afl-as.h

对 afl-as.h 的分析。

forkserver mode 示意图

更新日志

2024-10-16：更新部分 main_payload_64 内容

trampoline_fmt_32

static const u8* trampoline_fmt_32 =
 
"\n"
"/* --- AFL TRAMPOLINE (32-BIT) --- */\n"
"\n"
".align 4\n"
"\n"
"leal -16(esp\n"
"movl esp)\n"
"movl esp)\n"
"movl esp)\n"
"movl esp)\n"
"movl $0x%08x, esp), esp), esp), esp), esp), rsp), rdx,  0(rcx,  8(rax, 16(rcx\n"
"call __afl_maybe_log\n"
"movq 16(rax\n"
"movq  8(rcx\n"
"movq  0(rdx\n"
"leaq (128+24)(rsp\n"
"\n"
"/* --- END --- */\n"
"\n";

main_payload_32

static const u8* main_payload_32 = 
 
  "\n"
  "/* --- AFL MAIN PAYLOAD (32-BIT) --- */\n"
  "\n"
  ".text\n"
  ".att_syntax\n"
  ".code32\n"
  ".align 8\n"
  "\n"

`__afl_maybe_log`

  "__afl_maybe_log:\n"
  "\n"
  "  lahf\n"
  "  seto %al\n"
  "\n"
  "  /* Check if SHM region is already mapped. */\n"
  "\n"
  "  movl  __afl_area_ptr, %edx\n"
  "  testl %edx, %edx\n"
  "  je    __afl_setup\n"
  "\n"

使用 lahf（Load AH with Flags）将标志寄存器 eflags 的低八位存储到 ah 寄存器中。

接下来将 __afl_area_ptr 的值移入 edx 寄存器中，如果 edx 寄存器为 0，说明此时已经初始化了共享内存，当前程序位于子进程中，接下来会跳入 [[#__afl_setup|__afl_setup]] 函数中，否则按顺序执行 [[#__afl_store|__afl_store]] 函数。

`__afl_store`

  "__afl_store:\n"
  "\n"
  "  /* Calculate and store hit for the code location specified in ecx. There\n"
  "     is a double-XOR way of doing this without tainting another register,\n"
  "     and we use it on 64-bit systems; but it's slower for 32-bit ones. */\n"
  "\n"
#ifndef COVERAGE_ONLY
  "  movl __afl_prev_loc, %edi\n"
  "  xorl %ecx, %edi\n"
  "  shrl $1, %ecx\n"
  "  movl %ecx, __afl_prev_loc\n"
#else
  "  movl %ecx, %edi\n"
#endif /* ^!COVERAGE_ONLY */
  "\n"
#ifdef SKIP_COUNTS
  "  orb  $1, (%edx, %edi, 1)\n"
#else
  "  incb (%edx, %edi, 1)\n"
#endif /* ^SKIP_COUNTS */
  "\n"

上述代码中，ecx 指的是插桩核心代码中生成的随机数，也就是 R(MAP_SIZE) 的值。__afl_prev_loc 指的是上一个访问的基本块的哈希。

如果未定义 COVERAGE_ONLY 宏：
- 将 __afl_prev_loc 的值移入 edi；
- 将 edi 与 ecx 异或，相当于存储一条路径；
- ecx 逻辑右移；
- 将 ecx 存入 __afl_prev_loc；
如果定义了 COVERAGE_ONLY 宏：
- 直接将 ecx 存入 edi；
如果定义了 SKIP_COUNTS 宏：
- 将 [edx+edi*1] 的值与 1 进行或操作，将结果存回原处，这种说不定很适合服务器的持续运行的情况~；
如果未定义 SKIP_COUNTS 宏：
- 将 [edx+edi*1] 的值加 1。

`__afl_return`

  "__afl_return:\n"
  "\n"
  "  addb $127, %al\n"
  "  sahf\n"
  "  ret\n"
  "\n"
  ".align 8\n"
  "\n"

