1 #include <assert.h>
2 #include "pauth.h"
3
4 static int x;
5
main()6 int main()
7 {
8 int *p0 = &x, *p1, *p2, *p3;
9 unsigned long salt = 0;
10 int pac_feature = get_pac_feature();
11
12 /*
13 * Exit if no PAuth or FEAT_FPAC, which will SIGILL on AUTDA failure
14 * rather than return an error for us to check below.
15 */
16 if (pac_feature == 0 || pac_feature >= 4) {
17 return 0;
18 }
19
20 /*
21 * With TBI enabled and a 48-bit VA, there are 7 bits of auth, and so
22 * a 1/128 chance of auth = pac(ptr,key,salt) producing zero.
23 * Find a salt that creates auth != 0.
24 */
25 do {
26 salt++;
27 asm("pacda %0, %1" : "=r"(p1) : "r"(salt), "0"(p0));
28 } while (p0 == p1);
29
30 /*
31 * This pac must fail, because the input pointer bears an encryption,
32 * and so is not properly extended within bits [55:47]. This will
33 * toggle bit 54 in the output...
34 */
35 asm("pacda %0, %1" : "=r"(p2) : "r"(salt), "0"(p1));
36
37 /* ... so that the aut must fail, setting bit 53 in the output ... */
38 asm("autda %0, %1" : "=r"(p3) : "r"(salt), "0"(p2));
39
40 /* ... which means this equality must not hold. */
41 assert(p3 != p0);
42 return 0;
43 }
44