/**
* @brief Return the page mapped at virtual address 'va' in
* page directory 'pgdir'.
*
* If pte_store is not NULL, then we store in it the address
* of the pte for this page. This is used by page_remove
* but should not be used by other callers.
*
* For jumbos, right now this returns the first Page* in the 4MB range
*
* @param[in] pgdir the page directory from which we should do the lookup
* @param[in] va the virtual address of the page we are looking up
* @param[out] pte_store the address of the page table entry for the returned page
*
* @return PAGE the page mapped at virtual address 'va'
* @return NULL No mapping exists at virtual address 'va', or it's paged out
*/
page_t *page_lookup(pde_t *pgdir, void *va, pte_t **pte_store)
{
pte_t* pte = pgdir_walk(pgdir, va, 0);
if (!pte || !PAGE_PRESENT(*pte))
return 0;
if (pte_store)
*pte_store = pte;
return pa2page(PTE_ADDR(*pte));
}
/**
* @brief Unmaps the physical page at virtual address 'va' in page directory
* 'pgdir'.
*
* If there is no physical page at that address, this function silently
* does nothing.
*
* Details:
* - The ref count on the physical page is decrement when the page is removed
* - The physical page is freed if the refcount reaches 0.
* - The pg table entry corresponding to 'va' is set to 0.
* (if such a PTE exists)
* - The TLB is invalidated if an entry is removes from the pg dir/pg table.
*
* This may be wonky wrt Jumbo pages and decref.
*
* @param pgdir the page directory from with the page sholuld be removed
* @param va the virtual address at which the page we are trying to
* remove is mapped
* TODO: consider deprecating this, or at least changing how it works with TLBs.
* Might want to have the caller need to manage the TLB. Also note it is used
* in env_user_mem_free, minus the walk. */
void page_remove(pde_t *pgdir, void *va)
{
pte_t *pte;
page_t *page;
pte = pgdir_walk(pgdir,va,0);
if (!pte || PAGE_UNMAPPED(*pte))
return;
if (PAGE_PRESENT(*pte)) {
/* TODO: (TLB) need to do a shootdown, inval sucks. And might want to
* manage the TLB / free pages differently. (like by the caller).
* Careful about the proc/memory lock here. */
page = ppn2page(PTE2PPN(*pte));
*pte = 0;
tlb_invalidate(pgdir, va);
page_decref(page);
} else if (PAGE_PAGED_OUT(*pte)) {
/* TODO: (SWAP) need to free this from the swap */
panic("Swapping not supported!");
*pte = 0;
}
}
/* Convert a kernel guest virtual address to physical address.
* Assumes that the guest VA is in the high negative address space.
* TODO: Takes the vm_thread argument so that we can walk the page tables
* instead of just coercing the pointer. Therefore, this is not in vmm.h
* since it may get complex. */
int gvatogpa(struct guest_thread *vm_thread, uint64_t va, uint64_t *pa)
{
assert(vm_thread != NULL);
struct vm_trapframe *vm_tf = gth_to_vmtf(vm_thread);
uint64_t *ptptr = (uint64_t *)vm_tf->tf_cr3;
uint64_t entry;
for (int shift = PML4_SHIFT; shift >= PML1_SHIFT; shift -= BITS_PER_PML) {
entry = ptptr[PMLx(va, shift)];
if (!PAGE_PRESENT(entry))
return -1;
if ((entry & PTE_PS) != 0) {
uint64_t bitmask = ((1 << shift) - 1);
*pa = (((uint64_t)va & bitmask) | (entry & ~bitmask));
return 0;
}
ptptr = (uint64_t *)PG_ADDR(entry);
}
*pa = ((uint64_t)va & 0xfff) | (uint64_t)ptptr;
return 0;
}