Add beginning of better vmem allocator

NOTES.md

@@ -6,4 +6,5 @@
 - Allow for more than one IOAPIC in ACPI module
 - Slab allocator for kernel structures
 - mark kernel memory pages global
+- kernel allocator free()
 

src/kernel/memory.cpp

@@ -1,46 +1,52 @@
+#include "kutil/memory.h"
 #include "assert.h"
+#include "log.h"
 #include "memory.h"
 #include "memory_pages.h"
 
 memory_manager g_kernel_memory_manager;
 
-struct memory_allocation_header
+struct memory_manager::alloc_header
 {
-	uint64_t pages;
+	uint64_t size;
 	uint64_t reserved;
 	uint8_t data[0];
 } __attribute__ ((packed));
 
+struct memory_manager::free_header
+{
+	free_header *next;
+	uint64_t size;
+} __attribute__ ((packed));
+
 memory_manager::memory_manager() :
 	m_start(nullptr),
 	m_length(0)
 {
+	kutil::memset(m_free, 0, sizeof(m_free));
 }
 
-memory_manager::memory_manager(void *start, size_t length) :
+memory_manager::memory_manager(void *start) :
 	m_start(start),
-	m_length(length)
+	m_length(0)
 {
+	kutil::memset(m_free, 0, sizeof(m_free));
+	grow_memory();
 }
 
 void *
 memory_manager::allocate(size_t length)
 {
-	length = page_align(length + sizeof(memory_allocation_header));
+	size_t total = length + sizeof(alloc_header);
+	unsigned size = min_size;
+	while (total > (1 << size)) size++;
+	kassert(size < max_size, "Tried to allocate a block bigger than max_size");
+	log::debug(logs::memory, "Allocating %d bytes, which is size %d", total, size);
 
-	if (length > m_length) return nullptr;
+	alloc_header *header = reinterpret_cast<alloc_header *>(pop_free(size));
+	header->size = size;
 
-	m_length -= length;
+	log::debug(logs::memory, "  Returning %d bytes at %lx", length, &header->data);
-	memory_allocation_header *header =
-		reinterpret_cast<memory_allocation_header *>(m_start);
-	m_start = reinterpret_cast<uint8_t *>(m_start) + length;
-
-	size_t pages = length / page_manager::page_size;
-	g_page_manager.map_pages(
-			reinterpret_cast<page_manager::addr_t>(header),
-			pages);
-
-	header->pages = pages;
 	return &header->data;
 }
 
@@ -49,3 +55,62 @@ memory_manager::free(void *p)
 {
 	// In this simple version, we don't care about freed pointers
 }
+
+void
+memory_manager::grow_memory()
+{
+	size_t length = (1 << max_size);
+
+	free_header *block = reinterpret_cast<free_header *>(
+			reinterpret_cast<uint64_t>(m_start) + m_length);
+
+	g_page_manager.map_pages(
+			reinterpret_cast<page_manager::addr_t>(block),
+			length / page_manager::page_size);
+
+	block->size = max_size;
+	block->next = get_free(max_size);
+	get_free(max_size) = block;
+	m_length += length;
+
+	log::debug(logs::memory, "Allocated new block at %lx: size %d next %lx",
+			block, block->size, block->next);
+}
+
+void
+memory_manager::ensure_block(unsigned size)
+{
+	free_header *header = get_free(size);
+	if (header != nullptr) return;
+	else if (size == max_size) {
+		grow_memory();
+		return;
+	}
+
+	free_header *bigger = pop_free(size + 1);
+
+	uint64_t new_size = bigger->size - 1;
+	free_header *next = reinterpret_cast<free_header *>(
+			reinterpret_cast<uint64_t>(bigger) + (1 << new_size));
+
+	next->next = bigger->next;
+	next->size = new_size;
+
+	bigger->next = next;
+	bigger->size = new_size;
+	log::debug(logs::memory, "ensure_block[%2d] split blocks:", size);
+	log::debug(logs::memory, "   %lx: size %d next %lx", bigger, bigger->size, bigger->next);
+	log::debug(logs::memory, "   %lx: size %d next %lx", next, next->size, next->next);
+
+	get_free(size) = bigger;
+}
+
+memory_manager::free_header *
+memory_manager::pop_free(unsigned size)
+{
+	ensure_block(size);
+	free_header *block = get_free(size);
+	get_free(size) = block->next;
+	block->next = nullptr;
+	return block;
+}

src/kernel/memory.h

@@ -5,14 +5,13 @@
 #include <stddef.h>
 #include <stdint.h>
 
-struct memory_block_node;
 
 /// Manager for allocation of virtual memory.
 class memory_manager
 {
 public:
 	memory_manager();
-	memory_manager(void *start, size_t length);
+	memory_manager(void *start);
 
 	/// Allocate memory from the area managed.
 	/// \arg length  The amount of memory to allocate, in bytes
@@ -25,12 +24,30 @@ public:
 	void free(void *p);
 
 private:
-	friend class page_manager;
+	struct alloc_header;
+	struct free_header;
 
-	// Simple incrementing pointer.
+	/// Expand the size of memory
+	void grow_memory();
+
+	/// Ensure there is a block of a given size, recursively splitting
+	/// \arg size   Size category of the block we want
+	void ensure_block(unsigned size);
+
+	/// Helper accessor for the list of blocks of a given size
+	free_header *& get_free(unsigned size)  { return m_free[size - min_size]; }
+
+	/// Helper to get a block of the given size, growing if necessary
+	free_header * pop_free(unsigned size);
+
+	static const unsigned min_size = 6;  ///< Minimum block size is (2^min_size)
+	static const unsigned max_size = 16; ///< Maximum block size is (2^max_size)
+
+	free_header *m_free[max_size - min_size];
 	void *m_start;
 	size_t m_length;
 
+	friend class page_manager;
 	memory_manager(const memory_manager &) = delete;
 };
 

src/kernel/memory_pages.cpp

@@ -199,15 +199,14 @@ page_manager::init(
 	// Initialize the kernel memory manager
 	addr_t end = 0;
 	for (page_block *b = m_used; b; b = b->next) {
-		if (b->virtual_address < page_offset)
+		if (b->virtual_address < page_offset) {
 			end = b->virtual_end();
-		else
+		} else {
 			break;
-
 		}
-	new (&g_kernel_memory_manager) memory_manager(
+	}
-			reinterpret_cast<void *>(end),
+
-			page_offset - end);
+	new (&g_kernel_memory_manager) memory_manager(reinterpret_cast<void *>(end));
 }
 
 void
@@ -229,7 +228,7 @@ page_manager::map_offset_pointer(void **pointer, size_t length)
 		page_block_flags::mapped |
 		page_block_flags::mmio;
 
-	log::info(logs::memory, "Fixing up pointer %lx [%3d] -> %lx", *p, c, v);
+	log::debug(logs::memory, "Fixing up pointer %lx [%3d] -> %lx", *p, c, v);
 
 	m_used = page_block::insert(m_used, block);