1 // SPDX-License-Identifier: GPL-2.0 2 /* 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> 13 #include <linux/cpu.h> 14 15 #include <asm/nospec-branch.h> 16 #include <asm/cmdline.h> 17 #include <asm/bugs.h> 18 #include <asm/processor.h> 19 #include <asm/processor-flags.h> 20 #include <asm/fpu/internal.h> 21 #include <asm/msr.h> 22 #include <asm/paravirt.h> 23 #include <asm/alternative.h> 24 #include <asm/pgtable.h> 25 #include <asm/set_memory.h> 26 27 static void __init spectre_v2_select_mitigation(void); 28 29 void __init check_bugs(void) 30 { 31 identify_boot_cpu(); 32 33 if (!IS_ENABLED(CONFIG_SMP)) { 34 pr_info("CPU: "); 35 print_cpu_info(&boot_cpu_data); 36 } 37 38 /* Select the proper spectre mitigation before patching alternatives */ 39 spectre_v2_select_mitigation(); 40 41 #ifdef CONFIG_X86_32 42 /* 43 * Check whether we are able to run this kernel safely on SMP. 44 * 45 * - i386 is no longer supported. 46 * - In order to run on anything without a TSC, we need to be 47 * compiled for a i486. 48 */ 49 if (boot_cpu_data.x86 < 4) 50 panic("Kernel requires i486+ for 'invlpg' and other features"); 51 52 init_utsname()->machine[1] = 53 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86); 54 alternative_instructions(); 55 56 fpu__init_check_bugs(); 57 #else /* CONFIG_X86_64 */ 58 alternative_instructions(); 59 60 /* 61 * Make sure the first 2MB area is not mapped by huge pages 62 * There are typically fixed size MTRRs in there and overlapping 63 * MTRRs into large pages causes slow downs. 64 * 65 * Right now we don't do that with gbpages because there seems 66 * very little benefit for that case. 67 */ 68 if (!direct_gbpages) 69 set_memory_4k((unsigned long)__va(0), 1); 70 #endif 71 } 72 73 /* The kernel command line selection */ 74 enum spectre_v2_mitigation_cmd { 75 SPECTRE_V2_CMD_NONE, 76 SPECTRE_V2_CMD_AUTO, 77 SPECTRE_V2_CMD_FORCE, 78 SPECTRE_V2_CMD_RETPOLINE, 79 SPECTRE_V2_CMD_RETPOLINE_GENERIC, 80 SPECTRE_V2_CMD_RETPOLINE_AMD, 81 }; 82 83 static const char *spectre_v2_strings[] = { 84 [SPECTRE_V2_NONE] = "Vulnerable", 85 [SPECTRE_V2_RETPOLINE_MINIMAL] = "Vulnerable: Minimal generic ASM retpoline", 86 [SPECTRE_V2_RETPOLINE_MINIMAL_AMD] = "Vulnerable: Minimal AMD ASM retpoline", 87 [SPECTRE_V2_RETPOLINE_GENERIC] = "Mitigation: Full generic retpoline", 88 [SPECTRE_V2_RETPOLINE_AMD] = "Mitigation: Full AMD retpoline", 89 }; 90 91 #undef pr_fmt 92 #define pr_fmt(fmt) "Spectre V2 mitigation: " fmt 93 94 static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE; 95 96 static void __init spec2_print_if_insecure(const char *reason) 97 { 98 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) 99 pr_info("%s\n", reason); 100 } 101 102 static void __init spec2_print_if_secure(const char *reason) 103 { 104 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) 105 pr_info("%s\n", reason); 106 } 107 108 static inline bool retp_compiler(void) 109 { 110 return __is_defined(RETPOLINE); 111 } 112 113 static inline bool match_option(const char *arg, int arglen, const char *opt) 114 { 115 int len = strlen(opt); 116 117 return len == arglen && !strncmp(arg, opt, len); 118 } 119 120 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void) 121 { 122 char arg[20]; 123 int ret; 124 125 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, 126 sizeof(arg)); 127 if (ret > 0) { 128 if (match_option(arg, ret, "off")) { 129 goto disable; 130 } else if (match_option(arg, ret, "on")) { 131 spec2_print_if_secure("force enabled on command line."); 132 return SPECTRE_V2_CMD_FORCE; 133 } else if (match_option(arg, ret, "retpoline")) { 134 spec2_print_if_insecure("retpoline selected on