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#include <stdint.h>
#include <assert.h>
asm(".arch armv8.4-a");
void do_test(uint64_t value)
{
uint64_t salt1, salt2;
uint64_t encode, decode;
/*
* With TBI enabled and a 48-bit VA, there are 7 bits of auth,
* and so a 1/128 chance of encode = pac(value,key,salt) producing
* an auth for which leaves value unchanged.
* Iterate until we find a salt for which encode != value.
*/
for (salt1 = 1; ; salt1++) {
asm volatile("pacda %0, %2" : "=r"(encode) : "0"(value), "r"(salt1));
if (encode != value) {
break;
}
}
/* A valid salt must produce a valid authorization. */
asm volatile("autda %0, %2" : "=r"(decode) : "0"(encode), "r"(salt1));
assert(decode == value);
/*
* An invalid salt usually fails authorization, but again there
* is a chance of choosing another salt that works.
* Iterate until we find another salt which does fail.
*/
for (salt2 = salt1 + 1; ; salt2++) {
asm volatile("autda %0, %2" : "=r"(decode) : "0"(encode), "r"(salt2));
if (decode != value) {
break;
}
}
/* The VA bits, bit 55, and the TBI bits, should be unchanged. */
assert(((decode ^ value) & 0xff80ffffffffffffull) == 0);
/*
* Bits [54:53] are an error indicator based on the key used;
* the DA key above is keynumber 0, so error == 0b01. Otherwise
* bit 55 of the original is sign-extended into the rest of the auth.
*/
if ((value >> 55) & 1) {
assert(((decode >> 48) & 0xff) == 0b10111111);
} else {
assert(((decode >> 48) & 0xff) == 0b00100000);
}
}
int main()
{
do_test(0);
do_test(-1);
do_test(0xda004acedeadbeefull);
return 0;
}
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