| 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 | |
| 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 | */ |
| 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 | |
| 39 | enum mitigation_state ghostwrite_get_state(void) |
| 40 | { |
| 41 | return ghostwrite_state; |
| 42 | } |
| 43 | |
| 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, fmt: "Not affected\n"); |
| 50 | case MITIGATED: |
| 51 | return sprintf(buf, fmt: "Mitigation: xtheadvector disabled\n"); |
| 52 | case VULNERABLE: |
| 53 | fallthrough; |
| 54 | default: |
| 55 | return sprintf(buf, fmt: "Vulnerable\n"); |
| 56 | } |
| 57 | } else { |
| 58 | return sprintf(buf, fmt: "Not affected\n"); |
| 59 | } |
| 60 | } |
| 61 |