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#include <kernel/arch/generic.h>
#include <kernel/malloc.h>
#include <kernel/panic.h>
#include <kernel/util.h>
#include <shared/mem.h>
#include <stdbool.h>
#include <stdint.h>
typedef struct FreePage FreePage;
struct FreePage {
FreePage *next;
};
static FreePage *firstfreepage;
extern uint8_t pbitmap[]; /* linker.ld */
static size_t pbitmap_len; /* in bytes */
static void *watermark; /* first nonallocated page */
static void *memtop; /* end of physical memory */
static int curallocs = 0;
static size_t
toindex(void *p)
{
assert((void*)pbitmap <= p);
return ((uintptr_t)p - (uintptr_t)pbitmap) / PAGE_SIZE;
}
static bool
pbitmap_get(void *p)
{
size_t i = toindex(p);
size_t b = i / 8;
uint8_t m = 1 << (i&7);
assert(b < pbitmap_len);
return (pbitmap[b]&m) != 0;
}
static bool
pbitmap_set(void *p, bool v)
{
size_t i = toindex(p);
size_t b = i / 8;
uint8_t m = 1 << (i&7);
assert(b < pbitmap_len);
bool prev = (pbitmap[b]&m) != 0;
if (v) {
pbitmap[b] |= m;
} else {
pbitmap[b] &= ~m;
}
return prev;
}
/* watermark allocator. doesn't mark the page as allocated in the bitmap. */
static void *
wmalloc(void)
{
/* skip over reserved pages */
while (watermark < memtop && pbitmap_get(watermark)) {
watermark += PAGE_SIZE;
}
if (watermark < memtop) {
void *p = watermark;
watermark += PAGE_SIZE;
return p;
} else {
return NULL;
}
}
void
mem_init(void *p)
{
memtop = p;
kprintf("memory %8x -> %8x\n", &_bss_end, memtop);
pbitmap_len = (toindex(memtop) + 7) / 8; /* rounds up */
memset(pbitmap, 0, pbitmap_len);
mem_reserve(pbitmap, pbitmap_len);
mem_reserve(memtop, 4096 * 8);
watermark = pbitmap;
}
void
mem_reserve(void *addr, size_t len)
{
kprintf("reserved %8x -> %8x\n", addr, addr + len);
void *top = min(addr + len, memtop);
addr = (void*)((uintptr_t)addr & ~PAGE_MASK); /* round down to page */
for (void *p = max(addr, (void*)pbitmap); p < top; p += PAGE_SIZE) {
/* This doesn't allow overlapping reserved regions, but, more
* importantly, it prevents reserving an already allocated page.
* Note that a reserved page can be freed. */
if (pbitmap_get(p)) {
panic_invalid_state();
}
pbitmap_set(p, true);
curallocs++;
}
}
void *
page_zalloc(size_t pages)
{
void *p = page_alloc(pages);
memset(p, 0, pages * PAGE_SIZE);
return p;
}
void *
page_alloc(size_t pages)
{
void *ret;
assert(pages == 1);
if (firstfreepage != NULL) {
ret = firstfreepage;
firstfreepage = firstfreepage->next;
} else {
ret = wmalloc();
}
if (ret == NULL) {
mem_debugprint();
kprintf("we ran out of memory :(\ngoodbye.\n");
panic_unimplemented();
} else {
assert(pbitmap_get(ret) == false);
pbitmap_set(ret, true);
curallocs += pages;
return ret;
}
}
void
page_free(void *addr, size_t pages)
{
assert((void*)pbitmap <= addr);
for (size_t i = 0; i < pages; i++) {
FreePage *fp = addr + i*PAGE_SIZE;
assert(pbitmap_get(fp) == true);
pbitmap_set(fp, false);
fp->next = firstfreepage;
firstfreepage = fp;
}
curallocs -= pages;
}
void
mem_debugprint(void)
{
kprintf(
"[kern] %d pages allocated, watermark at %08p / %08p\n",
curallocs, watermark, memtop
);
kmalloc_debugprint();
}
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