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Kernel: Rewrote kmalloc to be much simpler and allow alignment

This commit is contained in:
Bananymous 2023-01-10 21:10:36 +02:00
parent d89b6aa9ce
commit 7d45b3cbd6
2 changed files with 106 additions and 212 deletions
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1
kernel/include/kernel/kmalloc.h
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@ -7,4 +7,5 @@ void kmalloc_dump_nodes();
void* kmalloc_eternal(size_t); void* kmalloc_eternal(size_t);
void* kmalloc(size_t); void* kmalloc(size_t);
void* kmalloc(size_t, size_t);
void kfree(void*); void kfree(void*);

305
kernel/kernel/kmalloc.cpp
View File

@ -1,60 +1,71 @@
#include <kernel/multiboot.h> #include <BAN/Errors.h>
#include <BAN/Math.h>
#include <kernel/kmalloc.h> #include <kernel/kmalloc.h>
#include <kernel/Panic.h> #include <kernel/multiboot.h>
#include <kernel/Serial.h>
#include <stdint.h> #include <stdint.h>
#define MB (1 << 20) #define MB (1 << 20)
#define ALIGN (alignof(max_align_t)) /*
Kmalloc holds a bitmap of free/allocated chunks
When allocating n chunks, kmalloc will put the number of chunks
to address, and return pointer to the byte after the stored size
*/
static constexpr uintptr_t s_kmalloc_base = 0x00200000;
static constexpr size_t s_kmalloc_size = 1 * MB;
static constexpr uintptr_t s_kmalloc_end = s_kmalloc_base + s_kmalloc_size;
static constexpr uintptr_t s_kmalloc_eternal_base = s_kmalloc_end;
static constexpr size_t s_kmalloc_eternal_size = 1 * MB;
static constexpr uintptr_t s_kmalloc_eternal_end = s_kmalloc_eternal_base + s_kmalloc_eternal_size;
static constexpr size_t s_kmalloc_default_align = alignof(max_align_t);
static constexpr size_t s_kmalloc_chunk_size = s_kmalloc_default_align;
static constexpr size_t s_kmalloc_chunks_per_size = sizeof(size_t) * 8 / s_kmalloc_chunk_size;
static constexpr size_t s_kmalloc_total_chunks = s_kmalloc_size / s_kmalloc_chunk_size;
static uint8_t s_kmalloc_bitmap[s_kmalloc_total_chunks / 8] { 0 };
extern "C" uintptr_t g_kernel_end; extern "C" uintptr_t g_kernel_end;
/* static bool is_kmalloc_chunk_used(size_t index)
#### KMALLOC ################
*/
struct kmalloc_node
{ {
uintptr_t addr; ASSERT(index < s_kmalloc_total_chunks);
size_t size : sizeof(size_t) * 8 - 1; return s_kmalloc_bitmap[index / 8] & (1 << (index % 8));
size_t free : 1; }
};
static kmalloc_node* s_kmalloc_node_head = nullptr;
static size_t s_kmalloc_node_count;
static uintptr_t s_kmalloc_node_base = 0x00200000; static uintptr_t chunk_address(size_t index)
static size_t s_kmalloc_max_nodes = 1000; {
ASSERT(index < s_kmalloc_total_chunks);
return s_kmalloc_base + s_kmalloc_chunk_size * index;
}
static uintptr_t s_kmalloc_base = s_kmalloc_node_base + s_kmalloc_max_nodes * sizeof(kmalloc_node); static void free_chunks(size_t start)
static size_t s_kmalloc_size = 1 * MB; {
static uintptr_t s_kmalloc_end = s_kmalloc_base + s_kmalloc_size; ASSERT(s_kmalloc_chunks_per_size <= start && start < s_kmalloc_total_chunks);
start -= s_kmalloc_chunks_per_size;
static size_t s_kmalloc_available = 0; size_t size = *(size_t*)chunk_address(start);
