src/lj_mcode.c

   1 /*
   2 ** Machine code management.
   3 ** Copyright (C) 2005-2012 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_jit.h"
  13 #include "lj_mcode.h"
  14 #include "lj_trace.h"
  15 #include "lj_dispatch.h"
  16 #endif
  17 #if LJ_HASJIT || LJ_HASFFI
  18 #include "lj_vm.h"
  19 #endif
  20
  21 /* -- OS-specific functions ----------------------------------------------- */
  22
  23 #if LJ_HASJIT || LJ_HASFFI
  24
  25 /* Define this if you want to run LuaJIT with Valgrind. */
  26 #ifdef LUAJIT_USE_VALGRIND
  27 #include <valgrind/valgrind.h>
  28 #endif
  29
  30 #if LJ_TARGET_IOS
  31 void sys_icache_invalidate(void *start, size_t len);
  32 #endif
  33
  34 /* Synchronize data/instruction cache. */
  35 void lj_mcode_sync(void *start, void *end)
  36 {
  37 #ifdef LUAJIT_USE_VALGRIND
  38   VALGRIND_DISCARD_TRANSLATIONS(start, (char *)end-(char *)start);
  39 #endif
  40 #if LJ_TARGET_X86ORX64
  41   UNUSED(start); UNUSED(end);
  42 #elif LJ_TARGET_IOS
  43   sys_icache_invalidate(start, (char *)end-(char *)start);
  44 #elif LJ_TARGET_PPC
  45   lj_vm_cachesync(start, end);
  46 #elif defined(__GNUC__)
  47   __clear_cache(start, end);
  48 #else
  49 #error "Missing builtin to flush instruction cache"
  50 #endif
  51 }
  52
  53 #endif
  54
  55 #if LJ_HASJIT
  56
  57 #if LJ_TARGET_WINDOWS
  58
  59 #define WIN32_LEAN_AND_MEAN
  60 #include <windows.h>
  61
  62 #define MCPROT_RW       PAGE_READWRITE
  63 #define MCPROT_RX       PAGE_EXECUTE_READ
  64 #define MCPROT_RWX      PAGE_EXECUTE_READWRITE
  65
  66 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, DWORD prot)
  67 {
  68   void *p = VirtualAlloc((void *)hint, sz,
  69                          MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, prot);
  70   if (!p && !hint)
  71     lj_trace_err(J, LJ_TRERR_MCODEAL);
  72   return p;
  73 }
  74
  75 static void mcode_free(jit_State *J, void *p, size_t sz)
  76 {
  77   UNUSED(J); UNUSED(sz);
  78   VirtualFree(p, 0, MEM_RELEASE);
  79 }
  80
  81 static void mcode_setprot(void *p, size_t sz, DWORD prot)
  82 {
  83   DWORD oprot;
  84   VirtualProtect(p, sz, prot, &oprot);
  85 }
  86
  87 #elif LJ_TARGET_POSIX
  88
  89 #include <sys/mman.h>
  90
  91 #ifndef MAP_ANONYMOUS
  92 #define MAP_ANONYMOUS   MAP_ANON
  93 #endif
  94
  95 #define MCPROT_RW       (PROT_READ|PROT_WRITE)
  96 #define MCPROT_RX       (PROT_READ|PROT_EXEC)
  97 #define MCPROT_RWX      (PROT_READ|PROT_WRITE|PROT_EXEC)
  98
  99 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
 100 {
 101   void *p = mmap((void *)hint, sz, prot, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 102   if (p == MAP_FAILED && !hint)
 103     lj_trace_err(J, LJ_TRERR_MCODEAL);
 104   return p;
 105 }
 106
 107 static void mcode_free(jit_State *J, void *p, size_t sz)
 108 {
 109   UNUSED(J);
 110   munmap(p, sz);
 111 }
 112
 113 static void mcode_setprot(void *p, size_t sz, int prot)
 114 {
 115   mprotect(p, sz, prot);
 116 }
 117
 118 #elif LJ_64
 119
 120 #error "Missing OS support for explicit placement of executable memory"
 121
 122 #else
 123
 124 /* Fallback allocator. This will fail if memory is not executable by default. */
 125 #define LUAJIT_UNPROTECT_MCODE
 126 #define MCPROT_RW       0
 127 #define MCPROT_RX       0
 128 #define MCPROT_RWX      0
 129
 130 static void *mcode_alloc_at(jit_State *J, uintptr_t hint, size_t sz, int prot)
 131 {
 132   UNUSED(hint); UNUSED(prot);
 133   return lj_mem_new(J->L, sz);
 134 }
 135
 136 static void mcode_free(jit_State *J, void *p, size_t sz)
 137 {
 138   lj_mem_free(J2G(J), p, sz);
 139 }
 140
 141 #define mcode_setprot(p, sz, prot)      UNUSED(p)
 142
 143 #endif
 144
 145 /* -- MCode area protection ----------------------------------------------- */
 146
 147 /* Define this ONLY if the page protection twiddling becomes a bottleneck. */
 148 #ifdef LUAJIT_UNPROTECT_MCODE
 149
 150 /* It's generally considered to be a potential security risk to have
 151 ** pages with simultaneous write *and* execute access in a process.