从插桩代码返回，首先还原 al，再还原 eflags 寄存器，最后返回。

`__afl_setup`

这一段代码主要用于分配共享内存

  "__afl_setup:\n"
  "\n"
  "  /* Do not retry setup if we had previous failures. */\n"
  "\n"
  "  cmpb $0, __afl_setup_failure\n"
  "  jne  __afl_return\n"
  "\n"

如果已经失败了，就直接返回，不再尝试启动；

  "  /* Map SHM, jumping to __afl_setup_abort if something goes wrong.\n"
  "     We do not save FPU/MMX/SSE registers here, but hopefully, nobody\n"
  "     will notice this early in the game. */\n"
  "\n"
  "  pushl %eax\n"
  "  pushl %ecx\n"
  "\n"

保存 eax 和 ecx；

  "  pushl $.AFL_SHM_ENV\n"
  "  call  getenv\n"
  "  addl  $4, %esp\n"
  "\n"
  "  testl %eax, %eax\n"
  "  je    __afl_setup_abort\n"
  "\n"

调用 getenv("AFL_SHM_ENV")，失败的话跳转到 [[#__afl_setup_abort|__afl_setup_abort]]；

  "  pushl %eax\n"
  "  call  atoi\n"
  "  addl  $4, %esp\n"
  "\n"
  "  pushl $0          /* shmat flags    */\n"
  "  pushl $0          /* requested addr */\n"
  "  pushl %eax        /* SHM ID         */\n"
  "  call  shmat\n"
  "  addl  $12, %esp\n"
  "\n"
  "  cmpl $-1, %eax\n"
  "  je   __afl_setup_abort\n"
  "\n"

调用 atoi 函数，将获取到的 AFL_SHM_ENV 值转换为数字；
调用 shmat 函数访问这一段共享内存；
失败的话跳转到 [[#__afl_setup_abort|__afl_setup_abort]]；

  "  /* Store the address of the SHM region. */\n"
  "\n"
  "  movl %eax, __afl_area_ptr\n"
  "  movl %eax, %edx\n"
  "\n"

将获取到的内存地址放入 __afl_area_ptr 和 edx 中；

  "  popl %ecx\n"
  "  popl %eax\n"
  "\n"

恢复 ecx 和 eax；

`__afl_forkserver`

该函数会向 (FORKSRV_FD + 1) 写入四字节数据，这个 (FORKSRV_FD + 1) 就是之前在 init_forkserver 中子进程设置的状态管道：

  "__afl_forkserver:\n"
  "\n"
  "  /* Enter the fork server mode to avoid the overhead of execve() calls. */\n"
  "\n"
  "  pushl %eax\n"
  "  pushl %ecx\n"
  "  pushl %edx\n"
  "\n"
  "  /* Phone home and tell the parent that we're OK. (Note that signals with\n"
  "     no SA_RESTART will mess it up). If this fails, assume that the fd is\n"
  "     closed because we were execve()d from an instrumented binary, or because\n" 
  "     the parent doesn't want to use the fork server. */\n"
  "\n"
  "  pushl $4          /* length    */\n"
  "  pushl $__afl_temp /* data      */\n"
  "  pushl $" STRINGIFY((FORKSRV_FD + 1)) "  /* file desc */\n"
  "  call  write\n"
  "  addl  $12, %esp\n"
  "\n"
  "  cmpl  $4, %eax\n"
  "  jne   __afl_fork_resume\n"
  "\n"

在写入数据后，检查返回值是否为 4，代表是否真的向管道内写入了 4 字节，如果不为 4 字节的话跳转到 [[#__afl_fork_resume|__afl_fork_resume]]，否则继续向下，进入 [[#__afl_fork_wait_loop|__afl_fork_wait_loop]]。

`__afl_fork_wait_loop`

这一段是插桩代码的主逻辑，插桩代码将在此处循环。

  "__afl_fork_wait_loop:\n"
  "\n"
  "  /* Wait for parent by reading from the pipe. Abort if read fails. */\n"
  "\n"
  "  pushl $4          /* length    */\n"
  "  pushl $__afl_temp /* data      */\n"
  "  pushl $" STRINGIFY(FORKSRV_FD) "        /* file desc */\n"
  "  call  read\n"
  "  addl  $12, %esp\n"
  "\n"
  "  cmpl  $4, %eax\n"
  "  jne   __afl_die\n"
  "\n"

