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Kernel: Make the x86 paging code slightly less insane.
Instead of PDE's and PTE's being weird wrappers around dword*, just have MemoryManager::ensure_pte() return a PageDirectoryEntry&, which in turn has a PageTableEntry* entries(). I've been trying to understand how things ended up this way, and I suspect it was because I inadvertently invoked the PageDirectoryEntry copy ctor in the original work on this, which must have made me very confused.. Anyways, now things are a bit saner and we can move forward towards a better future, etc. :^)
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4 changed files with 126 additions and 123 deletions
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@ -1,11 +1,16 @@
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#pragma once
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#include <AK/Badge.h>
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#include <AK/Noncopyable.h>
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#include <Kernel/VirtualAddress.h>
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#include <Kernel/kstdio.h>
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#define PAGE_SIZE 4096
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#define PAGE_MASK 0xfffff000
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class MemoryManager;
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class PageTableEntry;
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struct [[gnu::packed]] TSS32
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{
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word backlink, __blh;
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@ -79,6 +84,106 @@ union [[gnu::packed]] Descriptor
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}
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};
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class PageDirectoryEntry {
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AK_MAKE_NONCOPYABLE(PageDirectoryEntry);
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public:
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PageTableEntry* page_table_base() { return reinterpret_cast<PageTableEntry*>(m_raw & 0xfffff000u); }
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void set_page_table_base(dword value)
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{
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m_raw &= 0xfff;
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m_raw |= value & 0xfffff000;
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}
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dword raw() const { return m_raw; }
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void copy_from(Badge<MemoryManager>, const PageDirectoryEntry& other) { m_raw = other.m_raw; }
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enum Flags {
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Present = 1 << 0,
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ReadWrite = 1 << 1,
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UserSupervisor = 1 << 2,
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WriteThrough = 1 << 3,
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CacheDisabled = 1 << 4,
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};
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bool is_present() const { return raw() & Present; }
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void set_present(bool b) { set_bit(Present, b); }
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bool is_user_allowed() const { return raw() & UserSupervisor; }
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void set_user_allowed(bool b) { set_bit(UserSupervisor, b); }
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bool is_writable() const { return raw() & ReadWrite; }
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void set_writable(bool b) { set_bit(ReadWrite, b); }
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bool is_write_through() const { return raw() & WriteThrough; }
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void set_write_through(bool b) { set_bit(WriteThrough, b); }
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bool is_cache_disabled() const { return raw() & CacheDisabled; }
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void set_cache_disabled(bool b) { set_bit(CacheDisabled, b); }
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void set_bit(byte bit, bool value)
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{
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if (value)
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m_raw |= bit;
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else
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m_raw &= ~bit;
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}
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private:
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dword m_raw;
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};
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class PageTableEntry {
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AK_MAKE_NONCOPYABLE(PageTableEntry);
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public:
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void* physical_page_base() { return reinterpret_cast<void*>(m_raw & 0xfffff000u); }
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void set_physical_page_base(dword value)
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{
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m_raw &= 0xfff;
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m_raw |= value & 0xfffff000;
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}
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dword raw() const { return m_raw; }
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enum Flags {
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Present = 1 << 0,
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ReadWrite = 1 << 1,
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UserSupervisor = 1 << 2,
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WriteThrough = 1 << 3,
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CacheDisabled = 1 << 4,
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};
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bool is_present() const { return raw() & Present; }
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void set_present(bool b) { set_bit(Present, b); }
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bool is_user_allowed() const { return raw() & UserSupervisor; }
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void set_user_allowed(bool b) { set_bit(UserSupervisor, b); }
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bool is_writable() const { return raw() & ReadWrite; }
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void set_writable(bool b) { set_bit(ReadWrite, b); }
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bool is_write_through() const { return raw() & WriteThrough; }
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void set_write_through(bool b) { set_bit(WriteThrough, b); }
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bool is_cache_disabled() const { return raw() & CacheDisabled; }
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void set_cache_disabled(bool b) { set_bit(CacheDisabled, b); }
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void set_bit(byte bit, bool value)
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{
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if (value)
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m_raw |= bit;
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else
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m_raw &= ~bit;
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}
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private:
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dword m_raw;
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};
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static_assert(sizeof(PageDirectoryEntry) == 4);
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static_assert(sizeof(PageTableEntry) == 4);
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class IRQHandler;
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void gdt_init();
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