 152 **
 153 ** Do not even think about using this mode for server processes or
 154 ** apps handling untrusted external data (such as a browser).
 155 **
 156 ** The security risk is not in LuaJIT itself -- but if an adversary finds
 157 ** any *other* flaw in your C application logic, then any RWX memory page
 158 ** simplifies writing an exploit considerably.
 159 */
 160 #define MCPROT_GEN      MCPROT_RWX
 161 #define MCPROT_RUN      MCPROT_RWX
 162
 163 static void mcode_protect(jit_State *J, int prot)
 164 {
 165   UNUSED(J); UNUSED(prot);
 166 }
 167
 168 #else
 169
 170 /* This is the default behaviour and much safer:
 171 **
 172 ** Most of the time the memory pages holding machine code are executable,
 173 ** but NONE of them is writable.
 174 **
 175 ** The current memory area is marked read-write (but NOT executable) only
 176 ** during the short time window while the assembler generates machine code.
 177 */
 178 #define MCPROT_GEN      MCPROT_RW
 179 #define MCPROT_RUN      MCPROT_RX
 180
 181 /* Change protection of MCode area. */
 182 static void mcode_protect(jit_State *J, int prot)
 183 {
 184   if (J->mcprot != prot) {
 185     mcode_setprot(J->mcarea, J->szmcarea, prot);
 186     J->mcprot = prot;
 187   }
 188 }
 189
 190 #endif
 191
 192 /* -- MCode area allocation ----------------------------------------------- */
 193
 194 #if LJ_TARGET_X64
 195 #define mcode_validptr(p)       ((p) && (uintptr_t)(p) < (uintptr_t)1<<47)
 196 #else
 197 #define mcode_validptr(p)       ((p) && (uintptr_t)(p) < 0xffff0000)
 198 #endif
 199
 200 #ifdef LJ_TARGET_JUMPRANGE
 201
 202 /* Get memory within relative jump distance of our code in 64 bit mode. */
 203 static void *mcode_alloc(jit_State *J, size_t sz)
 204 {
 205   /* Target an address in the static assembler code (64K aligned).
 206   ** Try addresses within a distance of target-range/2+1MB..target+range/2-1MB.
 207   */
 208 #if LJ_TARGET_MIPS
 209   /* Use the middle of the 256MB-aligned region. */
 210   uintptr_t target = ((uintptr_t)(void *)lj_vm_exit_handler & 0xf0000000u) +
 211                      0x08000000u;
 212 #else
 213   uintptr_t target = (uintptr_t)(void *)lj_vm_exit_handler & ~(uintptr_t)0xffff;
 214 #endif
 215   const uintptr_t range = (1u << LJ_TARGET_JUMPRANGE) - (1u << 21);
 216   /* First try a contiguous area below the last one. */
 217   uintptr_t hint = J->mcarea ? (uintptr_t)J->mcarea - sz : 0;
 218   int i;
 219   for (i = 0; i < 32; i++) {  /* 32 attempts ought to be enough ... */
 220     if (mcode_validptr(hint)) {
 221       void *p = mcode_alloc_at(J, hint, sz, MCPROT_GEN);
 222
 223       if (mcode_validptr(p)) {
 224         if ((uintptr_t)p + sz - target < range || target - (uintptr_t)p < range)
 225           return p;
 226         mcode_free(J, p, sz);  /* Free badly placed area. */
 227       }
 228     }
 229     /* Next try probing pseudo-random addresses. */
 230     do {
 231       hint = (0x78fb ^ LJ_PRNG_BITS(J, 15)) << 16;  /* 64K aligned. */
 232     } while (!(hint + sz < range));
 233     hint = target + hint - (range>>1);
 234   }
 235   lj_trace_err(J, LJ_TRERR_MCODEAL);  /* Give up. OS probably ignores hints? */
 236   return NULL;
 237 }
 238
 239 #else
 240
 241 /* All memory addresses are reachable by relative jumps. */
 242 #define mcode_alloc(J, sz)      mcode_alloc_at((J), 0, (sz), MCPROT_GEN)
 243
 244 #endif
 245
 246 /* -- MCode area management ----------------------------------------------- */
 247
 248 /* Linked list of MCode areas. */
 249 typedef struct MCLink {
