src/lj_state.c

   1 /*
   2 ** State and stack handling.
   3 ** Copyright (C) 2005-2025 Mike Pall. See Copyright Notice in luajit.h
   4 **
   5 ** Portions taken verbatim or adapted from the Lua interpreter.
   6 ** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
   7 */
   8
   9 #define lj_state_c
  10 #define LUA_CORE
  11
  12 #include "lj_obj.h"
  13 #include "lj_gc.h"
  14 #include "lj_err.h"
  15 #include "lj_buf.h"
  16 #include "lj_str.h"
  17 #include "lj_tab.h"
  18 #include "lj_func.h"
  19 #include "lj_meta.h"
  20 #include "lj_state.h"
  21 #include "lj_frame.h"
  22 #if LJ_HASFFI
  23 #include "lj_ctype.h"
  24 #endif
  25 #include "lj_trace.h"
  26 #include "lj_dispatch.h"
  27 #include "lj_vm.h"
  28 #include "lj_prng.h"
  29 #include "lj_lex.h"
  30 #include "lj_alloc.h"
  31 #include "luajit.h"
  32
  33 /* -- Stack handling ------------------------------------------------------ */
  34
  35 /* Stack sizes. */
  36 #define LJ_STACK_MIN    LUA_MINSTACK    /* Min. stack size. */
  37 #define LJ_STACK_MAX    LUAI_MAXSTACK   /* Max. stack size. */
  38 #define LJ_STACK_START  (2*LJ_STACK_MIN)        /* Starting stack size. */
  39 #define LJ_STACK_MAXEX  (LJ_STACK_MAX + 1 + LJ_STACK_EXTRA)
  40
  41 /* Explanation of LJ_STACK_EXTRA:
  42 **
  43 ** Calls to metamethods store their arguments beyond the current top
  44 ** without checking for the stack limit. This avoids stack resizes which
  45 ** would invalidate passed TValue pointers. The stack check is performed
  46 ** later by the function header. This can safely resize the stack or raise
  47 ** an error. Thus we need some extra slots beyond the current stack limit.
  48 **
  49 ** Most metamethods need 4 slots above top (cont, mobj, arg1, arg2) plus
  50 ** one extra slot if mobj is not a function. Only lj_meta_tset needs 5
  51 ** slots above top, but then mobj is always a function. So we can get by
  52 ** with 5 extra slots.
  53 ** LJ_FR2: We need 2 more slots for the frame PC and the continuation PC.
  54 */
  55
  56 /* Resize stack slots and adjust pointers in state. */
  57 static void resizestack(lua_State *L, MSize n)
  58 {
  59   TValue *st, *oldst = tvref(L->stack);
  60   ptrdiff_t delta;
  61   MSize oldsize = L->stacksize;
  62   MSize realsize = n + 1 + LJ_STACK_EXTRA;
  63   GCobj *up;
  64   lj_assertL((MSize)(tvref(L->maxstack)-oldst) == L->stacksize-LJ_STACK_EXTRA-1,
  65              "inconsistent stack size");
  66   st = (TValue *)lj_mem_realloc(L, tvref(L->stack),
  67                                 (MSize)(oldsize*sizeof(TValue)),
  68                                 (MSize)(realsize*sizeof(TValue)));
  69   setmref(L->stack, st);
  70   delta = (char *)st - (char *)oldst;
  71   setmref(L->maxstack, st + n);
  72   while (oldsize < realsize)  /* Clear new slots. */
  73     setnilV(st + oldsize++);
  74   L->stacksize = realsize;
  75   if ((size_t)(mref(G(L)->jit_base, char) - (char *)oldst) < oldsize)
  76     setmref(G(L)->jit_base, mref(G(L)->jit_base, char) + delta);
  77   L->base = (TValue *)((char *)L->base + delta);
  78   L->top = (TValue *)((char *)L->top + delta);
  79   for (up = gcref(L->openupval); up != NULL; up = gcnext(up))
  80     setmref(gco2uv(up)->v, (TValue *)((char *)uvval(gco2uv(up)) + delta));
  81 }
  82
  83 /* Relimit stack after error, in case the limit was overdrawn. */
  84 void lj_state_relimitstack(lua_State *L)
  85 {
  86   if (L->stacksize > LJ_STACK_MAXEX && L->top-tvref(L->stack) < LJ_STACK_MAX-1)
  87     resizestack(L, LJ_STACK_MAX);
  88 }
  89
