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#include <stdint.h>
#include <string.h>
#include <sys.h>
#include <panic.h>
#include "memory.h"
#include "boot/tag.h"
#include "print.h"
struct MemoryArea {
uint32_t len;
struct MemoryArea *prev;
struct MemoryArea *next;
};
typedef unsigned char page[4096];
extern unsigned char kernel_start, kernel_end;
static uintptr_t kernel_start_addr, kernel_end_addr;
static uint32_t *bitmap;
static uint32_t total_memory;
static uint32_t free_memory;
static uint32_t page_count;
static uint32_t page_free_start;
static struct MemoryArea *page_start;
int memory_lock(void) {
int_disable();
return 0;
}
int memory_unlock(void) {
int_enable();
return 0;
}
static int n_pages(const struct MemoryArea *m) {
return (m->len - sizeof(*m)) / sizeof(page);
}
static void *page_at(int i) {
int cur_page = 0;
for (struct MemoryArea *m = page_start; m != NULL; m = m->next) {
int pages = n_pages(m);
if (i - cur_page < pages) {
page *page_array = (page *) (m + 1);
return page_array[i - cur_page];
}
cur_page += pages;
}
return NULL;
}
static int page_idx(page p) {
uintptr_t addr = (uintptr_t) p;
int cur_page = 0;
for (struct MemoryArea *m = page_start; m != NULL; m = m->next) {
if ((uintptr_t) m + m->len > addr) {
return cur_page + (addr - (uintptr_t) m) / sizeof(page);
}
cur_page += n_pages(m);
}
return -1;
}
static inline bool bitmap_get(int i) {
return (bitmap[i / 32] >> i % 32) & 1;
}
static inline void bitmap_set(int i, bool v) {
int idx = i / 32;
bitmap[idx] &= ~(1 << i % 32);
bitmap[idx] |= (v << i % 32);
}
void *memory_alloc_page(int pages) {
if (pages < 1) return NULL;
int n_contiguous = 0;
int free_region_start = 0;
bool first = true;
for (uint32_t i = page_free_start; i < page_count; i++) {
bool free = !bitmap_get(i);
if (first) {
first = false;
page_free_start = i;
}
if (free) {
if (n_contiguous == 0) free_region_start = i;
n_contiguous++;
if (n_contiguous == pages) {
for (int j = 0; j < pages; j++)
bitmap_set(free_region_start + j, true);
return page_at(free_region_start);
}
} else n_contiguous = 0;
}
return NULL;
}
int memory_free_page(void *ptr, int pages) {
int idx = page_idx(ptr);
if (idx == -1) return 1;
if ((unsigned) idx < page_free_start) page_free_start = idx;
for (int i = 0; i < pages; i++)
bitmap_set(idx + pages, false);
return 0;
}
void memory_init(void) {
debugk("Loading memory pages");
memory_lock();
bitmap = NULL;
total_memory = 0;
free_memory = 0;
page_count = 0;
page_free_start = 0;
page_start = NULL;
kernel_start_addr = (uintptr_t) &kernel_start;
kernel_end_addr = (uintptr_t) &kernel_end;
struct BootTag *tag;
if (!get_boot_tag(iD_MEMORYMAP, &tag)) {
panic("No multiboot memory map found");
}
uintptr_t end = (uintptr_t) tag->data.memory_map;
end += tag->size;
struct MemoryArea *prev = NULL;
struct MemorySegment *segment = &tag->data.memory_map->entries[0];
for(; (uintptr_t) segment < end; segment++) {
if (segment->type != 1) continue;
if (segment->addr >= UINT32_MAX) continue;
if (segment->addr < kernel_start_addr) continue;
uint32_t length;
if (segment->addr + segment->len > UINT32_MAX) {
length = UINT32_MAX - segment->addr;
} else {
length = segment->len;
}
uintptr_t addr;
if (segment->addr < kernel_end_addr) {
addr = kernel_end_addr;
length -= addr - segment->addr;
} else {
addr = segment->addr;
}
struct MemoryArea *current = (struct MemoryArea *) addr;
current->prev = prev;
current->next = NULL;
current->len = length;
if (prev != NULL) {
prev->next = current;
} else {
page_start = current;
}
page_count += n_pages(current);
total_memory += length;
prev = current;
}
int bitmap_pages = page_count / 32 / sizeof(page) + 1;
bitmap = (uint32_t *) page_at(page_count - bitmap_pages);
page_count -= bitmap_pages;
memset(bitmap, 0, bitmap_pages * sizeof(page));
free_memory = page_count * sizeof(page);
memory_unlock();
succek("Memory loaded. %k total %k free", total_memory, free_memory);
}
uint32_t memory_total(void) {
return total_memory;
}
uint32_t memory_free(void) {
return free_memory;
}
uint32_t memory_used(void) {
return total_memory - free_memory;
}
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