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