Kernel: Track user accessibility per Region.

Region now has is_user_accessible(), which informs the memory manager how
to map these pages. Previously, we were just passing a "bool user_allowed"
to various functions and I'm not at all sure that any of that was correct.

All the Region constructors are now hidden, and you must go through one of
these helpers to construct a region:

- Region::create_user_accessible(...)
- Region::create_kernel_only(...)

That ensures that we don't accidentally create a Region without specifying
user accessibility. :^)

1 files changed, 15 insertions, 14 deletions

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index adccf9a7a7..aa58797031 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -305,7 +305,7 @@ bool MemoryManager::zero_page(Region& region, unsigned page_index_in_region)
 #ifdef PAGE_FAULT_DEBUG
         dbgprintf("MM: zero_page() but page already present. Fine with me!\n");
 #endif
-        remap_region_page(region, page_index_in_region, true);
+        remap_region_page(region, page_index_in_region);
         return true;
     }
     auto physical_page = allocate_user_physical_page(ShouldZeroFill::Yes);
@@ -314,7 +314,7 @@ bool MemoryManager::zero_page(Region& region, unsigned page_index_in_region)
 #endif
     region.set_should_cow(page_index_in_region, false);
     vmo.physical_pages()[page_index_in_region] = move(physical_page);
-    remap_region_page(region, page_index_in_region, true);
+    remap_region_page(region, page_index_in_region);
     return true;
 }
 
@@ -327,7 +327,7 @@ bool MemoryManager::copy_on_write(Region& region, unsigned page_index_in_region)
         dbgprintf("    >> It's a COW page but nobody is sharing it anymore. Remap r/w\n");
 #endif
         region.set_should_cow(page_index_in_region, false);
-        remap_region_page(region, page_index_in_region, true);
+        remap_region_page(region, page_index_in_region);
         return true;
     }
 
@@ -345,7 +345,7 @@ bool MemoryManager::copy_on_write(Region& region, unsigned page_index_in_region)
     vmo.physical_pages()[page_index_in_region] = move(physical_page);
     unquickmap_page();
     region.set_should_cow(page_index_in_region, false);
-    remap_region_page(region, page_index_in_region, true);
+    remap_region_page(region, page_index_in_region);
     return true;
 }
 
@@ -366,7 +366,7 @@ bool MemoryManager::page_in_from_inode(Region& region, unsigned page_index_in_re
 
     if (!vmo_page.is_null()) {
         dbgprintf("MM: page_in_from_inode() but page already present. Fine with me!\n");
-        remap_region_page(region, page_index_in_region, true);
+        remap_region_page(region, page_index_in_region);
         return true;
     }
 
@@ -391,7 +391,7 @@ bool MemoryManager::page_in_from_inode(Region& region, unsigned page_index_in_re
         kprintf("MM: page_in_from_inode was unable to allocate a physical page\n");
         return false;
     }
-    remap_region_page(region, page_index_in_region, true);
+    remap_region_page(region, page_index_in_region);
     u8* dest_ptr = region.vaddr().offset(page_index_in_region * PAGE_SIZE).as_ptr();
     memcpy(dest_ptr, page_buffer, PAGE_SIZE);
     return true;
@@ -457,8 +457,9 @@ RefPtr<Region> MemoryManager::allocate_kernel_region(size_t size, String&& name)
     ASSERT(!(size % PAGE_SIZE));
     auto range = kernel_page_directory().range_allocator().allocate_anywhere(size);
     ASSERT(range.is_valid());
-    auto region = adopt(*new Region(range, move(name), PROT_READ | PROT_WRITE | PROT_EXEC, false));
-    MM.map_region_at_address(*m_kernel_page_directory, *region, range.base(), false);
+    auto region = Region::create_kernel_only(range, move(name), PROT_READ | PROT_WRITE | PROT_EXEC, false);
+    region->set_user_accessible(false);
+    MM.map_region_at_address(*m_kernel_page_directory, *region, range.base());
     // FIXME: It would be cool if these could zero-fill on demand instead.
     region->commit();
     return region;
@@ -641,7 +642,7 @@ void MemoryManager::unquickmap_page()
     m_quickmap_in_use = false;
 }
 
-void MemoryManager::remap_region_page(Region& region, unsigned page_index_in_region, bool user_allowed)
+void MemoryManager::remap_region_page(Region& region, unsigned page_index_in_region)
 {
     ASSERT(region.page_directory());
     InterruptDisabler disabler;
@@ -657,7 +658,7 @@ void MemoryManager::remap_region_page(Region& region, unsigned page_index_in_reg
         pte.set_writable(region.is_writable());
     pte.set_cache_disabled(!region.vmo().m_allow_cpu_caching);
     pte.set_write_through(!region.vmo().m_allow_cpu_caching);
-    pte.set_user_allowed(user_allowed);
+    pte.set_user_allowed(region.is_user_accessible());
     region.page_directory()->flush(page_vaddr);
 #ifdef MM_DEBUG
     dbgprintf("MM: >> remap_region_page (PD=%x, PTE=P%x) '%s' L%x => P%x (@%p)\n", region.page_directory()->cr3(), pte.ptr(), region.name().characters(), page_vaddr.get(), physical_page->paddr().get(), physical_page.ptr());
@@ -668,10 +669,10 @@ void MemoryManager::remap_region(PageDirectory& page_directory, Region& region)
 {
     InterruptDisabler disabler;
     ASSERT(region.page_directory() == &page_directory);
-    map_region_at_address(page_directory, region, region.vaddr(), true);
+    map_region_at_address(page_directory, region, region.vaddr());
 }
 
-void MemoryManager::map_region_at_address(PageDirectory& page_directory, Region& region, VirtualAddress vaddr, bool user_allowed)
+void MemoryManager::map_region_at_address(PageDirectory& page_directory, Region& region, VirtualAddress vaddr)
 {
     InterruptDisabler disabler;
     region.set_page_directory(page_directory);
@@ -698,7 +699,7 @@ void MemoryManager::map_region_at_address(PageDirectory& page_directory, Region&
             pte.set_present(false);
             pte.set_writable(region.is_writable());
         }
-        pte.set_user_allowed(user_allowed);
+        pte.set_user_allowed(region.is_user_accessible());
         page_directory.flush(page_vaddr);
 #ifdef MM_DEBUG
         dbgprintf("MM: >> map_region_at_address (PD=%x) '%s' L%x => P%x (@%p)\n", &page_directory, region.name().characters(), page_vaddr, physical_page ? physical_page->paddr().get() : 0, physical_page.ptr());
@@ -729,7 +730,7 @@ bool MemoryManager::unmap_region(Region& region)
 
 bool MemoryManager::map_region(Process& process, Region& region)
 {
-    map_region_at_address(process.page_directory(), region, region.vaddr(), true);
+    map_region_at_address(process.page_directory(), region, region.vaddr());
     return true;
 }