vm_anon.c

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#include <core/system.h>
#include <core/panic.h>
#include <mm/vm.h>
 
MALLOC_DEFINE(M_VM_ANON, "vm-anon", "anonymous virtual memory object");

static int vm_aref_eq(void *_a, void *_b)
{
    struct vm_aref *a = (struct vm_aref *) _a;
 
    if (!a->vm_page)
        return 0;
 
    size_t *b = (size_t *) _b;
 
    return a->vm_page->off == *b;
}

struct vm_anon *vm_anon_new(void)
{
    struct vm_anon *vm_anon = kmalloc(sizeof(struct vm_anon), &M_VM_ANON, M_ZERO);
    if (!vm_anon) goto error;
 
    vm_anon->arefs = hashmap_new(0, vm_aref_eq);
 
    if (!vm_anon->arefs)
        goto error;
 
    return vm_anon;
 
error:
    if (vm_anon) {
        if (vm_anon->arefs)
            hashmap_free(vm_anon->arefs);
        kfree(vm_anon);
    }
 
    return NULL;
}

void vm_aref_destroy(struct vm_aref *vm_aref)
{
    /* nothing to do */
}

void vm_aref_decref(struct vm_aref *vm_aref)
{
    vm_aref->ref--;
}

void vm_anon_destroy(struct vm_anon *vm_anon)
{
    if (!vm_anon) return;
 
    struct hashmap *arefs = vm_anon->arefs;
 
    if (!arefs)
        return;
 
    hashmap_for (qnode, vm_anon->arefs) {
        struct hashmap_node *hnode = (struct hashmap_node *) qnode->value;
        struct vm_aref *aref = (struct vm_aref *) hnode->entry;
 
        vm_aref_decref(aref);
 
        if (!aref->ref) {
            if (aref->vm_page) {
                mm_page_dealloc(aref->vm_page->paddr);
            }
 
            kfree(aref);
        }
    }
 
    hashmap_free(vm_anon->arefs);
}

void vm_anon_incref(struct vm_anon *vm_anon)
{
    if (!vm_anon)
        return;
 
    vm_anon->ref++;
}

void vm_anon_decref(struct vm_anon *vm_anon)
{
    if (!vm_anon)
        return;
 
    vm_anon->ref--;
 
    if (!vm_anon->ref) {
        vm_anon_destroy(vm_anon);
        kfree(vm_anon);
    }
}

static int vm_anon_copy_arefs(struct vm_anon *src, struct vm_anon *dst)
{
    if (!src || !dst || !src->arefs || !dst->arefs)
        return -EINVAL;
 
    hashmap_for (qnode, src->arefs) {
        struct hashmap_node *node = (struct hashmap_node *) qnode->value;
        struct vm_aref *aref = (struct vm_aref *) node->entry;
 
        if (hashmap_insert(dst->arefs, node->hash, aref))
            return -ENOMEM;
 
        aref->ref++;
    }
 
    return 0;
}

struct vm_anon *vm_anon_copy(struct vm_anon *vm_anon)
{
    if (!vm_anon)
        return NULL;
 
    struct vm_anon *new_anon = vm_anon_new();
 
    if (!new_anon)
        return NULL;
 
    new_anon->flags = vm_anon->flags & ~VM_COPY;
    new_anon->ref   = 1;
 
    /* on failure, the arefs copied so far give back their references,
     * and the hashmap goes */
    if (vm_anon_copy_arefs(vm_anon, new_anon)) {
        vm_anon_destroy(new_anon);
        kfree(new_anon);
        return NULL;
    }
 
    return new_anon;
}