arm32_hijack.h

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>

void hijack(uintptr_t *addr, uintptr_t *newa, uint8_t buf[4]) {
	uint32_t temp = (uintptr_t)newa;
	if (addr < newa) {
		temp = (temp - 8) / 4;
		memcpy(buf, &temp, 4);
	} else {	
		temp = 0xffffff - (temp / 4 - 4);
		memcpy(buf, &temp, 4);
	}
	
	// arm32 branch
	buf[3] = 0xea;
}

int main() {
    unsigned char inst[] = {0x62, 0x00, 0x00, 0xEA};
    
    uintptr_t a = 0x;
    uintptr_t b = 120;
    
    hijack(a, b, inst);
    
    printf("%x %x %x %x\n", inst[0], inst[1], inst[2], inst[3]);
}