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-rw-r--r--Kernel/VM/AnonymousVMObject.cpp5
-rw-r--r--Kernel/VM/MemoryManager.cpp4
-rw-r--r--Kernel/VM/MemoryManager.h9
-rw-r--r--Kernel/VM/PhysicalPage.h2
-rw-r--r--Kernel/VM/Region.cpp29
5 files changed, 41 insertions, 8 deletions
diff --git a/Kernel/VM/AnonymousVMObject.cpp b/Kernel/VM/AnonymousVMObject.cpp
index 60e905f4ec..0cc0711d86 100644
--- a/Kernel/VM/AnonymousVMObject.cpp
+++ b/Kernel/VM/AnonymousVMObject.cpp
@@ -25,6 +25,7 @@
*/
#include <Kernel/VM/AnonymousVMObject.h>
+#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PhysicalPage.h>
NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_size(size_t size)
@@ -51,6 +52,10 @@ NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_page(Ph
AnonymousVMObject::AnonymousVMObject(size_t size)
: VMObject(size)
{
+#ifndef MAP_SHARED_ZERO_PAGE_LAZILY
+ for (size_t i = 0; i < page_count(); ++i)
+ physical_pages()[i] = MM.shared_zero_page();
+#endif
}
AnonymousVMObject::AnonymousVMObject(PhysicalAddress paddr, size_t size)
diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index 8573f52561..a4433ed036 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -53,6 +53,8 @@ MemoryManager::MemoryManager()
write_cr3(kernel_page_directory().cr3());
setup_low_identity_mapping();
protect_kernel_image();
+
+ m_shared_zero_page = allocate_user_physical_page();
}
MemoryManager::~MemoryManager()
@@ -297,7 +299,7 @@ OwnPtr<Region> MemoryManager::allocate_kernel_region(size_t size, const StringVi
region = Region::create_user_accessible(range, name, access, cacheable);
else
region = Region::create_kernel_only(range, name, access, cacheable);
- region->set_page_directory(kernel_page_directory());
+ region->map(kernel_page_directory());
if (should_commit)
region->commit();
return region;
diff --git a/Kernel/VM/MemoryManager.h b/Kernel/VM/MemoryManager.h
index abb4591401..9c6955507f 100644
--- a/Kernel/VM/MemoryManager.h
+++ b/Kernel/VM/MemoryManager.h
@@ -132,6 +132,8 @@ public:
void dump_kernel_regions();
+ PhysicalPage& shared_zero_page() { return *m_shared_zero_page; }
+
private:
MemoryManager();
~MemoryManager();
@@ -172,6 +174,8 @@ private:
RefPtr<PageDirectory> m_kernel_page_directory;
RefPtr<PhysicalPage> m_low_page_table;
+ RefPtr<PhysicalPage> m_shared_zero_page;
+
unsigned m_user_physical_pages { 0 };
unsigned m_user_physical_pages_used { 0 };
unsigned m_super_physical_pages { 0 };
@@ -223,3 +227,8 @@ inline bool is_user_range(VirtualAddress vaddr, size_t size)
return false;
return is_user_address(vaddr) && is_user_address(vaddr.offset(size));
}
+
+inline bool PhysicalPage::is_shared_zero_page() const
+{
+ return this == &MM.shared_zero_page();
+}
diff --git a/Kernel/VM/PhysicalPage.h b/Kernel/VM/PhysicalPage.h
index 2d96307b00..d8dda694ea 100644
--- a/Kernel/VM/PhysicalPage.h
+++ b/Kernel/VM/PhysicalPage.h
@@ -60,6 +60,8 @@ public:
u16 ref_count() const { return m_retain_count; }
+ bool is_shared_zero_page() const;
+
private:
PhysicalPage(PhysicalAddress paddr, bool supervisor, bool may_return_to_freelist = true);
~PhysicalPage() {}
diff --git a/Kernel/VM/Region.cpp b/Kernel/VM/Region.cpp
index ab0f7da74b..d07f0da383 100644
--- a/Kernel/VM/Region.cpp
+++ b/Kernel/VM/Region.cpp
@@ -144,7 +144,7 @@ bool Region::commit(size_t page_index)
