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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1353ebb4 | 2 | /* |
1353ebb4 JF |
3 | * Copyright (C) 1994 Linus Torvalds |
4 | * | |
5 | * Cyrix stuff, June 1998 by: | |
6 | * - Rafael R. Reilova (moved everything from head.S), | |
7 | * <rreilova@ececs.uc.edu> | |
8 | * - Channing Corn (tests & fixes), | |
9 | * - Andrew D. Balsa (code cleanup). | |
10 | */ | |
11 | #include <linux/init.h> | |
12 | #include <linux/utsname.h> | |
61dc0f55 | 13 | #include <linux/cpu.h> |
caf7501a | 14 | #include <linux/module.h> |
da285121 DW |
15 | |
16 | #include <asm/nospec-branch.h> | |
17 | #include <asm/cmdline.h> | |
91eb1b79 | 18 | #include <asm/bugs.h> |
1353ebb4 | 19 | #include <asm/processor.h> |
7ebad705 | 20 | #include <asm/processor-flags.h> |
952f07ec | 21 | #include <asm/fpu/internal.h> |
1353ebb4 JF |
22 | #include <asm/msr.h> |
23 | #include <asm/paravirt.h> | |
24 | #include <asm/alternative.h> | |
62a67e12 | 25 | #include <asm/pgtable.h> |
d1163651 | 26 | #include <asm/set_memory.h> |
c995efd5 | 27 | #include <asm/intel-family.h> |
1353ebb4 | 28 | |
da285121 DW |
29 | static void __init spectre_v2_select_mitigation(void); |
30 | ||
1353ebb4 JF |
31 | void __init check_bugs(void) |
32 | { | |
33 | identify_boot_cpu(); | |
55a36b65 | 34 | |
62a67e12 BP |
35 | if (!IS_ENABLED(CONFIG_SMP)) { |
36 | pr_info("CPU: "); | |
37 | print_cpu_info(&boot_cpu_data); | |
38 | } | |
39 | ||
da285121 DW |
40 | /* Select the proper spectre mitigation before patching alternatives */ |
41 | spectre_v2_select_mitigation(); | |
42 | ||
62a67e12 | 43 | #ifdef CONFIG_X86_32 |
55a36b65 BP |
44 | /* |
45 | * Check whether we are able to run this kernel safely on SMP. | |
46 | * | |
47 | * - i386 is no longer supported. | |
48 | * - In order to run on anything without a TSC, we need to be | |
49 | * compiled for a i486. | |
50 | */ | |
51 | if (boot_cpu_data.x86 < 4) | |
52 | panic("Kernel requires i486+ for 'invlpg' and other features"); | |
53 | ||
bfe4bb15 MV |
54 | init_utsname()->machine[1] = |
55 | '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); | |
1353ebb4 | 56 | alternative_instructions(); |
304bceda | 57 | |
4d164092 | 58 | fpu__init_check_bugs(); |
62a67e12 BP |
59 | #else /* CONFIG_X86_64 */ |
60 | alternative_instructions(); | |
61 | ||
62 | /* | |
63 | * Make sure the first 2MB area is not mapped by huge pages | |
64 | * There are typically fixed size MTRRs in there and overlapping | |
65 | * MTRRs into large pages causes slow downs. | |
66 | * | |
67 | * Right now we don't do that with gbpages because there seems | |
68 | * very little benefit for that case. | |
69 | */ | |
70 | if (!direct_gbpages) | |
71 | set_memory_4k((unsigned long)__va(0), 1); | |
72 | #endif | |
1353ebb4 | 73 | } |
61dc0f55 | 74 | |
da285121 DW |
75 | /* The kernel command line selection */ |
76 | enum spectre_v2_mitigation_cmd { | |
77 | SPECTRE_V2_CMD_NONE, | |
78 | SPECTRE_V2_CMD_AUTO, | |
79 | SPECTRE_V2_CMD_FORCE, | |
80 | SPECTRE_V2_CMD_RETPOLINE, | |
81 | SPECTRE_V2_CMD_RETPOLINE_GENERIC, | |
82 | SPECTRE_V2_CMD_RETPOLINE_AMD, | |
83 | }; | |
84 | ||
85 | static const char *spectre_v2_strings[] = { | |
86 | [SPECTRE_V2_NONE] = "Vulnerable", | |
87 | [SPECTRE_V2_RETPOLINE_MINIMAL] = "Vulnerable: Minimal generic ASM retpoline", | |
88 | [SPECTRE_V2_RETPOLINE_MINIMAL_AMD] = "Vulnerable: Minimal AMD ASM retpoline", | |
89 | [SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline", | |
90 | [SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline", | |
91 | }; | |
92 | ||
93 | #undef pr_fmt | |
94 | #define pr_fmt(fmt) "Spectre V2 mitigation: " fmt | |
95 | ||
96 | static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE; | |
caf7501a AK |
97 | static bool spectre_v2_bad_module; |
98 | ||
99 | #ifdef RETPOLINE | |