  90 /* Try to shrink the stack (called from GC). */
  91 void lj_state_shrinkstack(lua_State *L, MSize used)
  92 {
  93   if (L->stacksize > LJ_STACK_MAXEX)
  94     return;  /* Avoid stack shrinking while handling stack overflow. */
  95   if (4*used < L->stacksize &&
  96       2*(LJ_STACK_START+LJ_STACK_EXTRA) < L->stacksize &&
  97       /* Don't shrink stack of live trace. */
  98       (tvref(G(L)->jit_base) == NULL || obj2gco(L) != gcref(G(L)->cur_L)))
  99     resizestack(L, L->stacksize >> 1);
 100 }
 101
 102 /* Try to grow stack. */
 103 void LJ_FASTCALL lj_state_growstack(lua_State *L, MSize need)
 104 {
 105   MSize n = L->stacksize + need;
 106   if (LJ_LIKELY(n < LJ_STACK_MAX)) {  /* The stack can grow as requested. */
 107     if (n < 2 * L->stacksize) {  /* Try to double the size. */
 108       n = 2 * L->stacksize;
 109       if (n > LJ_STACK_MAX)
 110         n = LJ_STACK_MAX;
 111     }
 112     resizestack(L, n);
 113   } else {  /* Request would overflow. Raise a stack overflow error. */
 114     if (LJ_HASJIT) {
 115       TValue *base = tvref(G(L)->jit_base);
 116       if (base) L->base = base;
 117     }
 118     if (curr_funcisL(L)) {
 119       L->top = curr_topL(L);
 120       if (L->top > tvref(L->maxstack)) {
 121         /* The current Lua frame violates the stack, so replace it with a
 122         ** dummy. This can happen when BC_IFUNCF is trying to grow the stack.
 123         */
 124         L->top = L->base;
 125         setframe_gc(L->base - 1 - LJ_FR2, obj2gco(L), LJ_TTHREAD);
 126       }
 127     }
 128     if (L->stacksize <= LJ_STACK_MAXEX) {
 129       /* An error handler might want to inspect the stack overflow error, but
 130       ** will need some stack space to run in. We give it a stack size beyond
 131       ** the normal limit in order to do so, then rely on lj_state_relimitstack
 132       ** calls during unwinding to bring us back to a convential stack size.
 133       ** The + 1 is space for the error message, and 2 * LUA_MINSTACK is for
 134       ** the lj_state_checkstack() call in lj_err_run().
 135       */
 136       resizestack(L, LJ_STACK_MAX + 1 + 2 * LUA_MINSTACK);
 137       lj_err_stkov(L);  /* May invoke an error handler. */
 138     } else {
 139       /* If we're here, then the stack overflow error handler is requesting
 140       ** to grow the stack even further. We have no choice but to abort the
 141       ** error handler.
 142       */
 143       GCstr *em = lj_err_str(L, LJ_ERR_STKOV);  /* Might OOM. */
 144       setstrV(L, L->top++, em);  /* There is always space to push an error. */
 145       lj_err_throw(L, LUA_ERRERR);  /* Does not invoke an error handler. */
 146     }
 147   }
 148 }
 149
 150 void LJ_FASTCALL lj_state_growstack1(lua_State *L)
 151 {
 152   lj_state_growstack(L, 1);
 153 }
 154
 155 static TValue *cpgrowstack(lua_State *co, lua_CFunction dummy, void *ud)
 156 {
 157   UNUSED(dummy);
 158   lj_state_growstack(co, *(MSize *)ud);
 159   return NULL;
 160 }
 161
 162 int LJ_FASTCALL lj_state_cpgrowstack(lua_State *L, MSize need)
 163 {
 164   return lj_vm_cpcall(L, NULL, &need, cpgrowstack);
 165 }
 166
 167 /* Allocate basic stack for new state. */
 168 static void stack_init(lua_State *L1, lua_State *L)
 169 {
 170   TValue *stend, *st = lj_mem_newvec(L, LJ_STACK_START+LJ_STACK_EXTRA, TValue);
 171   setmref(L1->stack, st);
 172   L1->stacksize = LJ_STACK_START + LJ_STACK_EXTRA;
 173   stend = st + L1->stacksize;
 174   setmref(L1->maxstack, stend - LJ_STACK_EXTRA - 1);
 175   setthreadV(L1, st++, L1);  /* Needed for curr_funcisL() on empty stack. */
