在AArch64架构中，如果一个地址被多重映射到多个物理地址上，会出现内存同步问题。此时需要使用“memory tagging”机制，对这些多重映射的地址进行标记，以便操作系统进行内存同步。下面是一个使用“memory tagging”的代码示例：

#include 
#include 
#include 
#include 

#define PAGE_SIZE 4096
#define PAGE_MASK (~(PAGE_SIZE-1))

uintptr_t memtag(void * p) {
    uintptr_t val = (uintptr_t) p;
    return (val >> 56);
}

void * memuntag(void * p) {
    uintptr_t val = (uintptr_t) p;
    return (void*) (val & PAGE_MASK);
}

int main() {
    void * buf;
    uintptr_t tag = 0x80;
    int i;

    buf = mmap(NULL, 3 * PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
    if (buf == MAP_FAILED) {
        perror("mmap failed");
        exit(1);
    }

    /* assign tag to the last page */
    if (mprotect((void *)((uintptr_t)buf + 2 * PAGE_SIZE), PAGE_SIZE, PROT_NONE) == -1) {
        perror("mprotect failed");
        exit(1);
    }

    /* write to buf */
    for (i = 0; i < PAGE_SIZE/sizeof(uintptr_t); i++) {
        *((uintptr_t *)buf + i) = i;
    }

    /* read from buf */
    for (i = 0; i < PAGE_SIZE/sizeof(uintptr_t); i++) {
        uintptr_t val = *((uintptr_t *)buf + i);
        printf("val[%d]: ptr=%p, val=%ld\n", i, (void *)val, val);
        if ((val & 0xFF) != tag) {
            printf("Error: tag mismatch\n");
        }
    }

    return 0;
}

在这个示例中，我们使用“