release/src-rt-6.x/linux/linux-2.6/arch/i386/kernel/alternative.c

   1 #include <linux/module.h>
   2 #include <linux/sched.h>
   3 #include <linux/spinlock.h>
   4 #include <linux/list.h>
   5 #include <asm/alternative.h>
   6 #include <asm/sections.h>
   7
   8 static int noreplace_smp     = 0;
   9 static int smp_alt_once      = 0;
  10 static int debug_alternative = 0;
  11
  12 static int __init bootonly(char *str)
  13 {
  14         smp_alt_once = 1;
  15         return 1;
  16 }
  17 __setup("smp-alt-boot", bootonly);
  18
  19 static int __init debug_alt(char *str)
  20 {
  21         debug_alternative = 1;
  22         return 1;
  23 }
  24 __setup("debug-alternative", debug_alt);
  25
  26 static int __init setup_noreplace_smp(char *str)
  27 {
  28         noreplace_smp = 1;
  29         return 1;
  30 }
  31 __setup("noreplace-smp", setup_noreplace_smp);
  32
  33 #ifdef CONFIG_PARAVIRT
  34 static int noreplace_paravirt = 0;
  35
  36 static int __init setup_noreplace_paravirt(char *str)
  37 {
  38         noreplace_paravirt = 1;
  39         return 1;
  40 }
  41 __setup("noreplace-paravirt", setup_noreplace_paravirt);
  42 #endif
  43
  44 #define DPRINTK(fmt, args...) if (debug_alternative) \
  45         printk(KERN_DEBUG fmt, args)
  46
  47 #ifdef GENERIC_NOP1
  48 /* Use inline assembly to define this because the nops are defined
  49    as inline assembly strings in the include files and we cannot
  50    get them easily into strings. */
  51 asm("\t.data\nintelnops: "
  52         GENERIC_NOP1 GENERIC_NOP2 GENERIC_NOP3 GENERIC_NOP4 GENERIC_NOP5 GENERIC_NOP6
  53         GENERIC_NOP7 GENERIC_NOP8);
  54 extern unsigned char intelnops[];
  55 static unsigned char *intel_nops[ASM_NOP_MAX+1] = {
  56         NULL,
  57         intelnops,
  58         intelnops + 1,
  59         intelnops + 1 + 2,
  60         intelnops + 1 + 2 + 3,
  61         intelnops + 1 + 2 + 3 + 4,
  62         intelnops + 1 + 2 + 3 + 4 + 5,
  63         intelnops + 1 + 2 + 3 + 4 + 5 + 6,
  64         intelnops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
  65 };
  66 #endif
  67
  68 #ifdef K8_NOP1
  69 asm("\t.data\nk8nops: "
  70         K8_NOP1 K8_NOP2 K8_NOP3 K8_NOP4 K8_NOP5 K8_NOP6
  71         K8_NOP7 K8_NOP8);
  72 extern unsigned char k8nops[];
  73 static unsigned char *k8_nops[ASM_NOP_MAX+1] = {
  74         NULL,
  75         k8nops,
  76         k8nops + 1,
  77         k8nops + 1 + 2,
  78         k8nops + 1 + 2 + 3,
  79         k8nops + 1 + 2 + 3 + 4,
  80         k8nops + 1 + 2 + 3 + 4 + 5,
  81         k8nops + 1 + 2 + 3 + 4 + 5 + 6,
  82         k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
  83 };
  84 #endif
  85
  86 #ifdef K7_NOP1
  87 asm("\t.data\nk7nops: "
  88         K7_NOP1 K7_NOP2 K7_NOP3 K7_NOP4 K7_NOP5 K7_NOP6
  89         K7_NOP7 K7_NOP8);
  90 extern unsigned char k7nops[];
  91 static unsigned char *k7_nops[ASM_NOP_MAX+1] = {
  92         NULL,
  93         k7nops,
  94         k7nops + 1,
  95         k7nops + 1 + 2,
  96         k7nops + 1 + 2 + 3,
  97         k7nops + 1 + 2 + 3 + 4,
  98         k7nops + 1 + 2 + 3 + 4 + 5,
  99         k7nops + 1 + 2 + 3 + 4 + 5 + 6,
 100         k7nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
 101 };
 102 #endif
 103
 104 #ifdef CONFIG_X86_64
 105
 106 extern char __vsyscall_0;
 107 static inline unsigned char** find_nop_table(void)
 108 {
 109         return k8_nops;
 110 }
 111
 112 #else /* CONFIG_X86_64 */
 113
 114 static struct nop {
 115         int cpuid;
 116         unsigned char **noptable;
 117 } noptypes[] = {
 118         { X86_FEATURE_K8, k8_nops },
 119         { X86_FEATURE_K7, k7_nops },
 120         { -1, NULL }
 121 };
 122
 123 static unsigned char** find_nop_table(void)
 124 {
 125         unsigned char **noptable = intel_nops;
 126         int i;
 127
 128         for (i = 0; noptypes[i].cpuid >= 0; i++) {
 129                 if (boot_cpu_has(noptypes[i].cpuid)) {
 130                         noptable = noptypes[i].noptable;
 131                         break;
 132                 }
 133         }
 134         return noptable;
 135 }
 136
 137 #endif /* CONFIG_X86_64 */
 138
 139 static void nop_out(void *insns, unsigned int len)
 140 {
 141         unsigned char **noptable = find_nop_table();
 142
 143         while (len > 0) {
 144                 unsigned int noplen = len;
 145                 if (noplen > ASM_NOP_MAX)
 146                         noplen = ASM_NOP_MAX;
 147                 memcpy(insns, noptable[noplen], noplen);
 148                 insns += noplen;
 149                 len -= noplen;
 150         }
 151 }
 152
 153 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
 154 extern u8 *__smp_locks[], *__smp_locks_end[];
 155
 156 /* Replace instructions with better alternatives for this CPU type.
