afl-as.h

/*
   american fuzzy lop - injectable parts
   -------------------------------------

   Written and maintained by Michal Zalewski <lcamtuf@google.com>

   Forkserver design by Jann Horn <jannhorn@googlemail.com>

   Copyright 2013, 2014, 2015 Google Inc. 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

   This file houses the assembly-level instrumentation injected into fuzzed
   programs. The instrumentation stores XORed pairs of data: identifiers of the
   currently executing branch and the one that executed immediately before.

   TL;DR: the instrumentation does shm_trace_map[cur_loc ^ prev_loc]++

   The code is designed for 32-bit and 64-bit x86 systems. Both modes should
   work everywhere except for Apple systems. Apple does relocations differently
   from everybody else, so since their OSes have been 64-bit for a longer while,
   I didn't go through the mental effort of porting the 32-bit code.

   In principle, similar code should be easy to inject into any well-behaved
   binary-only code (e.g., using DynamoRIO). Conditional jumps offer natural
   targets for instrumentation, and should offer comparable probe density.

 */

#ifndef _HAVE_AFL_AS_H
#define _HAVE_AFL_AS_H

#include "config.h"
#include "types.h"

/* 
   ------------------
   Performances notes
   ------------------

   Contributions to make this code faster are appreciated! Here are some
   rough notes that may help with the task:

   - Only the trampoline_fmt and the non-setup __afl_maybe_log code paths are
     really worth optimizing; the setup / fork server stuff matters a lot less
     and should be mostly just kept readable.

   - We're aiming for modern CPUs with out-of-order execution and large
     pipelines; the code is mostly follows intuitive, human-readable
     instruction ordering, because "textbook" manual reorderings make no
     substantial difference.

   - Interestingly, instrumented execution isn't a lot faster if we store a
     variable pointer to the setup, log, or return routine and then do a reg
     call from within trampoline_fmt. It does speed up non-instrumented
     execution quite a bit, though, since that path just becomes
     push-call-ret-pop.

   - There is also not a whole lot to be gained by doing SHM attach at a
     fixed address instead of retrieving __afl_area_ptr. Although it allows us
     to have a shorter log routine inserted for conditional jumps and jump
     labels (for a ~10% perf gain), there is a risk of bumping into other
     allocations created by the program or by tools such as ASAN.

   - popf is *awfully* slow, which is why we're doing the lahf / sahf +
     overflow test trick. Unfortunately, this forces us to taint eax / rax, but
     this dependency on a commonly-used register still beats the alternative of
     using pushf / popf.

     One possible optimization is to avoid touching flags by using a circular
     buffer that stores just a sequence of current locations, with the XOR stuff
     happening offline. Alas, this doesn't seem to have a huge impact:

     https://groups.google.com/d/msg/afl-users/MsajVf4fRLo/2u6t88ntUBIJ

   - Preforking one child a bit sooner, and then waiting for the "go" command
     from within the child, doesn't offer major performance gains; fork() seems
     to be relatively inexpensive these days. Preforking multiple children does
     help, but badly breaks the "~1 core per fuzzer" design, making it harder to
     scale up. Maybe there is some middle ground.

   Perhaps of note: in the 64-bit version for all platforms except for Apple,
   the instrumentation is done slightly differently than on 32-bit, with
   __afl_prev_loc and __afl_area_ptr being local to the object file (.lcomm),
   rather than global (.comm). This is to avoid GOTRELPC lookups in the critical
   code path, which AFAICT, are otherwise unavoidable if we want gcc -shared to
   work; simple relocations between .bss and .text won't work on most 64-bit
   platforms in such a case.

   (Fun fact: on Apple systems, .lcomm can segfault the linker.)

   The side effect is that state transitions are measured in a somewhat
   different way, with previous tuple being recorded separately within the scope
   of every .c file. This should have no impact in any practical sense.

   Another side effect of this design is that getenv() will be called once per
   every .o file when running in non-instrumented mode; and since getenv() tends
   to be optimized in funny ways, we need to be very careful to save every
   oddball register it may touch.

