src/lj_mcode.c

   1 /*
   2 ** Machine code management.
   3 ** Copyright (C) 2005-2017 Mike Pall. See Copyright Notice in luajit.h
   4 */
   5
   6 #define lj_mcode_c
   7 #define LUA_CORE
   8
   9 #include "lj_obj.h"
  10 #if LJ_HASJIT
  11 #include "lj_gc.h"
  12 #include "lj_err.h"
  13 #include "lj_jit.h"
  14 #include "lj_mcode.h"
  15 #include "lj_trace.h"
  16 #include "lj_dispatch.h"
  17 #endif
  18 #if LJ_HASJIT || LJ_HASFFI
  19 #include "lj_vm.h"
  20 #endif
  21
  22 /* -- OS-specific functions ----------------------------------------------- */
  23
  24 #if LJ_HASJIT || LJ_HASFFI
  25
  26 /* Define this if you want to run LuaJIT with Valgrind. */
  27 #ifdef LUAJIT_USE_VALGRIND
  28 #include <valgrind/valgrind.h>
  29 #endif
  30
  31 #if LJ_TARGET_IOS
  32 void sys_icache_invalidate(void *start, size_t len);
  33 #endif
  34
  35 /* Synchronize data/instruction cache. */
  36 void lj_mcode_sync(void *start, void *end)
  37 {
  38 #ifdef LUAJIT_USE_VALGRIND
  39   VALGRIND_DISCARD_TRANSLATIONS(start, (char *)end-(char *)start);
  40 #endif
  41 #if LJ_TARGET_X86ORX64
  42   UNUSED(start); UNUSED(end);
  43 #elif LJ_TARGET_IOS
  44   sys_icache_invalidate(start, (char *)end-(char *)start);
  45 #elif LJ_TARGET_PPC
  46   lj_vm_cachesync(start, end);
  47 #elif defined(__GNUC__)
  48   __clear_cache(start, end);
  49 #else
  50 #error "Missing builtin to flush instruction cache"
  51 #endif
  52 }
  53
  54 #endif
  55
  56 #if LJ_HASJIT
  57
  58 #if LJ_TARGET_WINDOWS
  59
  60 #define WIN32_LEAN_AND_MEAN
  61 #include <windows.h>
  62
  63 #define MCPROT_RW       PAGE_READWRITE
  64 #define MCPROT_RX       PAGE_EXECUTE_READ
  65 #define MCPROT_RWX      PAGE_EXECUTE_READWRITE
  66
  67 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, DWORD prot)
  68 {
  69   void *p = VirtualAlloc((void *)hint, sz,
  70                          MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, prot);
  71   if (!p && !hint)
  72     lj_trace_err(J, LJ_TRERR_MCODEAL);
  73   return p;
  74 }
  75
  76 static void mcode_free(jit_State *J, void *p, size_t sz)
  77 {
  78   UNUSED(J); UNUSED(sz);
  79   VirtualFree(p, 0, MEM_RELEASE);
  80 }
  81
  82 static int mcode_setprot(void *p, size_t sz, DWORD prot)
  83 {
  84   DWORD oprot;
  85   return !VirtualProtect(p, sz, prot, &oprot);
  86 }
  87
  88 #elif LJ_TARGET_POSIX
  89
  90 #include <sys/mman.h>
  91
  92 #ifndef MAP_ANONYMOUS
  93 #define MAP_ANONYMOUS   MAP_ANON
  94 #endif
  95
  96 #define MCPROT_RW       (PROT_READ|PROT_WRITE)
  97 #define MCPROT_RX       (PROT_READ|PROT_EXEC)
  98 #define MCPROT_RWX      (PROT_READ|PROT_WRITE|PROT_EXEC)
  99
 100 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
 101 {
 102   void *p = mmap((void *)hint, sz, prot, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 103   if (p == MAP_FAILED) {
 104     if (!hint) lj_trace_err(J, LJ_TRERR_MCODEAL);
 105     p = NULL;
 106   }
 107   return p;
 108 }
 109
 110 static void mcode_free(jit_State *J, void *p, size_t sz)
 111 {
 112   UNUSED(J);
 113   munmap(p, sz);
 114 }
 115
 116 static int mcode_setprot(void *p, size_t sz, int prot)
 117 {
 118   return mprotect(p, sz, prot);
 119 }
 120
 121 #elif LJ_64
 122
 123 #error "Missing OS support for explicit placement of executable memory"
 124
 125 #else
 126
 127 /* Fallback allocator. This will fail if memory is not executable by default. */
 128 #define LUAJIT_UNPROTECT_MCODE
 129 #define MCPROT_RW       0
 130 #define MCPROT_RX       0
 131 #define MCPROT_RWX      0
 132
 133 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
 134 {
 135   UNUSED(hint); UNUSED(prot);
 136   return lj_mem_new(J->L, sz);
 137 }
 138
 139 static void mcode_free(jit_State *J, void *p, size_t sz)
 140 {
 141   lj_mem_free(J2G(J), p, sz);
 142 }
 143
 144 #endif
 145
 146 /* -- MCode area protection ----------------------------------------------- */
 147
 148 /* Define this ONLY if page protection twiddling becomes a bottleneck. */
 149 #ifdef LUAJIT_UNPROTECT_MCODE
 150
 151 /* It's generally considered to be a potential security risk to have
 152 ** pages with simultaneous write *and* execute access in a process.
