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Rewriting memory management, part one.

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This commit is contained in:
Curle 2021-03-15 21:48:51 +00:00
parent 5bc7ec5b79
commit 51ce7fe132
Signed by: TheCurle
GPG Key ID: 5942F13718443F79
4 changed files with 329 additions and 8 deletions
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1
build.json
View File

@ -34,6 +34,7 @@
"$root/chroma/system/memory/stack.c",
"$root/chroma/system/memory/abstract_allocator.c",
"$root/chroma/system/memory/physmem.c",
"$root/chroma/system/memory/paging.c",
"$root/chroma/system/drivers/keyboard.c",
"$root/chroma/system/drivers/elf.c"
],

15
chroma/inc/kernel/system/memory.h
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@ -139,6 +139,9 @@
#define PAGE_SHIFT 12
#define TO_DIRECT(addr) ((size_t)(addr) + DIRECT_REGION)
#define FROM_DIRECT(addr) ((size_t)(addr) - DIRECT_REGION)
/*********************************************
* T Y P E D E F I N I T I O N S
**********************************************/
@ -148,7 +151,7 @@ typedef void* directptr_t;
typedef struct {
ticketlock_t Lock;
directptr_t PML4;
size_t* PML4;
} address_space_t;
typedef enum {
@ -258,12 +261,14 @@ void* memcpy(void* dest, void const* src, size_t len);
* C h r o m a A l l o c a t o r
**********************************************/
void SetAddressSpace(address_space_t* Space);
//TODO: Copy to/from Userspace
void MapVirtualMemory(address_space_t* Space, void* VirtualAddress, size_t PhysicalAddress, mapflags_t Flags);
void UnmapVirtualMemory(address_space_t* Space, void* VirtualAddress);
void MapVirtualPage(address_space_t* AddressSpace, size_t Physical, size_t Virtual, size_t PageFlags);
void MapVirtualPageNoDirect(address_space_t* AddressSpace, size_t Physical, size_t Virtual, size_t PageFlags);
void CacheVirtualMemory(address_space_t* Space, void* VirtualAddress, pagecache_t CacheType);
size_t DecodeVirtualAddress(address_space_t* AddressSpace, size_t VirtualAddress);
size_t DecodeVirtualAddressNoDirect(address_space_t* AddressSpace, size_t VirtualAddress);
size_t* CreateNewPageTable(address_space_t* AddressSpace);
void* AllocateMemory(size_t Bits);

4
chroma/kernel.c
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@ -18,8 +18,6 @@ size_t KernelEnd = (size_t) &end;
address_space_t KernelAddressSpace;
size_t KernelLocation;
int Main(void) {
KernelAddressSpace = (address_space_t) {0};
@ -48,7 +46,7 @@ int Main(void) {
//DrawSplash();
//InitPaging();
InitPaging();
for(;;) { }

317
chroma/system/memory/paging.c Normal file
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@ -0,0 +1,317 @@
#include <kernel/chroma.h>
/************************
*** Team Kitty, 2020 ***
*** Chroma ***
***********************/
#define PAGE_TABLES_GET_PDPT(address) \
(address & ((size_t) 0x1FF << 39)) >> 39
#define PAGE_TABLES_GET_PDP(address) \
(address & ((size_t) 0x1FF << 30)) >> 30
#define PAGE_TABLES_GET_PDE(address) \
(address & ((size_t) 0x1FF << 21)) >> 21
#define PAGE_TABLES_GET_PT(address) \
(address & ((size_t) 0x1FF << 12)) >> 12
// The flag bit, per page, that determines whether this page is present.
#define PRESENT_BIT 1
// Default flags for a new page table. 7 = 1 | 2 | 4 = Present, writeable, accessible from userspace
#define DEFAULT_PAGE_FLAGS 7
size_t KernelLocation;
/**
* Bootstrap the paging process.
* Seeds the page tables, maps the kernel and framebuffer, etc.
