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FFI: Turn FFI finalizer table into a proper GC root.

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Reported by Sergey Bronnikov. #1168
This commit is contained in:
Mike Pall 2024-04-19 01:33:19 +02:00
parent 7110b93567
commit f5affaa6c4
7 changed files with 39 additions and 44 deletions
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20
src/lib_ffi.c
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@ -513,7 +513,7 @@ LJLIB_CF(ffi_new) LJLIB_REC(.)
/* Handle ctype __gc metamethod. Use the fast lookup here. */
cTValue *tv = lj_tab_getinth(cts->miscmap, -(int32_t)id);
if (tv && tvistab(tv) && (tv = lj_meta_fast(L, tabV(tv), MM_gc))) {
GCtab *t = cts->finalizer;
GCtab *t = tabref(G(L)->gcroot[GCROOT_FFI_FIN]);
if (gcref(t->metatable)) {
/* Add to finalizer table, if still enabled. */
copyTV(L, lj_tab_set(L, t, o-1), tv);
@ -765,7 +765,7 @@ LJLIB_CF(ffi_abi) LJLIB_REC(.)
return 1;
}
LJLIB_PUSH(top-8) LJLIB_SET(!) /* Store reference to miscmap table. */
LJLIB_PUSH(top-7) LJLIB_SET(!) /* Store reference to miscmap table. */
LJLIB_CF(ffi_metatype)
{
@ -791,8 +791,6 @@ LJLIB_CF(ffi_metatype)
return 1;
}
LJLIB_PUSH(top-7) LJLIB_SET(!) /* Store reference to finalizer table. */
LJLIB_CF(ffi_gc) LJLIB_REC(.)
{
GCcdata *cd = ffi_checkcdata(L, 1);
@ -825,19 +823,6 @@ LJLIB_PUSH(top-2) LJLIB_SET(arch)
/* ------------------------------------------------------------------------ */
/* Create special weak-keyed finalizer table. */
static GCtab *ffi_finalizer(lua_State *L)
{
/* NOBARRIER: The table is new (marked white). */
GCtab *t = lj_tab_new(L, 0, 1);
settabV(L, L->top++, t);
setgcref(t->metatable, obj2gco(t));
setstrV(L, lj_tab_setstr(L, t, lj_str_newlit(L, "__mode")),
lj_str_newlit(L, "k"));
t->nomm = (uint8_t)(~(1u<<MM_mode));
return t;
}
/* Register FFI module as loaded. */
static void ffi_register_module(lua_State *L)
{
@ -853,7 +838,6 @@ LUALIB_API int luaopen_ffi(lua_State *L)
{
CTState *cts = lj_ctype_init(L);
settabV(L, L->top++, (cts->miscmap = lj_tab_new(L, 0, 1)));
cts->finalizer = ffi_finalizer(L);
LJ_LIB_REG(L, NULL, ffi_meta);
/* NOBARRIER: basemt is a GC root. */
setgcref(basemt_it(G(L), LJ_TCDATA), obj2gco(tabV(L->top-1)));

2
src/lj_cdata.c
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@ -86,7 +86,7 @@ void LJ_FASTCALL lj_cdata_free(global_State *g, GCcdata *cd)
void lj_cdata_setfin(lua_State *L, GCcdata *cd, GCobj *obj, uint32_t it)
{
GCtab *t = ctype_ctsG(G(L))->finalizer;
GCtab *t = tabref(G(L)->gcroot[GCROOT_FFI_FIN]);
if (gcref(t->metatable)) {
/* Add cdata to finalizer table, if still enabled. */
TValue *tv, tmp;

12
src/lj_ctype.c
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@ -643,6 +643,18 @@ CTState *lj_ctype_init(lua_State *L)
return cts;
}
/* Create special weak-keyed finalizer table. */
void lj_ctype_initfin(lua_State *L)
{
/* NOBARRIER: The table is new (marked white). */
GCtab *t = lj_tab_new(L, 0, 1);
setgcref(t->metatable, obj2gco(t));
setstrV(L, lj_tab_setstr(L, t, lj_str_newlit(L, "__mode")),
lj_str_newlit(L, "k"));
t->nomm = (uint8_t)(~(1u<<MM_mode));
setgcref(G(L)->gcroot[GCROOT_FFI_FIN], obj2gco(t));
}
/* Free C type table and state. */
void lj_ctype_freestate(global_State *g)
{