100 | bool retpoline_module_ok(bool has_retpoline) | |
101 | { | |
102 | if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline) | |
103 | return true; | |
104 | ||
105 | pr_err("System may be vunerable to spectre v2\n"); | |
106 | spectre_v2_bad_module = true; | |
107 | return false; | |
108 | } | |
109 | #endif | |
da285121 DW |
110 | |
111 | static void __init spec2_print_if_insecure(const char *reason) | |
112 | { | |
113 | if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) | |
114 | pr_info("%s\n", reason); | |
115 | } | |
116 | ||
117 | static void __init spec2_print_if_secure(const char *reason) | |
118 | { | |
119 | if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) | |
120 | pr_info("%s\n", reason); | |
121 | } | |
122 | ||
123 | static inline bool retp_compiler(void) | |
124 | { | |
125 | return __is_defined(RETPOLINE); | |
126 | } | |
127 | ||
128 | static inline bool match_option(const char *arg, int arglen, const char *opt) | |
129 | { | |
130 | int len = strlen(opt); | |
131 | ||
132 | return len == arglen && !strncmp(arg, opt, len); | |
133 | } | |
134 | ||
135 | static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) | |
136 | { | |
137 | char arg[20]; | |
138 | int ret; | |
139 | ||
140 | ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, | |
141 | sizeof(arg)); | |
142 | if (ret > 0) { | |
143 | if (match_option(arg, ret, "off")) { | |
144 | goto disable; | |
145 | } else if (match_option(arg, ret, "on")) { | |
146 | spec2_print_if_secure("force enabled on command line."); | |
147 | return SPECTRE_V2_CMD_FORCE; | |
148 | } else if (match_option(arg, ret, "retpoline")) { | |
149 | spec2_print_if_insecure("retpoline selected on command line."); | |
150 | return SPECTRE_V2_CMD_RETPOLINE; | |
151 | } else if (match_option(arg, ret, "retpoline,amd")) { | |
152 | if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) { | |
153 | pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n"); | |
154 | return SPECTRE_V2_CMD_AUTO; | |
155 | } | |
156 | spec2_print_if_insecure("AMD retpoline selected on command line."); | |
157 | return SPECTRE_V2_CMD_RETPOLINE_AMD; | |
158 | } else if (match_option(arg, ret, "retpoline,generic")) { | |
159 | spec2_print_if_insecure("generic retpoline selected on command line."); | |
160 | return SPECTRE_V2_CMD_RETPOLINE_GENERIC; | |
161 | } else if (match_option(arg, ret, "auto")) { | |
162 | return SPECTRE_V2_CMD_AUTO; | |
163 | } | |
164 | } | |
165 | ||
166 | if (!cmdline_find_option_bool(boot_command_line, "nospectre_v2")) | |
167 | return SPECTRE_V2_CMD_AUTO; | |
168 | disable: | |
169 | spec2_print_if_insecure("disabled on command line."); | |
170 | return SPECTRE_V2_CMD_NONE; | |
171 | } | |
172 | ||
c995efd5 DW |
173 | /* Check for Skylake-like CPUs (for RSB handling) */ |
174 | static bool __init is_skylake_era(void) | |
175 | { | |
176 | if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && | |
177 | boot_cpu_data.x86 == 6) { | |
178 | switch (boot_cpu_data.x86_model) { | |
179 | case INTEL_FAM6_SKYLAKE_MOBILE: | |
180 | case INTEL_FAM6_SKYLAKE_DESKTOP: | |
181 | case INTEL_FAM6_SKYLAKE_X: | |
182 | case INTEL_FAM6_KABYLAKE_MOBILE: | |
183 | case INTEL_FAM6_KABYLAKE_DESKTOP: | |
184 | return true; | |
185 | } | |
186 | } | |
187 | return false; | |
188 | } | |
189 | ||
da285121 DW |
190 | static void __init spectre_v2_select_mitigation(void) |
191 | { | |
192 | enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); | |
193 | enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; | |
194 | ||
195 | /* | |
196 | * If the CPU is not affected and the command line mode is NONE or AUTO | |
197 | * then nothing to do. | |
198 | */ | |
199 | if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && | |
200 | (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO)) | |
201 | return; | |
