Magisk/jni/magiskboot/hexpatch.c

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#include "magiskboot.h"
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static void hex2byte(const char *hex, unsigned char *str) {
char high, low;
for (int i = 0, length = strlen(hex); i < length; i += 2) {
high = toupper(hex[i]) - '0';
low = toupper(hex[i + 1]) - '0';
str[i / 2] = ((high > 9 ? high - 7 : high) << 4) + (low > 9 ? low - 7 : low);
}
}
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void hexpatch(const char *image, const char *from, const char *to) {
int patternsize = strlen(from) / 2, patchsize = strlen(to) / 2;
size_t filesize;
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unsigned char *file, *pattern, *patch;
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mmap_rw(image, &file, &filesize);
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pattern = malloc(patternsize);
patch = malloc(patchsize);
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hex2byte(from, pattern);
hex2byte(to, patch);
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for (size_t i = 0; i < filesize - patternsize; ++i) {
if (memcmp(file + i, pattern, patternsize) == 0) {
printf("Pattern %s found!\nPatching to %s\n", from, to);
memset(file + i, 0, patternsize);
memcpy(file + i, patch, patchsize);
i += patternsize - 1;
}
}
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munmap(file, filesize);
free(pattern);
free(patch);
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}