 176   if (LJ_FR2) setnilV(st++);
 177   L1->base = L1->top = st;
 178   while (st < stend)  /* Clear new slots. */
 179     setnilV(st++);
 180 }
 181
 182 /* -- State handling ------------------------------------------------------ */
 183
 184 /* Open parts that may cause memory-allocation errors. */
 185 static TValue *cpluaopen(lua_State *L, lua_CFunction dummy, void *ud)
 186 {
 187   global_State *g = G(L);
 188   UNUSED(dummy);
 189   UNUSED(ud);
 190   stack_init(L, L);
 191   /* NOBARRIER: State initialization, all objects are white. */
 192   setgcref(L->env, obj2gco(lj_tab_new(L, 0, LJ_MIN_GLOBAL)));
 193   settabV(L, registry(L), lj_tab_new(L, 0, LJ_MIN_REGISTRY));
 194   lj_str_init(L);
 195   lj_meta_init(L);
 196   lj_lex_init(L);
 197   fixstring(lj_err_str(L, LJ_ERR_ERRMEM));  /* Preallocate memory error msg. */
 198   g->gc.threshold = 4*g->gc.total;
 199 #if LJ_HASFFI
 200   lj_ctype_initfin(L);
 201 #endif
 202   lj_trace_initstate(g);
 203   lj_err_verify();
 204   return NULL;
 205 }
 206
 207 static void close_state(lua_State *L)
 208 {
 209   global_State *g = G(L);
 210   lj_func_closeuv(L, tvref(L->stack));
 211   lj_gc_freeall(g);
 212   lj_assertG(gcref(g->gc.root) == obj2gco(L),
 213              "main thread is not first GC object");
 214   lj_assertG(g->str.num == 0, "leaked %d strings", g->str.num);
 215   lj_trace_freestate(g);
 216 #if LJ_HASFFI
 217   lj_ctype_freestate(g);
 218 #endif
 219   lj_str_freetab(g);
 220   lj_buf_free(g, &g->tmpbuf);
 221   lj_mem_freevec(g, tvref(L->stack), L->stacksize, TValue);
 222 #if LJ_64
 223   if (mref(g->gc.lightudseg, uint32_t)) {
 224     MSize segnum = g->gc.lightudnum ? (2 << lj_fls(g->gc.lightudnum)) : 2;
 225     lj_mem_freevec(g, mref(g->gc.lightudseg, uint32_t), segnum, uint32_t);
 226   }
 227 #endif
 228   lj_assertG(g->gc.total == sizeof(GG_State),
 229              "memory leak of %lld bytes",
 230              (long long)(g->gc.total - sizeof(GG_State)));
 231 #ifndef LUAJIT_USE_SYSMALLOC
 232   if (g->allocf == lj_alloc_f)
 233     lj_alloc_destroy(g->allocd);
 234   else
 235 #endif
 236     g->allocf(g->allocd, G2GG(g), sizeof(GG_State), 0);
 237 }
 238
 239 #if LJ_64 && !LJ_GC64 && !(defined(LUAJIT_USE_VALGRIND) && defined(LUAJIT_USE_SYSMALLOC))
 240 lua_State *lj_state_newstate(lua_Alloc allocf, void *allocd)
 241 #else
 242 LUA_API lua_State *lua_newstate(lua_Alloc allocf, void *allocd)
 243 #endif
 244 {
 245   PRNGState prng;
 246   GG_State *GG;
 247   lua_State *L;
 248   global_State *g;
 249   /* We need the PRNG for the memory allocator, so initialize this first. */
 250   if (!lj_prng_seed_secure(&prng)) {
 251     lj_assertX(0, "secure PRNG seeding failed");
 252     /* Can only return NULL here, so this errors with "not enough memory". */
 253     return NULL;
 254   }
 255 #ifndef LUAJIT_USE_SYSMALLOC
 256   if (allocf == LJ_ALLOCF_INTERNAL) {
 257     allocd = lj_alloc_create(&prng);
 258     if (!allocd) return NULL;
 259     allocf = lj_alloc_f;
 260   }
 261 #endif
 262   GG = (GG_State *)allocf(allocd, NULL, 0, sizeof(GG_State));
 263   if (GG == NULL || !checkptrGC(GG)) return NULL;
 264   memset(GG, 0, sizeof(GG_State));
 265   L = &GG->L;
 266   g = &GG->g;
 267   L->gct = ~LJ_TTHREAD;
 268   L->marked = LJ_GC_WHITE0 | LJ_GC_FIXED | LJ_GC_SFIXED;  /* Prevent free. */
 269   L->dummy_ffid = FF_C;
 270   setmref(L->glref, g);
 271   g->gc.currentwhite = LJ_GC_WHITE0 | LJ_GC_FIXED;
 272   g->strempty.marked = LJ_GC_WHITE0;
 273   g->strempty.gct = ~LJ_TSTR;
