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Kernel: Implement very basic, but functional kmalloc/kfree

This commit is contained in:
Bananymous 2022-12-09 00:23:20 +02:00
parent ef56f9a239
commit 26f1ebe26f
2 changed files with 165 additions and 18 deletions
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11
kernel/include/kernel/kmalloc.h
View File

@ -3,9 +3,16 @@
#include <stddef.h>
void kmalloc_initialize();
void kmalloc_dump_nodes();
void* kmalloc(size_t);
void kfree(void*);
inline void* operator new(size_t size) { return kmalloc(size); }
inline void* operator new[](size_t size) { return kmalloc(size); }
inline void* operator new(size_t size) { return kmalloc(size); }
inline void* operator new[](size_t size) { return kmalloc(size); }
inline void operator delete(void* addr) { kfree(addr); }
inline void operator delete[](void* addr) { kfree(addr); }
inline void operator delete(void* addr, size_t) { kfree(addr); }
inline void operator delete[](void* addr, size_t) { kfree(addr); }

172
kernel/kernel/kmalloc.cpp
View File

@ -7,19 +7,31 @@
#define MB (1 << 20)
struct kmalloc_info_t
struct kmalloc_node
{
static constexpr size_t total_size = 1 * MB;
void* base_addr = (void*)0x00200000;
size_t used;
uint8_t* addr = nullptr;
size_t size : sizeof(size_t) * 8 - 1;
size_t free : 1;
};
static kmalloc_info_t s_kmalloc_info;
static kmalloc_node* s_kmalloc_node_head = nullptr;
static size_t s_kmalloc_node_count;
static uint8_t* const s_kmalloc_node_base = (uint8_t*)0x00200000;
static constexpr size_t s_kmalloc_max_nodes = 1000;
static uint8_t* const s_kmalloc_base = s_kmalloc_node_base + s_kmalloc_max_nodes * sizeof(kmalloc_node);
static constexpr size_t s_kmalloc_size = 1 * MB;
static uint8_t* const s_kmalloc_end = s_kmalloc_base + s_kmalloc_size;
static size_t s_kmalloc_available = 0;
static size_t s_kmalloc_allocated = 0;
void kmalloc_initialize()
{
if (!(s_multiboot_info->flags & (1 << 6)))
Kernel::panic("Bootloader didn't give a memory map");
// Validate kmalloc memory
bool valid = false;
for (size_t i = 0; i < s_multiboot_info->mmap_length;)
{
@ -27,10 +39,10 @@ void kmalloc_initialize()
if (mmmt->type == 1)
{
char* ptr1 = (char*)mmmt->base_addr;
char* ptr2 = (char*)s_kmalloc_info.base_addr;
size_t len1 = mmmt->length;
size_t len2 = s_kmalloc_info.total_size;
uint8_t* ptr1 = (uint8_t*)mmmt->base_addr;
uint8_t* ptr2 = (uint8_t*)s_kmalloc_base;
size_t len1 = mmmt->length;
size_t len2 = s_kmalloc_size;
if (ptr1 <= ptr2 && ptr1 + len1 >= ptr2 + len2)
{
@ -45,20 +57,148 @@ void kmalloc_initialize()
if (!valid)
Kernel::panic("Could not find enough space for kmalloc");
s_kmalloc_info.used = 0;
s_kmalloc_node_count = 1;
s_kmalloc_node_head = (kmalloc_node*)s_kmalloc_node_base;
s_kmalloc_allocated = 0;
s_kmalloc_available = s_kmalloc_size;
kmalloc_node& head = s_kmalloc_node_head[0];
head.addr = s_kmalloc_base;
head.size = s_kmalloc_size;
head.free = true;
}
void kmalloc_dump_nodes()
{
for (size_t i = 0; i < s_kmalloc_node_count; i++)
{
kmalloc_node& node = s_kmalloc_node_head[i];
if (i < 10) kprint(" ");
kprint(" ({}) {}, node at {}, free: {}, size: {}\n", i, (void*)&node, (void*)node.addr, node.free, node.size);
}
}
void* kmalloc(size_t size)
{
if (s_kmalloc_info.total_size - s_kmalloc_info.used < size)
Kernel::panic("Out of kernel memory");
// Search for node with free memory and big enough size
size_t valid_node_index = -1;
for (size_t i = 0; i < s_kmalloc_node_count; i++)
{
kmalloc_node& current = s_kmalloc_node_head[i];
if (current.free && current.size >= size)
{
valid_node_index = i;
break;
}
}
char* result = (char*)s_kmalloc_info.base_addr + s_kmalloc_info.used;
s_kmalloc_info.used += size;
return (void*)result;
if (valid_node_index == size_t(-1))
{
kprint("Could not allocate {} bytes\n", size);
return nullptr;
}
kmalloc_node& valid_node = s_kmalloc_node_head[valid_node_index];
// If node's size happens to match requested size,
// just flip free bit and return the address
if (valid_node.size == size)
{
valid_node.free = false;
return valid_node.addr;
}
if (s_kmalloc_node_count == s_kmalloc_max_nodes)
{
kprint("Out of kmalloc nodes\n");
return nullptr;
}
// Shift every node after valid_node one place to right
for (size_t i = s_kmalloc_node_count - 1; i > valid_node_index; i--)
s_kmalloc_node_head[i + 1] = s_kmalloc_node_head[i];
// Create new node after the valid node
s_kmalloc_node_count++;
kmalloc_node& new_node = s_kmalloc_node_head[valid_node_index + 1];
new_node.addr = valid_node.addr + size;
new_node.size = valid_node.size - size;
new_node.free = true;
// Update the valid node
valid_node.size = size;
valid_node.free = false;
s_kmalloc_allocated += size;
s_kmalloc_available -= size;
return valid_node.addr;
}
void kfree(void*)
void kfree(void* addr)
{
// TODO: use binary search etc.
size_t node_index = -1;
for (size_t i = 0; i < s_kmalloc_node_count; i++)
{
if (s_kmalloc_node_head[i].addr == addr)
{
node_index = i;
break;
}
}
if (node_index == size_t(-1))
{
kprint("Attempting to free unallocated pointer {}\n", addr);
return;
}
// Mark this node as free
kmalloc_node* node = &s_kmalloc_node_head[node_index];
node->free = true;
size_t size = node->size;
// If node before this node is free, merge them
if (node_index > 0)
{
kmalloc_node& prev = s_kmalloc_node_head[node_index - 1];
if (prev.free)
{
prev.size += node->size;
s_kmalloc_node_count--;
for (size_t i = node_index; i < s_kmalloc_node_count; i++)
s_kmalloc_node_head[i] = s_kmalloc_node_head[i + 1];
node_index--;
node = &s_kmalloc_node_head[node_index];
}
}
// If node after this node is free, merge them
if (node_index < s_kmalloc_node_count - 1)
{
kmalloc_node& next = s_kmalloc_node_head[node_index + 1];
if (next.free)
{
node->size += next.size;
s_kmalloc_node_count--;
for (size_t i = node_index; i < s_kmalloc_node_count; i++)
s_kmalloc_node_head[i + 1] = s_kmalloc_node_head[i + 2];
node_index--;
node = &s_kmalloc_node_head[node_index];
}
}
s_kmalloc_allocated -= size;
s_kmalloc_available += size;
}