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Lots of fussing about getting the PageEntry stuff right

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I think I got something I am mostly happy with... :-)
This commit is contained in:
Eryn Wells 2016-04-25 10:34:16 -04:00
parent 7414aec667
commit 65513588f8
2 changed files with 90 additions and 50 deletions
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124
src/memory/PageAllocator.cc
View file

@ -1,4 +1,4 @@
/* Pager.cc
/* PageAllocator.cc
* vim: set tw=80:
* Eryn Wells <eryn@erynwells.me>
*/
@ -7,89 +7,123 @@
*/
#include "Attributes.hh"
#include "Pager.hh"
#include "kstd/Bitmap.hh"
#include "kstd/Memory.hh"
#include "kstd/PrintFormat.hh"
#include "memory/Memory.hh"
#include "memory/PageAllocator.hh"
namespace kernel {
struct PageDirectoryEntry
struct PageEntry
{
PageDirectoryEntry();
PageEntry();
/** Mark the whole entry not present. */
void setNotPresent();
bool isNotPresent() const;
enum class Present { No = 0, Yes = 1 };
enum class ReadWrite { No = 0, Yes = 1 };
enum class UserAccess { No = 0, Yes = 1 };
void set(Present present);
void set(ReadWrite readWrite);
void set(UserAccess user);
void setAddress(void* address);
private:
static const u8 OneBit = 0;
static const u8 ReadWriteBit = 1;
static const u8 UserAccessBit = 2;
static const u8 PageWriteThroughBit = 3;
static const u8 PageCacheDisabledBit = 4;
static const u8 AccessedBit = 5;
static const u8 DirtyBit = 6;
static const u8 ZeroBit = 7;
static const u32 IgnoredMask = 0x00000F00;
protected:
struct Flag {
static const u8 Present = 0;
static const u8 ReadWrite = 1;
static const u8 UserAccess = 2;
static const u8 PageWriteThrough = 3;
static const u8 PageCacheDisabled = 4;
static const u8 Accessed = 5;
static const u8 Dirty = 6;
static const u8 PageAttributeTable = 7;
static const u8 Global = 8;
};
static const u32 AddressMask = 0xFFFFF000;
static const u32 FlagMask = 0x00000FFF;
u32 mEntry;
void setRequiredBits();
};
PageDirectoryEntry::PageDirectoryEntry()
PageEntry::PageEntry()
: mEntry(0)
{
static_assert(sizeof(PageDirectoryEntry) == 4, "PageDirectoryEntry must be 4 bytes long.");
static_assert(sizeof(PageEntry) == 4, "PageEntry must be 4 bytes long.");
}
bool
PageDirectoryEntry::isNotPresent()
const
{
return mEntry == 0;
}
void
PageDirectoryEntry::setNotPresent()
PageEntry::set(Present present)
{
mEntry = 0;
if (present == Present::Yes) {
kstd::Bit::set(mEntry, Flag::Present);
} else {
kstd::Bit::clear(mEntry, Flag::Present);
}
}
void
PageEntry::set(ReadWrite rw)
{
if (rw == ReadWrite::Yes) {
kstd::Bit::set(mEntry, Flag::ReadWrite);
} else {
kstd::Bit::clear(mEntry, Flag::ReadWrite);
}
}
void
PageDirectoryEntry::setAddress(void* address)
PageEntry::set(UserAccess user)
{
if (user == UserAccess::Yes) {
kstd::Bit::set(mEntry, Flag::UserAccess);
} else {
kstd::Bit::clear(mEntry, Flag::UserAccess);
}
}
void
PageEntry::setAddress(void* address)
{
kstd::Bit::setMask(mEntry, memory::pageAlignDown(uptr(address)), AddressMask);
}
void
PageDirectoryEntry::setRequiredBits()
struct PageDirectoryEntry
: public PageEntry
{
kstd::Bit::set(mEntry, OneBit);
kstd::Bit::clear(mEntry, ZeroBit);
kstd::Bit::clearMask(mEntry, IgnoredMask);
void setFlagsForSystemDirectory();
};
void
PageDirectoryEntry::setFlagsForSystemDirectory()
{
set(PageEntry::Present::Yes);
set(PageEntry::ReadWrite::Yes);
set(PageEntry::UserAccess::No);
}
struct PageTableEntry
: public PageEntry
{ };
/*
* Public
*/
void
PageAllocator::initialize(const StartupInformation& startupInformation,
void* pageDirectory)
FrameAllocator* frameAllocator)
{
mPageDirectory = reinterpret_cast<PageDirectoryEntry*>(pageDirectory);
for (usize i = 0; i < NumberOfEntries; i++) {
mPageDirectory[i].setNotPresent();
}
mPageDirectory = reinterpret_cast<PageDirectoryEntry*>(frameAllocator->allocate());
kstd::printFormat("Page directory at 0x%08lX\n", uptr(mPageDirectory));
kstd::Memory::zero(mPageDirectory, memory::pageSize * (memory::pageSize / sizeof(PageDirectoryEntry)));
auto& firstPageTable = mPageDirectory[0];
firstPageTable.setAddress(frameAllocator->allocate());
firstPageTable.setFlagsForSystemDirectory();
}
/*

16
src/memory/PageAllocator.hh
View file

@ -1,4 +1,4 @@
/* Pager.hh
/* PageAllocator.hh
* vim: set tw=80:
* Eryn Wells <eryn@erynwells.me>
*/
@ -6,8 +6,8 @@
* Page tables 'n stuff.
*/
#ifndef __MEMORY_PAGE_HH__
#define __MEMORY_PAGE_HH__
#ifndef __MEMORY_PAGEALLOCATOR_HH__
#define __MEMORY_PAGEALLOCATOR_HH__
#include "StartupInformation.hh"
#include "kstd/Types.hh"
@ -21,7 +21,13 @@ struct PageDirectoryEntry;
*/
struct PageAllocator
{
void initialize(const StartupInformation& startupInformation, void* pageDirectory);
/**
* Initialize the page allocator.
*
* @param [in] startupInformation The kernel startup information struct.
* @param [in] frameAllocator The kernel's page frame allocator.
*/
void initialize(const StartupInformation& startupInformation, FrameAllocator* frameAllocator);
// TODO: A method to install a page table into the system. For per-process page tables, I'll need a way to set the current page table so the system knows where to look.
@ -34,4 +40,4 @@ private:
} /* namespace kernel */
#endif /* __MEMORY_PAGE_HH__ */
#endif /* __MEMORY_PAGEALLOCATOR_HH__ */