jsix/src/kernel/page_manager.h

#pragma once
/// \file page_manager.h
/// The page memory manager and related definitions.

#include <stddef.h>
#include <stdint.h>

#include "kutil/address_manager.h"
#include "kutil/enum_bitfields.h"
#include "kutil/frame_allocator.h"
#include "kutil/linked_list.h"
#include "kutil/slab_allocator.h"
#include "kernel_memory.h"
#include "page_table.h"

struct free_page_header;

/// Manager for allocation and mapping of pages
class page_manager
{
public:
	page_manager(
		kutil::frame_allocator &frames,
		kutil::address_manager &addrs);

	/// Helper to get the number of pages needed for a given number of bytes.
	/// \arg bytes  The number of bytes desired
	/// \returns    The number of pages needed to contain the desired bytes
	static inline size_t page_count(size_t bytes)
	{
		return (bytes - 1) / memory::frame_size + 1;
	}

	/// Helper to read the PML4 table from CR3.
	/// \returns  A pointer to the current PML4 table.
	static inline page_table * get_pml4()
	{
		uintptr_t pml4 = 0;
		__asm__ __volatile__ ( "mov %%cr3, %0" : "=r" (pml4) );
		return reinterpret_cast<page_table *>((pml4 & ~0xfffull) + memory::page_offset);
	}

	/// Helper to set the PML4 table pointer in CR3.
	/// \arg pml4  A pointer to the PML4 table to install.
	static inline void set_pml4(page_table *pml4)
	{
		uintptr_t p = reinterpret_cast<uintptr_t>(pml4) - memory::page_offset;
		__asm__ __volatile__ ( "mov %0, %%cr3" :: "r" (p & ~0xfffull) );
	}

	/// Allocate but don't switch to a new PML4 table. This table
	/// should only have global kernel pages mapped.
	/// \returns      A pointer to the PML4 table
	page_table * create_process_map();

	/// Deallocate a process' PML4 table and entries.
	/// \arg pml4  The process' PML4 table
	void delete_process_map(page_table *pml4);

	/// Copy a process' memory mappings (and memory pages).
	/// \arg from  Page table to copy from
	/// \arg lvl   Level of the given tables (default is PML4)
	/// \returns   The new page table
	page_table * copy_table(page_table *from,
			page_table::level lvl = page_table::level::pml4,
			page_table_indices index = {});

	/// Allocate and map pages into virtual memory.
	/// \arg address  The virtual address at which to map the pages
	/// \arg count    The number of pages to map
	/// \arg user     True is this memory is user-accessible
	/// \arg pml4     The pml4 to map into - null for the current one
	/// \returns      A pointer to the start of the mapped region
	void * map_pages(uintptr_t address, size_t count, bool user = false, page_table *pml4 = nullptr);

	/// Unmap and free existing pages from memory.
	/// \arg address  The virtual address of the memory to unmap
	/// \arg count    The number of pages to unmap
	/// \arg pml4     The pml4 to unmap from - null for the current one
	void unmap_pages(void *address, size_t count, page_table *pml4 = nullptr);

	/// Offset-map a pointer. No physical pages will be mapped.
	/// \arg pointer  Pointer to a pointer to the memory area to be mapped
	/// \arg length   Length of the memory area to be mapped
	void map_offset_pointer(void **pointer, size_t length);

	/// Get the physical address of an offset-mapped pointer
	/// \arg p   Virtual address of memory that has been offset-mapped
	/// \returns Physical address of the memory pointed to by p
	inline uintptr_t offset_phys(void *p) const
	{
		return reinterpret_cast<uintptr_t>(kutil::offset_pointer(p, -memory::page_offset));
	}

	/// Get the virtual address of an offset-mapped physical address
	/// \arg a   Physical address of memory that has been offset-mapped
	/// \returns Virtual address of the memory at address a
	inline void * offset_virt(uintptr_t a) const
	{
		return kutil::offset_pointer(reinterpret_cast<void *>(a), memory::page_offset);
	}