 157    This runs before SMP is initialized to avoid SMP problems with
 158    self modifying code. This implies that assymetric systems where
 159    APs have less capabilities than the boot processor are not handled.
 160    Tough. Make sure you disable such features by hand. */
 161
 162 void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
 163 {
 164         struct alt_instr *a;
 165         u8 *instr;
 166         int diff;
 167
 168         DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
 169         for (a = start; a < end; a++) {
 170                 BUG_ON(a->replacementlen > a->instrlen);
 171                 if (!boot_cpu_has(a->cpuid))
 172                         continue;
 173                 instr = a->instr;
 174 #ifdef CONFIG_X86_64
 175                 /* vsyscall code is not mapped yet. resolve it manually. */
 176                 if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
 177                         instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
 178                         DPRINTK("%s: vsyscall fixup: %p => %p\n",
 179                                 __FUNCTION__, a->instr, instr);
 180                 }
 181 #endif
 182                 memcpy(instr, a->replacement, a->replacementlen);
 183                 diff = a->instrlen - a->replacementlen;
 184                 nop_out(instr + a->replacementlen, diff);
 185         }
 186 }
 187
 188 #ifdef CONFIG_SMP
 189
 190 static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 191 {
 192         u8 **ptr;
 193
 194         for (ptr = start; ptr < end; ptr++) {
 195                 if (*ptr < text)
 196                         continue;
 197                 if (*ptr > text_end)
 198                         continue;
 199                 **ptr = 0xf0; /* lock prefix */
 200         };
 201 }
 202
 203 static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
 204 {
 205         u8 **ptr;
 206
 207         if (noreplace_smp)
 208                 return;
 209
 210         for (ptr = start; ptr < end; ptr++) {
 211                 if (*ptr < text)
 212                         continue;
 213                 if (*ptr > text_end)
 214                         continue;
 215                 nop_out(*ptr, 1);
 216         };
 217 }
 218
 219 struct smp_alt_module {
 220         /* what is this ??? */
 221         struct module   *mod;
 222         char            *name;
 223
 224         /* ptrs to lock prefixes */
 225         u8              **locks;
 226         u8              **locks_end;
 227
 228         /* .text segment, needed to avoid patching init code ;) */
 229         u8              *text;
 230         u8              *text_end;
 231
 232         struct list_head next;
 233 };
 234 static LIST_HEAD(smp_alt_modules);
 235 static DEFINE_SPINLOCK(smp_alt);
 236
 237 void alternatives_smp_module_add(struct module *mod, char *name,
 238                                  void *locks, void *locks_end,
 239                                  void *text,  void *text_end)
 240 {
 241         struct smp_alt_module *smp;
 242         unsigned long flags;
 243
 244         if (noreplace_smp)
 245                 return;
 246
 247         if (smp_alt_once) {
 248                 if (boot_cpu_has(X86_FEATURE_UP))
 249                         alternatives_smp_unlock(locks, locks_end,
 250                                                 text, text_end);
 251                 return;
 252         }
 253
 254         smp = kzalloc(sizeof(*smp), GFP_KERNEL);
 255         if (NULL == smp)
 256                 return; /* we'll run the (safe but slow) SMP code then ... */
 257
 258         smp->mod        = mod;
 259         smp->name       = name;
 260         smp->locks      = locks;
 261         smp->locks_end  = locks_end;
 262         smp->text       = text;
 263         smp->text_end   = text_end;
 264         DPRINTK("%s: locks %p -> %p, text %p -> %p, name %s\n",
 265                 __FUNCTION__, smp->locks, smp->locks_end,
 266                 smp->text, smp->text_end, smp->name);
 267
 268         spin_lock_irqsave(&smp_alt, flags);
 269         list_add_tail(&smp->next, &smp_alt_modules);
 270         if (boot_cpu_has(X86_FEATURE_UP))
 271                 alternatives_smp_unlock(smp->locks, smp->locks_end,
 272                                         smp->text, smp->text_end);
 273         spin_unlock_irqrestore(&smp_alt, flags);
 274 }
 275
 276 void alternatives_smp_module_del(struct module *mod)
 277 {
 278         struct smp_alt_module *item;
 279         unsigned long flags;
 280
 281         if (smp_alt_once || noreplace_smp)
 282                 return;
 283
 284         spin_lock_irqsave(&smp_alt, flags);
 285         list_for_each_entry(item, &smp_alt_modules, next) {
 286                 if (mod != item->mod)
