86_64__)
+  u8 m32_set = 0;
+#endif
+
+  cc_params = ck_alloc((argc + 128) * sizeof(u8*));//分配内存以存储修改后的参数列表，大小为argc + 128个u8*类型的指针。
+
+  name = strrchr(argv[0], '/');//找到argv[0]（程序的路径）中最后一个'/'字符，这通常用于获取程序的名称。
+  if (!name) name = argv[0]; else name++;//如果name为NULL（即argv[0]中没有'/'），则name指向argv[0]的开始。否则，name向前移动一个字符，跳过'/'。
+
+  if (!strncmp(name, "afl-clang", 9)) {
+
+    clang_mode = 1;//检查程序名称是否以"afl-clang"开头，如果是，设置clang_mode标志为1
+
+    setenv(CLANG_ENV_VAR, "1", 1);//设置环境变量CLANG_ENV_VAR为"1"，这可能用于通知其他部分的AFL工具链正在使用Clang。
+
+    if (!strcmp(name, "afl-clang++")) {
+      u8* alt_cxx = getenv("AFL_CXX");
+      cc_params[0] = alt_cxx ? alt_cxx : (u8*)"clang++";//如果AFL_CXX设置，将其值作为第一个参数；否则，使用"clang++"。
+    } else {
+      u8* alt_cc = getenv("AFL_CC");
+      cc_params[0] = alt_cc ? alt_cc : (u8*)"clang";//否则尝试获取环境变量AFL_CC的值。
+    }
+
+  } else {
+
+    /* With GCJ and Eclipse installed, you can actually compile Java! The
+       instrumentation will work (amazingly). Alas, unhandled exceptions do
+       not call abort(), so afl-fuzz would need to be modified to equate
+       non-zero exit codes with crash conditions when working with Java
+       binaries. Meh. */
+
+#ifdef __APPLE__
+    //在Apple系统上，根据程序名称设置不同的编译器。如果AFL_CXX、AFL_GCJ或AFL_CC环境变量设置，使用它们的值；否则，使用默认的编译器名称
+    if (!strcmp(name, "afl-g++")) cc_params[0] = getenv("AFL_CXX");
+    else if (!strcmp(name, "afl-gcj")) cc_params[0] = getenv("AFL_GCJ");
+    else cc_params[0] = getenv("AFL_CC");
+
+    if (!cc_params[0]) {
+      //输出错误信息，指出在MacOS X上需要设置AFL_CC或AFL_CXX环境变量。
+      SAYF("\n" cLRD "[-] " cRST
+           "On Apple systems, 'gcc' is usually just a wrapper for clang. Please use the\n"
+           "    'afl-clang' utility instead of 'afl-gcc'. If you really have GCC installed,\n"
+           "    set AFL_CC or AFL_CXX to specify the correct path to that compiler.\n");
+
+      FATAL("AFL_CC or AFL_CXX required on MacOS X");
+
+    }
+
+#else
+    //对于非Apple系统，根据程序名称设置不同的编译器。如果相应的环境变量设置，使用它们的值；否则，使用默认的编译器名称。
+    if (!strcmp(name, "afl-g++")) {
+      u8* alt_cxx = getenv("AFL_CXX");
+      cc_params[0] = alt_cxx ? alt_cxx : (u8*)"g++";
+    } else if (!strcmp(name, "afl-gcj")) {
+      u8* alt_cc = getenv("AFL_GCJ");
+      cc_params[0] = alt_cc ? alt_cc : (u8*)"gcj";
+    } else {
+      u8* alt_cc = getenv("AFL_CC");
+      cc_params[0] = alt_cc ? alt_cc : (u8*)"gcc";
+    }
+
+#endif /* __APPLE__ */
+
+  }
+
+  while (--argc) {
+    u8* cur = *(++argv);
+
+    if (!strncmp(cur, "-B", 2)) {//如果当前参数以"-B"开头，输出警告信息，并跳过后续参数（如果当前参数后面紧跟着的是编译器的路径）。
+
+      if (!be_quiet) WARNF("-B is already set, overriding");//如果程序不在静默模式，输出警告信息。
+
+      if (!cur[2] && argc > 1) { argc--; argv++; }//如果-B后面紧跟着的是编译器的路径，跳过这个路径。
+      continue;
+
+    }
+
+    if (!strcmp(cur, "-integrated-as")) continue;//如果参数是"-integrated-as"，跳过它。
+
+    if (!strcmp(cur, "-pipe")) continue;//如果参数是"-pipe"，跳过它。
+
+#if defined(__FreeBSD__) && defined(__x86_64__)
+    if (!strcmp(cur, "-m32")) m32_set = 1;
+#endif
+
+    if (!strcmp(cur, "-fsanitize=address") ||
+        !strcmp(cur, "-fsanitize=memory")) asan_set = 1;//如果参数是"-fsanitize=address"或"-fsanitize=memory"，设置asan_set标志。
+
+    if (strstr(cur, "FORTIFY_SOURCE")) fortify_set = 1;//如果参数包含"FORTIFY_SOURCE"，设置fortify_set标志。
+
+    cc_params[cc_par_cnt++] = cur;
+
+  }
+
+  cc_params[cc_par_cnt++] = "-B";
+  cc_params[cc_par_cnt++] = as_path;
+  //向参数列表中添加"-B"和AFL汇编器的路径。
+
+
+  if (clang_mode)
+    cc_params[cc_par_cnt++] = "-no-integrated-as";//如果clang_mode标志设置，向参数列表中添加`"-no-integrated-as"
+
+  if (getenv("AFL_HARDEN")) {
+
+    cc_params[cc_par_cnt++] = "-fstack-protector-all";
+
+    if (!fortify_set)
+      cc_params[cc_par_cnt++] = "-D_FORTIFY_SOURCE=2";
+
+  }
+
