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#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#include <vga.h>
#include <multiboot.h>
#include <memory.h>
#include <mem.h>
extern uint64_t multiboot_magic;
extern struct multiboot_info *multiboot_header;
extern void *kernel_end;
extern uint64_t pml4[512];
struct memory {
struct memory *prev, *next;
bool free;
size_t size;
uint8_t block[];
} *blocklist;
void print_blocks() {
struct memory *block = NULL;
for (block = blocklist; block; block = block->next) {
vga_puts("block at: ");
vga_putx((size_t)block);
vga_puts(", size: ");
vga_putx(block->size);
if (block->free)
vga_puts(", free");
vga_putc('\n');
}
}
void *kmalloc_a(size_t size, size_t alignment) {
struct memory *block = NULL;
for (block = blocklist; block; block = block->next) {
if (!block->free || block->size < size + sizeof(struct memory))
continue;
size_t offset = (uintptr_t)block->block % alignment;
if (offset) {
if (block->size < (2 * sizeof(struct memory)) + size + (alignment - offset)) {
continue;
}
struct memory *new_block = (void *)block + (alignment - offset);
*new_block = (struct memory) {
.size = block->size - (alignment - offset),
.free = true,
.prev = block,
.next = block->next,
};
block->next = new_block;
block->size = alignment - offset;
block = new_block;
break;
}
}
if (!block) {
print_blocks();
vga_puts("\n\noom");
while(1);
}
struct memory *nextblock = (void *)block->block + size;
*nextblock = (struct memory) {
.size = block->size - size,
.free = true,
.prev = block,
.next = block->next
};
block->next = nextblock;
block->size = size;
block->free = false;
return block->block;
}
void *kmalloc(size_t size) {
struct memory *block = NULL;
for (block = blocklist; block && (!block->free || block->size < size + sizeof(struct memory)); block = block->next);
if (!block) {
print_blocks();
vga_puts("\n\noom");
while(1);
}
struct memory *nextblock = (void *)block->block + size;
*nextblock = (struct memory) {
.size = block->size - size,
.free = true,
.prev = block,
.next = block->next
};
block->next = nextblock;
block->size = size;
block->free = false;
return block->block;
}
void kfree(void *ptr) {
struct memory *header = ptr - sizeof(struct memory);
if (header->next && header->next == (void*)header->block + header->size && header->next->free) {
header->size += header->next->size + sizeof(struct memory);
header->next = header->next->next;
if (header->next)
header->next->prev = header;
}
if (header->prev && header == (void*)header->prev->block + header->prev->size && header->prev->free) {
header->prev->size += header->size + sizeof(struct memory);
header->prev->next = header->next;
if (header->next)
header->next->prev = header->prev;
header = header->prev;
}
header->free = true;
}
uint64_t alloc_page() {
uint64_t *page = kmalloc_a(sizeof(uint64_t) * 512, 0x1000);
memset(page, 0, sizeof(uint64_t) * 512);
return (uint64_t)page | 0x3;
}
uint64_t *addr_to_page(uint64_t addr) {
size_t index = (addr >> 39) & 0x1ff;
if (!(pml4[index] & 0x1))
pml4[index] = alloc_page();
uint64_t *pdpr = (uint64_t*)(pml4[index] & ~0xfff);
index = (addr >> 30) & 0x1ff;
if (!(pdpr[index] & 0x1))
pdpr[index] = alloc_page();
uint64_t *pd = (uint64_t*)(pdpr[index] & ~0xfff);
index = (addr >> 21) & 0x1ff;
if (!(pd[index] & 0x1))
pd[index] = alloc_page();
uint64_t *pt = (uint64_t*)(pd[index] & ~0xfff);
index = (addr >> 12) & 0x1ff;
return &pt[index];
};
bool paging_init() {
blocklist = (void *)0x7e00;
*blocklist = (struct memory) {
.size = 0x7ffff - 0x7e00,
.free = true
};
if (multiboot_magic != 0x2badb002)
return false;
for (size_t i = 0; i < multiboot_header->mmap_length / sizeof(struct multiboot_mmap_entry); i++) {
struct multiboot_mmap_entry *mmap = &((struct multiboot_mmap_entry *) (uintptr_t) multiboot_header->mmap_addr)[i];
if (mmap->type == MULTIBOOT_MEMORY_AVAILABLE && mmap->addr > 0x1000) {
struct memory *header = mmap->addr > (uint64_t)&kernel_end ? (void*) mmap->addr : (void *)&kernel_end;
// map the first header, in case we need to use this region for paging itself
uint64_t *page = addr_to_page((uintptr_t) header);
*page = ((uintptr_t)header & ~0xfff) | 0x3;
*header = (struct memory) {
.size = mmap->len,
.free = true
};
struct memory *last;
for (last = blocklist; last->next; last = last->next);
last->next = header;
header->prev = last;
}
size_t end = mmap->addr + mmap->len;
for (size_t addr = mmap->addr & ~0xfff; addr < end; addr += 0x1000) {
uint64_t *page = addr_to_page(addr);
*page = addr | 0x3;
}
}
return true;
}
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