202 | ||
203 | switch (cmd) { | |
204 | case SPECTRE_V2_CMD_NONE: | |
205 | return; | |
206 | ||
207 | case SPECTRE_V2_CMD_FORCE: | |
208 | /* FALLTRHU */ | |
209 | case SPECTRE_V2_CMD_AUTO: | |
210 | goto retpoline_auto; | |
211 | ||
212 | case SPECTRE_V2_CMD_RETPOLINE_AMD: | |
213 | if (IS_ENABLED(CONFIG_RETPOLINE)) | |
214 | goto retpoline_amd; | |
215 | break; | |
216 | case SPECTRE_V2_CMD_RETPOLINE_GENERIC: | |
217 | if (IS_ENABLED(CONFIG_RETPOLINE)) | |
218 | goto retpoline_generic; | |
219 | break; | |
220 | case SPECTRE_V2_CMD_RETPOLINE: | |
221 | if (IS_ENABLED(CONFIG_RETPOLINE)) | |
222 | goto retpoline_auto; | |
223 | break; | |
224 | } | |
225 | pr_err("kernel not compiled with retpoline; no mitigation available!"); | |
226 | return; | |
227 | ||
228 | retpoline_auto: | |
229 | if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { | |
230 | retpoline_amd: | |
231 | if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { | |
232 | pr_err("LFENCE not serializing. Switching to generic retpoline\n"); | |
233 | goto retpoline_generic; | |
234 | } | |
235 | mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD : | |
236 | SPECTRE_V2_RETPOLINE_MINIMAL_AMD; | |
237 | setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD); | |
238 | setup_force_cpu_cap(X86_FEATURE_RETPOLINE); | |
239 | } else { | |
240 | retpoline_generic: | |
241 | mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC : | |
242 | SPECTRE_V2_RETPOLINE_MINIMAL; | |
243 | setup_force_cpu_cap(X86_FEATURE_RETPOLINE); | |
244 | } | |
245 | ||
246 | spectre_v2_enabled = mode; | |
247 | pr_info("%s\n", spectre_v2_strings[mode]); | |
c995efd5 DW |
248 | |
249 | /* | |
250 | * If neither SMEP or KPTI are available, there is a risk of | |
251 | * hitting userspace addresses in the RSB after a context switch | |
252 | * from a shallow call stack to a deeper one. To prevent this fill | |
253 | * the entire RSB, even when using IBRS. | |
254 | * | |
255 | * Skylake era CPUs have a separate issue with *underflow* of the | |
256 | * RSB, when they will predict 'ret' targets from the generic BTB. | |
257 | * The proper mitigation for this is IBRS. If IBRS is not supported | |
258 | * or deactivated in favour of retpolines the RSB fill on context | |
259 | * switch is required. | |
260 | */ | |
261 | if ((!boot_cpu_has(X86_FEATURE_PTI) && | |
262 | !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) { | |
263 | setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); | |
264 | pr_info("Filling RSB on context switch\n"); | |
265 | } | |
da285121 DW |
266 | } |
267 | ||
268 | #undef pr_fmt | |
269 | ||
61dc0f55 TG |
270 | #ifdef CONFIG_SYSFS |
271 | ssize_t cpu_show_meltdown(struct device *dev, | |
272 | struct device_attribute *attr, char *buf) | |
273 | { | |
274 | if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) | |
275 | return sprintf(buf, "Not affected\n"); | |
276 | if (boot_cpu_has(X86_FEATURE_PTI)) | |
277 | return sprintf(buf, "Mitigation: PTI\n"); | |
278 | return sprintf(buf, "Vulnerable\n"); | |
279 | } | |
280 | ||
281 | ssize_t cpu_show_spectre_v1(struct device *dev, | |
282 | struct device_attribute *attr, char *buf) | |
283 | { | |
284 | if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1)) | |
285 | return sprintf(buf, "Not affected\n"); | |
286 | return sprintf(buf, "Vulnerable\n"); | |
287 | } | |
288 | ||
289 | ssize_t cpu_show_spectre_v2(struct device *dev, | |
290 | struct device_attribute *attr, char *buf) | |
291 | { | |
292 | if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) | |
293 | return sprintf(buf, "Not affected\n"); | |
da285121 | 294 | |
caf7501a AK |
295 | return sprintf(buf, "%s%s\n", spectre_v2_strings[spectre_v2_enabled], |
296 | spectre_v2_bad_module ? " - vulnerable module loaded" : ""); | |
61dc0f55 TG |
297 | } |
298 | #endif |