*
*/
void InitPaging() {
KernelAddressSpace = (address_space_t) {
.Lock = {0},
.PML4 = PhysAllocateZeroMem(4096)
};
SerialPrintf("[ Mem] Identity mapping 2MB\r\n");
for(size_t i = 0; i < 8192; i++) {
size_t Addr = i * 4096;
MapVirtualPageNoDirect(&KernelAddressSpace, Addr, Addr, DEFAULT_PAGE_FLAGS);
MapVirtualPageNoDirect(&KernelAddressSpace, Addr, TO_DIRECT(Addr), DEFAULT_PAGE_FLAGS);
// TODO: Map kernel mem
}
SerialPrintf("[ Mem] Mapping kernel\r\n");
for(size_t i = KERNEL_PHYSICAL + KERNEL_TEXT; i < KERNEL_END; i += 4096)
MapVirtualPageNoDirect(&KernelAddressSpace, i, (i - KERNEL_PHYSICAL) + KERNEL_REGION, 0x3);
SerialPrintf("[ Mem] Mapping framebuffer\r\n");
for(size_t i = FB_PHYSICAL; i < bootldr.fb_size + FB_PHYSICAL; i += 4096)
MapVirtualPageNoDirect(&KernelAddressSpace, i, (i - FB_PHYSICAL) + FB_REGION, 0x3);
SerialPrintf("[ Mem] Mapping stack\r\n");
MapVirtualPageNoDirect(&KernelAddressSpace, CORE_STACK_PHYSICAL, STACK_TOP, 0x3);
SerialPrintf("[ Mem] Diagnostic: Querying existing page tables\r\n");
address_space_t BootloaderAddressSpace = (address_space_t) {
.Lock = {0},
.PML4 = (size_t*) ReadControlRegister(3)
};
size_t AddressToFind = 0xffffffffffe021ba;
size_t BootloaderAddress = DecodeVirtualAddressNoDirect(&BootloaderAddressSpace, AddressToFind);
size_t KernelDisoveredAddress = DecodeVirtualAddressNoDirect(&KernelAddressSpace, AddressToFind);
SerialPrintf("[ Mem] Diagnostic: Existing pagetables put 0x%p at 0x%p.\r\n", AddressToFind, BootloaderAddress);
SerialPrintf("[ Mem] Diagnostic: Our pagetables put 0x%p at 0x%p.\r\n", AddressToFind, KernelDisoveredAddress);
SerialPrintf("[ Mem] %s\r\n", BootloaderAddress == KernelDisoveredAddress ? "These match. Continuing." : "These do not match. Halting..");
//if(BootloaderAddress != KernelDisoveredAddress)
//for(;;) {}
SerialPrintf("[ Mem] Attempting to jump into our new pagetables.\r\n");
WriteControlRegister(3, (size_t) KernelAddressSpace.PML4);
SerialPrintf("[ Mem] Worked\r\n");
for(;;) {}
}
/**
* Given the offsets in the page tables, construct a virtual address.
*
* Bits 0 to 16 reflect the first digit of the PDPT.
* @param pdpt Page Directory Pointer Table - Bits 16 to 25
* @param pdp Page Directory Pointer - Bits 26 to 34
* @param pde Page Directory Entry - Bits 35 to 43
* @param pt Page Table - Bits 44 to 52
* Bits 52 to 64 are the Page Offset.
*
* @return size_t The corresponding virtual address
*/
size_t ConstructVirtualAddress(size_t pdpt, size_t pdp, size_t pde, size_t pt) {
return 0 | pdpt << 39 | pdp << 30 | pde << 21 | pt << 12;
}
/**
* Given a virtual address, walk the page tables to retrieve the physical frame.
* Note that the lowest 12 bits are CLEARED.
*
* The page tables are a 4 (5) dimensional array, so this function
* walks the tables, checking that each step is present, before moving onto the next.
* NOTE: this can be replaced with a loop.
* WARNING: this leads to instability.
* TODO: figure out if we can fix that?
*
* @param AddressSpace The address space of the process to walk
* @param VirtualAddress The address to decode
* @return size_t The physical frame that the virtual address encodes
*/
size_t DecodeVirtualAddress(address_space_t* AddressSpace, size_t VirtualAddress) {
size_t PDPT = PAGE_TABLES_GET_PDPT(VirtualAddress);
size_t PDP = PAGE_TABLES_GET_PDP(VirtualAddress);
size_t PDE = PAGE_TABLES_GET_PDE(VirtualAddress);
size_t PT = PAGE_TABLES_GET_PT(VirtualAddress);
size_t* PDPT_T, *PDE_T, *PT_T;
if(AddressSpace->PML4[PDPT] & PRESENT_BIT)
PDPT_T = (size_t*) TO_DIRECT(AddressSpace->PML4[PDPT] & STACK_TOP);
else
return VirtualAddress;
if(PDPT_T[PDP] & PRESENT_BIT)
PDE_T = (size_t*) TO_DIRECT(PDPT_T[PDP] & STACK_TOP);
else
return VirtualAddress;
if(PDE_T[PDE] & PRESENT_BIT)
PT_T = (size_t*) TO_DIRECT(PDE_T[PDE] & STACK_TOP);
else
return VirtualAddress;
return PT_T[PT] & STACK_TOP;
}
/**
* Walk the tables, generating the structures required to map the specified Physical address to the specified Virtual Address.