static size_t s_kmalloc_allocated = 0; for (size_t i = 0; i < size; i++)
s_kmalloc_bitmap[(start + i) / 8] &= ~(1 << ((start + i) % 8));
/* }
#### KMALLOC ETERNAL ########
*/
static uintptr_t s_kmalloc_eternal_ptr = 0;
static uintptr_t s_kmalloc_eternal_base = s_kmalloc_end;
static size_t s_kmalloc_eternal_size = 1 * MB;
static uintptr_t s_kmalloc_eternal_end = s_kmalloc_eternal_base + s_kmalloc_eternal_size;
/*
#############################
*/
static bool s_initialized = false;
void kmalloc_initialize() void kmalloc_initialize()
{ {
if (!(g_multiboot_info->flags & (1 << 6))) if (!(g_multiboot_info->flags & (1 << 6)))
Kernel::Panic("Kmalloc: Bootloader didn't provide a memory map"); Kernel::Panic("Kmalloc: Bootloader didn't provide a memory map");
if (g_kernel_end > s_kmalloc_node_base) if (g_kernel_end > s_kmalloc_base)
Kernel::Panic("Kmalloc: Kernel end is over kmalloc base"); Kernel::Panic("Kmalloc: Kernel end is over kmalloc base");
dprintln("initializing kmalloc");
dprintln("kmalloc {} -> {}", (void*)s_kmalloc_base, (void*)s_kmalloc_end);
dprintln("kmalloc eternal {} -> {}", (void*)s_kmalloc_eternal_base, (void*)s_kmalloc_eternal_end);
// Validate kmalloc memory // Validate kmalloc memory
bool valid = false; bool valid = false;
for (size_t i = 0; i < g_multiboot_info->mmap_length;) for (size_t i = 0; i < g_multiboot_info->mmap_length;)
@ -77,198 +88,80 @@ void kmalloc_initialize()
if (!valid) if (!valid)
{ {
Kernel::Panic("Kmalloc: Could not find {}.{} MB of memory", Kernel::Panic("Kmalloc: Could not find {}.{} MB of memory",
(s_kmalloc_eternal_end - s_kmalloc_node_base) / MB, (s_kmalloc_eternal_end - s_kmalloc_base) / MB,
(s_kmalloc_eternal_end - s_kmalloc_node_base) % MB (s_kmalloc_eternal_end - s_kmalloc_base) % MB
); );
} }
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;
s_kmalloc_eternal_ptr = s_kmalloc_eternal_base;
s_initialized = true;
} }
void kmalloc_dump_nodes() void kmalloc_dump_nodes()
{ {
if (!s_initialized) dprintln("kmalloc dump: {8b}{8b}{8b}{8b}{8b}{8b}{8b}{8b}",
Kernel::Panic("kmalloc not initialized!"); s_kmalloc_bitmap[7], s_kmalloc_bitmap[6], s_kmalloc_bitmap[5], s_kmalloc_bitmap[4],
s_kmalloc_bitmap[3], s_kmalloc_bitmap[2], s_kmalloc_bitmap[1], s_kmalloc_bitmap[0]
dprintln("Kmalloc memory available {}.{} MB", s_kmalloc_available / MB, s_kmalloc_available % MB); );
dprintln("Kmalloc memory allocated {}.{} MB", s_kmalloc_allocated / MB, s_kmalloc_allocated % MB);
dprintln("Using {}/{} nodes", s_kmalloc_node_count, s_kmalloc_max_nodes);
for (size_t i = 0; i < s_kmalloc_node_count; i++)
{
kmalloc_node& node = s_kmalloc_node_head[i];
dprintln(" ({3}) {}, node at {}, free: {}, size: {}", i, (void*)&node, (void*)node.addr, node.free, node.size);
}
}
void* kmalloc_eternal(size_t size)
{
if (!s_initialized)
Kernel::Panic("kmalloc not initialized!");
if (size % ALIGN)
size += ALIGN - (size % ALIGN);
if (s_kmalloc_eternal_ptr % ALIGN)
Kernel::Panic("Unaligned ptr in kmalloc_eternal");
if (s_kmalloc_eternal_ptr + size > s_kmalloc_eternal_end)
{
dprintln("\e[33mKmalloc eternal: Could not allocate {} bytes\e[0m", size);
return nullptr;
}
void* result = (void*)s_kmalloc_eternal_ptr;