 153 **
 154 ** Do not even think about using this mode for server processes or
 155 ** apps handling untrusted external data (such as a browser).
 156 **
 157 ** The security risk is not in LuaJIT itself -- but if an adversary finds
 158 ** any *other* flaw in your C application logic, then any RWX memory page
 159 ** simplifies writing an exploit considerably.
 160 */
 161 #define MCPROT_GEN      MCPROT_RWX
 162 #define MCPROT_RUN      MCPROT_RWX
 163
 164 static void mcode_protect(jit_State *J, int prot)
 165 {
 166   UNUSED(J); UNUSED(prot);
 167 }
 168
 169 #else
 170
 171 /* This is the default behaviour and much safer:
 172 **
 173 ** Most of the time the memory pages holding machine code are executable,
 174 ** but NONE of them is writable.
 175 **
 176 ** The current memory area is marked read-write (but NOT executable) only
 177 ** during the short time window while the assembler generates machine code.
 178 */
 179 #define MCPROT_GEN      MCPROT_RW
 180 #define MCPROT_RUN      MCPROT_RX
 181
 182 /* Protection twiddling failed. Probably due to kernel security. */
 183 static LJ_NOINLINE void mcode_protfail(jit_State *J)
 184 {
 185   lua_CFunction panic = J2G(J)->panic;
 186   if (panic) {
 187     lua_State *L = J->L;
 188     setstrV(L, L->top++, lj_err_str(L, LJ_ERR_JITPROT));
 189     panic(L);
 190   }
 191 }
 192
 193 /* Change protection of MCode area. */
 194 static void mcode_protect(jit_State *J, int prot)
 195 {
 196   if (J->mcprot != prot) {
 197     if (LJ_UNLIKELY(mcode_setprot(J->mcarea, J->szmcarea, prot)))
 198       mcode_protfail(J);
 199     J->mcprot = prot;
 200   }
 201 }
 202
 203 #endif
 204
 205 /* -- MCode area allocation ----------------------------------------------- */
 206
 207 #if LJ_64
 208 #define mcode_validptr(p)       (p)
 209 #else
 210 #define mcode_validptr(p)       ((p) && (uintptr_t)(p) < 0xffff0000)
 211 #endif
 212
 213 #ifdef LJ_TARGET_JUMPRANGE
 214
 215 /* Get memory within relative jump distance of our code in 64 bit mode. */
 216 static void *mcode_alloc(jit_State *J, size_t sz)
 217 {
 218   /* Target an address in the static assembler code (64K aligned).
 219   ** Try addresses within a distance of target-range/2+1MB..target+range/2-1MB.
 220   ** Use half the jump range so every address in the range can reach any other.
 221   */
 222 #if LJ_TARGET_MIPS
 223   /* Use the middle of the 256MB-aligned region. */
 224   uintptr_t target = ((uintptr_t)(void *)lj_vm_exit_handler & 0xf0000000u) +
 225                      0x08000000u;
 226 #else
 227   uintptr_t target = (uintptr_t)(void *)lj_vm_exit_handler & ~(uintptr_t)0xffff;
 228 #endif
 229   const uintptr_t range = (1u << (LJ_TARGET_JUMPRANGE-1)) - (1u << 21);
 230   /* First try a contiguous area below the last one. */
 231   uintptr_t hint = J->mcarea ? (uintptr_t)J->mcarea - sz : 0;
 232   int i;
 233   /* Limit probing iterations, depending on the available pool size. */
 234   for (i = 0; i < LJ_TARGET_JUMPRANGE; i++) {
 235     if (mcode_validptr(hint)) {
 236       void *p = mcode_alloc_at(J, hint, sz, MCPROT_GEN);
 237
 238       if (mcode_validptr(p) &&
 239           ((uintptr_t)p + sz - target < range || target - (uintptr_t)p < range))
 240         return p;
 241       if (p) mcode_free(J, p, sz);  /* Free badly placed area. */
 242     }
 243     /* Next try probing 64K-aligned pseudo-random addresses. */
 244     do {
 245       hint = LJ_PRNG_BITS(J, LJ_TARGET_JUMPRANGE-16) << 16;
 246     } while (!(hint + sz < range+range));
 247     hint = target + hint - range;
 248   }
 249   lj_trace_err(J, LJ_TRERR_MCODEAL);  /* Give up. OS probably ignores hints? */
 250   return NULL;
 251 }
 252
 253 #else
 254
 255 /* All memory addresses are reachable by relative jumps. */
 256 static void *mcode_alloc(jit_State *J, size_t sz)
 257 {
 258 #ifdef __OpenBSD__
 259   /* Allow better executable memory allocation for OpenBSD W^X mode. */
