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vm: implement private and shared address space mappings

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whether a mapping is private or shared determines how the mapping is handled
when a task is duplicated.
This commit is contained in:
max 🍓
2026-04-21 21:12:00 +01:00
parent 8b7382fa13
commit 278fe39c0d
9 changed files with 63 additions and 24 deletions
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vm/address-space.c
+33 -2
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@@ -706,6 +706,7 @@ kern_status_t address_space_map(
struct vm_object *object,
off_t object_offset,
size_t length,
vm_flags_t flags,
vm_prot_t prot,
virt_addr_t *out)
{
@@ -763,6 +764,7 @@ kern_status_t address_space_map(
area->vma_space = root;
area->vma_object = object;
area->vma_prot = prot;
area->vma_flags = flags;
area->vma_object_offset = object_offset;
area->vma_base = map_address;
area->vma_limit = map_address + length - 1;
@@ -1215,6 +1217,7 @@ static struct vm_area *area_duplicate(struct vm_area *area)
}
out->vma_prot = area->vma_prot;
out->vma_flags = area->vma_flags;
out->vma_object_offset = area->vma_object_offset;
out->vma_base = area->vma_base;
out->vma_limit = area->vma_limit;
@@ -1281,7 +1284,8 @@ static kern_status_t prepare_duplicate_areas(
struct vm_object *src_vmo = tmp_area->vma_object;
vm_object_lock(src_vmo);
struct vm_object *dest_vmo = NULL;
struct vm_object *dest_vmo_link = NULL;
struct vm_object *dest_vmo_cow = NULL;
struct queue_entry *cur_entry
= queue_first(&src_vmo->vo_mappings);
@@ -1312,6 +1316,13 @@ static kern_status_t prepare_duplicate_areas(
continue;
}
struct vm_object *dest_vmo = NULL;
if (src_area->vma_flags & VM_SHARED) {
dest_vmo = dest_vmo_link;
} else {
dest_vmo = dest_vmo_cow;
}
if (!dest_vmo) {
tracek("[%zx-%zx %x] creating COW duplicate of "
"vmo %p",
@@ -1319,7 +1330,18 @@ static kern_status_t prepare_duplicate_areas(
src_area->vma_limit,
src_area->vma_prot,
src_vmo);
dest_vmo = vm_object_duplicate_cow(src_vmo);
if (src_area->vma_flags & VM_SHARED) {
dest_vmo_link = src_vmo;
object_ref(&dest_vmo_link->vo_base);
dest_vmo = dest_vmo_link;
} else {
dest_vmo_cow = vm_object_duplicate_cow(
src_vmo);
dest_vmo = dest_vmo_cow;
}
tracek("[%zx-%zx %x] created COW duplicate of "
"vmo %p -> %p",
src_area->vma_base,
@@ -1329,11 +1351,20 @@ static kern_status_t prepare_duplicate_areas(
dest_vmo);
}
object_ref(&dest_vmo->vo_base);
dest_area->vma_object = dest_vmo;
update_area_pte_cow(src, dest, src_area);
cur_entry = queue_next(cur_entry);
}
if (dest_vmo_link) {
object_unref(&dest_vmo_link->vo_base);
}
if (dest_vmo_cow) {
object_unref(&dest_vmo_cow->vo_base);
}
vm_object_unlock(src_vmo);
cur_node = btree_next(cur_node);