+  if (asan_set) {//检查是否设置了asan_set标志。
+
+    /* Pass this on to afl-as to adjust map density. */
+
+    setenv("AFL_USE_ASAN", "1", 1);//如果设置，设置环境变量AFL_USE_ASAN为"1"
+
+  } else if (getenv("AFL_USE_ASAN")) {//如果asan_set标志未设置，但设置了环境变量AFL_USE_ASAN。
+
+    if (getenv("AFL_USE_MSAN"))
+      FATAL("ASAN and MSAN are mutually exclusive");//如果同时设置了AFL_USE_MSAN，输出错误信息并终止程序。
+
+    if (getenv("AFL_HARDEN"))
+      FATAL("ASAN and AFL_HARDEN are mutually exclusive");//如果同时设置了AFL_HARDEN，输出错误信息并终止程序。
+
+    cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
+    cc_params[cc_par_cnt++] = "-fsanitize=address";//向参数列表中添加"-U_FORTIFY_SOURCE"和"-fsanitize=address"。
+
+  } else if (getenv("AFL_USE_MSAN")) {
+
+    if (getenv("AFL_USE_ASAN"))
+      FATAL("ASAN and MSAN are mutually exclusive");//如果同时设置了AFL_USE_ASAN，输出错误信息并终止程序。
+
+    if (getenv("AFL_HARDEN"))
+      FATAL("MSAN and AFL_HARDEN are mutually exclusive");//如果同时设置了AFL_HARDEN，输出错误信息并终止程序。
+
+    cc_params[cc_par_cnt++] = "-U_FORTIFY_SOURCE";
+    cc_params[cc_par_cnt++] = "-fsanitize=memory";//向参数列表中添加"-U_FORTIFY_SOURCE"和"-fsanitize=memory"。
+
+
+  }
+
+  if (!getenv("AFL_DONT_OPTIMIZE")) {//检查是否设置了环境变量AFL_DONT_OPTIMIZE。
+
+#if defined(__FreeBSD__) && defined(__x86_64__)
+
+    /* On 64-bit FreeBSD systems, clang -g -m32 is broken, but -m32 itself
+       works OK. This has nothing to do with us, but let's avoid triggering
+       that bug. */
+
+    if (!clang_mode || !m32_set)
+      cc_params[cc_par_cnt++] = "-g";//如果不是Clang模式或没有设置m32_set标志，向参数列表中添加"-g"。
+
+#else
+
+      cc_params[cc_par_cnt++] = "-g";
+
+#endif//结束#if defined(__FreeBSD__) && defined(__x86_64__)条件编译块。
+
+    cc_params[cc_par_cnt++] = "-O3";
+    cc_params[cc_par_cnt++] = "-funroll-loops";//向参数列表中添加"-O3"和"-funroll-loops"，这些是优化选项。
+
+    /* Two indicators that you're building for fuzzing; one of them is
+       AFL-specific, the other is shared with libfuzzer. */
+
+    cc_params[cc_par_cnt++] = "-D__AFL_COMPILER=1";
+    cc_params[cc_par_cnt++] = "-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION=1";
+    //向参数列表中添加两个宏定义，这些宏定义指示编译器代码将用于模糊测试。
+
+  }
+
+  if (getenv("AFL_NO_BUILTIN")) {
+
+    cc_params[cc_par_cnt++] = "-fno-builtin-strcmp";
+    cc_params[cc_par_cnt++] = "-fno-builtin-strncmp";
+    cc_params[cc_par_cnt++] = "-fno-builtin-strcasecmp";
+    cc_params[cc_par_cnt++] = "-fno-builtin-strncasecmp";
+    cc_params[cc_par_cnt++] = "-fno-builtin-memcmp";
+    cc_params[cc_par_cnt++] = "-fno-builtin-strstr";
+    cc_params[cc_par_cnt++] = "-fno-builtin-strcasestr";
+    //如果设置，向参数列表中添加一系列"-fno-builtin-*"选项，这些选项禁用编译器的内置函数。
+  }
+
+  cc_params[cc_par_cnt] = NULL;
+
+}
+
+
+/* Main entry point */
+//最后是函数结束语，结束函数定义。
+int main(int argc, char** argv) {
+
+  if (isatty(2) && !getenv("AFL_QUIET")) {
+
+    SAYF(cCYA "afl-cc " cBRI VERSION cRST " by <lcamtuf@google.com>\n");
+
+  } else be_quiet = 1;
+
+  if (argc < 2) {
+
+    SAYF("\n"
+         "This is a helper application for afl-fuzz. It serves as a drop-in replacement\n"
+         "for gcc or clang, letting you recompile third-party code with the required\n"
+         "runtime instrumentation. A common use pattern would be one of the following:\n\n"
+
+         "  CC=%s/afl-gcc ./configure\n"
+         "  CXX=%s/afl-g++ ./configure\n\n"
+
+         "You can specify custom next-stage toolchain via AFL_CC, AFL_CXX, and AFL_AS.\n"
+         "Setting AFL_HARDEN enables hardening optimizations in the compiled code.\n\n",
+         BIN_PATH, BIN_PATH);
+
+    exit(1);
+
+  }
+
+  find_as(argv[0]);
+
+  edit_params(argc, argv);
+
+  execvp(cc_params[0], (char**)cc_params);
+
+  FATAL("Oops, failed to execute '%s' - check your PATH", cc_params[0]);
+
+  return 0;
+
+}