 */

static const u8* trampoline_fmt_32 =

  "\n"
  "/* --- AFL TRAMPOLINE (32-BIT) --- */\n"
  "\n"
  ".align 4\n"
  "\n"
  "leal -16(%%esp), %%esp\n"
  "movl %%edi,  0(%%esp)\n"
  "movl %%edx,  4(%%esp)\n"
  "movl %%ecx,  8(%%esp)\n"
  "movl %%eax, 12(%%esp)\n"
  "movl $0x%08x, %%ecx\n"
  "call __afl_maybe_log\n"
  "movl 12(%%esp), %%eax\n"
  "movl  8(%%esp), %%ecx\n"
  "movl  4(%%esp), %%edx\n"
  "movl  0(%%esp), %%edi\n"
  "leal 16(%%esp), %%esp\n"
  "\n"
  "/* --- END --- */\n"
  "\n";

static const u8* trampoline_fmt_64 =

  "\n"
  "/* --- AFL TRAMPOLINE (64-BIT) --- */\n"
  "\n"
  ".align 4\n"
  "\n"
  "leaq -(128+24)(%%rsp), %%rsp\n"
  "movq %%rdx,  0(%%rsp)\n"
  "movq %%rcx,  8(%%rsp)\n"
  "movq %%rax, 16(%%rsp)\n"
  "movq $0x%08x, %%rcx\n"
  "call __afl_maybe_log\n"
  "movq 16(%%rsp), %%rax\n"
  "movq  8(%%rsp), %%rcx\n"
  "movq  0(%%rsp), %%rdx\n"
  "leaq (128+24)(%%rsp), %%rsp\n"
  "\n"
  "/* --- END --- */\n"
  "\n";

static const u8 *trampoline_fmt_arm = 
  "\n"
  "/* --- AFL TRAMPOLINE --- */\n"
  "\tpush {r0, lr}\n"
  "\tmovw r0, #%u\n"
 "\tbl __afl_maybe_log\n"
  "\tb 1f\n"
  "\t.ltorg\n"
  "\t1:\n"
  "\tpop {r0, lr}\n"
  "/* --- END --- */\n"
  "\n";

