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Disallow weak pointers to stack (#274)
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@vtereshkov
vtereshkov committed Apr 27, 2023
1 parent 5343c83 commit 72d7c80
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Showing 3 changed files with 34 additions and 26 deletions.
2 changes: 1 addition & 1 deletion playground/umka.js
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56 changes: 31 additions & 25 deletions src/umka_vm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -337,7 +337,7 @@ static FORCE_INLINE void stackChangeFrameRefCnt(Fiber *fiber, HeapPages *pages,
}


static FORCE_INLINE void *chunkAlloc(HeapPages *pages, int64_t size, Type *type, ExternFunc onFree, Error *error)
static FORCE_INLINE void *chunkAlloc(HeapPages *pages, int64_t size, Type *type, ExternFunc onFree, bool isStack, Error *error)
{
// Page layout: header, data, footer (char), padding, header, data, footer (char), padding...
int64_t chunkSize = align(sizeof(HeapChunkHeader) + align(size + 1, sizeof(int64_t)), VM_MIN_HEAP_CHUNK);
Expand Down Expand Up @@ -365,6 +365,7 @@ static FORCE_INLINE void *chunkAlloc(HeapPages *pages, int64_t size, Type *type,
chunk->type = type;
chunk->onFree = onFree;
chunk->ip = pages->fiber->ip;
chunk->isStack = isStack;

page->numOccupiedChunks++;
page->refCnt++;
Expand Down Expand Up @@ -538,7 +539,7 @@ void vmInit(VM *vm, int stackSize, bool fileSystemEnabled, Error *error)

pageInit(&vm->pages, vm->fiber, &vm->strLenCache, error);

vm->fiber->stack = chunkAlloc(&vm->pages, stackSize * sizeof(Slot), NULL, NULL, error);
vm->fiber->stack = chunkAlloc(&vm->pages, stackSize * sizeof(Slot), NULL, NULL, true, error);
vm->fiber->stackSize = stackSize;

candidateInit(&vm->refCntChangeCandidates);
Expand Down Expand Up @@ -910,7 +911,7 @@ static FORCE_INLINE void doAllocDynArray(HeapPages *pages, DynArray *array, Type

DynArrayDimensions dims = {.len = len, .capacity = 2 * (len + 1)};

char *dimsAndData = chunkAlloc(pages, sizeof(DynArrayDimensions) + dims.capacity * array->itemSize, array->type, NULL, error);
char *dimsAndData = chunkAlloc(pages, sizeof(DynArrayDimensions) + dims.capacity * array->itemSize, array->type, NULL, false, error);
*(DynArrayDimensions *)dimsAndData = dims;

array->data = dimsAndData + sizeof(DynArrayDimensions);
Expand All @@ -930,7 +931,7 @@ static FORCE_INLINE void doGetEmptyDynArray(DynArray *array, Type *type)
static FORCE_INLINE void doAllocMap(HeapPages *pages, Map *map, Type *type, Error *error)
{
map->type = type;
map->root = chunkAlloc(pages, typeSizeNoCheck(type->base), type->base, NULL, error);
map->root = chunkAlloc(pages, typeSizeNoCheck(type->base), type->base, NULL, false, error);
map->root->len = 0;
}

Expand Down Expand Up @@ -1013,7 +1014,7 @@ static FORCE_INLINE MapNode *doGetMapNode(Map *map, Slot key, bool createMissing
return NULL;

Type *nodeType = map->type->base;
*child = (MapNode *)chunkAlloc(pages, typeSizeNoCheck(nodeType), nodeType, NULL, error);
*child = (MapNode *)chunkAlloc(pages, typeSizeNoCheck(nodeType), nodeType, NULL, false, error);
}

if (nodePtrInParent)
Expand All @@ -1032,7 +1033,7 @@ static MapNode *doCopyMapNode(Map *map, MapNode *node, Fiber *fiber, HeapPages *
return NULL;

Type *nodeType = map->type->base;
MapNode *result = (MapNode *)chunkAlloc(pages, typeSizeNoCheck(nodeType), nodeType, NULL, error);
MapNode *result = (MapNode *)chunkAlloc(pages, typeSizeNoCheck(nodeType), nodeType, NULL, false, error);

result->len = node->len;

Expand All @@ -1045,7 +1046,7 @@ static MapNode *doCopyMapNode(Map *map, MapNode *node, Fiber *fiber, HeapPages *
doBasicDeref(&srcKey, keyType->kind, error);

