1 /*
2 * Copyright (c) 2023, Google, Inc. All rights reserved
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files
6 * (the "Software"), to deal in the Software without restriction,
7 * including without limitation the rights to use, copy, modify, merge,
8 * publish, distribute, sublicense, and/or sell copies of the Software,
9 * and to permit persons to whom the Software is furnished to do so,
10 * subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
22 */
23
24 #define TLOG_TAG "pac"
25
26 #include <arch/ops.h>
27 #include <stdbool.h>
28 #include <stdint.h>
29
30 /*
31 * FEAT_PAuth is mandatory at ARM-A v8.3.
32 * FEAT_FPAC is mandatory at ARM-A v8.6.
33 * Assume present at v9 (and above), otherwise probe ID registers.
34 */
35 #if __ARM_ARCH >= 9
arch_pac_address_supported(void)36 bool arch_pac_address_supported(void) {
37 return true;
38 }
39
arch_pac_exception_supported(void)40 bool arch_pac_exception_supported(void) {
41 return true;
42 }
43 #else
44
45 #include <arch/arm64/sregs.h>
46 #include <arch/arm64.h>
47
get_nibble(uint64_t reg,uint8_t shift)48 static uint8_t get_nibble(uint64_t reg, uint8_t shift) {
49 return (reg >> shift) & 0xf;
50 }
51
arch_pac_address_supported(void)52 bool arch_pac_address_supported(void) {
53 const uint64_t isar1 = ARM64_READ_SYSREG(id_aa64isar1_el1);
54 const uint64_t isar2 = ARM64_READ_SYSREG(id_aa64isar2_el1);
55
56 /* Address & Data authentication (APIxKey_EL1, APDxKey_EL1)*/
57 return get_nibble(isar1, ID_AA64ISAR1_EL1_APA_SHIFT) != 0 ||
58 get_nibble(isar1, ID_AA64ISAR1_EL1_API_SHIFT) != 0 ||
59 get_nibble(isar2, ID_AA64ISAR2_EL1_APA3_SHIFT) != 0;
60 }
61
arch_pac_exception_supported(void)62 bool arch_pac_exception_supported(void) {
63
64 /*
65 * Check each of the sysregs.
66 * Only one register should be populated, and gives which algorithm is
67 * implemented. We check bit 0x4 in the field for FPAC or FPACCOMBINE.
68 */
69 const uint64_t isar1 = ARM64_READ_SYSREG(id_aa64isar1_el1);
70 const uint8_t apa = get_nibble(isar1, ID_AA64ISAR1_EL1_APA_SHIFT);
71 if (apa) {
72 return (apa & 0x4) != 0;
73 }
74
75 const uint8_t api = get_nibble(isar1, ID_AA64ISAR1_EL1_API_SHIFT);
76 if (api) {
77 return (api & 0x4) != 0;
78 }
79
80 const uint64_t isar2 = ARM64_READ_SYSREG(id_aa64isar2_el1);
81 const uint8_t apa3 = get_nibble(isar2, ID_AA64ISAR2_EL1_APA3_SHIFT);
82 if (apa3) {
83 return (apa3 & 0x4) != 0;
84 }
85
86 return false;
87 }
88 #endif
89