static
void *
subpage_kmalloc(size_t sz)
{
unsigned blktype; // index into sizes[] that we're using
struct pageref *pr; // pageref for page we're allocating from
vaddr_t prpage; // PR_PAGEADDR(pr)
vaddr_t fla; // free list entry address
struct freelist *volatile fl; // free list entry
void *retptr; // our result
volatile int i;
blktype = blocktype(sz);
sz = sizes[blktype];
spinlock_acquire(&kmalloc_spinlock);
checksubpages();
for (pr = sizebases[blktype]; pr != NULL; pr = pr->next_samesize) {
/* check for corruption */
KASSERT(PR_BLOCKTYPE(pr) == blktype);
checksubpage(pr);
if (pr->nfree > 0) {
doalloc: /* comes here after getting a whole fresh page */
KASSERT(pr->freelist_offset < PAGE_SIZE);
prpage = PR_PAGEADDR(pr);
fla = prpage + pr->freelist_offset;
fl = (struct freelist *)fla;
retptr = fl;
fl = fl->next;
pr->nfree--;
if (fl != NULL) {
KASSERT(pr->nfree > 0);
fla = (vaddr_t)fl;
KASSERT(fla - prpage < PAGE_SIZE);
pr->freelist_offset = fla - prpage;
}
else {
KASSERT(pr->nfree == 0);
pr->freelist_offset = INVALID_OFFSET;
}
checksubpages();
spinlock_release(&kmalloc_spinlock);
return retptr;
}
}
/*
* No page of the right size available.
* Make a new one.
*
* We release the spinlock while calling alloc_kpages. This
* avoids deadlock if alloc_kpages needs to come back here.
* Note that this means things can change behind our back...
*/
spinlock_release(&kmalloc_spinlock);
prpage = alloc_kpages(1);
if (prpage==0) {
/* Out of memory. */
kprintf("kmalloc: Subpage allocator couldn't get a page\n");
return NULL;
}
spinlock_acquire(&kmalloc_spinlock);
pr = allocpageref();
if (pr==NULL) {
/* Couldn't allocate accounting space for the new page. */
spinlock_release(&kmalloc_spinlock);
free_kpages(prpage);
kprintf("kmalloc: Subpage allocator couldn't get pageref\n");
return NULL;
}
pr->pageaddr_and_blocktype = MKPAB(prpage, blktype);
pr->nfree = PAGE_SIZE / sizes[blktype];
/*
* Note: fl is volatile because the MIPS toolchain we were
* using in spring 2001 attempted to optimize this loop and
* blew it. Making fl volatile inhibits the optimization.
*/
fla = prpage;
fl = (struct freelist *)fla;
fl->next = NULL;
for (i=1; i<pr->nfree; i++) {
fl = (struct freelist *)(fla + i*sizes[blktype]);
fl->next = (struct freelist *)(fla + (i-1)*sizes[blktype]);
KASSERT(fl != fl->next);
}
fla = (vaddr_t) fl;
pr->freelist_offset = fla - prpage;
KASSERT(pr->freelist_offset == (pr->nfree-1)*sizes[blktype]);
pr->next_samesize = sizebases[blktype];
sizebases[blktype] = pr;
pr->next_all = allbase;
allbase = pr;
/* This is kind of cheesy, but avoids duplicating the alloc code. */
goto doalloc;
}
static
int
subpage_kfree(void *ptr)
{
int blktype; // index into sizes[] that we're using
vaddr_t ptraddr; // same as ptr
struct pageref *pr; // pageref for page we're freeing in
vaddr_t prpage; // PR_PAGEADDR(pr)
vaddr_t fla; // free list entry address
struct freelist *fl; // free list entry
vaddr_t offset; // offset into page
ptraddr = (vaddr_t)ptr;
spinlock_acquire(&kmalloc_spinlock);
checksubpages();
for (pr = allbase; pr; pr = pr->next_all) {
prpage = PR_PAGEADDR(pr);
blktype = PR_BLOCKTYPE(pr);
/* check for corruption */
KASSERT(blktype>=0 && blktype<NSIZES);
checksubpage(pr);
if (ptraddr >= prpage && ptraddr < prpage + PAGE_SIZE) {
break;
}
}
if (pr==NULL) {
/* Not on any of our pages - not a subpage allocation */
spinlock_release(&kmalloc_spinlock);
return -1;
}
offset = ptraddr - prpage;
/* Check for proper positioning and alignment */
if (offset >= PAGE_SIZE || offset % sizes[blktype] != 0) {
panic("kfree: subpage free of invalid addr %p\n", ptr);
}
/*
* Clear the block to 0xdeadbeef to make it easier to detect
* uses of dangling pointers.
*/
fill_deadbeef(ptr, sizes[blktype]);
/*
* We probably ought to check for free twice by seeing if the block
* is already on the free list. But that's expensive, so we don't.