 260   void *p = mcode_alloc_at(J, 0, sz, MCPROT_RUN);
 261   if (p && mcode_setprot(p, sz, MCPROT_GEN)) {
 262     mcode_free(J, p, sz);
 263     return NULL;
 264   }
 265   return p;
 266 #else
 267   return mcode_alloc_at(J, 0, sz, MCPROT_GEN);
 268 #endif
 269 }
 270
 271 #endif
 272
 273 /* -- MCode area management ----------------------------------------------- */
 274
 275 /* Allocate a new MCode area. */
 276 static void mcode_allocarea(jit_State *J)
 277 {
 278   MCode *oldarea = J->mcarea;
 279   size_t sz = (size_t)J->param[JIT_P_sizemcode] << 10;
 280   sz = (sz + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
 281   J->mcarea = (MCode *)mcode_alloc(J, sz);
 282   J->szmcarea = sz;
 283   J->mcprot = MCPROT_GEN;
 284   J->mctop = (MCode *)((char *)J->mcarea + J->szmcarea);
 285   J->mcbot = (MCode *)((char *)J->mcarea + sizeof(MCLink));
 286   ((MCLink *)J->mcarea)->next = oldarea;
 287   ((MCLink *)J->mcarea)->size = sz;
 288   J->szallmcarea += sz;
 289 }
 290
 291 /* Free all MCode areas. */
 292 void lj_mcode_free(jit_State *J)
 293 {
 294   MCode *mc = J->mcarea;
 295   J->mcarea = NULL;
 296   J->szallmcarea = 0;
 297   while (mc) {
 298     MCode *next = ((MCLink *)mc)->next;
 299     mcode_free(J, mc, ((MCLink *)mc)->size);
 300     mc = next;
 301   }
 302 }
 303
 304 /* -- MCode transactions -------------------------------------------------- */
 305
 306 /* Reserve the remainder of the current MCode area. */
 307 MCode *lj_mcode_reserve(jit_State *J, MCode **lim)
 308 {
 309   if (!J->mcarea)
 310     mcode_allocarea(J);
 311   else
 312     mcode_protect(J, MCPROT_GEN);
 313   *lim = J->mcbot;
 314   return J->mctop;
 315 }
 316
 317 /* Commit the top part of the current MCode area. */
 318 void lj_mcode_commit(jit_State *J, MCode *top)
 319 {
 320   J->mctop = top;
 321   mcode_protect(J, MCPROT_RUN);
 322 }
 323
 324 /* Abort the reservation. */
 325 void lj_mcode_abort(jit_State *J)
 326 {
 327   if (J->mcarea)
 328     mcode_protect(J, MCPROT_RUN);
 329 }
 330
 331 /* Set/reset protection to allow patching of MCode areas. */
 332 MCode *lj_mcode_patch(jit_State *J, MCode *ptr, int finish)
 333 {
 334 #ifdef LUAJIT_UNPROTECT_MCODE
 335   UNUSED(J); UNUSED(ptr); UNUSED(finish);
 336   return NULL;
 337 #else
 338   if (finish) {
 339     if (J->mcarea == ptr)
 340       mcode_protect(J, MCPROT_RUN);
 341     else if (LJ_UNLIKELY(mcode_setprot(ptr, ((MCLink *)ptr)->size, MCPROT_RUN)))
 342       mcode_protfail(J);
 343     return NULL;
 344   } else {
 345     MCode *mc = J->mcarea;
 346     /* Try current area first to use the protection cache. */
 347     if (ptr >= mc && ptr < (MCode *)((char *)mc + J->szmcarea)) {
 348       mcode_protect(J, MCPROT_GEN);
 349       return mc;
 350     }
 351     /* Otherwise search through the list of MCode areas. */
 352     for (;;) {
 353       mc = ((MCLink *)mc)->next;
 354       lua_assert(mc != NULL);
 355       if (ptr >= mc && ptr < (MCode *)((char *)mc + ((MCLink *)mc)->size)) {
 356         if (LJ_UNLIKELY(mcode_setprot(mc, ((MCLink *)mc)->size, MCPROT_GEN)))
 357           mcode_protfail(J);
 358         return mc;
 359       }
 360     }
 361   }
 362 #endif
 363 }
 364
 365 /* Limit of MCode reservation reached. */
 366 void lj_mcode_limiterr(jit_State *J, size_t need)
 367 {
 368   size_t sizemcode, maxmcode;
 369   lj_mcode_abort(J);
 370   sizemcode = (size_t)J->param[JIT_P_sizemcode] << 10;
 371   sizemcode = (sizemcode + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
 372   maxmcode = (size_t)J->param[JIT_P_maxmcode] << 10;
 373   if ((size_t)need > sizemcode)
 374     lj_trace_err(J, LJ_TRERR_MCODEOV);  /* Too long for any area. */
 375   if (J->szallmcarea + sizemcode > maxmcode)
 376     lj_trace_err(J, LJ_TRERR_MCODEAL);
 377   mcode_allocarea(J);
 378   lj_trace_err(J, LJ_TRERR_MCODELM);  /* Retry with new area. */
 379 }
 380
 381 #endif