// When allocating dynamic arrays, we mark with type the data chunk, not the header chunk
result->key = chunkAlloc(pages, typeSizeNoCheck(keyType), keyType->kind == TYPE_DYNARRAY ? NULL : keyType, NULL, error);
result->key = chunkAlloc(pages, typeSizeNoCheck(keyType), keyType->kind == TYPE_DYNARRAY ? NULL : keyType, NULL, false, error);

if (typeGarbageCollected(keyType))
doBasicChangeRefCnt(fiber, pages, srcKey.ptrVal, keyType, TOK_PLUSPLUS);
Expand All @@ -1062,7 +1063,7 @@ static MapNode *doCopyMapNode(Map *map, MapNode *node, Fiber *fiber, HeapPages *
doBasicDeref(&srcItem, itemType->kind, error);

// When allocating dynamic arrays, we mark with type the data chunk, not the header chunk
result->data = chunkAlloc(pages, typeSizeNoCheck(itemType), itemType->kind == TYPE_DYNARRAY ? NULL : itemType, NULL, error);
result->data = chunkAlloc(pages, typeSizeNoCheck(itemType), itemType->kind == TYPE_DYNARRAY ? NULL : itemType, NULL, false, error);

if (typeGarbageCollected(itemType))
doBasicChangeRefCnt(fiber, pages, srcItem.ptrVal, itemType, TOK_PLUSPLUS);
Expand Down Expand Up @@ -1473,7 +1474,7 @@ static FORCE_INLINE void doBuiltinPrintf(Fiber *fiber, HeapPages *pages, bool co

if (needRealloc)
{
char *newStream = chunkAlloc(pages, 2 * (prevLen + len) + 1, NULL, NULL, error);
char *newStream = chunkAlloc(pages, 2 * (prevLen + len) + 1, NULL, NULL, false, error);
if (stream)
memcpy(newStream, stream, prevLen);
newStream[prevLen] = 0;
Expand Down Expand Up @@ -1550,7 +1551,7 @@ static FORCE_INLINE void doBuiltinScanf(Fiber *fiber, HeapPages *pages, bool con
doBasicChangeRefCnt(fiber, pages, *dest, &destType, TOK_MINUSMINUS);

// Allocate new string
*dest = chunkAlloc(pages, strlen(src) + 1, NULL, NULL, error);
*dest = chunkAlloc(pages, strlen(src) + 1, NULL, NULL, false, error);
strcpy(*dest, src);
free(src);

Expand Down Expand Up @@ -1580,7 +1581,7 @@ static FORCE_INLINE void doBuiltinNew(Fiber *fiber, HeapPages *pages, Error *err
if (type && type->kind == TYPE_DYNARRAY)
type = NULL;

void *result = chunkAlloc(pages, size, type, NULL, error);
void *result = chunkAlloc(pages, size, type, NULL, false, error);

(--fiber->top)->ptrVal = result;
}
Expand Down Expand Up @@ -1676,7 +1677,7 @@ static FORCE_INLINE void doBuiltinMaketostr(Fiber *fiber, HeapPages *pages, Erro

if (src->data)
{
dest = chunkAlloc(pages, getDims(src)->len + 1, NULL, NULL, error);
dest = chunkAlloc(pages, getDims(src)->len + 1, NULL, NULL, false, error);
memcpy(dest, src->data, getDims(src)->len);
dest[getDims(src)->len] = 0;
}
Expand Down Expand Up @@ -1984,7 +1985,7 @@ static FORCE_INLINE void doBuiltinSlice(Fiber *fiber, HeapPages *pages, Error *e
else
{
// String
char *substr = chunkAlloc(pages, endIndex - startIndex + 1, NULL, NULL, error);
char *substr = chunkAlloc(pages, endIndex - startIndex + 1, NULL, NULL, false, error);
memcpy(substr, &str[startIndex], endIndex - startIndex);
substr[endIndex - startIndex] = 0;

Expand Down Expand Up @@ -2174,10 +2175,10 @@ static FORCE_INLINE void doBuiltinFiberspawn(Fiber *fiber, HeapPages *pages, Err
int childEntryOffset = (fiber->top++)->intVal;

// Copy whole fiber context
Fiber *child = chunkAlloc(pages, sizeof(Fiber), NULL, NULL, error);
Fiber *child = chunkAlloc(pages, sizeof(Fiber), NULL, NULL, false, error);

*child = *fiber;
child->stack = chunkAlloc(pages, child->stackSize * sizeof(Slot), NULL, NULL, error);
child->stack = chunkAlloc(pages, child->stackSize * sizeof(Slot), NULL, NULL, true, error);
child->top = child->base = child->stack + child->stackSize - 1;