*/
fla = prpage + offset;
fl = (struct freelist *)fla;
if (pr->freelist_offset == INVALID_OFFSET) {
fl->next = NULL;
} else {
fl->next = (struct freelist *)(prpage + pr->freelist_offset);
}
pr->freelist_offset = offset;
pr->nfree++;
KASSERT(pr->nfree <= PAGE_SIZE / sizes[blktype]);
if (pr->nfree == PAGE_SIZE / sizes[blktype]) {
/* Whole page is free. */
remove_lists(pr, blktype);
freepageref(pr);
/* Call free_kpages without kmalloc_spinlock. */
spinlock_release(&kmalloc_spinlock);
free_kpages(prpage);
}
else {
spinlock_release(&kmalloc_spinlock);
}
#ifdef SLOWER /* Don't get the lock unless checksubpages does something. */
spinlock_acquire(&kmalloc_spinlock);
checksubpages();
spinlock_release(&kmalloc_spinlock);
#endif
return 0;
}
/*
* Free a pointer previously returned from subpage_kmalloc. If the
* pointer is not on any heap page we recognize, return -1.
*/
static
int
subpage_kfree(void *ptr)
{
int blktype; // index into sizes[] that we're using
vaddr_t ptraddr; // same as ptr
struct pageref *pr; // pageref for page we're freeing in
vaddr_t prpage; // PR_PAGEADDR(pr)
vaddr_t fla; // free list entry address
struct freelist *fl; // free list entry
vaddr_t offset; // offset into page
#ifdef GUARDS
size_t blocksize, smallerblocksize;
#endif
ptraddr = (vaddr_t)ptr;
#ifdef GUARDS
if (ptraddr % PAGE_SIZE == 0) {
/*
* With guard bands, all client-facing subpage
* pointers are offset by GUARD_PTROFFSET (which is 4)
* from the underlying blocks and are therefore not
* page-aligned. So a page-aligned pointer is not one
* of ours. Catch this up front, as otherwise
* subtracting GUARD_PTROFFSET could give a pointer on
* a page we *do* own, and then we'll panic because
* it's not a valid one.
*/
return -1;
}
ptraddr -= GUARD_PTROFFSET;
#endif
#ifdef LABELS
if (ptraddr % PAGE_SIZE == 0) {
/* ditto */
return -1;
}
ptraddr -= LABEL_PTROFFSET;
#endif
spinlock_acquire(&kmalloc_spinlock);
checksubpages();
for (pr = allbase; pr; pr = pr->next_all) {
prpage = PR_PAGEADDR(pr);
blktype = PR_BLOCKTYPE(pr);
KASSERT(blktype >= 0 && blktype < NSIZES);
/* check for corruption */
KASSERT(blktype>=0 && blktype<NSIZES);
checksubpage(pr);
if (ptraddr >= prpage && ptraddr < prpage + PAGE_SIZE) {
break;
}
}
if (pr==NULL) {
/* Not on any of our pages - not a subpage allocation */
spinlock_release(&kmalloc_spinlock);
return -1;
}
offset = ptraddr - prpage;
/* Check for proper positioning and alignment */
if (offset >= PAGE_SIZE || offset % sizes[blktype] != 0) {
panic("kfree: subpage free of invalid addr %p\n", ptr);
}
#ifdef GUARDS
blocksize = sizes[blktype];
smallerblocksize = blktype > 0 ? sizes[blktype - 1] : 0;
checkguardband(ptraddr, smallerblocksize, blocksize);
#endif
/*
* Clear the block to 0xdeadbeef to make it easier to detect
* uses of dangling pointers.
*/
fill_deadbeef((void *)ptraddr, sizes[blktype]);
/*
* We probably ought to check for free twice by seeing if the block
* is already on the free list. But that's expensive, so we don't.
*/
fla = prpage + offset;
fl = (struct freelist *)fla;
if (pr->freelist_offset == INVALID_OFFSET) {
fl->next = NULL;
} else {
fl->next = (struct freelist *)(prpage + pr->freelist_offset);
/* this block should not already be on the free list! */
#ifdef SLOW
{
struct freelist *fl2;
for (fl2 = fl->next; fl2 != NULL; fl2 = fl2->next) {
KASSERT(fl2 != fl);
}
}
#else
/* check just the head */
KASSERT(fl != fl->next);
#endif
}
pr->freelist_offset = offset;
pr->nfree++;
KASSERT(pr->nfree <= PAGE_SIZE / sizes[blktype]);
if (pr->nfree == PAGE_SIZE / sizes[blktype]) {
/* Whole page is free. */
remove_lists(pr, blktype);
freepageref(pr);
/* Call free_kpages without kmalloc_spinlock. */
spinlock_release(&kmalloc_spinlock);
free_kpages(prpage);
}
else {
spinlock_release(&kmalloc_spinlock);
}
#ifdef SLOWER /* Don't get the lock unless checksubpages does something. */
spinlock_acquire(&kmalloc_spinlock);
checksubpages();
spinlock_release(&kmalloc_spinlock);
#endif
return 0;
}