static const u8 *main_payload_arm =
  "\n"
  "/* --- AFL MAIN PAYLOAD --- */\n"
  "\n"
  ".text\n"
  "__afl_maybe_log:\n"
  "\n"
  "\n"
  "\tpush {r1-r7, lr}\n"
  "\tmrs r7, APSR\n"
  "\tmov r4, r0\n"
  "\tldr r0, =__afl_setup_failure\n"
  "\tldr r0, [r0]\n"
  "\tcmp r0, #0\n"
  "\tbne __afl_return\n"
  "\n"
  "\tldr r0, =__afl_area_ptr\n"
  "\tldr r0, [r0]\n"
  "\tcmp r0, #0\n"
  "\tbne __afl_store\n"
  "\n"
  "\tldr r0, =.AFL_SHM_ENV\n"
  "\tbl getenv\n"
  "\n"
  "\tcmp r0, #0\n"
  "\tbeq __afl_setup_abort\n"
  "\n"
  "\tbl atoi\n"
  "\n"
  "\tmov r5, r0\n"
  "\tldr r1, =#0x7704\n"
  "\tmov r2, #0\n"
  "\tbl ioctl\n"
  "\n"
  "\tcmp r0, #0\n"
  "\tblt __afl_setup_abort\n"
  "\n"
  "\tmov r1, r0\n"
  "\tmov r0, #0\n"
  "\tmov r2, #3\n"
  "\tmov r3, #1\n"
  "\tmov r6, #0\n"
  "\tpush {r5, r6}\n"
  "\tbl mmap\n"
  "\tpop {r5, r6}\n"
  "\n"
  "\tadd r1, r0, #1\n"
  "\tcmp r1, #1\n"
  "\tbhi __afl_forkserver\n"
  "\n"
  "__afl_setup_abort:\n"
  "\tldr r0, =__afl_setup_failure\n"
  "\tldr r1, [r0]\n"
  "\tadd r1, r1, #1\n"
  "\tstr r1, [r0]\n"
  "\tb __afl_return\n"
  "\n"
  "\t__afl_forkserver:\n"
  "\tldr r1, =__afl_area_ptr\n"
  "\tstr r0, [r1]\n"
  "\tldr r5, =__afl_temp\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD + 1) "\n"
  "\tmov r1, r5\n"
  "\tmov r2, #4\n"
  "\tbl write\n"
  "\n"
  "\tcmp r0, #4\n"
  "\tbne __afl_fork_resume\n"
  "\n"
  "\t__afl_fork_wait_loop:\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD) "\n"
  "\tmov r1, r5\n"
  "\tmov r2, #4\n"
  "\tbl read\n"
  "\n"
  "\tcmp r0, #4\n"
  "\tbne __afl_die\n"
  "\n"
  "\tbl fork\n"
  // "\n"
  "\tcmp r0, #0\n"
  "\tblt __afl_die\n"
  "\n"
  "\tbeq __afl_fork_resume\n"
  "\n"
  "\tldr r1, =__afl_fork_pid\n"
  "\tstr r0, [r1]\n"
  "\tmov r6, r0\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD + 1) "\n"
  "\tmov r2, #4\n"
  "\tbl write\n"
  "\n"
  "\tcmp r0, #4\n"
  "\tbne __afl_die\n"
  "\n"
  "\tmov r0, r6\n"
  "\tmov r1, r5\n"
  "\tmov r2, #0\n"
  "\tbl waitpid\n"
  "\n"
  "\tcmp r0, #0\n"
  "\tblt __afl_die\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD + 1) "\n"
  "\tmov r1, r5\n"
  "\tmov r2, #4\n"
  "\tbl write\n"
  "\n"
  "\tcmp r0, #4\n"
  "\tbeq __afl_fork_wait_loop\n"
  "\n"
  "\tb __afl_die\n"
  "\n"
  "__afl_fork_resume:\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD) "\n"
  "\tbl close\n"
  "\n"
  "\tmov r0, #" STRINGIFY(FORKSRV_FD + 1) "\n"
  "\tbl close\n"
  "\n"
  "__afl_store:\n"
  "\tldr r0, =__afl_area_ptr\n"
  "\tldr r0, [r0]\n"
  "\tldr r1, =__afl_prev_loc\n"
  "\tldr r2, [r1]\n"
  "\teor r2, r2, r4\n"
  "\tldrb r3, [r0, r2]\n"
  "\tadd r3, r3, #1\n"
  "\tstrb r3, [r0, r2]\n"
  "\tmov r0, r4, asr#1\n"
  "\tstr r0, [r1]\n"
  "__afl_return:\n"
  "msr APSR_nzcvq, r7\n"
  "\tpop {r1-r7, pc}\n"
  "__afl_die:\n"
  "\tmov r0, #0\n"
  "\tbl exit\n"
  "\n"
  ".AFL_VARS:\n"
  "\n"
  "\t.comm __afl_area_ptr, 4, 4\n"
  "\t.comm __afl_setup_failure, 4, 4\n"
// #ifndef COVERAGE_ONLY
  "\t.comm __afl_prev_loc, 4, 4\n"
// #endif /* !COVERAGE_ONLY */
  "\t.comm __afl_fork_pid, 4, 4\n"
  "\t.comm __afl_temp, 4, 4\n"
  "\n"
  ".AFL_SHM_ENV:\n"
  "\t.string \"" SHM_ENV_VAR "\"\n"
  "\n"
  "/* --- END -- */\n"
  "\n";

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:\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"
  "__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"
  "__afl_return:\n"
  "\n"
  "  addb $127, %al\n"
  "  sahf\n"
  "  ret\n"
  "\n"
  ".align 8\n"
  "\n"
  "__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"
  "  /* 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"
  "  pushl $.AFL_SHM_ENV\n"
  "  call  getenv\n"
  "  addl  $4, %esp\n"
  "\n"
  "  testl %eax, %eax\n"
  "  je    __afl_setup_abort\n"
  "\n"
  "  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"
  "  /* Store the address of the SHM region. */\n"
  "\n"
  "  movl %eax, __afl_area_ptr\n"
  "  movl %eax, %edx\n"
  "\n"
  "  popl %ecx\n"
  "  popl %eax\n"
  "\n"
  "__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"
  "__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"
  "  /* 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"
  "  /* In parent process: write PID to pipe, then wait for child. */\n"
  "\n"
  "  movl  %eax, __afl_fork_pid\n"
  "\n"
  "  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"
  "  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"
  "  /* 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"
  "__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:\n"
  "\n"
  "  xorl %eax, %eax\n"
  "  call _exit\n"
  "\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\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";

/* 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:\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:\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:\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"
  "  /* 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:\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"
  "  /* 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"
  "  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"
  "__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:\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"
  "  /* 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"
  "  /* 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")
  "\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"
  "  /* 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:\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:\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"

#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__ */

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

#endif /* !_HAVE_AFL_AS_H */