首先从控制管道读取 4 字节数据。

  "  /* Once woken up, create a clone of our process. This is an excellent use\n"
  "     case for syscall(__NR_clone, 0, CLONE_PARENT), but glibc boneheadedly\n"
  "     caches getpid() results and offers no way to update the value, breaking\n"
  "     abort(), raise(), and a bunch of other things :-( */\n"
  "\n"
  "  call fork\n"
  "\n"
  "  cmpl $0, %eax\n"
  "  jl   __afl_die\n"
  "  je   __afl_fork_resume\n"
  "\n"

接下来调用 fork，如果调用成功且在子进程，跳转到 [[#__afl_fork_resume|__afl_fork_resume]]，如果是父进程则继续执行；

父进程 forkserver32

  "  /* In parent process: write PID to pipe, then wait for child. */\n"
  "\n"
  "  movl  %eax, __afl_fork_pid\n"
  "\n"

在父进程中，首先将 fork 的返回值，也就是 fork 出的子进程 pid 存放在 __afl_fork_pid 中；

  "  pushl $4              /* length    */\n"
  "  pushl $__afl_fork_pid /* data      */\n"
  "  pushl $" STRINGIFY((FORKSRV_FD + 1)) "      /* file desc */\n"
  "  call  write\n"
  "  addl  $12, %esp\n"
  "\n"

接下来向状态管道发送子进程 pid 信息；

  "  pushl $0             /* no flags  */\n"
  "  pushl $__afl_temp    /* status    */\n"
  "  pushl __afl_fork_pid /* PID       */\n"
  "  call  waitpid\n"
  "  addl  $12, %esp\n"
  "\n"
  "  cmpl  $0, %eax\n"
  "  jle   __afl_die\n"
  "\n"

接下来调用 waitpid(__afl_fork_pid, __afl_temp, 0) 等待子进程发来信号，__afl_temp 会保存子进程的程序状态；

  "  /* Relay wait status to pipe, then loop back. */\n"
  "\n"
  "  pushl $4          /* length    */\n"
  "  pushl $__afl_temp /* data      */\n"
  "  pushl $" STRINGIFY((FORKSRV_FD + 1)) "  /* file desc */\n"
  "  call  write\n"
  "  addl  $12, %esp\n"
  "\n"
  "  jmp __afl_fork_wait_loop\n"
  "\n"

在收到子进程状态后，会向 status 管道发送四字节数据，告知父进程现在处于等待状态，然后跳转到 [[#__afl_fork_wait_loop|__afl_fork_wait_loop]] 函数。

`__afl_fork_resume`

子进程会进入这一段逻辑。这段逻辑会关闭两个管道并恢复现场，跳转到 [[#__afl_store|__afl_store]]。

  "__afl_fork_resume:\n"
  "\n"
  "  /* In child process: close fds, resume execution. */\n"
  "\n"
  "  pushl $" STRINGIFY(FORKSRV_FD) "\n"
  "  call  close\n"
  "\n"
  "  pushl $" STRINGIFY((FORKSRV_FD + 1)) "\n"
  "  call  close\n"
  "\n"
  "  addl  $8, %esp\n"
  "\n"
  "  popl %edx\n"
  "  popl %ecx\n"
  "  popl %eax\n"
  "  jmp  __afl_store\n"
  "\n"

`__afl_die`

  "__afl_die:\n"
  "\n"
  "  xorl %eax, %eax\n"
  "  call _exit\n"
  "\n"