	/// Dump the given or current PML4 to the console
	/// \arg pml4     The page table to use, null for the current one
	/// \arg recurse  Whether to print sub-tables
	void dump_pml4(page_table *pml4 = nullptr, bool recurse = true);

	/// Get the system page manager.
	/// \returns  A pointer to the system page manager
	static page_manager * get();

	/// Get a pointer to the kernel's PML4
	inline page_table * get_kernel_pml4() { return m_kernel_pml4; }

private:
	/// Copy a physical page
	/// \arg orig  Physical address of the page to copy
	/// \returns   Physical address of the new page
	uintptr_t copy_page(uintptr_t orig);

	/// Allocate a page for a page table, or pull one from the cache
	/// \returns  An empty page mapped in page space
	page_table * get_table_page();

	/// Return a set of mapped contiguous pages to the page cache.
	/// \arg pages  Pointer to the first page to be returned
	/// \arg count  Number of pages in the range
	void free_table_pages(void *pages, size_t count);

	/// Helper function to allocate a new page table. If table entry `i` in
	/// table `base` is empty, allocate a new page table and point `base[i]` at
	/// it.
	/// \arg base  Existing page table being indexed into
	/// \arg i     Index into the existing table to check
	/// \art user  True if this is a userspace mapping
	void check_needs_page(page_table *base, unsigned i, bool user);

	/// Low-level routine for mapping a number of pages into the given page table.
	/// \arg pml4       The root page table to map into
	/// \arg phys_addr  The starting physical address of the pages to be mapped
	/// \arg virt_addr  The starting virtual address ot the memory to be mapped
	/// \arg count      The number of pages to map
	/// \arg user       True if this is a userspace mapping
	/// \arg large      Whether to allow large pages
	void page_in(
			page_table *pml4,
			uintptr_t phys_addr,
			uintptr_t virt_addr,
			size_t count,
			bool user = false,
			bool large = false);

	/// Low-level routine for unmapping a number of pages from the given page table.
	/// \arg pml4       The root page table for this mapping
	/// \arg virt_addr  The starting virtual address ot the memory to be unmapped
	/// \arg count      The number of pages to unmap
	/// \arg free       Whether to return the pages to the frame allocator
	void page_out(
			page_table *pml4,
			uintptr_t virt_addr,
			size_t count,
			bool free = false);

	/// Low-level routine for unmapping an entire table of memory at once
	void unmap_table(page_table *table, page_table::level lvl, bool free,
			page_table_indices index = {});

	page_table *m_kernel_pml4; ///< The PML4 of just kernel pages
	free_page_header *m_page_cache; ///< Cache of free pages to use for tables

	kutil::frame_allocator &m_frames;
	kutil::address_manager &m_addrs;

	friend void memory_initialize(uint16_t, const void *, size_t, size_t);
	page_manager(const page_manager &) = delete;
};

/// Global page manager.
extern page_manager g_page_manager;

inline page_manager * page_manager::get() { return &g_page_manager; }


/// Calculate a page-aligned address.
/// \arg p    The address to align.
/// \returns  The next page-aligned address _after_ `p`.
template <typename T> inline T
page_align(T p)
{
	return reinterpret_cast<T>(
		((reinterpret_cast<uintptr_t>(p) - 1) & ~(memory::frame_size - 1))
		+ memory::frame_size);
}

/// Calculate a page-table-aligned address. That is, an address that is
/// page-aligned to the first page in a page table.
/// \arg p    The address to align.
/// \returns  The next page-table-aligned address _after_ `p`.
template <typename T> inline T
page_table_align(T p)
{
	return ((p - 1) & ~0x1fffffull) + 0x200000;
}


/// Bootstrap the memory managers.
void memory_initialize(uint16_t scratch_pages, const void *memory_map, size_t map_length, size_t desc_length);