 250   MCode *next;          /* Next area. */
 251   size_t size;          /* Size of current area. */
 252 } MCLink;
 253
 254 /* Allocate a new MCode area. */
 255 static void mcode_allocarea(jit_State *J)
 256 {
 257   MCode *oldarea = J->mcarea;
 258   size_t sz = (size_t)J->param[JIT_P_sizemcode] << 10;
 259   sz = (sz + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
 260   J->mcarea = (MCode *)mcode_alloc(J, sz);
 261   J->szmcarea = sz;
 262   J->mcprot = MCPROT_GEN;
 263   J->mctop = (MCode *)((char *)J->mcarea + J->szmcarea);
 264   J->mcbot = (MCode *)((char *)J->mcarea + sizeof(MCLink));
 265   ((MCLink *)J->mcarea)->next = oldarea;
 266   ((MCLink *)J->mcarea)->size = sz;
 267   J->szallmcarea += sz;
 268 }
 269
 270 /* Free all MCode areas. */
 271 void lj_mcode_free(jit_State *J)
 272 {
 273   MCode *mc = J->mcarea;
 274   J->mcarea = NULL;
 275   J->szallmcarea = 0;
 276   while (mc) {
 277     MCode *next = ((MCLink *)mc)->next;
 278     mcode_free(J, mc, ((MCLink *)mc)->size);
 279     mc = next;
 280   }
 281 }
 282
 283 /* -- MCode transactions -------------------------------------------------- */
 284
 285 /* Reserve the remainder of the current MCode area. */
 286 MCode *lj_mcode_reserve(jit_State *J, MCode **lim)
 287 {
 288   if (!J->mcarea)
 289     mcode_allocarea(J);
 290   else
 291     mcode_protect(J, MCPROT_GEN);
 292   *lim = J->mcbot;
 293   return J->mctop;
 294 }
 295
 296 /* Commit the top part of the current MCode area. */
 297 void lj_mcode_commit(jit_State *J, MCode *top)
 298 {
 299   J->mctop = top;
 300   mcode_protect(J, MCPROT_RUN);
 301 }
 302
 303 /* Abort the reservation. */
 304 void lj_mcode_abort(jit_State *J)
 305 {
 306   mcode_protect(J, MCPROT_RUN);
 307 }
 308
 309 /* Set/reset protection to allow patching of MCode areas. */
 310 MCode *lj_mcode_patch(jit_State *J, MCode *ptr, int finish)
 311 {
 312 #ifdef LUAJIT_UNPROTECT_MCODE
 313   UNUSED(J); UNUSED(ptr); UNUSED(finish);
 314   return NULL;
 315 #else
 316   if (finish) {
 317     if (J->mcarea == ptr)
 318       mcode_protect(J, MCPROT_RUN);
 319     else
 320       mcode_setprot(ptr, ((MCLink *)ptr)->size, MCPROT_RUN);
 321     return NULL;
 322   } else {
 323     MCode *mc = J->mcarea;
 324     /* Try current area first to use the protection cache. */
 325     if (ptr >= mc && ptr < (MCode *)((char *)mc + J->szmcarea)) {
 326       mcode_protect(J, MCPROT_GEN);
 327       return mc;
 328     }
 329     /* Otherwise search through the list of MCode areas. */
 330     for (;;) {
 331       mc = ((MCLink *)mc)->next;
 332       lua_assert(mc != NULL);
 333       if (ptr >= mc && ptr < (MCode *)((char *)mc + ((MCLink *)mc)->size)) {
 334         mcode_setprot(mc, ((MCLink *)mc)->size, MCPROT_GEN);
 335         return mc;
 336       }
 337     }
 338   }
 339 #endif
 340 }
 341
 342 /* Limit of MCode reservation reached. */
 343 void lj_mcode_limiterr(jit_State *J, size_t need)
 344 {
 345   size_t sizemcode, maxmcode;
 346   lj_mcode_abort(J);
 347   sizemcode = (size_t)J->param[JIT_P_sizemcode] << 10;
 348   sizemcode = (sizemcode + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
 349   maxmcode = (size_t)J->param[JIT_P_maxmcode] << 10;
 350   if ((size_t)need > sizemcode)
 351     lj_trace_err(J, LJ_TRERR_MCODEOV);  /* Too long for any area. */
 352   if (J->szallmcarea + sizemcode > maxmcode)
 353     lj_trace_err(J, LJ_TRERR_MCODEAL);
 354   mcode_allocarea(J);
 355   lj_trace_err(J, LJ_TRERR_MCODELM);  /* Retry with new area. */
 356 }
 357
 358 #endif