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afl-gotcpu.c

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+/*
+  Copyright 2015 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.
+*/
+
+/*
+   american fuzzy lop - free CPU gizmo
+   -----------------------------------
+
+   Written and maintained by Michal Zalewski <lcamtuf@google.com>
+
+   This tool provides a fairly accurate measurement of CPU preemption rate.
+   It is meant to complement the quick-and-dirty load average widget shown
+   in the afl-fuzz UI. See docs/parallel_fuzzing.txt for more info.
+
+   For some work loads, the tool may actually suggest running more instances
+   than you have CPU cores. This can happen if the tested program is spending
+   a portion of its run time waiting for I/O, rather than being 100%
+   CPU-bound.
+
+   The idea for the getrusage()-based approach comes from Jakub Wilk.
+*/
+
+#define AFL_MAIN
+#include "android-ashmem.h"
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sched.h>
+
+#include <sys/time.h>
+#include <sys/times.h>
+#include <sys/resource.h>
+#include <sys/wait.h>
+
+#include "types.h"
+#include "debug.h"
+
+#ifdef __linux__
+#  define HAVE_AFFINITY 1
+#endif /* __linux__ */
+
+
+/* Get unix time in microseconds. */
+
+static u64 get_cur_time_us(void) {
+
+  struct timeval tv;
+  struct timezone tz;
+
+  gettimeofday(&tv, &tz);
+
+  return (tv.tv_sec * 1000000ULL) + tv.tv_usec;
+
+}
+
+
+/* Get CPU usage in microseconds. */
+
+static u64 get_cpu_usage_us(void) {
+
+  struct rusage u;
+
+  getrusage(RUSAGE_SELF, &u);
+
+  return (u.ru_utime.tv_sec * 1000000ULL) + u.ru_utime.tv_usec +
+         (u.ru_stime.tv_sec * 1000000ULL) + u.ru_stime.tv_usec;
+
+}
+
+
+/* Measure preemption rate. */
+
+static u32 measure_preemption(u32 target_ms) {
+
+  static volatile u32 v1, v2;
+
+  u64 st_t, en_t, st_c, en_c, real_delta, slice_delta;
+  s32 loop_repeats = 0;
+
+  st_t = get_cur_time_us();
+  st_c = get_cpu_usage_us();
+
+repeat_loop:
+
+  v1 = CTEST_BUSY_CYCLES;
+
+  while (v1--) v2++;
+  sched_yield();
+
+  en_t = get_cur_time_us();
+
+  if (en_t - st_t < target_ms * 1000) {
+    loop_repeats++;
+    goto repeat_loop;
+  }
+
+  /* Let's see what percentage of this time we actually had a chance to
+     run, and how much time was spent in the penalty box. */
+
+  en_c = get_cpu_usage_us();
+
+  real_delta  = (en_t - st_t) / 1000;
+  slice_delta = (en_c - st_c) / 1000;
+
+  return real_delta * 100 / slice_delta;
+
+}
+
+
+/* Do the benchmark thing. */
+
+int main(int argc, char** argv) {
+
+#ifdef HAVE_AFFINITY
+
+  u32 cpu_cnt = sysconf(_SC_NPROCESSORS_ONLN),
+      idle_cpus = 0, maybe_cpus = 0, i;
+
+  SAYF(cCYA "afl-gotcpu " cBRI VERSION cRST " by <lcamtuf@google.com>\n");
+
+  ACTF("Measuring per-core preemption rate (this will take %0.02f sec)...",
+       ((double)CTEST_CORE_TRG_MS) / 1000);
+
+  for (i = 0; i < cpu_cnt; i++) {
+
+    s32 fr = fork();
+
+    if (fr < 0) PFATAL("fork failed");
+
+    if (!fr) {
+
+      cpu_set_t c;
+      u32 util_perc;
+
+      CPU_ZERO(&c);
+      CPU_SET(i, &c);
+
+      if (sched_setaffinity(0, sizeof(c), &c))
+        PFATAL("sched_setaffinity failed for cpu %d", i);
+
+      util_perc = measure_preemption(CTEST_CORE_TRG_MS);
+
+      if (util_perc < 110) {
+
+        SAYF("    Core #%u: " cLGN "AVAILABLE " cRST "(%u%%)\n", i, util_perc);
+        exit(0);
+
+      } else if (util_perc < 250) {
+
+        SAYF("    Core #%u: " cYEL "CAUTION " cRST "(%u%%)\n", i, util_perc); 
+        exit(1);
+
+      }
+
+      SAYF("    Core #%u: " cLRD "OVERBOOKED " cRST "(%u%%)\n" cRST, i,
+           util_perc);
+      exit(2);
+
+    }
+
+  }
+
+  for (i = 0; i < cpu_cnt; i++) {
+
+    int ret;
+    if (waitpid(-1, &ret, 0) < 0) PFATAL("waitpid failed");
+
+    if (WEXITSTATUS(ret) == 0) idle_cpus++;
+    if (WEXITSTATUS(ret) <= 1) maybe_cpus++;
+
+  }
+
+  SAYF(cGRA "\n>>> ");
+
+  if (idle_cpus) {
+
+    if (maybe_cpus == idle_cpus) {
+
+      SAYF(cLGN "PASS: " cRST "You can run more processes on %u core%s.",
+           idle_cpus, idle_cpus > 1 ? "s" : "");
+
+    } else {
+
+      SAYF(cLGN "PASS: " cRST "You can run more processes on %u to %u core%s.",
+           idle_cpus, maybe_cpus, maybe_cpus > 1 ? "s" : "");
+
+    }
+
+    SAYF(cGRA " <<<" cRST "\n\n");
+    return 0;
+
+  }
+
+  if (maybe_cpus) {
+
+    SAYF(cYEL "CAUTION: " cRST "You may still have %u core%s available.",
+         maybe_cpus, maybe_cpus > 1 ? "s" : "");
+    SAYF(cGRA " <<<" cRST "\n\n");
+    return 1;
+
+  }
+
+  SAYF(cLRD "FAIL: " cRST "All cores are overbooked.");
+  SAYF(cGRA " <<<" cRST "\n\n");
+  return 2;
+
+#else
+
+  u32 util_perc;
+
+  SAYF(cCYA "afl-gotcpu " cBRI VERSION cRST " by <lcamtuf@google.com>\n");
+
+  /* Run a busy loop for CTEST_TARGET_MS. */
+
+  ACTF("Measuring gross preemption rate (this will take %0.02f sec)...",
+       ((double)CTEST_TARGET_MS) / 1000);
+
+  util_perc = measure_preemption(CTEST_TARGET_MS);
+
+  /* Deliver the final verdict. */
+
+  SAYF(cGRA "\n>>> ");
+
+  if (util_perc < 105) {
+
+    SAYF(cLGN "PASS: " cRST "You can probably run additional processes.");
+
+  } else if (util_perc < 130) {
+
+    SAYF(cYEL "CAUTION: " cRST "Your CPU may be somewhat overbooked (%u%%).",
+         util_perc);
+
+  } else {
+
+    SAYF(cLRD "FAIL: " cRST "Your CPU is overbooked (%u%%).", util_perc);
+
+  }
+
+  SAYF(cGRA " <<<" cRST "\n\n");
+
+  return (util_perc > 105) + (util_perc > 130);
+
+#endif /* ^HAVE_AFFINITY */
+
+}