* It generates new intermediary pages as required.
* The page table entry's flags are set to the specified PageFlags.
*
* @param AddressSpace The address space to map this page into
* @param Physical The physical address to map
* @param Virtual The virtual address to map into the physical address
* @param PageFlags Wanted flags for the final page.
*/
void MapVirtualPage(address_space_t* AddressSpace, size_t Physical, size_t Virtual, size_t PageFlags) {
size_t PDPT = PAGE_TABLES_GET_PDPT(Virtual);
size_t PDP = PAGE_TABLES_GET_PDP(Virtual);
size_t PDE = PAGE_TABLES_GET_PDE(Virtual);
size_t PT = PAGE_TABLES_GET_PT(Virtual);
size_t* PDPT_T, *PDE_T, *PT_T;
// Read the top level's bits. If it's marked as present..
if(AddressSpace->PML4[PDPT] & PRESENT_BIT)
// Set the variable for the next level. Mask off the lower 12 bits, shift it into the "direct region".
PDPT_T = (size_t*) TO_DIRECT(AddressSpace->PML4[PDPT] & STACK_TOP);
else {
// Otherwise, allocate a new page in the direct region.
PDPT_T = (size_t*) TO_DIRECT(PhysAllocateZeroMem(4096));
// Pull it down from the direct region, and save it as the level's page for future reads of this block.
AddressSpace->PML4[PDPT] = FROM_DIRECT(PDPT_T) | DEFAULT_PAGE_FLAGS;
}
// The above repeats.
if(PDPT_T[PDP] & PRESENT_BIT)
PDE_T = (size_t*) TO_DIRECT(PDPT_T[PDP] & STACK_TOP);
else {
PDE_T = (size_t*) TO_DIRECT(PhysAllocateZeroMem(4096));
PDPT_T[PDP] = FROM_DIRECT(PDE_T) | DEFAULT_PAGE_FLAGS;
}
if(PDE_T[PDE] & PRESENT_BIT)
PT_T = (size_t*) TO_DIRECT(PDE_T[PDE] & STACK_TOP);
else {
PT_T = (size_t*) TO_DIRECT(PhysAllocateZeroMem(4096));
PDE_T[PDE] = FROM_DIRECT(PT_T) | DEFAULT_PAGE_FLAGS;
}
// Finally, set the last page table content to the physical page + the flags we specified.
PT_T[PT] = (size_t) (Physical | PageFlags);
}
/**
* Given a virtual address, walk the page tables to retrieve the physical frame.
* Note that the lowest 12 bits are CLEARED.
*
* This function does not touch the Direct Region, ergo making it suitable for querying
* the initial memory maps.
*
* The page tables are a 4 (5) dimensional array, so this function
* walks the tables, checking that each step is present, before moving onto the next.
* NOTE: this can be replaced with a loop.
* WARNING: this leads to instability.
* TODO: figure out if we can fix that?
*
* @param AddressSpace The address space of the process to walk
* @param VirtualAddress The address to decode
* @return size_t The physical frame that the virtual address encodes
*/
size_t DecodeVirtualAddressNoDirect(address_space_t* AddressSpace, size_t VirtualAddress) {
size_t PDPT = PAGE_TABLES_GET_PDPT(VirtualAddress);
size_t PDP = PAGE_TABLES_GET_PDP(VirtualAddress);
size_t PDE = PAGE_TABLES_GET_PDE(VirtualAddress);
size_t PT = PAGE_TABLES_GET_PT(VirtualAddress);
size_t* PDPT_T, *PDE_T, *PT_T;
if(AddressSpace->PML4[PDPT] & PRESENT_BIT)
PDPT_T = (size_t*) (AddressSpace->PML4[PDPT] & STACK_TOP);
else
return VirtualAddress;
if(PDPT_T[PDP] & PRESENT_BIT)
PDE_T = (size_t*) (PDPT_T[PDP] & STACK_TOP);
else
return VirtualAddress;
if(PDE_T[PDE] & PRESENT_BIT)
PT_T = (size_t*) (PDE_T[PDE] & STACK_TOP);
else
return VirtualAddress;
return PT_T[PT] & STACK_TOP;
}
/**
* Walk the tables, generating the structures required to map the specified Physical address to the specified Virtual Address.