`__afl_setup_abort`

  "__afl_setup_abort:\n"
  "\n"
  "  /* Record setup failure so that we don't keep calling\n"
  "     shmget() / shmat() over and over again. */\n"
  "\n"
  "  incb __afl_setup_failure\n"
  "  popl %ecx\n"
  "  popl %eax\n"
  "  jmp __afl_return\n"
  "\n"
  ".AFL_VARS:\n"
  "\n"
  "  .comm   __afl_area_ptr, 4, 32\n"
  "  .comm   __afl_setup_failure, 1, 32\n"
#ifndef COVERAGE_ONLY
  "  .comm   __afl_prev_loc, 4, 32\n"
#endif /* !COVERAGE_ONLY */
  "  .comm   __afl_fork_pid, 4, 32\n"
  "  .comm   __afl_temp, 4, 32\n"
  "\n"
  ".AFL_SHM_ENV:\n"
  "  .asciz \"" SHM_ENV_VAR "\"\n"
  "\n"
  "/* --- END --- */\n"
  "\n";

main_payload_64

/* The OpenBSD hack is due to lahf and sahf not being recognized by some
   versions of binutils: http://marc.info/?l=openbsd-cvs&m=141636589924400
 
   The Apple code is a bit different when calling libc functions because
   they are doing relocations differently from everybody else. We also need
   to work around the crash issue with .lcomm and the fact that they don't
   recognize .string. */
 
#ifdef __APPLE__
#  define CALL_L64(str)"call _" str "\n"
#else
#  define CALL_L64(str)"call " str "@PLT\n"
#endif /* ^__APPLE__ */
 
static const u8* main_payload_64 = 
 
  "\n"
  "/* --- AFL MAIN PAYLOAD (64-BIT) --- */\n"
  "\n"
  ".text\n"
  ".att_syntax\n"
  ".code64\n"
  ".align 8\n"
  "\n"

`__afl_maybe_log` 64

在 64 位的 main_payload_64 中也会先触发 __afl_maybe_log，先检查是否 map 了共享内存，如果没有的话，跳转到 [[#__afl_setup-64|__afl_setup 64]]，有发话则继续执行 [[#__afl_store-64|__afl_store 64]]。

  "__afl_maybe_log:\n"
  "\n"
#if defined(__OpenBSD__)  || (defined(__FreeBSD__) && (__FreeBSD__ < 9))
  "  .byte 0x9f /* lahf */\n"
#else
  "  lahf\n"
#endif /* ^__OpenBSD__, etc */
  "  seto  %al\n"
  "\n"
  "  /* Check if SHM region is already mapped. */\n"
  "\n"
  "  movq  __afl_area_ptr(%rip), %rdx\n"
  "  testq %rdx, %rdx\n"
  "  je    __afl_setup\n"
  "\n"

`__afl_store` 64

  "__afl_store:\n"
  "\n"
  "  /* Calculate and store hit for the code location specified in rcx. */\n"
  "\n"
#ifndef COVERAGE_ONLY
  "  xorq __afl_prev_loc(%rip), %rcx\n"
  "  xorq %rcx, __afl_prev_loc(%rip)\n"
  "  shrq $1, __afl_prev_loc(%rip)\n"
#endif /* ^!COVERAGE_ONLY */
  "\n"
#ifdef SKIP_COUNTS
  "  orb  $1, (%rdx, %rcx, 1)\n"
#else
  "  incb (%rdx, %rcx, 1)\n"
#endif /* ^SKIP_COUNTS */
  "\n"
  "__afl_return:\n"
  "\n"
  "  addb $127, %al\n"
#if defined(__OpenBSD__)  || (defined(__FreeBSD__) && (__FreeBSD__ < 9))
  "  .byte 0x9e /* sahf */\n"
#else
  "  sahf\n"
#endif /* ^__OpenBSD__, etc */
  "  ret\n"
  "\n"
  ".align 8\n"
  "\n"

`__afl_setup` 64

如果 __afl_setup_failure 不为零，则之前哪里出现了问题，直接退出。

  "__afl_setup:\n"
  "\n"
  "  /* Do not retry setup if we had previous failures. */\n"
  "\n"
  "  cmpb $0, __afl_setup_failure(%rip)\n"
  "  jne __afl_return\n"
  "\n"

这里使用了一个在结尾定义的变量 __afl_global_area_ptr，如果里面有值，则用该值替代 __afl_area_ptr，之后执行 [[#__afl_store-64|__afl_store 64]]。如果没有值，则执行 [[#__afl_setup_first-64|__afl_setup_first 64]]。

