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#include <sys/mem.h>
#include <sys/stddef.h>
#include <early/dtb.h>
static char eheap[EHEAP_SIZE] = {0};
static size_t eheap_off = 0;
static struct free_list *page_list = NULL;
static struct free_list *buddy_head = NULL;
static void *buddy_start;
static uint16_t buddy_bitmap = 0;
static inline size_t round_pow2(size_t n) {
if (n == 0) return 1;
n--;
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
if (sizeof(size_t) >= 8) {
n |= n >> 32;
}
n++;
return n;
}
static inline int cnt_zeros_below(uint16_t mask, int bit) {
uint16_t lower = mask & ((1 << bit) - 1);
return lower == 0 ? bit : bit - 1 - (7 - __builtin_clz(lower));
}
static void merge_free_list(struct free_list *head) {
while (head && head->next) {
if ((uintptr_t)head + head->size == (uintptr_t)head->next) {
head->next = head->next->next;
head->next->prev = head;
head->next->size = (uintptr_t)head->next - (uintptr_t)head;
} else {
head = head->next;
}
}
}
static void *buddy_alloc(size_t size) {
if (!buddy_head) {
struct free_list *free_page = page_list;
page_list->next->prev = NULL;
free_page->next = NULL;
free_page->prev = NULL;
buddy_head = free_page;
buddy_start = free_page;
}
size = round_pow2(size);
if (size < 256)
size = 256;
struct free_list *first = buddy_head;
while (first && first->size > size) {
size_t new_size = first->size / 2;
struct free_list *next = (struct free_list *)((uintptr_t)first + new_size);
next->next = first->next;
next->prev = first;
next->size = new_size;
first->next = next;
first->size = new_size;
}
buddy_bitmap |= (1 << (((uintptr_t)first - (uintptr_t)buddy_start)/256));
if (!first->prev && !first->next) {
buddy_head = NULL;
return first;
}
if (!first->prev) {
first->next->prev = NULL;
return first;
}
first->prev->next = first->next;
first->next->prev = first->prev;
return first;
}
static void buddy_free(void *ptr) {
struct free_list *head = buddy_head;
while (head && (uintptr_t)head < (uintptr_t)ptr) {
if (head->next == NULL) {
struct free_list *ins_page = ptr;
head->next = ins_page;
ins_page->prev = head;
ins_page->size = cnt_zeros_below(buddy_bitmap, ((uintptr_t)ptr - (uintptr_t)buddy_head)/256);
goto merge;
}
head = head->next;
}
struct free_list *ins_page = ptr;
ins_page->next = head->next;
ins_page->prev = head;
ins_page->size = (uintptr_t)ins_page->next - (uintptr_t)ins_page;
head->next = ins_page;
ins_page->next->prev = ins_page;
merge:
merge_free_list(buddy_head);
}
void* kemalloc(size_t size) {
size = (size + 7) & ~7;
if (eheap_off + size > EHEAP_SIZE) {
return NULL;
}
void *ptr = &eheap[eheap_off];
eheap_off += size;
return ptr;
}
void* kmalloc(size_t size, enum AllocationType type) {
if (type == MEMPAGE_FREEPAGE) {
buddy_alloc(size);
}
return NULL;
}
void* kzalloc(size_t size, enum AllocationType type) {
char *ptr = kmalloc(size, type);
if (!ptr)
return NULL;
for (size_t i = 0; i < size; i++) {
*(ptr + i) = 0;
}
return ptr;
}
void kfree(void *ptr) {
if ((uintptr_t)ptr >= (uintptr_t)buddy_start &&
(uintptr_t)ptr < (uintptr_t)buddy_start + PAGE_SIZE) {
buddy_free(ptr);
}
(void)ptr;
}
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