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#include <kernel/arch/generic.h>
#include <kernel/mem/alloc.h>
#include <kernel/panic.h>
#include <kernel/util.h>
#include <shared/mem.h>
#include <stdbool.h>
#include <stdint.h>
#define MALLOC_MAGIC 0xACAB1312
struct malloc_hdr {
uint32_t magic;
uint32_t page_amt;
struct malloc_hdr *next, *prev;
void *stacktrace[4];
};
struct malloc_hdr *malloc_last = NULL;
static void *memtop;
static uint8_t *page_bitmap;
static void *page_bitmap_start;
static size_t page_bitmap_len;
static void *closest_page(void *p) {
return (void*)(((uintptr_t)p + PAGE_MASK) & ~PAGE_MASK);
}
void mem_init(struct kmain_info *info) {
memtop = info->memtop;
/* place the page_bitmap right at the first free spot in memory */
page_bitmap = max((void*)&_bss_end, closest_page(info->init.at + info->init.size));
page_bitmap_len = ((uintptr_t)memtop - (uintptr_t)page_bitmap) / PAGE_SIZE / 8;
/* the page_bitmap_len calculation doesn't account for the space lost to itself,
* so just take away a few pages to account for it. this could be solved with
* actual math, but eh. */
page_bitmap_len -= 8;
memset(page_bitmap, 0, page_bitmap_len);
/* start allocation on the page immediately following the page bitmap */
page_bitmap_start = closest_page(page_bitmap + page_bitmap_len);
}
void mem_debugprint(void) {
size_t total = 0;
kprintf("current kmallocs:\n");
kprintf("addr pages\n");
for (struct malloc_hdr *iter = malloc_last; iter; iter = iter->prev) {
kprintf("%08x %05x", iter, iter->page_amt);
for (size_t i = 0; i < 4; i++)
kprintf(" k/%08x", iter->stacktrace[i]);
kprintf("\n peek 0x%x\n", *(uint32_t*)(&iter[1]));
total++;
}
kprintf(" total 0x%x\n", total);
}
static bool bitmap_get(size_t i) {
size_t b = i / 8;
assert(b < page_bitmap_len);
return 0 < (page_bitmap[b] & (1 << (i&7)));
}
static void bitmap_set(size_t i, bool v) {
size_t b = i / 8;
uint8_t m = 1 << (i&7);
assert(b < page_bitmap_len);
if (v) page_bitmap[b] |= m;
else page_bitmap[b] &= ~m;
}
void *page_alloc(size_t pages) {
/* i do realize how painfully slow this is */
size_t streak = 0;
for (size_t i = 0; i < page_bitmap_len * 8; i++) {
if (bitmap_get(i)) {
streak = 0;
continue;
}
if (++streak >= pages) {
/* found hole big enough for this allocation */
i = i + 1 - streak;
for (size_t j = 0; j < streak; j++)
bitmap_set(i + j, true);
return page_bitmap_start + i * PAGE_SIZE;
}
}
kprintf("we ran out of memory :(\ngoodbye.\n");
panic_unimplemented();
}
// frees `pages` consecutive pages starting from *first
void page_free(void *first_addr, size_t pages) {
size_t first = (uintptr_t)(first_addr - page_bitmap_start) / PAGE_SIZE;
for (size_t i = 0; i < pages; i++) {
assert(bitmap_get(first + i));
bitmap_set(first + i, false);
}
}
void kmalloc_sanity(const void *addr) {
assert(addr);
const struct malloc_hdr *hdr = addr - sizeof(struct malloc_hdr);
assert(hdr->magic == MALLOC_MAGIC);
if (hdr->next) assert(hdr->next->prev == hdr);
if (hdr->prev) assert(hdr->prev->next == hdr);
}
void *kmalloc(size_t len) {
// TODO better kmalloc
struct malloc_hdr *hdr;
void *addr;
uint32_t pages;
len += sizeof(struct malloc_hdr);
pages = len / PAGE_SIZE + 1;
hdr = page_alloc(pages);
hdr->magic = MALLOC_MAGIC;
hdr->page_amt = pages;
hdr->next = NULL;
hdr->prev = malloc_last;
if (hdr->prev) {
assert(!hdr->prev->next);
hdr->prev->next = hdr;
}
for (size_t i = 0; i < 4; i++)
hdr->stacktrace[i] = debug_caller(i);
malloc_last = hdr;
addr = (void*)hdr + sizeof(struct malloc_hdr);
kmalloc_sanity(addr);
return addr;
}
void kfree(void *ptr) {
struct malloc_hdr *hdr;
if (ptr == NULL) return;
hdr = ptr - sizeof(struct malloc_hdr);
kmalloc_sanity(ptr);
hdr->magic = ~MALLOC_MAGIC; // (hopefully) detect double frees
if (hdr->next)
hdr->next->prev = hdr->prev;
if (hdr->prev)
hdr->prev->next = hdr->next;
if (malloc_last == hdr)
malloc_last = hdr->prev;
page_free(hdr, hdr->page_amt);
}
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