 274   g->allocf = allocf;
 275   g->allocd = allocd;
 276   g->prng = prng;
 277 #ifndef LUAJIT_USE_SYSMALLOC
 278   if (allocf == lj_alloc_f) {
 279     lj_alloc_setprng(allocd, &g->prng);
 280   }
 281 #endif
 282   setgcref(g->mainthref, obj2gco(L));
 283   setgcref(g->uvhead.prev, obj2gco(&g->uvhead));
 284   setgcref(g->uvhead.next, obj2gco(&g->uvhead));
 285   g->str.mask = ~(MSize)0;
 286   setnilV(registry(L));
 287   setnilV(&g->nilnode.val);
 288   setnilV(&g->nilnode.key);
 289 #if !LJ_GC64
 290   setmref(g->nilnode.freetop, &g->nilnode);
 291 #endif
 292   lj_buf_init(NULL, &g->tmpbuf);
 293   g->gc.state = GCSpause;
 294   setgcref(g->gc.root, obj2gco(L));
 295   setmref(g->gc.sweep, &g->gc.root);
 296   g->gc.total = sizeof(GG_State);
 297   g->gc.pause = LUAI_GCPAUSE;
 298   g->gc.stepmul = LUAI_GCMUL;
 299   lj_dispatch_init((GG_State *)L);
 300   L->status = LUA_ERRERR+1;  /* Avoid touching the stack upon memory error. */
 301   if (lj_vm_cpcall(L, NULL, NULL, cpluaopen) != 0) {
 302     /* Memory allocation error: free partial state. */
 303     close_state(L);
 304     return NULL;
 305   }
 306   L->status = LUA_OK;
 307   return L;
 308 }
 309
 310 static TValue *cpfinalize(lua_State *L, lua_CFunction dummy, void *ud)
 311 {
 312   UNUSED(dummy);
 313   UNUSED(ud);
 314   lj_gc_finalize_cdata(L);
 315   lj_gc_finalize_udata(L);
 316   /* Frame pop omitted. */
 317   return NULL;
 318 }
 319
 320 LUA_API void lua_close(lua_State *L)
 321 {
 322   global_State *g = G(L);
 323   int i;
 324   L = mainthread(g);  /* Only the main thread can be closed. */
 325 #if LJ_HASPROFILE
 326   luaJIT_profile_stop(L);
 327 #endif
 328   setgcrefnull(g->cur_L);
 329   lj_func_closeuv(L, tvref(L->stack));
 330   lj_gc_separateudata(g, 1);  /* Separate udata which have GC metamethods. */
 331 #if LJ_HASJIT
 332   G2J(g)->flags &= ~JIT_F_ON;
 333   G2J(g)->state = LJ_TRACE_IDLE;
 334   lj_dispatch_update(g);
 335 #endif
 336   for (i = 0;;) {
 337     hook_enter(g);
 338     L->status = LUA_OK;
 339     L->base = L->top = tvref(L->stack) + 1 + LJ_FR2;
 340     L->cframe = NULL;
 341     if (lj_vm_cpcall(L, NULL, NULL, cpfinalize) == LUA_OK) {
 342       if (++i >= 10) break;
 343       lj_gc_separateudata(g, 1);  /* Separate udata again. */
 344       if (gcref(g->gc.mmudata) == NULL)  /* Until nothing is left to do. */
 345         break;
 346     }
 347   }
 348   close_state(L);
 349 }
 350
 351 lua_State *lj_state_new(lua_State *L)
 352 {
 353   lua_State *L1 = lj_mem_newobj(L, lua_State);
 354   L1->gct = ~LJ_TTHREAD;
 355   L1->dummy_ffid = FF_C;
 356   L1->status = LUA_OK;
 357   L1->stacksize = 0;
 358   setmref(L1->stack, NULL);
 359   L1->cframe = NULL;
 360   /* NOBARRIER: The lua_State is new (marked white). */
 361   setgcrefnull(L1->openupval);
 362   setmrefr(L1->glref, L->glref);
 363   setgcrefr(L1->env, L->env);
 364   stack_init(L1, L);  /* init stack */
 365   lj_assertL(iswhite(obj2gco(L1)), "new thread object is not white");
 366   return L1;
 367 }
 368
 369 void LJ_FASTCALL lj_state_free(global_State *g, lua_State *L)
 370 {
 371   lj_assertG(L != mainthread(g), "free of main thread");
 372   if (obj2gco(L) == gcref(g->cur_L))
 373     setgcrefnull(g->cur_L);
 374   if (gcref(L->openupval) != NULL) {
 375     lj_func_closeuv(L, tvref(L->stack));
 376     lj_trace_abort(g);  /* For aa_uref soundness. */
 377     lj_assertG(gcref(L->openupval) == NULL, "stale open upvalues");
 378   }
 379   lj_mem_freevec(g, tvref(L->stack), L->stacksize, TValue);
 380   lj_mem_freet(g, L);
 381 }
 382