/*
   american fuzzy lop - GCC plugin instrumentation bootstrap
   ---------------------------------------------------------

   Written by Austin Seipp <aseipp@pobox.com> and
              Laszlo Szekeres <lszekeres@google.com> and
              Michal Zalewski <lcamtuf@google.com>

   GCC integration design is based on the LLVM design, which comes
   from Laszlo Szekeres.

   Copyright 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 code is the rewrite of afl-as.h's main_payload.

*/

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

#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <assert.h>

#include <sys/mman.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <sys/types.h>

/* Globals needed by the injected instrumentation. The __afl_area_initial region
   is used for instrumentation output before __afl_map_shm() has a chance to
   run. It will end up as .comm, so it shouldn't be too wasteful. */

u8  __afl_area_initial[MAP_SIZE];
u8 *__afl_area_ptr = __afl_area_initial;
u32 __afl_prev_loc;

/* Running in persistent mode? */

static u8 is_persistent;

/* Trace a basic block with some ID */
void __afl_trace(u32 x) {

  u32 l = __afl_prev_loc;
  u32 n = l ^ x;
  *(__afl_area_ptr + n) += 1;
  __afl_prev_loc = (x >> 1);
  return;

}

/* SHM setup. */

static void __afl_map_shm(void) {

  u8 *id_str = getenv(SHM_ENV_VAR);

  /* If we're running under AFL, attach to the appropriate region, replacing the
     early-stage __afl_area_initial region that is needed to allow some really
     hacky .init code to work correctly in projects such as OpenSSL. */

  if (id_str) {

    u32 shm_id = atoi(id_str);

    __afl_area_ptr = shmat(shm_id, NULL, 0);

    /* Whooooops. */

    if (__afl_area_ptr == (void *)-1) exit(1);

    /* Write something into the bitmap so that even with low AFL_INST_RATIO,
       our parent doesn't give up on us. */

    __afl_area_ptr[0] = 1;

  }

}

/* Fork server logic. */

static void __afl_start_forkserver(void) {

  static u8 tmp[4];
  s32       child_pid;

  u8 child_stopped = 0;

  /* Phone home and tell the parent that we're OK. If parent isn't there,
     assume we're not running in forkserver mode and just execute program. */

  if (write(FORKSRV_FD + 1, tmp, 4) != 4) return;

  while (1) {

    u32 was_killed;
    int status;

    /* Wait for parent by reading from the pipe. Abort if read fails. */

    if (read(FORKSRV_FD, &was_killed, 4) != 4) exit(1);

    /* If we stopped the child in persistent mode, but there was a race
       condition and afl-fuzz already issued SIGKILL, write off the old
       process. */

    if (child_stopped && was_killed) {

      child_stopped = 0;
      if (waitpid(child_pid, &status, 0) < 0) exit(1);

    }

    if (!child_stopped) {

      /* Once woken up, create a clone of our process. */

      child_pid = fork();
      if (child_pid < 0) exit(1);

      /* In child process: close fds, resume execution. */

      if (!child_pid) {

        close(FORKSRV_FD);
        close(FORKSRV_FD + 1);
        return;

      }

    } else {

      /* Special handling for persistent mode: if the child is alive but
         currently stopped, simply restart it with SIGCONT. */

      kill(child_pid, SIGCONT);
      child_stopped = 0;

    }

    /* In parent process: write PID to pipe, then wait for child. */

    if (write(FORKSRV_FD + 1, &child_pid, 4) != 4) exit(1);

    if (waitpid(child_pid, &status, is_persistent ? WUNTRACED : 0) < 0) exit(1);

    /* In persistent mode, the child stops itself with SIGSTOP to indicate
       a successful run. In this case, we want to wake it up without forking
       again. */

    if (WIFSTOPPED(status)) child_stopped = 1;

    /* Relay wait status to pipe, then loop back. */

    if (write(FORKSRV_FD + 1, &status, 4) != 4) exit(1);

  }

}

/* A simplified persistent mode handler, used as explained in README.llvm. */

int __afl_persistent_loop(unsigned int max_cnt) {

  static u8  first_pass = 1;
  static u32 cycle_cnt;

  if (first_pass) {

    cycle_cnt = max_cnt;
    first_pass = 0;
    return 1;

  }

  if (is_persistent && --cycle_cnt) {

    raise(SIGSTOP);
    return 1;

  } else

    return 0;

}

/* This one can be called from user code when deferred forkserver mode
    is enabled. */

void __afl_manual_init(void) {

  static u8 init_done;

  if (!init_done) {

    __afl_map_shm();
    __afl_start_forkserver();
    init_done = 1;

  }

}

/* Proper initialization routine. */

__attribute__((constructor(101))) void __afl_auto_init(void) {

  is_persistent = !!getenv(PERSIST_ENV_VAR);

  if (getenv(DEFER_ENV_VAR)) return;

  __afl_manual_init();

}