45 lines
1.3 KiB
C
45 lines
1.3 KiB
C
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <stdint.h>
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#include <libcore/libcore.h>
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#define PREPARE_PATCH(start) \
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size_t page_size = sysconf(_SC_PAGESIZE); \
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uintptr_t end = ((uintptr_t) start) + 1; \
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uintptr_t page_start = ((uintptr_t) start) & -page_size; \
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mprotect((void *) page_start, end - page_start, PROT_READ | PROT_WRITE); \
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\
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unsigned char *data = (unsigned char *) start; \
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int thumb = ((size_t) start) & 1; \
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if (thumb) { \
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data--; \
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} \
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fprintf(stderr, "Patching - original: %i %i %i %i %i\n", data[0], data[1], data[2], data[3], data[4]);
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#define END_PATCH() \
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fprintf(stderr, "Patching - result: %i %i %i %i %i\n", data[0], data[1], data[2], data[3], data[4]); \
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\
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mprotect((void *) page_start, end - page_start, PROT_READ | PROT_EXEC);
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void overwrite(void *start, void *target) {
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PREPARE_PATCH(start);
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if (thumb) {
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unsigned char patch[4] = {0xdf, 0xf8, 0x00, 0xf0};
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memcpy(data, patch, 4);
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} else {
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unsigned char patch[4] = {0x04, 0xf0, 0x1f, 0xe5};
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memcpy(data, patch, 4);
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}
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memcpy(&data[4], &target, sizeof (int));
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END_PATCH();
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}
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void patch(void *start, unsigned char patch[]) {
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PREPARE_PATCH(start);
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memcpy(data, patch, 4);
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END_PATCH();
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}
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