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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>
extern uint8_t pbitmap[]; /* linker.ld */
static size_t pbitmap_len; /* in bytes */
static void *memtop;
static void *firstfreepage; /* not necessarily actually free */
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); // TODO the bitmap should be a tad longer
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;
}
void
mem_init(void *p)
{
memtop = p;
kprintf("memory %8x -> %8x\n", &_bss_end, memtop);
pbitmap_len = toindex(memtop) / 8;
memset(pbitmap, 0, pbitmap_len);
mem_reserve(pbitmap, pbitmap_len);
firstfreepage = 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 */
if (pbitmap_get(p)) {
panic_invalid_state();
}
pbitmap_set(p, true);
}
}
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)
{
assert(pages == 1);
for (void *p = firstfreepage; p < memtop; p += PAGE_SIZE) {
if (!pbitmap_get(p)) {
pbitmap_set(p, true);
firstfreepage = p + PAGE_SIZE;
return p;
}
}
kprintf("we ran out of memory :(\ngoodbye.\n");
panic_unimplemented();
}
void
page_free(void *addr, size_t pages)
{
assert((void*)pbitmap <= addr);
for (size_t i = 0; i < pages; i++) {
if (pbitmap_set(addr + i*PAGE_SIZE, false) == false) {
panic_invalid_state();
}
}
firstfreepage = min(firstfreepage, addr);
}
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