kerneldiff.c

# Courtesy of OpenAI

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

#define MAX_DIFF 16384
#define DIFF_COMP_MAX_SIZE 20

int main(int argc, char *argv[]) {
  if (argc < 4) {
    printf("Usage: kernelcache_raw kernelcache_patched kc.bpatch\n");
    return 0;
  }

  char *patched = argv[2];
  char *original = argv[1];

  struct stat stP;
  struct stat stO;

  int ret_patched = stat(patched, &stP);
  int ret_original = stat(original, &stO);

  if (ret_patched) { perror("stat() patched"); abort(); }
  if (ret_original) { perror("stat() original"); abort(); }

  if (stP.st_size != stO.st_size) {
    printf("size does not match, can't compare files! exiting...\n");
    return 1;
  }

  FILE *fP = fopen(patched, "rb");
  FILE *fO = fopen(original, "rb");

  if (fP == NULL) { perror("fopen() patched"); abort(); }
  if (fO == NULL) { perror("fopen() original"); abort(); }

  char *p = malloc(stP.st_size);
  char *o = malloc(stO.st_size);

  if (p == NULL) { perror("malloc() patched"); abort(); }
  if (o == NULL) { perror("malloc() original"); abort(); }

  fread(p, 1, stP.st_size, fP);
  fread(o, 1, stO.st_size, fO);

  fclose(fP);
  fclose(fO);

  char diff[MAX_DIFF][3][DIFF_COMP_MAX_SIZE];
  int diffIndex = 0;

  for (int i = 0; i < stO.st_size; i++) {
    char originalByte = o[i];
    char patchedByte = p[i];

    if (originalByte != patchedByte) {
     if ((diffIndex + 1) > MAX_DIFF) {
        fprintf(stderr, "too many differences, only a maximum %d 8-byte differences are supported\n", MAX_DIFF);
        abort();
      }
      snprintf(diff[diffIndex][0], DIFF_COMP_MAX_SIZE, "0x%x", i);

      snprintf(diff[diffIndex][1], DIFF_COMP_MAX_SIZE, "0x%x", originalByte);

      snprintf(diff[diffIndex][2], DIFF_COMP_MAX_SIZE, "0x%x", patchedByte);

      diffIndex++;
    }
  }

  free(p);
  free(o);

  FILE *diffFile = fopen(argv[3], "w+");
  fwrite("#AMFI\n\n", 1, 7, diffFile);

  for (int i = 0; i < diffIndex; i++) {
    int dataSize = strlen(diff[i][0]) + strlen(diff[i][1]) + strlen(diff[i][2]) + 3;
    char data[dataSize];
    sprintf(data, "%s %s %s\n", diff[i][0], diff[i][1], diff[i][2]);

    fwrite(data, 1, dataSize, diffFile);
    printf("%s", data);
  }

  fclose(diffFile);

  return 0;
}