// Call child fiber function
Expand Down Expand Up @@ -2220,7 +2221,7 @@ static FORCE_INLINE void doBuiltinRepr(Fiber *fiber, HeapPages *pages, Error *er
enum {MAX_REPR_DEPTH = 20};

int len = doFillReprBuf(val, type, NULL, 0, MAX_REPR_DEPTH, fiber->strLenCache, error); // Predict buffer length
char *buf = chunkAlloc(pages, len + 1, NULL, NULL, error); // Allocate buffer
char *buf = chunkAlloc(pages, len + 1, NULL, NULL, false, error); // Allocate buffer
doFillReprBuf(val, type, buf, INT_MAX, MAX_REPR_DEPTH, fiber->strLenCache, error); // Fill buffer

fiber->top->ptrVal = buf;
Expand Down Expand Up @@ -2488,7 +2489,7 @@ static FORCE_INLINE void doBinary(Fiber *fiber, HeapPages *pages, Error *error)
}
else
{
buf = chunkAlloc(pages, 2 * (lhsLen + rhsLen) + 1, NULL, NULL, error);
buf = chunkAlloc(pages, 2 * (lhsLen + rhsLen) + 1, NULL, NULL, false, error);
memmove(buf, lhsStr, lhsLen);
}

Expand Down Expand Up @@ -2707,8 +2708,8 @@ static FORCE_INLINE void doGetMapPtr(Fiber *fiber, HeapPages *pages, Error *erro
if (!node->data)
{
// When allocating dynamic arrays, we mark with type the data chunk, not the header chunk
node->key = chunkAlloc(pages, typeSizeNoCheck(keyType), keyType->kind == TYPE_DYNARRAY ? NULL : keyType, NULL, error);
node->data = chunkAlloc(pages, typeSizeNoCheck(itemType), itemType->kind == TYPE_DYNARRAY ? NULL : itemType, NULL, error);
node->key = chunkAlloc(pages, typeSizeNoCheck(keyType), keyType->kind == TYPE_DYNARRAY ? NULL : keyType, NULL, false, error);
node->data = chunkAlloc(pages, typeSizeNoCheck(itemType), itemType->kind == TYPE_DYNARRAY ? NULL : itemType, NULL, false, error);

// Increase key ref count
if (typeGarbageCollected(keyType))
Expand Down Expand Up @@ -2772,11 +2773,15 @@ static FORCE_INLINE void doWeakenPtr(Fiber *fiber, HeapPages *pages)
uint64_t weakPtr = 0;

HeapPage *page = pageFind(pages, ptr, false);
if (page && pageGetChunkHeader(page, ptr)->refCnt > 0)
if (page)
{
int pageId = page->id;
int pageOffset = (char *)ptr - (char *)page->ptr;
weakPtr = ((uint64_t)pageId << 32) | pageOffset;
HeapChunkHeader *chunk = pageGetChunkHeader(page, ptr);
if (chunk->refCnt > 0 && !chunk->isStack)
{
int pageId = page->id;
int pageOffset = (char *)ptr - (char *)page->ptr;
weakPtr = ((uint64_t)pageId << 32) | pageOffset;
}
}

fiber->top->weakPtrVal = weakPtr;
Expand All @@ -2796,7 +2801,8 @@ static FORCE_INLINE void doStrengthenPtr(Fiber *fiber, HeapPages *pages)
int pageOffset = weakPtr & 0x7FFFFFFF;
ptr = (char *)page->ptr + pageOffset;

if (pageGetChunkHeader(page, ptr)->refCnt == 0)
HeapChunkHeader * chunk = pageGetChunkHeader(page, ptr);
if (chunk->refCnt == 0 || chunk->isStack)
ptr = NULL;
}

Expand Down Expand Up @@ -3224,7 +3230,7 @@ void vmSetHook(VM *vm, HookEvent event, HookFunc hook)

void *vmAllocData(VM *vm, int size, ExternFunc onFree)
{
return chunkAlloc(&vm->pages, size, NULL, onFree, vm->error);
return chunkAlloc(&vm->pages, size, NULL, onFree, false, vm->error);
}


Expand Down
2 changes: 2 additions & 0 deletions src/umka_vm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -197,6 +197,8 @@ typedef struct
struct tagType *type; // Optional type for garbage collection
ExternFunc onFree; // Optional callback called when ref count reaches zero
int64_t ip; // Optional instruction pointer at which the chunk has been allocated
bool isStack;
bool reserved[7];
} HeapChunkHeader;


Expand Down

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