  "  /* Check out if we have a global pointer on file. */\n"
  "\n"
#ifndef __APPLE__
  "  movq  __afl_global_area_ptr@GOTPCREL(%rip), %rdx\n"
  "  movq  (%rdx), %rdx\n"
#else
  "  movq  __afl_global_area_ptr(%rip), %rdx\n"
#endif /* !^__APPLE__ */
  "  testq %rdx, %rdx\n"
  "  je    __afl_setup_first\n"
  "\n"
  "  movq %rdx, __afl_area_ptr(%rip)\n"
  "  jmp  __afl_store\n" 
  "\n"

`__afl_setup_first` 64

这里开始初始化共享内存区域。记录一下栈帧偏移。

rsp = -0x160

  "__afl_setup_first:\n"
  "\n"
  "  /* Save everything that is not yet saved and that may be touched by\n"
  "     getenv() and several other libcalls we'll be relying on. */\n"
  "\n"
  "  leaq -352(%rsp), %rsp\n"
  "\n"
  "  movq %rax,   0(%rsp)\n"
  "  movq %rcx,   8(%rsp)\n"
  "  movq %rdi,  16(%rsp)\n"
  "  movq %rsi,  32(%rsp)\n"
  "  movq %r8,   40(%rsp)\n"
  "  movq %r9,   48(%rsp)\n"
  "  movq %r10,  56(%rsp)\n"
  "  movq %r11,  64(%rsp)\n"
  "\n"
  "  movq %xmm0,  96(%rsp)\n"
  "  movq %xmm1,  112(%rsp)\n"
  "  movq %xmm2,  128(%rsp)\n"
  "  movq %xmm3,  144(%rsp)\n"
  "  movq %xmm4,  160(%rsp)\n"
  "  movq %xmm5,  176(%rsp)\n"
  "  movq %xmm6,  192(%rsp)\n"
  "  movq %xmm7,  208(%rsp)\n"
  "  movq %xmm8,  224(%rsp)\n"
  "  movq %xmm9,  240(%rsp)\n"
  "  movq %xmm10, 256(%rsp)\n"
  "  movq %xmm11, 272(%rsp)\n"
  "  movq %xmm12, 288(%rsp)\n"
  "  movq %xmm13, 304(%rsp)\n"
  "  movq %xmm14, 320(%rsp)\n"
  "  movq %xmm15, 336(%rsp)\n"
  "\n"

rsp=-0x168

这里在 r12 中保存了 rsp。最后也是在这里恢复的，后面的 rsp 可以不用计算了。

  "  /* Map SHM, jumping to __afl_setup_abort if something goes wrong. */\n"
  "\n"
  "  /* The 64-bit ABI requires 16-byte stack alignment. We'll keep the\n"
  "     original stack ptr in the callee-saved r12. */\n"
  "\n"
  "  pushq %r12\n"
  "  movq  %rsp, %r12\n"

这里是初始化过程

  "  subq  $16, %rsp\n"
  "  andq  $0xfffffffffffffff0, %rsp\n"
  "\n"
  "  leaq .AFL_SHM_ENV(%rip), %rdi\n"
  CALL_L64("getenv")
  "\n"
  "  testq %rax, %rax\n"
  "  je    __afl_setup_abort\n"
  "\n"
  "  movq  %rax, %rdi\n"
  CALL_L64("atoi")
  "\n"
  "  xorq %rdx, %rdx   /* shmat flags    */\n"
  "  xorq %rsi, %rsi   /* requested addr */\n"
  "  movq %rax, %rdi   /* SHM ID         */\n"
  CALL_L64("shmat")
  "\n"
  "  cmpq $-1, %rax\n"
  "  je   __afl_setup_abort\n"
  "\n"
  "  /* Store the address of the SHM region. */\n"
  "\n"
  "  movq %rax, %rdx\n"
  "  movq %rax, __afl_area_ptr(%rip)\n"
  "\n"
#ifdef __APPLE__
  "  movq %rax, __afl_global_area_ptr(%rip)\n"
#else
  "  movq __afl_global_area_ptr@GOTPCREL(%rip), %rdx\n"
  "  movq %rax, (%rdx)\n"
#endif /* ^__APPLE__ */
  "  movq %rax, %rdx\n"
  "\n"

