1 /*
2 * To be compiled with -march=armv8.5-a+memtag
3 *
4 * This test is adapted from a Linux test. Please see:
5 *
6 * https://www.kernel.org/doc/html/next/arch/arm64/memory-tagging-extension.html#example-of-correct-usage
7 */
8 #include <errno.h>
9 #include <stdint.h>
10 #include <stdio.h>
11 #include <stdlib.h>
12 #include <unistd.h>
13 #include <sys/auxv.h>
14 #include <sys/mman.h>
15 #include <sys/prctl.h>
16 #include <string.h>
17 /*
18 * From arch/arm64/include/uapi/asm/hwcap.h
19 */
20 #define HWCAP2_MTE (1 << 18)
21
22 /*
23 * From arch/arm64/include/uapi/asm/mman.h
24 */
25 #define PROT_MTE 0x20
26
27 /*
28 * Insert a random logical tag into the given pointer.
29 */
30 #define insert_random_tag(ptr) ({ \
31 uint64_t __val; \
32 asm("irg %0, %1" : "=r" (__val) : "r" (ptr)); \
33 __val; \
34 })
35
36 /*
37 * Set the allocation tag on the destination address.
38 */
39 #define set_tag(tagged_addr) do { \
40 asm volatile("stg %0, [%0]" : : "r" (tagged_addr) : "memory"); \
41 } while (0)
42
43
main(int argc,char * argv[])44 int main(int argc, char *argv[])
45 {
46 unsigned char *a;
47 unsigned long page_sz = sysconf(_SC_PAGESIZE);
48 unsigned long hwcap2 = getauxval(AT_HWCAP2);
49
50 /* check if MTE is present */
51 if (!(hwcap2 & HWCAP2_MTE)) {
52 return EXIT_FAILURE;
53 }
54
55 /*
56 * Enable the tagged address ABI, synchronous or asynchronous MTE
57 * tag check faults (based on per-CPU preference) and allow all
58 * non-zero tags in the randomly generated set.
59 */
60 if (prctl(PR_SET_TAGGED_ADDR_CTRL,
61 PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC | PR_MTE_TCF_ASYNC |
62 (0xfffe << PR_MTE_TAG_SHIFT),
63 0, 0, 0)) {
64 perror("prctl() failed");
65 return EXIT_FAILURE;
66 }
67
68 a = mmap(0, page_sz, PROT_READ | PROT_WRITE,
69 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
70 if (a == MAP_FAILED) {
71 perror("mmap() failed");
72 return EXIT_FAILURE;
73 }
74
75 printf("a[] address is %p\n", a);
76
77 /*
78 * Enable MTE on the above anonymous mmap. The flag could be passed
79 * directly to mmap() and skip this step.
80 */
81 if (mprotect(a, page_sz, PROT_READ | PROT_WRITE | PROT_MTE)) {
82 perror("mprotect() failed");
83 return EXIT_FAILURE;
84 }
85
86 /* access with the default tag (0) */
87 a[0] = 1;
88 a[1] = 2;
89
90 printf("a[0] = %hhu a[1] = %hhu\n", a[0], a[1]);
91
92 /* set the logical and allocation tags */
93 a = (unsigned char *)insert_random_tag(a);
94 set_tag(a);
95
96 printf("%p\n", a);
97
98 return 0;
99 }
100