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mm: handle work around shared character device mappings on fork

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Matheus
2026-07-08 13:03:19 -03:00
parent e18333c0ab
commit ecd16264cb
1 changed files with 7 additions and 1 deletions
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kernel-src/mm/mm.c
+7 -1
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@@ -582,7 +582,6 @@ mm_context_t *mm_fork_context(mm_context_t *old_context) {
VOP_HOLD(range->vnode); VOP_HOLD(range->vnode);
for (uintptr_t offset = 0; offset < new_range->size; offset += PAGE_SIZE) { for (uintptr_t offset = 0; offset < new_range->size; offset += PAGE_SIZE) {
// XXX some types of mappings, like framebuffer shared mappings, will break if done this way
void *vaddr = (void *)((uintptr_t)new_range->start + offset); void *vaddr = (void *)((uintptr_t)new_range->start + offset);
void *phys = arch_mmu_getphysical(old_context->pagetable, vaddr); void *phys = arch_mmu_getphysical(old_context->pagetable, vaddr);
if (phys == NULL) if (phys == NULL)
@@ -590,6 +589,13 @@ mm_context_t *mm_fork_context(mm_context_t *old_context) {
bool writeable = arch_mmu_iswritable(old_context->pagetable, vaddr); bool writeable = arch_mmu_iswritable(old_context->pagetable, vaddr);
bool private = !(range->flags & MM_RANGE_FLAGS_SHARED); bool private = !(range->flags & MM_RANGE_FLAGS_SHARED);
if ((range->flags & MM_RANGE_FLAGS_FILE) && range->vnode->type == V_TYPE_CHDEV && !private) {
// TODO: implement fork semantics for device mappings properly.
if (arch_mmu_map(new_context->pagetable, phys, vaddr, new_range->mmuflags) == false)
goto error;
continue;
}
page_t *page = mm_get_page(phys); page_t *page = mm_get_page(phys);
if (mm_is_page_locked(page) && writeable && private) { if (mm_is_page_locked(page) && writeable && private) {
// the page is a private locked page, eagerly copy it to ensure fork/futex correctness // the page is a private locked page, eagerly copy it to ensure fork/futex correctness