在 __afl_setup_first 之后，继续执行 __afl_forkserver。

`__afl_forkserver` 64

这里向 ST_PIPE 写四字节，如果没写进去，则跳转到 [[#__afl_fork_resume-64|__afl_fork_resume 64]]，否则向下执行 __afl_fork_wait_loop。

  "__afl_forkserver:\n"
  "\n"
  "  /* Enter the fork server mode to avoid the overhead of execve() calls. We\n"
  "     push rdx (area ptr) twice to keep stack alignment neat. */\n"
  "\n"
  "  pushq %rdx\n"
  "  pushq %rdx\n"
  "\n"
  "  /* Phone home and tell the parent that we're OK. (Note that signals with\n"
  "     no SA_RESTART will mess it up). If this fails, assume that the fd is\n"
  "     closed because we were execve()d from an instrumented binary, or because\n"
  "     the parent doesn't want to use the fork server. */\n"
  "\n"
  "  movq $4, %rdx               /* length    */\n"
  "  leaq __afl_temp(%rip), %rsi /* data      */\n"
  "  movq $" STRINGIFY((FORKSRV_FD + 1)) ", %rdi       /* file desc */\n"
  CALL_L64("write")
  "\n"
  "  cmpq $4, %rax\n"
  "  jne  __afl_fork_resume\n"
  "\n"

`__afl_fork_wait_loop` 64

从 CTL_PIPE 读四字节

  "__afl_fork_wait_loop:\n"
  "\n"
  "  /* Wait for parent by reading from the pipe. Abort if read fails. */\n"
  "\n"
  "  movq $4, %rdx               /* length    */\n"
  "  leaq __afl_temp(%rip), %rsi /* data      */\n"
  "  movq $" STRINGIFY(FORKSRV_FD) ", %rdi             /* file desc */\n"
  CALL_L64("read")
  "  cmpq $4, %rax\n"
  "  jne  __afl_die\n"
  "\n"

fork 出子进程，判断自己在哪个位置，如果 fork 失败了则跳到 [[#__afl_die-64|__afl_die 64]]，如果在子进程中则跳到 [[#__afl_fork_resume-64|__afl_fork_resume 64]]，注意此时 rsp=-0x188；如果在父进程中则继续执行。

  "  /* Once woken up, create a clone of our process. This is an excellent use\n"
  "     case for syscall(__NR_clone, 0, CLONE_PARENT), but glibc boneheadedly\n"
  "     caches getpid() results and offers no way to update the value, breaking\n"
  "     abort(), raise(), and a bunch of other things :-( */\n"
  "\n"
  CALL_L64("fork")
  "  cmpq $0, %rax\n"
  "  jl   __afl_die\n"
  "  je   __afl_fork_resume\n"
  "\n"

在父进程中，向 ST_PIPE 写四字节

  "  /* In parent process: write PID to pipe, then wait for child. */\n"
  "\n"
  "  movl %eax, __afl_fork_pid(%rip)\n"
  "\n"
  "  movq $4, %rdx                   /* length    */\n"
  "  leaq __afl_fork_pid(%rip), %rsi /* data      */\n"
  "  movq $" STRINGIFY((FORKSRV_FD + 1)) ", %rdi             /* file desc */\n"
  CALL_L64("write")

waitpid 等待子进程退出

  "\n"
  "  movq $0, %rdx                   /* no flags  */\n"
  "  leaq __afl_temp(%rip), %rsi     /* status    */\n"
  "  movq __afl_fork_pid(%rip), %rdi /* PID       */\n"
  CALL_L64("waitpid")
  "  cmpq $0, %rax\n"
  "  jle  __afl_die\n"
  "\n"

