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Kernel: Make sure the kernel info page is read-only for userspace

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To enforce this, we create two separate mappings of the same underlying
physical page. A writable mapping for the kernel, and a read-only one
for userspace (the one returned by sys$get_kernel_info_page.)
This commit is contained in:
Andreas Kling 2019-12-15 22:21:28 +01:00
parent 77cf607cda
commit 0a75a46501
3 changed files with 26 additions and 7 deletions
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11
Kernel/VM/MemoryManager.cpp
View file

@ -369,6 +369,17 @@ OwnPtr<Region> MemoryManager::allocate_user_accessible_kernel_region(size_t size
return allocate_kernel_region(size, name, true);
}
OwnPtr<Region> MemoryManager::allocate_kernel_region_with_vmobject(VMObject& vmobject, size_t size, const StringView& name)
{
InterruptDisabler disabler;
ASSERT(!(size % PAGE_SIZE));
auto range = kernel_page_directory().range_allocator().allocate_anywhere(size);
ASSERT(range.is_valid());
auto region = make<Region>(range, vmobject, 0, name, PROT_READ | PROT_WRITE | PROT_EXEC);
region->map(kernel_page_directory());
return region;
}
void MemoryManager::deallocate_user_physical_page(PhysicalPage&& page)
{
for (auto& region : m_user_physical_regions) {

1
Kernel/VM/MemoryManager.h
View file

@ -63,6 +63,7 @@ public:
void map_for_kernel(VirtualAddress, PhysicalAddress, bool cache_disabled = false);
OwnPtr<Region> allocate_kernel_region(size_t, const StringView& name, bool user_accessible = false, bool should_commit = true);
OwnPtr<Region> allocate_kernel_region_with_vmobject(VMObject&, size_t, const StringView& name);
OwnPtr<Region> allocate_user_accessible_kernel_region(size_t, const StringView& name);
unsigned user_physical_pages() const { return m_user_physical_pages; }