command line."); 135 return SPECTRE_V2_CMD_RETPOLINE; 136 } else if (match_option(arg, ret, "retpoline,amd")) { 137 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD) { 138 pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n"); 139 return SPECTRE_V2_CMD_AUTO; 140 } 141 spec2_print_if_insecure("AMD retpoline selected on command line."); 142 return SPECTRE_V2_CMD_RETPOLINE_AMD; 143 } else if (match_option(arg, ret, "retpoline,generic")) { 144 spec2_print_if_insecure("generic retpoline selected on command line."); 145 return SPECTRE_V2_CMD_RETPOLINE_GENERIC; 146 } else if (match_option(arg, ret, "auto")) { 147 return SPECTRE_V2_CMD_AUTO; 148 } 149 } 150 151 if (!cmdline_find_option_bool(boot_command_line, "nospectre_v2")) 152 return SPECTRE_V2_CMD_AUTO; 153 disable: 154 spec2_print_if_insecure("disabled on command line."); 155 return SPECTRE_V2_CMD_NONE; 156 } 157 158 static void __init spectre_v2_select_mitigation(void) 159 { 160 enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); 161 enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; 162 163 /* 164 * If the CPU is not affected and the command line mode is NONE or AUTO 165 * then nothing to do. 166 */ 167 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) && 168 (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO)) 169 return; 170 171 switch (cmd) { 172 case SPECTRE_V2_CMD_NONE: 173 return; 174 175 case SPECTRE_V2_CMD_FORCE: 176 /* FALLTRHU */ 177 case SPECTRE_V2_CMD_AUTO: 178 goto retpoline_auto; 179 180 case SPECTRE_V2_CMD_RETPOLINE_AMD: 181 if (IS_ENABLED(CONFIG_RETPOLINE)) 182 goto retpoline_amd; 183 break; 184 case SPECTRE_V2_CMD_RETPOLINE_GENERIC: 185 if (IS_ENABLED(CONFIG_RETPOLINE)) 186 goto retpoline_generic; 187 break; 188 case SPECTRE_V2_CMD_RETPOLINE: 189 if (IS_ENABLED(CONFIG_RETPOLINE)) 190 goto retpoline_auto; 191 break; 192 } 193 pr_err("kernel not compiled with retpoline; no mitigation available!"); 194 return; 195 196 retpoline_auto: 197 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { 198 retpoline_amd: 199 if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { 200 pr_err("LFENCE not serializing. Switching to generic retpoline\n"); 201 goto retpoline_generic; 202 } 203 mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD : 204 SPECTRE_V2_RETPOLINE_MINIMAL_AMD; 205 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD); 206 setup_force_cpu_cap(X86_FEATURE_RETPOLINE); 207 } else { 208 retpoline_generic: 209 mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC : 210 SPECTRE_V2_RETPOLINE_MINIMAL; 211 setup_force_cpu_cap(X86_FEATURE_RETPOLINE); 212 } 213 214 spectre_v2_enabled = mode; 215 pr_info("%s\n", spectre_v2_strings[mode]); 216 } 217 218 #undef pr_fmt 219 220 #ifdef CONFIG_SYSFS 221 ssize_t cpu_show_meltdown(struct device *dev, 222 struct device_attribute *attr, char *buf) 223 { 224 if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) 225 return sprintf(buf, "Not affected\n"); 226 if (boot_cpu_has(X86_FEATURE_PTI)) 227 return sprintf(buf, "Mitigation: PTI\n"); 228 return sprintf(buf, "Vulnerable\n"); 229 } 230 231 ssize_t cpu_show_spectre_v1(struct device *dev, 232 struct device_attribute *attr, char *buf) 233 { 234 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1)) 235 return sprintf(buf, "Not affected\n"); 236 return sprintf(buf, "Vulnerable\n"); 237 } 238 239 ssize_t cpu_show_spectre_v2(struct device *dev, 240 struct device_attribute *attr, char *buf) 241 { 242 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) 243 return sprintf(buf, "Not affected\n"); 244 245 return sprintf(buf, "%s\n", spectre_v2_strings[spectre_v2_enabled]); 246 } 247 #endif 248