退出之后再向 ST_PIPE 写四字节，然后跳回开头重复执行。

  "  /* Relay wait status to pipe, then loop back. */\n"
  "\n"
  "  movq $4, %rdx               /* length    */\n"
  "  leaq __afl_temp(%rip), %rsi /* data      */\n"
  "  movq $" STRINGIFY((FORKSRV_FD + 1)) ", %rdi         /* file desc */\n"
  CALL_L64("write")
  "\n"
  "  jmp  __afl_fork_wait_loop\n"
  "\n"

`__afl_fork_resume` 64

rsp=-0x188，这里做恢复，在 popq 两次之后从 r12 中恢复 rsp，然后 pop 一次再做完整恢复。在恢复之后就执行 [[#__afl_store-64|__afl_store 64]]。

  "__afl_fork_resume:\n"
  "\n"
  "  /* In child process: close fds, resume execution. */\n"
  "\n"
  "  movq $" STRINGIFY(FORKSRV_FD) ", %rdi\n"
  CALL_L64("close")
  "\n"
  "  movq $" STRINGIFY((FORKSRV_FD + 1)) ", %rdi\n"
  CALL_L64("close")
  "\n"
  "  popq %rdx\n"
  "  popq %rdx\n"
  "\n"
  "  movq %r12, %rsp\n"
  "  popq %r12\n"
  "\n"
  "  movq  0(%rsp), %rax\n"
  "  movq  8(%rsp), %rcx\n"
  "  movq 16(%rsp), %rdi\n"
  "  movq 32(%rsp), %rsi\n"
  "  movq 40(%rsp), %r8\n"
  "  movq 48(%rsp), %r9\n"
  "  movq 56(%rsp), %r10\n"
  "  movq 64(%rsp), %r11\n"
  "\n"
  "  movq  96(%rsp), %xmm0\n"
  "  movq 112(%rsp), %xmm1\n"
  "  movq 128(%rsp), %xmm2\n"
  "  movq 144(%rsp), %xmm3\n"
  "  movq 160(%rsp), %xmm4\n"
  "  movq 176(%rsp), %xmm5\n"
  "  movq 192(%rsp), %xmm6\n"
  "  movq 208(%rsp), %xmm7\n"
  "  movq 224(%rsp), %xmm8\n"
  "  movq 240(%rsp), %xmm9\n"
  "  movq 256(%rsp), %xmm10\n"
  "  movq 272(%rsp), %xmm11\n"
  "  movq 288(%rsp), %xmm12\n"
  "  movq 304(%rsp), %xmm13\n"
  "  movq 320(%rsp), %xmm14\n"
  "  movq 336(%rsp), %xmm15\n"
  "\n"
  "  leaq 352(%rsp), %rsp\n"
  "\n"
  "  jmp  __afl_store\n"
  "\n"

`__afl_die` 64

  "__afl_die:\n"
  "\n"
  "  xorq %rax, %rax\n"
  CALL_L64("_exit")
  "\n"
  "__afl_setup_abort:\n"
  "\n"
  "  /* Record setup failure so that we don't keep calling\n"
  "     shmget() / shmat() over and over again. */\n"
  "\n"
  "  incb __afl_setup_failure(%rip)\n"
  "\n"
  "  movq %r12, %rsp\n"
  "  popq %r12\n"
  "\n"
  "  movq  0(%rsp), %rax\n"
  "  movq  8(%rsp), %rcx\n"
  "  movq 16(%rsp), %rdi\n"
  "  movq 32(%rsp), %rsi\n"
  "  movq 40(%rsp), %r8\n"
  "  movq 48(%rsp), %r9\n"
  "  movq 56(%rsp), %r10\n"
  "  movq 64(%rsp), %r11\n"
  "\n"
  "  movq  96(%rsp), %xmm0\n"
  "  movq 112(%rsp), %xmm1\n"
  "  movq 128(%rsp), %xmm2\n"
  "  movq 144(%rsp), %xmm3\n"
  "  movq 160(%rsp), %xmm4\n"
  "  movq 176(%rsp), %xmm5\n"
  "  movq 192(%rsp), %xmm6\n"
  "  movq 208(%rsp), %xmm7\n"
  "  movq 224(%rsp), %xmm8\n"
  "  movq 240(%rsp), %xmm9\n"
  "  movq 256(%rsp), %xmm10\n"
  "  movq 272(%rsp), %xmm11\n"
  "  movq 288(%rsp), %xmm12\n"
  "  movq 304(%rsp), %xmm13\n"
  "  movq 320(%rsp), %xmm14\n"
  "  movq 336(%rsp), %xmm15\n"
  "\n"
  "  leaq 352(%rsp), %rsp\n"
  "\n"
  "  jmp __afl_return\n"
  "\n"
  ".AFL_VARS:\n"
  "\n"

