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heap: Fix edge case of reusing first node

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There is an edge case fixed where the whole would be freed and this would make use of a nullptr.

Additionally, remove usage of reserved names for vars and add comments on how it works.
This commit is contained in:
CTCaer 2020-03-03 04:16:20 +02:00
parent 03a8a11933
commit 6a52d44da6
2 changed files with 56 additions and 34 deletions
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45
bootloader/mem/heap.c
View file

@ -29,7 +29,7 @@ static void _heap_create(heap_t *heap, u32 start)
// Node info is before node address. // Node info is before node address.
static u32 _heap_alloc(heap_t *heap, u32 size) static u32 _heap_alloc(heap_t *heap, u32 size)
{ {
hnode_t *node, *new; hnode_t *node, *new_node;
// Align to cache line size. // Align to cache line size.
size = ALIGN(size, sizeof(hnode_t)); size = ALIGN(size, sizeof(hnode_t));
@ -49,22 +49,29 @@ static u32 _heap_alloc(heap_t *heap, u32 size)
node = heap->first; node = heap->first;
while (true) while (true)
{ {
// Check if there's available unused node.
if (!node->used && (size <= node->size)) if (!node->used && (size <= node->size))
{ {
// Size and offset of the new unused node.
u32 new_size = node->size - size; u32 new_size = node->size - size;
new = (hnode_t *)((u32)node + sizeof(hnode_t) + size); new_node = (hnode_t *)((u32)node + sizeof(hnode_t) + size);
// If there's aligned leftover space, create a new node. // If there's aligned unused space from the old node,
// create a new one and set the leftover size.
if (new_size >= (sizeof(hnode_t) << 2)) if (new_size >= (sizeof(hnode_t) << 2))
{ {
new->size = new_size - sizeof(hnode_t); new_node->size = new_size - sizeof(hnode_t);
new->used = 0; new_node->used = 0;
new->next = node->next; new_node->next = node->next;
new->next->prev = new;
new->prev = node; // Check that we are not on first node.
node->next = new; if (new_node->next)
new_node->next->prev = new_node;
new_node->prev = node;
node->next = new_node;
} }
else else // Unused node size is just enough.
size += new_size; size += new_size;
node->size = size; node->size = size;
@ -72,20 +79,23 @@ static u32 _heap_alloc(heap_t *heap, u32 size)
return (u32)node + sizeof(hnode_t); return (u32)node + sizeof(hnode_t);
} }
// No unused node found, try the next one.
if (node->next) if (node->next)
node = node->next; node = node->next;
else else
break; break;
} }
new = (hnode_t *)((u32)node + sizeof(hnode_t) + node->size); // No unused node found, create a new one.
new->used = 1; new_node = (hnode_t *)((u32)node + sizeof(hnode_t) + node->size);
new->size = size; new_node->used = 1;
new->prev = node; new_node->size = size;
new->next = NULL; new_node->prev = node;
node->next = new; new_node->next = NULL;
node->next = new_node;
return (u32)new + sizeof(hnode_t); return (u32)new_node + sizeof(hnode_t);
} }
static void _heap_free(heap_t *heap, u32 addr) static void _heap_free(heap_t *heap, u32 addr)
@ -101,6 +111,7 @@ static void _heap_free(heap_t *heap, u32 addr)
{ {
node->prev->size += node->size + sizeof(hnode_t); node->prev->size += node->size + sizeof(hnode_t);
node->prev->next = node->next; node->prev->next = node->next;
if (node->next) if (node->next)
node->next->prev = node->prev; node->next->prev = node->prev;
} }

45
nyx/nyx_gui/mem/heap.c
View file

@ -29,7 +29,7 @@ static void _heap_create(heap_t *heap, u32 start)
// Node info is before node address. // Node info is before node address.
static u32 _heap_alloc(heap_t *heap, u32 size) static u32 _heap_alloc(heap_t *heap, u32 size)
{ {
hnode_t *node, *new; hnode_t *node, *new_node;
// Align to cache line size. // Align to cache line size.
size = ALIGN(size, sizeof(hnode_t)); size = ALIGN(size, sizeof(hnode_t));
@ -49,22 +49,29 @@ static u32 _heap_alloc(heap_t *heap, u32 size)
node = heap->first; node = heap->first;
while (true) while (true)
{ {
// Check if there's available unused node.
if (!node->used && (size <= node->size)) if (!node->used && (size <= node->size))
{ {
// Size and offset of the new unused node.
u32 new_size = node->size - size; u32 new_size = node->size - size;
new = (hnode_t *)((u32)node + sizeof(hnode_t) + size); new_node = (hnode_t *)((u32)node + sizeof(hnode_t) + size);
// If there's aligned leftover space, create a new node. // If there's aligned unused space from the old node,
// create a new one and set the leftover size.
if (new_size >= (sizeof(hnode_t) << 2)) if (new_size >= (sizeof(hnode_t) << 2))
{ {
new->size = new_size - sizeof(hnode_t); new_node->size = new_size - sizeof(hnode_t);
new->used = 0; new_node->used = 0;
new->next = node->next; new_node->next = node->next;
new->next->prev = new;
new->prev = node; // Check that we are not on first node.
node->next = new; if (new_node->next)
new_node->next->prev = new_node;
new_node->prev = node;
node->next = new_node;
} }
else else // Unused node size is just enough.
size += new_size; size += new_size;
node->size = size; node->size = size;
@ -72,20 +79,23 @@ static u32 _heap_alloc(heap_t *heap, u32 size)
return (u32)node + sizeof(hnode_t); return (u32)node + sizeof(hnode_t);
} }
// No unused node found, try the next one.
if (node->next) if (node->next)
node = node->next; node = node->next;
else else
break; break;
} }
new = (hnode_t *)((u32)node + sizeof(hnode_t) + node->size); // No unused node found, create a new one.
new->used = 1; new_node = (hnode_t *)((u32)node + sizeof(hnode_t) + node->size);
new->size = size; new_node->used = 1;
new->prev = node; new_node->size = size;
new->next = NULL; new_node->prev = node;
node->next = new; new_node->next = NULL;
node->next = new_node;
return (u32)new + sizeof(hnode_t); return (u32)new_node + sizeof(hnode_t);
} }
static void _heap_free(heap_t *heap, u32 addr) static void _heap_free(heap_t *heap, u32 addr)
@ -101,6 +111,7 @@ static void _heap_free(heap_t *heap, u32 addr)
{ {
node->prev->size += node->size + sizeof(hnode_t); node->prev->size += node->size + sizeof(hnode_t);
node->prev->next = node->next; node->prev->next = node->next;
if (node->next) if (node->next)
node->next->prev = node->prev; node->next->prev = node->prev;
} }