s_kmalloc_eternal_ptr += size;
return result;
} }
void* kmalloc(size_t size) void* kmalloc(size_t size)
{ {
if (!s_initialized) return kmalloc(size, s_kmalloc_default_align);
Kernel::Panic("kmalloc not initialized!"); }
if (size % ALIGN) void* kmalloc(size_t size, size_t align)
size += ALIGN - (size % ALIGN); {
if (size == 0)
return nullptr;
// Search for node with free memory and big enough size if (align == 0)
size_t valid_node_index = -1; align = s_kmalloc_chunk_size;
for (size_t i = 0; i < s_kmalloc_node_count; i++)
if (align < s_kmalloc_chunk_size || align % s_kmalloc_chunk_size)
{ {
kmalloc_node& current = s_kmalloc_node_head[i]; size_t new_align = BAN::Math::lcm(align, s_kmalloc_chunk_size);
if (current.free && current.size >= size) dwarnln("kmalloc asked to align to {}, aliging to {} instead", align, new_align);
align = new_align;
}
size_t needed_chunks = (size - 1) / s_kmalloc_chunk_size + 1 + s_kmalloc_chunks_per_size;
for (size_t i = 0; i < s_kmalloc_total_chunks - needed_chunks; i++)
{ {
valid_node_index = i; if (chunk_address(i + s_kmalloc_chunks_per_size) % align)
continue;
bool free = true;
for (size_t j = 0; j < needed_chunks; j++)
{
if (is_kmalloc_chunk_used(i + j))
{
free = false;
i += j;
break; break;
} }
} }
if (free)
if (valid_node_index == size_t(-1))
{ {
dprintln("\e[33mKmalloc: Could not allocate {} bytes\e[0m", size); *(size_t*)chunk_address(i) = needed_chunks;
for (size_t j = 0; j < needed_chunks; j++)
s_kmalloc_bitmap[(i + j) / 8] |= (1 << ((i + j) % 8));
return (void*)chunk_address(i + s_kmalloc_chunks_per_size);
}
}
dwarnln("Could not allocate {} bytes", size);
return nullptr; return nullptr;
} }
kmalloc_node& valid_node = s_kmalloc_node_head[valid_node_index]; void kfree(void* address)
// 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; if (!address)
if (valid_node.addr % ALIGN)
Kernel::Panic("Unaligned ptr in kmalloc");
return (void*)valid_node.addr;
}
if (s_kmalloc_node_count == s_kmalloc_max_nodes)
{
dprintln("\e[33mKmalloc: Out of kmalloc nodes\e[0m");
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;
if (valid_node.addr % ALIGN)
Kernel::Panic("Unaligned ptr in kmalloc");
return (void*)valid_node.addr;
}
void kfree(void* addr)
{
if (!s_initialized) Kernel::Panic("kmalloc not initialized!");
if (addr == nullptr)
return; return;
ASSERT(((uintptr_t)address % s_kmalloc_chunk_size) == 0);
ASSERT(s_kmalloc_base <= (uintptr_t)address && (uintptr_t)address < s_kmalloc_end);
// TODO: use binary search etc. size_t first_chunk = ((uintptr_t)address - s_kmalloc_base) / s_kmalloc_chunk_size - s_kmalloc_chunks_per_size;
ASSERT(is_kmalloc_chunk_used(first_chunk));
size_t node_index = -1; size_t size = *(size_t*)chunk_address(first_chunk);
for (size_t i = 0; i < s_kmalloc_node_count; i++) for (size_t i = 0; i < size; i++)
{ s_kmalloc_bitmap[(first_chunk + i) / 8] &= ~(1 << ((first_chunk + i) % 8));
if (s_kmalloc_node_head[i].addr == (uintptr_t)addr)
{
node_index = i;
break;
}
}
if (node_index == size_t(-1))
{
dprintln("\e[33mKmalloc: Attempting to free unallocated pointer {}\e[0m", 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;
} }