arch/powerpc/kernel/security.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 //
   3 // Security related flags and so on.
   4 //
   5 // Copyright 2018, Michael Ellerman, IBM Corporation.
   6
   7 #include <linux/kernel.h>
   8 #include <linux/debugfs.h>
   9 #include <linux/device.h>
  10 #include <linux/seq_buf.h>
  11
  12 #include <asm/debug.h>
  13 #include <asm/security_features.h>
  14 #include <asm/setup.h>
  15
  16
  17 unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
  18
  19 bool barrier_nospec_enabled;
  20
  21 static void enable_barrier_nospec(bool enable)
  22 {
  23         barrier_nospec_enabled = enable;
  24         do_barrier_nospec_fixups(enable);
  25 }
  26
  27 void setup_barrier_nospec(void)
  28 {
  29         bool enable;
  30
  31         /*
  32          * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
  33          * But there's a good reason not to. The two flags we check below are
  34          * both are enabled by default in the kernel, so if the hcall is not
  35          * functional they will be enabled.
  36          * On a system where the host firmware has been updated (so the ori
  37          * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
  38          * not been updated, we would like to enable the barrier. Dropping the
  39          * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
  40          * we potentially enable the barrier on systems where the host firmware
  41          * is not updated, but that's harmless as it's a no-op.
  42          */
  43         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
  44                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
  45
  46         enable_barrier_nospec(enable);
  47 }
  48
  49 #ifdef CONFIG_DEBUG_FS
  50 static int barrier_nospec_set(void *data, u64 val)
  51 {
  52         switch (val) {
  53         case 0:
  54         case 1:
  55                 break;
  56         default:
  57                 return -EINVAL;
  58         }
  59
  60         if (!!val == !!barrier_nospec_enabled)
  61                 return 0;
  62
  63         enable_barrier_nospec(!!val);
  64
  65         return 0;
  66 }
  67
  68 static int barrier_nospec_get(void *data, u64 *val)
  69 {
  70         *val = barrier_nospec_enabled ? 1 : 0;
  71         return 0;
  72 }
  73
  74 DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
  75                         barrier_nospec_get, barrier_nospec_set, "%llu\n");
  76
  77 static __init int barrier_nospec_debugfs_init(void)
  78 {
  79         debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
  80                             &fops_barrier_nospec);
  81         return 0;
  82 }
  83 device_initcall(barrier_nospec_debugfs_init);
  84 #endif /* CONFIG_DEBUG_FS */
  85
  86 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
  87 {
  88         bool thread_priv;
  89
  90         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
  91
  92         if (rfi_flush || thread_priv) {
  93                 struct seq_buf s;
  94                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
  95
  96                 seq_buf_printf(&s, "Mitigation: ");
  97
  98                 if (rfi_flush)
  99                         seq_buf_printf(&s, "RFI Flush");
 100
 101                 if (rfi_flush && thread_priv)
 102                         seq_buf_printf(&s, ", ");
 103
 104                 if (thread_priv)
 105                         seq_buf_printf(&s, "L1D private per thread");
 106
 107                 seq_buf_printf(&s, "\n");
 108
 109                 return s.len;
 110         }
 111
 112         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 113             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 114                 return sprintf(buf, "Not affected\n");
 115
 116         return sprintf(buf, "Vulnerable\n");
 117 }
 118
 119 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 120 {
 121         struct seq_buf s;
 122
 123         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 124
 125         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 126                 if (barrier_nospec_enabled)
 127                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 128                 else
 129                         seq_buf_printf(&s, "Vulnerable");
 130
 131                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 132                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 133
 134                 seq_buf_printf(&s, "\n");
 135         } else
 136                 seq_buf_printf(&s, "Not affected\n");
 137
 138         return s.len;
 139 }
 140
 141 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 142 {
 143         struct seq_buf s;
 144         bool bcs, ccd;
 145
 146         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 147
 148         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 149         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 150
 151         if (bcs || ccd) {
 152                 seq_buf_printf(&s, "Mitigation: ");
 153
 154                 if (bcs)
 155                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 156
 157                 if (bcs && ccd)
 158                         seq_buf_printf(&s, ", ");
 159
 160                 if (ccd)
 161                         seq_buf_printf(&s, "Indirect branch cache disabled");
 162         } else
 163                 seq_buf_printf(&s, "Vulnerable");
 164
 165         seq_buf_printf(&s, "\n");
 166
 167         return s.len;
 168 }
 169
 170 /*
 171  * Store-forwarding barrier support.