 287                         continue;
 288                 list_del(&item->next);
 289                 spin_unlock_irqrestore(&smp_alt, flags);
 290                 DPRINTK("%s: %s\n", __FUNCTION__, item->name);
 291                 kfree(item);
 292                 return;
 293         }
 294         spin_unlock_irqrestore(&smp_alt, flags);
 295 }
 296
 297 void alternatives_smp_switch(int smp)
 298 {
 299         struct smp_alt_module *mod;
 300         unsigned long flags;
 301
 302 #ifdef CONFIG_LOCKDEP
 303         /*
 304          * A not yet fixed binutils section handling bug prevents
 305          * alternatives-replacement from working reliably, so turn
 306          * it off:
 307          */
 308         printk("lockdep: not fixing up alternatives.\n");
 309         return;
 310 #endif
 311
 312         if (noreplace_smp || smp_alt_once)
 313                 return;
 314         BUG_ON(!smp && (num_online_cpus() > 1));
 315
 316         spin_lock_irqsave(&smp_alt, flags);
 317         if (smp) {
 318                 printk(KERN_INFO "SMP alternatives: switching to SMP code\n");
 319                 clear_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
 320                 clear_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
 321                 list_for_each_entry(mod, &smp_alt_modules, next)
 322                         alternatives_smp_lock(mod->locks, mod->locks_end,
 323                                               mod->text, mod->text_end);
 324         } else {
 325                 printk(KERN_INFO "SMP alternatives: switching to UP code\n");
 326                 set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
 327                 set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
 328                 list_for_each_entry(mod, &smp_alt_modules, next)
 329                         alternatives_smp_unlock(mod->locks, mod->locks_end,
 330                                                 mod->text, mod->text_end);
 331         }
 332         spin_unlock_irqrestore(&smp_alt, flags);
 333 }
 334
 335 #endif
 336
 337 #ifdef CONFIG_PARAVIRT
 338 void apply_paravirt(struct paravirt_patch_site *start,
 339                     struct paravirt_patch_site *end)
 340 {
 341         struct paravirt_patch_site *p;
 342
 343         if (noreplace_paravirt)
 344                 return;
 345
 346         for (p = start; p < end; p++) {
 347                 unsigned int used;
 348
 349                 used = paravirt_ops.patch(p->instrtype, p->clobbers, p->instr,
 350                                           p->len);
 351
 352                 BUG_ON(used > p->len);
 353
 354                 /* Pad the rest with nops */
 355                 nop_out(p->instr + used, p->len - used);
 356         }
 357
 358         /* Sync to be conservative, in case we patched following
 359          * instructions */
 360         sync_core();
 361 }
 362 extern struct paravirt_patch_site __start_parainstructions[],
 363         __stop_parainstructions[];
 364 #endif  /* CONFIG_PARAVIRT */
 365
 366 void __init alternative_instructions(void)
 367 {
 368         unsigned long flags;
 369
 370         local_irq_save(flags);
 371         apply_alternatives(__alt_instructions, __alt_instructions_end);
 372
 373         /* switch to patch-once-at-boottime-only mode and free the
 374          * tables in case we know the number of CPUs will never ever
 375          * change */
 376 #ifdef CONFIG_HOTPLUG_CPU
 377         if (num_possible_cpus() < 2)
 378                 smp_alt_once = 1;
 379 #else
 380         smp_alt_once = 1;
 381 #endif
 382
 383 #ifdef CONFIG_SMP
 384         if (smp_alt_once) {
 385                 if (1 == num_possible_cpus()) {
 386                         printk(KERN_INFO "SMP alternatives: switching to UP code\n");
 387                         set_bit(X86_FEATURE_UP, boot_cpu_data.x86_capability);
 388                         set_bit(X86_FEATURE_UP, cpu_data[0].x86_capability);
 389                         alternatives_smp_unlock(__smp_locks, __smp_locks_end,
 390                                                 _text, _etext);
 391                 }
 392                 free_init_pages("SMP alternatives",
 393                                 (unsigned long)__smp_locks,
 394                                 (unsigned long)__smp_locks_end);
 395         } else {
 396                 alternatives_smp_module_add(NULL, "core kernel",
 397                                             __smp_locks, __smp_locks_end,
 398                                             _text, _etext);
 399                 alternatives_smp_switch(0);
 400         }
 401 #endif
 402         apply_paravirt(__parainstructions, __parainstructions_end);
 403         local_irq_restore(flags);
 404 }