int get_user_page(struct proc *p, unsigned long uvastart, int write, int force,
struct page **plist)
{
pte_t pte;
int ret = -1;
struct page *pp;
spin_lock(&p->pte_lock);
pte = pgdir_walk(p->env_pgdir, (void*)uvastart, TRUE);
if (!pte_walk_okay(pte))
goto err1;
if (!pte_is_present(pte)) {
unsigned long prot = PTE_P | PTE_U | PTE_A | PTE_W | PTE_D;
#if 0
printk("[akaros]: get_user_page() uva=0x%llx pte absent\n",
uvastart);
#endif
/*
* TODO: ok to allocate with pte_lock? "prot" needs to be
* based on VMR writability, refer to pgprot_noncached().
*/
if (upage_alloc(p, &pp, 0))
goto err1;
pte_write(pte, page2pa(pp), prot);
} else {
pp = pa2page(pte_get_paddr(pte));
/* __vmr_free_pgs() refcnt's pagemap pages differently */
if (atomic_read(&pp->pg_flags) & PG_PAGEMAP) {
printk("[akaros]: get_user_page(): uva=0x%llx\n",
uvastart);
goto err1;
}
}
if (write && (!pte_has_perm_urw(pte))) {
/* TODO: How is Linux using the "force" parameter */
printk("[akaros]: get_user_page() uva=0x%llx pte ro\n",
uvastart);
goto err1;
}
/* TODO (GUP): change the interface such that devices provide the memory and
* the user mmaps it, instead of trying to pin arbitrary user memory. */
warn_once("Extremely unsafe, unpinned memory mapped! If your process dies, you might scribble on RAM!");
plist[0] = pp;
ret = 1;
err1:
spin_unlock(&p->pte_lock);
return ret;
}
/* Frees (decrefs) all memory mapped in the given range */
void env_user_mem_free(env_t* e, void* start, size_t len)
{
assert((uintptr_t)start + len <= UVPT); //since this keeps f*****g happening
int user_page_free(env_t* e, pte_t pte, void* va, void* arg)
{
if (!pte_is_mapped(pte))
return 0;
page_t *page = pa2page(pte_get_paddr(pte));
pte_clear(pte);
page_decref(page);
/* TODO: consider other states here (like !P, yet still tracking a page,
* for VM tricks, page map stuff, etc. Should be okay: once we're
* freeing, everything else about this proc is dead. */
return 0;
}
env_user_mem_walk(e,start,len,&user_page_free,NULL);
tlbflush();
}
