bugs.c

 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
13static enum mitigation_state ghostwrite_state;
14
15void 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 */
27bool 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
39enum mitigation_state ghostwrite_get_state(void)
40{
41	return ghostwrite_state;
42}
43
44ssize_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}