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Fix paging breaking on VirtualBox. Dynamically figure out the starting location.

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This commit is contained in:
Curle 2021-06-12 01:49:43 +01:00
parent 54559a977d
commit 77933c3aa4
Signed by: TheCurle
GPG Key ID: 5942F13718443F79
1 changed files with 36 additions and 35 deletions
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71
chroma/system/memory/paging.c
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@ -25,7 +25,7 @@ size_t KernelLocation;
/**
* Bootstrap the paging process.
* Seeds the page tables, maps the kernel and framebuffer, etc.
*
*
*/
void InitPaging() {
@ -39,16 +39,17 @@ void InitPaging() {
.PML4 = (size_t*) ReadControlRegister(3)
};
size_t AddressToFind = (size_t) &fb;
size_t AddressToFind = KernelAddr + 0x2000;
size_t BootldrAddress = 0x8000;
KernelLocation = DecodeVirtualAddressNoDirect(&BootloaderAddressSpace, AddressToFind);
SerialPrintf("[ Mem] Double check: Kernel physically starts at 0x%p (0x%p), ends at 0x%p.\r\n", KernelLocation, AddressToFind, KERNEL_END);
SerialPrintf("[ Mem] Identity mapping the entirety of physical memory\r\n");
for(size_t i = 0; i < MemorySize / PAGE_SIZE; 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 0x%x bytes of bootloader structure, starting at 0x%p\r\n", bootldr.size, BootldrAddress);
@ -56,9 +57,11 @@ void InitPaging() {
MapVirtualPageNoDirect(&KernelAddressSpace, i, KERNEL_REGION + (i - BootldrAddress), 0x3);
// This allows the code to actually run
SerialPrintf("[ Mem] Mapping 0x%x bytes of kernel, starting at 0x%p\r\n", KernelEnd - KernelAddr, KERNEL_PHYSICAL + KERNEL_TEXT);
for(size_t i = KERNEL_PHYSICAL + KERNEL_TEXT; i < (KernelEnd - KernelAddr) + KERNEL_PHYSICAL; i += PAGE_SIZE)
MapVirtualPageNoDirect(&KernelAddressSpace, i, (i - KERNEL_PHYSICAL) + KERNEL_REGION, 0x3);
SerialPrintf("[ Mem] Mapping 0x%x bytes of kernel, starting at 0x%p\r\n", KERNEL_END - KERNEL_PHYSICAL, KERNEL_PHYSICAL);
for(size_t i = KERNEL_PHYSICAL; i < KERNEL_END; i += PAGE_SIZE)
MapVirtualPageNoDirect(&KernelAddressSpace, i, (i - KERNEL_PHYSICAL) + KERNEL_REGION + KERNEL_TEXT, 0x3);
// TODO: The above mapping loses the ELF header.
// This allows us to write to the screen
SerialPrintf("[ Mem] Mapping 0x%x bytes of framebuffer, starting at 0x%p\r\n", bootldr.fb_size, FB_PHYSICAL);
@ -66,7 +69,7 @@ void InitPaging() {
MapVirtualPageNoDirect(&KernelAddressSpace, i, i, 0x3); // FD000000 + (page)
MapVirtualPageNoDirect(&KernelAddressSpace, i, (i - FB_PHYSICAL) + FB_REGION, 0x3); // FFFFFFFFFC000000 + (page)
}
// This allows us to call functions
SerialPrintf("[ Mem] Mapping stack\r\n");
MapVirtualPageNoDirect(&KernelAddressSpace, CORE_STACK_PHYSICAL, STACK_TOP, 0x3);
@ -74,13 +77,11 @@ void InitPaging() {
// Make sure everything is sane
SerialPrintf("[ Mem] Diagnostic: Querying existing page tables\r\n");
AddressToFind = (size_t) &(bootldr);
size_t BootloaderAddress = DecodeVirtualAddressNoDirect(&BootloaderAddressSpace, AddressToFind);
size_t KernelDisoveredAddress = DecodeVirtualAddressNoDirect(&KernelAddressSpace, AddressToFind);
SerialPrintf("[ Mem] Diagnostic: Existing pagetables put 0x%p at 0x%p + 0x%p.\r\n", AddressToFind, BootloaderAddress, AddressToFind & ~STACK_TOP);
SerialPrintf("[ Mem] Diagnostic: Our pagetables put 0x%p at 0x%p + 0x%p.\r\n", AddressToFind, KernelDisoveredAddress, AddressToFind & ~STACK_TOP);
SerialPrintf("[ Mem] %s\r\n", BootloaderAddress == KernelDisoveredAddress ? "These match. Continuing." : "These do not match. Continuing with caution..");
size_t KernelAddress = DecodeVirtualAddressNoDirect(&KernelAddressSpace, AddressToFind);
SerialPrintf("[ Mem] Diagnostic: Our pagetables put 0x%p at 0x%p + 0x%p.\r\n", AddressToFind, KernelAddress, AddressToFind & ~STACK_TOP);
SerialPrintf("[ Mem] Diagnostic: Existing pagetables put 0x%p at 0x%p + 0x%p.\r\n", AddressToFind, KERNEL_PHYSICAL, AddressToFind & ~STACK_TOP);
SerialPrintf("[ Mem] %s\r\n", KernelAddress == KERNEL_PHYSICAL ? "These match. Continuing." : "These do not match. Continuing with caution..");
//if(BootloaderAddress != KernelDisoveredAddress)
//for(;;) {}
@ -92,14 +93,14 @@ void InitPaging() {
/**
* 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) {
@ -109,13 +110,13 @@ size_t ConstructVirtualAddress(size_t pdpt, size_t pdp, size_t pde, size_t pt) {
/**
* 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
@ -126,17 +127,17 @@ size_t DecodeVirtualAddress(address_space_t* AddressSpace, size_t 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
@ -149,7 +150,7 @@ size_t DecodeVirtualAddress(address_space_t* AddressSpace, size_t VirtualAddress
* 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
@ -195,16 +196,16 @@ void MapVirtualPage(address_space_t* AddressSpace, size_t Physical, size_t Virtu
/**
* 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
@ -215,17 +216,17 @@ size_t DecodeVirtualAddressNoDirect(address_space_t* AddressSpace, size_t Virtua
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
@ -238,10 +239,10 @@ size_t DecodeVirtualAddressNoDirect(address_space_t* AddressSpace, size_t Virtua
* 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
@ -289,7 +290,7 @@ void MapVirtualPageNoDirect(address_space_t* AddressSpace, size_t Physical, size
* 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
*/
@ -302,13 +303,13 @@ size_t* CreateNewPageTable(address_space_t* AddressSpace) {
};
// Initialize to zeros
for(size_t i = 0; i < 512; i++)
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