下文定义了一些变量。

#ifdef __APPLE__
 
  "  .comm   __afl_area_ptr, 8\n"
#ifndef COVERAGE_ONLY
  "  .comm   __afl_prev_loc, 8\n"
#endif /* !COVERAGE_ONLY */
  "  .comm   __afl_fork_pid, 4\n"
  "  .comm   __afl_temp, 4\n"
  "  .comm   __afl_setup_failure, 1\n"
 
#else
 
  "  .lcomm   __afl_area_ptr, 8\n"
#ifndef COVERAGE_ONLY
  "  .lcomm   __afl_prev_loc, 8\n"
#endif /* !COVERAGE_ONLY */
  "  .lcomm   __afl_fork_pid, 4\n"
  "  .lcomm   __afl_temp, 4\n"
  "  .lcomm   __afl_setup_failure, 1\n"
 
#endif /* ^__APPLE__ */

`__afl_global_area_ptr` 64

在结尾定义了一个 8 字节的变量 __afl_global_area_ptr

  "  .comm    __afl_global_area_ptr, 8, 8\n"
  "\n"
  ".AFL_SHM_ENV:\n"
  "  .asciz \"" SHM_ENV_VAR "\"\n"
  "\n"
  "/* --- END --- */\n"
  "\n";

🚂QRZ的星穹列车

开往

探索

Recent writing

从安全问题研究 C 中的未定义行为：有符号整数溢出

Fuzzing 101 with LibAFL 学习（一）

AFL 运行流程多图流（缓慢更新中）

afl-as.h

目录

trampoline_fmt_32

main_payload_32

`__afl_maybe_log`

`__afl_store`

`__afl_return`

`__afl_setup`

`__afl_forkserver`

`__afl_fork_wait_loop`

父进程 forkserver32

`__afl_fork_resume`

`__afl_die`

`__afl_setup_abort`

main_payload_64

`__afl_maybe_log` 64

`__afl_store` 64

`__afl_setup` 64

`__afl_setup_first` 64

`__afl_forkserver` 64

`__afl_fork_wait_loop` 64

`__afl_fork_resume` 64

`__afl_die` 64

`__afl_global_area_ptr` 64

参考资料

目录

关系图谱

反向链接

🚂QRZ的星穹列车

开往

探索

Recent writing

从安全问题研究 C 中的未定义行为：有符号整数溢出

Fuzzing 101 with LibAFL 学习（一）

AFL 运行流程多图流（缓慢更新中）

afl-as.h

目录

trampoline_fmt_32

main_payload_32

__afl_maybe_log

__afl_store

__afl_return

__afl_setup

__afl_forkserver

__afl_fork_wait_loop

父进程 forkserver32

__afl_fork_resume

__afl_die

__afl_setup_abort

main_payload_64

__afl_maybe_log 64

__afl_store 64

__afl_setup 64

__afl_setup_first 64

__afl_forkserver 64

__afl_fork_wait_loop 64

__afl_fork_resume 64

__afl_die 64

__afl_global_area_ptr 64

参考资料

目录

关系图谱

反向链接

`__afl_maybe_log`

`__afl_store`

`__afl_return`

`__afl_setup`

`__afl_forkserver`

`__afl_fork_wait_loop`

`__afl_fork_resume`

`__afl_die`

`__afl_setup_abort`

`__afl_maybe_log` 64

`__afl_store` 64

`__afl_setup` 64

`__afl_setup_first` 64

`__afl_forkserver` 64

`__afl_fork_wait_loop` 64

`__afl_fork_resume` 64

`__afl_die` 64

`__afl_global_area_ptr` 64