1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2024 Rivos Inc.
4 */
5
6 #include <linux/cpu.h>
7 #include <linux/device.h>
8 #include <linux/sprintf.h>
9
10 #include <asm/bugs.h>
11 #include <asm/vendor_extensions/thead.h>
12
13 static enum mitigation_state ghostwrite_state;
14
ghostwrite_set_vulnerable(void)15 void ghostwrite_set_vulnerable(void)
16 {
17 ghostwrite_state = VULNERABLE;
18 }
19
20 /*
21 * Vendor extension alternatives will use the value set at the time of boot
22 * alternative patching, thus this must be called before boot alternatives are
23 * patched (and after extension probing) to be effective.
24 *
25 * Returns true if mitgated, false otherwise.
26 */
ghostwrite_enable_mitigation(void)27 bool ghostwrite_enable_mitigation(void)
28 {
29 if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR) &&
30 ghostwrite_state == VULNERABLE && !cpu_mitigations_off()) {
31 disable_xtheadvector();
32 ghostwrite_state = MITIGATED;
33 return true;
34 }
35
36 return false;
37 }
38
ghostwrite_get_state(void)39 enum mitigation_state ghostwrite_get_state(void)
40 {
41 return ghostwrite_state;
42 }
43
cpu_show_ghostwrite(struct device * dev,struct device_attribute * attr,char * buf)44 ssize_t cpu_show_ghostwrite(struct device *dev, struct device_attribute *attr, char *buf)
45 {
46 if (IS_ENABLED(CONFIG_RISCV_ISA_XTHEADVECTOR)) {
47 switch (ghostwrite_state) {
48 case UNAFFECTED:
49 return sprintf(buf, "Not affected\n");
50 case MITIGATED:
51 return sprintf(buf, "Mitigation: xtheadvector disabled\n");
52 case VULNERABLE:
53 fallthrough;
54 default:
55 return sprintf(buf, "Vulnerable\n");
56 }
57 } else {
58 return sprintf(buf, "Not affected\n");
59 }
60 }
61