2
src/lj_ctype.h
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@ -177,7 +177,6 @@ typedef struct CTState {
MSize sizetab; /* Size of C type table. */
lua_State *L; /* Lua state (needed for errors and allocations). */
global_State *g; /* Global state. */
GCtab *finalizer; /* Map of cdata to finalizer. */
GCtab *miscmap; /* Map of -CTypeID to metatable and cb slot to func. */
CCallback cb; /* Temporary callback state. */
CTypeID1 hash[CTHASH_SIZE]; /* Hash anchors for C type table. */
@ -476,6 +475,7 @@ LJ_FUNC GCstr *lj_ctype_repr(lua_State *L, CTypeID id, GCstr *name);
LJ_FUNC GCstr *lj_ctype_repr_int64(lua_State *L, uint64_t n, int isunsigned);
LJ_FUNC GCstr *lj_ctype_repr_complex(lua_State *L, void *sp, CTSize size);
LJ_FUNC CTState *lj_ctype_init(lua_State *L);
LJ_FUNC void lj_ctype_initfin(lua_State *L);
LJ_FUNC void lj_ctype_freestate(global_State *g);
#endif

15
src/lj_gc.c
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@ -108,9 +108,6 @@ static void gc_mark_start(global_State *g)
gc_markobj(g, tabref(mainthread(g)->env));
gc_marktv(g, &g->registrytv);
gc_mark_gcroot(g);
#if LJ_HASFFI
if (ctype_ctsG(g)) gc_markobj(g, ctype_ctsG(g)->finalizer);
#endif
g->gc.state = GCSpropagate;
}
@ -190,8 +187,7 @@ static int gc_traverse_tab(global_State *g, GCtab *t)
}
if (weak) { /* Weak tables are cleared in the atomic phase. */
#if LJ_HASFFI
CTState *cts = ctype_ctsG(g);
if (cts && cts->finalizer == t) {
if (gcref(g->gcroot[GCROOT_FFI_FIN]) == obj2gco(t)) {
weak = (int)(~0u & ~LJ_GC_WEAKVAL);
} else
#endif
@ -556,7 +552,7 @@ static void gc_finalize(lua_State *L)
o->gch.marked &= (uint8_t)~LJ_GC_CDATA_FIN;
/* Resolve finalizer. */
setcdataV(L, &tmp, gco2cd(o));
tv = lj_tab_set(L, ctype_ctsG(g)->finalizer, &tmp);
tv = lj_tab_set(L, tabref(g->gcroot[GCROOT_FFI_FIN]), &tmp);
if (!tvisnil(tv)) {
g->gc.nocdatafin = 0;
copyTV(L, &tmp, tv);
@ -588,9 +584,7 @@ void lj_gc_finalize_udata(lua_State *L)
void lj_gc_finalize_cdata(lua_State *L)
{
global_State *g = G(L);
CTState *cts = ctype_ctsG(g);
if (cts) {
GCtab *t = cts->finalizer;
GCtab *t = tabref(g->gcroot[GCROOT_FFI_FIN]);
Node *node = noderef(t->node);
ptrdiff_t i;
setgcrefnull(t->metatable); /* Mark finalizer table as disabled. */
@ -605,7 +599,6 @@ void lj_gc_finalize_cdata(lua_State *L)
gc_call_finalizer(g, L, &tmp, o);
}
}
}
#endif
/* Free all remaining GC objects. */
@ -720,7 +713,7 @@ static size_t gc_onestep(lua_State *L)
return GCFINALIZECOST;
}
#if LJ_HASFFI
if (!g->gc.nocdatafin) lj_tab_rehash(L, ctype_ctsG(g)->finalizer);
if (!g->gc.nocdatafin) lj_tab_rehash(L, tabref(g->gcroot[GCROOT_FFI_FIN]));
#endif
g->gc.state = GCSpause; /* End of GC cycle. */
g->gc.debt = 0;

3
src/lj_obj.h
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@ -579,6 +579,9 @@ typedef enum {
GCROOT_BASEMT_NUM = GCROOT_BASEMT + ~LJ_TNUMX,
GCROOT_IO_INPUT, /* Userdata for default I/O input file. */
GCROOT_IO_OUTPUT, /* Userdata for default I/O output file. */
#if LJ_HASFFI
GCROOT_FFI_FIN, /* FFI finalizer table. */
#endif
GCROOT_MAX
} GCRootID;

3
src/lj_state.c
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@ -196,6 +196,9 @@ static TValue *cpluaopen(lua_State *L, lua_CFunction dummy, void *ud)
lj_lex_init(L);
fixstring(lj_err_str(L, LJ_ERR_ERRMEM)); /* Preallocate memory error msg. */
g->gc.threshold = 4*g->gc.total;
#if LJ_HASFFI
lj_ctype_initfin(L);
#endif
lj_trace_initstate(g);
lj_err_verify();
return NULL;