test_mte_malloc.cpp

#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <cstdlib>
#include <unistd.h>
#include <sys/auxv.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/types.h>

/*
 * From arch/arm64/include/uapi/asm/hwcap.h
 */
#define HWCAP2_MTE              (1 << 18)

/*
 * From arch/arm64/include/uapi/asm/mman.h
 */
#define PROT_MTE                 0x20

/*
 * From include/uapi/linux/prctl.h
 */
#define PR_SET_TAGGED_ADDR_CTRL 55
#define PR_GET_TAGGED_ADDR_CTRL 56
# define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
# define PR_MTE_TCF_SHIFT       1
# define PR_MTE_TCF_NONE        (0UL << PR_MTE_TCF_SHIFT)
# define PR_MTE_TCF_SYNC        (1UL << PR_MTE_TCF_SHIFT)
# define PR_MTE_TCF_ASYNC       (2UL << PR_MTE_TCF_SHIFT)
# define PR_MTE_TCF_MASK        (3UL << PR_MTE_TCF_SHIFT)
# define PR_MTE_TAG_SHIFT       3
# define PR_MTE_TAG_MASK        (0xffffUL << PR_MTE_TAG_SHIFT)

void pointerPrint(int* ip, char s[])
{
    // Print the address pointed to by iptr %p : void*
    printf("PTR: %s Addr_pointed_to_by_ptr:  %p %lu \n", s, ip, ip );

    /*Print the address of iptr itself*/
    printf("Size of ptr: %lu Address_of_ptr:  %p\n", sizeof(ip), &ip );
}
 
int main()
{
    unsigned long hwcap2 = getauxval(AT_HWCAP2);
    /* check if MTE is present */
    if (!(hwcap2 & HWCAP2_MTE))
        return EXIT_FAILURE;

    /*
     * Enable the tagged address ABI [for this thread], synchronous or asynchronous MTE
     * tag check faults (based on per-CPU preference) and allow all
     * non-zero tags in the randomly generated set.
     */
    if (prctl(PR_SET_TAGGED_ADDR_CTRL,
              PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC | PR_MTE_TCF_ASYNC |
              (0xfffe << PR_MTE_TAG_SHIFT),
              0, 0, 0)) {
            perror("prctl() failed");
            return EXIT_FAILURE;
    }

    // TESTING heap tagging, as per https://stackoverflow.com/questions/67071289/qemu-hosting-mte-enabled-kernel-does-not-raise-fault/71137575#71137575
        printf("Hi %ld\n", (long)getpid());
        printf("sizeof int: %lu [malloc'ed arr of szof(int)+1] \n", sizeof(int));
        int *array = (int*) malloc (sizeof(int) * 1);
        pointerPrint(array, "malloc_array");
        printf("About to write to array[32] \n");
        array[32] = 1;
        printf("here is the value of array[32]: %d \n", array[32]);
        return 0;
}