cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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i915_mitigations.c (3135B)

      1// SPDX-License-Identifier: MIT
      2/*
      3 * Copyright © 2021 Intel Corporation
      4 */
      5
      6#include <linux/kernel.h>
      7#include <linux/moduleparam.h>
      8#include <linux/slab.h>
      9#include <linux/string.h>
     10
     11#include "i915_driver.h"
     12#include "i915_drv.h"
     13#include "i915_mitigations.h"
     14
     15static unsigned long mitigations __read_mostly = ~0UL;
     16
     17enum {
     18	CLEAR_RESIDUALS = 0,
     19};
     20
     21static const char * const names[] = {
     22	[CLEAR_RESIDUALS] = "residuals",
     23};
     24
     25bool i915_mitigate_clear_residuals(void)
     26{
     27	return READ_ONCE(mitigations) & BIT(CLEAR_RESIDUALS);
     28}
     29
     30static int mitigations_set(const char *val, const struct kernel_param *kp)
     31{
     32	unsigned long new = ~0UL;
     33	char *str, *sep, *tok;
     34	bool first = true;
     35	int err = 0;
     36
     37	BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations));
     38
     39	str = kstrdup(val, GFP_KERNEL);
     40	if (!str)
     41		return -ENOMEM;
     42
     43	for (sep = str; (tok = strsep(&sep, ","));) {
     44		bool enable = true;
     45		int i;
     46
     47		/* Be tolerant of leading/trailing whitespace */
     48		tok = strim(tok);
     49
     50		if (first) {
     51			first = false;
     52
     53			if (!strcmp(tok, "auto"))
     54				continue;
     55
     56			new = 0;
     57			if (!strcmp(tok, "off"))
     58				continue;
     59		}
     60
     61		if (*tok == '!') {
     62			enable = !enable;
     63			tok++;
     64		}
     65
     66		if (!strncmp(tok, "no", 2)) {
     67			enable = !enable;
     68			tok += 2;
     69		}
     70
     71		if (*tok == '\0')
     72			continue;
     73
     74		for (i = 0; i < ARRAY_SIZE(names); i++) {
     75			if (!strcmp(tok, names[i])) {
     76				if (enable)
     77					new |= BIT(i);
     78				else
     79					new &= ~BIT(i);
     80				break;
     81			}
     82		}
     83		if (i == ARRAY_SIZE(names)) {
     84			pr_err("Bad \"%s.mitigations=%s\", '%s' is unknown\n",
     85			       DRIVER_NAME, val, tok);
     86			err = -EINVAL;
     87			break;
     88		}
     89	}
     90	kfree(str);
     91	if (err)
     92		return err;
     93
     94	WRITE_ONCE(mitigations, new);
     95	return 0;
     96}
     97
     98static int mitigations_get(char *buffer, const struct kernel_param *kp)
     99{
    100	unsigned long local = READ_ONCE(mitigations);
    101	int count, i;
    102	bool enable;
    103
    104	if (!local)
    105		return scnprintf(buffer, PAGE_SIZE, "%s\n", "off");
    106
    107	if (local & BIT(BITS_PER_LONG - 1)) {
    108		count = scnprintf(buffer, PAGE_SIZE, "%s,", "auto");
    109		enable = false;
    110	} else {
    111		enable = true;
    112		count = 0;
    113	}
    114
    115	for (i = 0; i < ARRAY_SIZE(names); i++) {
    116		if ((local & BIT(i)) != enable)
    117			continue;
    118
    119		count += scnprintf(buffer + count, PAGE_SIZE - count,
    120				   "%s%s,", enable ? "" : "!", names[i]);
    121	}
    122
    123	buffer[count - 1] = '\n';
    124	return count;
    125}
    126
    127static const struct kernel_param_ops ops = {
    128	.set = mitigations_set,
    129	.get = mitigations_get,
    130};
    131
    132module_param_cb_unsafe(mitigations, &ops, NULL, 0600);
    133MODULE_PARM_DESC(mitigations,
    134"Selectively enable security mitigations for all Intel® GPUs in the system.\n"
    135"\n"
    136"  auto -- enables all mitigations required for the platform [default]\n"
    137"  off  -- disables all mitigations\n"
    138"\n"
    139"Individual mitigations can be enabled by passing a comma-separated string,\n"
    140"e.g. mitigations=residuals to enable only clearing residuals or\n"
    141"mitigations=auto,noresiduals to disable only the clear residual mitigation.\n"
    142"Either '!' or 'no' may be used to switch from enabling the mitigation to\n"
    143"disabling it.\n"
    144"\n"
    145"Active mitigations for Ivybridge, Baytrail, Haswell:\n"
    146"  residuals -- clear all thread-local registers between contexts"
    147);