 172  */
 173
 174 static enum stf_barrier_type stf_enabled_flush_types;
 175 static bool no_stf_barrier;
 176 bool stf_barrier;
 177
 178 static int __init handle_no_stf_barrier(char *p)
 179 {
 180         pr_info("stf-barrier: disabled on command line.");
 181         no_stf_barrier = true;
 182         return 0;
 183 }
 184
 185 early_param("no_stf_barrier", handle_no_stf_barrier);
 186
 187 /* This is the generic flag used by other architectures */
 188 static int __init handle_ssbd(char *p)
 189 {
 190         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 191                 /* Until firmware tells us, we have the barrier with auto */
 192                 return 0;
 193         } else if (strncmp(p, "off", 3) == 0) {
 194                 handle_no_stf_barrier(NULL);
 195                 return 0;
 196         } else
 197                 return 1;
 198
 199         return 0;
 200 }
 201 early_param("spec_store_bypass_disable", handle_ssbd);
 202
 203 /* This is the generic flag used by other architectures */
 204 static int __init handle_no_ssbd(char *p)
 205 {
 206         handle_no_stf_barrier(NULL);
 207         return 0;
 208 }
 209 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 210
 211 static void stf_barrier_enable(bool enable)
 212 {
 213         if (enable)
 214                 do_stf_barrier_fixups(stf_enabled_flush_types);
 215         else
 216                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 217
 218         stf_barrier = enable;
 219 }
 220
 221 void setup_stf_barrier(void)
 222 {
 223         enum stf_barrier_type type;
 224         bool enable, hv;
 225
 226         hv = cpu_has_feature(CPU_FTR_HVMODE);
 227
 228         /* Default to fallback in case fw-features are not available */
 229         if (cpu_has_feature(CPU_FTR_ARCH_300))
 230                 type = STF_BARRIER_EIEIO;
 231         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 232                 type = STF_BARRIER_SYNC_ORI;
 233         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 234                 type = STF_BARRIER_FALLBACK;
 235         else
 236                 type = STF_BARRIER_NONE;
 237
 238         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 239                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 240                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 241
 242         if (type == STF_BARRIER_FALLBACK) {
 243                 pr_info("stf-barrier: fallback barrier available\n");
 244         } else if (type == STF_BARRIER_SYNC_ORI) {
 245                 pr_info("stf-barrier: hwsync barrier available\n");
 246         } else if (type == STF_BARRIER_EIEIO) {
 247                 pr_info("stf-barrier: eieio barrier available\n");
 248         }
 249
 250         stf_enabled_flush_types = type;
 251
 252         if (!no_stf_barrier)
 253                 stf_barrier_enable(enable);
 254 }
 255
 256 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 257 {
 258         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 259                 const char *type;
 260                 switch (stf_enabled_flush_types) {
 261                 case STF_BARRIER_EIEIO:
 262                         type = "eieio";
 263                         break;
 264                 case STF_BARRIER_SYNC_ORI:
 265                         type = "hwsync";
 266                         break;
 267                 case STF_BARRIER_FALLBACK:
 268                         type = "fallback";
 269                         break;
 270                 default:
 271                         type = "unknown";
 272                 }
 273                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 274         }
 275
 276         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 277             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 278                 return sprintf(buf, "Not affected\n");
 279
 280         return sprintf(buf, "Vulnerable\n");
 281 }
 282
 283 #ifdef CONFIG_DEBUG_FS
 284 static int stf_barrier_set(void *data, u64 val)
 285 {
 286         bool enable;
 287
 288         if (val == 1)
 289                 enable = true;
 290         else if (val == 0)
 291                 enable = false;
 292         else
 293                 return -EINVAL;
 294
 295         /* Only do anything if we're changing state */
 296         if (enable != stf_barrier)
 297                 stf_barrier_enable(enable);
 298
 299         return 0;
 300 }
 301
 302 static int stf_barrier_get(void *data, u64 *val)
 303 {
 304         *val = stf_barrier ? 1 : 0;
 305         return 0;
 306 }
 307
 308 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 309
 310 static __init int stf_barrier_debugfs_init(void)
 311 {
 312         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 313         return 0;
 314 }
 315 device_initcall(stf_barrier_debugfs_init);
 316 #endif /* CONFIG_DEBUG_FS */