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MM: Allocate page tables from a separate set of physical pages.

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The old approach only worked because of an overpermissive accident.
There's now a concept of supervisor physical pages that can be allocated.
They all sit in the low 4 MB of physical memory and are identity mapped,
shared between all processes, and only ring 0 can access them.
This commit is contained in:
Andreas Kling 2019-01-01 02:09:43 +01:00
parent a5ffa2eec7
commit 683185e4aa
5 changed files with 65 additions and 105 deletions
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26
Kernel/MemoryManager.h
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@ -39,15 +39,16 @@ public:
return_to_freelist();
}
unsigned retain_count() const { return m_retain_count; }
unsigned short retain_count() const { return m_retain_count; }
private:
explicit PhysicalPage(PhysicalAddress paddr);
PhysicalPage(PhysicalAddress paddr, bool supervisor);
~PhysicalPage() = delete;
void return_to_freelist();
unsigned m_retain_count { 1 };
unsigned short m_retain_count { 1 };
bool m_supervisor { false };
PhysicalAddress m_paddr;
};
@ -174,16 +175,13 @@ public:
void populate_page_directory(PageDirectory&);
byte* create_kernel_alias_for_region(Region&);
void remove_kernel_alias_for_region(Region&, byte*);
void enter_kernel_paging_scope();
void enter_process_paging_scope(Process&);
bool validate_user_read(const Process&, LinearAddress) const;
bool validate_user_write(const Process&, LinearAddress) const;
RetainPtr<PhysicalPage> allocate_physical_page();
RetainPtr<PhysicalPage> allocate_supervisor_physical_page();
void remap_region(Process&, Region&);
@ -196,7 +194,6 @@ private:
void register_region(Region&);
void unregister_region(Region&);
LinearAddress allocate_linear_address_range(size_t);
void map_region_at_address(PageDirectory&, Region&, LinearAddress, bool user_accessible);
void unmap_range(PageDirectory&, LinearAddress, size_t);
void remap_region_page(PageDirectory&, Region&, unsigned page_index_in_region, bool user_allowed);
@ -209,8 +206,8 @@ private:
void map_protected(LinearAddress, size_t length);
void create_identity_mapping(LinearAddress, size_t length);
void remove_identity_mapping(LinearAddress, size_t);
void create_identity_mapping(PageDirectory&, LinearAddress, size_t length);
void remove_identity_mapping(PageDirectory&, LinearAddress, size_t);
static Region* region_from_laddr(Process&, LinearAddress);
@ -305,21 +302,16 @@ private:
OwnPtr<PageDirectory> m_kernel_page_directory;
dword* m_page_table_zero;
dword* m_page_table_one;
LinearAddress m_next_laddr;
LinearAddress m_quickmap_addr;
Vector<RetainPtr<PhysicalPage>> m_free_physical_pages;
Vector<RetainPtr<PhysicalPage>> m_free_supervisor_physical_pages;
HashTable<VMObject*> m_vmos;
HashTable<Region*> m_regions;
};
struct KernelPagingScope {
KernelPagingScope() { MM.enter_kernel_paging_scope(); }
~KernelPagingScope() { MM.enter_process_paging_scope(*current); }
};
struct ProcessPagingScope {
ProcessPagingScope(Process& process) { MM.enter_process_paging_scope(process); }
~ProcessPagingScope() { MM.enter_process_paging_scope(*current); }