dbgprintf("MM: commit single page (%zu) in Region %p (VMO=%p) at V%p\n", page_index, vmobject().page_count(), this, &vmobject(), vaddr().get());
#endif
auto& vmobject_physical_page_entry = vmobject().physical_pages()[first_page_index() + page_index];
- if (!vmobject_physical_page_entry.is_null())
+ if (!vmobject_physical_page_entry.is_null() && !vmobject_physical_page_entry->is_shared_zero_page())
return true;
auto physical_page = MM.allocate_user_physical_page(MemoryManager::ShouldZeroFill::Yes);
if (!physical_page) {
@@ -177,7 +177,8 @@ size_t Region::amount_resident() const
{
size_t bytes = 0;
for (size_t i = 0; i < page_count(); ++i) {
- if (m_vmobject->physical_pages()[first_page_index() + i])
+ auto& physical_page = m_vmobject->physical_pages()[first_page_index() + i];
+ if (physical_page && !physical_page->is_shared_zero_page())
bytes += PAGE_SIZE;
}
return bytes;
@@ -188,7 +189,7 @@ size_t Region::amount_shared() const
size_t bytes = 0;
for (size_t i = 0; i < page_count(); ++i) {
auto& physical_page = m_vmobject->physical_pages()[first_page_index() + i];
- if (physical_page && physical_page->ref_count() > 1)
+ if (physical_page && physical_page->ref_count() > 1 && !physical_page->is_shared_zero_page())
bytes += PAGE_SIZE;
}
return bytes;
@@ -231,6 +232,8 @@ NonnullOwnPtr<Region> Region::create_kernel_only(const Range& range, const Strin
bool Region::should_cow(size_t page_index) const
{
+ if (vmobject().physical_pages()[page_index]->is_shared_zero_page())
+ return true;
if (m_shared)
return false;
return m_cow_map && m_cow_map->get(page_index);
@@ -339,16 +342,28 @@ PageFaultResponse Region::handle_fault(const PageFault& fault)
#endif
return handle_inode_fault(page_index_in_region);
}
-#ifdef PAGE_FAULT_DEBUG
- dbgprintf("NP(zero) fault in Region{%p}[%u]\n", this, page_index_in_region);
-#endif
+#ifdef MAP_SHARED_ZERO_PAGE_LAZILY
+ if (fault.is_read()) {
+ vmobject().physical_pages()[first_page_index() + page_index_in_region] = MM.shared_zero_page();
+ remap_page(page_index_in_region);
+ return PageFaultResponse::Continue;
+ }
return handle_zero_fault(page_index_in_region);
+#else
+ ASSERT_NOT_REACHED();
+#endif
}
ASSERT(fault.type() == PageFault::Type::ProtectionViolation);
if (fault.access() == PageFault::Access::Write && is_writable() && should_cow(page_index_in_region)) {
#ifdef PAGE_FAULT_DEBUG
dbgprintf("PV(cow) fault in Region{%p}[%u]\n", this, page_index_in_region);
#endif
+ if (vmobject().physical_pages()[first_page_index() + page_index_in_region]->is_shared_zero_page()) {
+#ifdef PAGE_FAULT_DEBUG
+ dbgprintf("NP(zero) fault in Region{%p}[%u]\n", this, page_index_in_region);
+#endif
+ return handle_zero_fault(page_index_in_region);
+ }
return handle_cow_fault(page_index_in_region);
}
kprintf("PV(error) fault in Region{%p}[%u] at V%p\n", this, page_index_in_region, fault.vaddr().get());
@@ -366,7 +381,7 @@ PageFaultResponse Region::handle_zero_fault(size_t page_index_in_region)
auto& vmobject_physical_page_entry = vmobject().physical_pages()[first_page_index() + page_index_in_region];
- if (!vmobject_physical_page_entry.is_null()) {
+ if (!vmobject_physical_page_entry.is_null() && !vmobject_physical_page_entry->is_shared_zero_page()) {
#ifdef PAGE_FAULT_DEBUG
dbgprintf("MM: zero_page() but page already present. Fine with me!\n");
#endif
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-17 04:43:53 +0000