* It generates new intermediary pages as required.
* The page table entry's flags are set to the specified PageFlags.
*
* This function does not reference the Direct region.
* Ergo, it is suitable for initializing the first memory map the kernel needs to use.
*
* @param AddressSpace The address space to map this page into
* @param Physical The physical address to map
* @param Virtual The virtual address to map into the physical address
* @param PageFlags Wanted flags for the final page.
*/
void MapVirtualPageNoDirect(address_space_t* AddressSpace, size_t Physical, size_t Virtual, size_t PageFlags) {
size_t PDPT = PAGE_TABLES_GET_PDPT(Virtual);
size_t PDP = PAGE_TABLES_GET_PDP(Virtual);
size_t PDE = PAGE_TABLES_GET_PDE(Virtual);
size_t PT = PAGE_TABLES_GET_PT(Virtual);
size_t* PDPT_T, *PDE_T, *PT_T;
// Read the top level's bits. If it's marked as present..
if(AddressSpace->PML4[PDPT] & PRESENT_BIT)
// Set the variable for the next level. Mask off the lower 12 bits, shift it into the "direct region".
PDPT_T = (size_t*) (AddressSpace->PML4[PDPT] & STACK_TOP);
else {
// Otherwise, allocate a new page in the direct region.
PDPT_T = (size_t*) PhysAllocateZeroMem(4096);
// Pull it down from the direct region, and save it as the level's page for future reads of this block.
AddressSpace->PML4[PDPT] = (size_t) PDPT_T | DEFAULT_PAGE_FLAGS;
}
// The above repeats.
if(PDPT_T[PDP] & PRESENT_BIT)
PDE_T = (size_t*) (PDPT_T[PDP] & STACK_TOP);
else {
PDE_T = (size_t*) PhysAllocateZeroMem(4096);
PDPT_T[PDP] = (size_t) PDE_T | DEFAULT_PAGE_FLAGS;
}
if(PDE_T[PDE] & PRESENT_BIT)
PT_T = (size_t*) (PDE_T[PDE] & STACK_TOP);
else {
PT_T = (size_t*) PhysAllocateZeroMem(4096);
PDE_T[PDE] = (size_t) PT_T | DEFAULT_PAGE_FLAGS;
}
// Finally, set the last page table content to the physical page + the flags we specified.
PT_T[PT] = (size_t) (Physical | PageFlags);
}
/**
* Initialize and create a new page table.
* The higher half of the current page table will be copied into the new one.
* The lower 4GB will be identity mapped onto itself.
* Therefore, it will be ready for population for a new process immediately.
*
* @param AddressSpace The currently loaded AddressSpace, to seed the higher half
* @return size_t* The location of the fresh PML4
*/
size_t* CreateNewPageTable(address_space_t* AddressSpace) {
// Allocate the first page
size_t* NewPML4 = (size_t*) TO_DIRECT(PhysAllocateZeroMem(4096));
address_space_t TempAddressSpace = (address_space_t) {
.Lock = {0},
.PML4 = NewPML4
};
// Initialize to zeros
for(size_t i = 0; i < 512; i++)
NewPML4[i] = 0;
// Copy the current Address Space's higher half
for(size_t i = 255; i < 512; i++)
NewPML4[i] = AddressSpace->PML4[i];
// Identity map the bottom two megabytes into the higher half
for(size_t i = 0; i < 8192; i++) {
// Get page offset
size_t Addr = i * 4096;
// Identity map
MapVirtualPage(&TempAddressSpace, Addr, Addr, DEFAULT_PAGE_FLAGS);
// Map higher half
MapVirtualPage(&TempAddressSpace, Addr, TO_DIRECT(Addr), DEFAULT_PAGE_FLAGS);
// TODO: Map into kernel space
}
// Identity map the next 4gb
for(size_t i = 8192; i < 0x100000; i++) {
size_t Addr = i * 4096;
MapVirtualPage(&TempAddressSpace, Addr, Addr, DEFAULT_PAGE_FLAGS);
}
return NewPML4;
}