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core: Fix a couple of bugs in VMM and add a few utility functions

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This commit is contained in:
Gabriel 2025-02-15 22:23:00 +01:00
parent f93158645b
commit 56f2c018a7
1 changed files with 114 additions and 5 deletions
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119
core/src/arch/x86_64/vmm.zig
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@ -2,9 +2,10 @@ const std = @import("std");
const easyboot = @cImport(@cInclude("easyboot.h"));
const mmap = @import("../../mmap.zig");
const pmm = @import("../../pmm.zig");
const platform = @import("platform.zig");
const USER_ADDRESS_RANGE_END = 0x0000_7fff_ffff_ffff;
const PHYSICAL_MAPPING_BASE = 0xffff_8000_0000_0000;
pub const PHYSICAL_MAPPING_BASE = 0xffff_8000_0000_0000;
const HUGE_PAGE_SIZE = 0x200000; // 2 MiB
pub const PageTableEntry = packed struct {
@ -14,7 +15,7 @@ pub const PageTableEntry = packed struct {
write_through: u1,
cache_disabled: u1,
accessed: u1,
ignore0: u1,
reserved: u1,
larger_pages: u1,
global: u1,
available: u3,
@ -31,7 +32,7 @@ pub const PageTableEntry = packed struct {
}
pub fn clear(self: *PageTableEntry) void {
self = std.mem.zeroes(@TypeOf(self));
self.* = std.mem.zeroes(PageTableEntry);
}
};
@ -39,7 +40,7 @@ pub const PageDirectory = struct {
entries: [512]PageTableEntry,
};
const Flags = enum(u32) {
pub const Flags = enum(u32) {
None = 0,
ReadWrite = 1,
User = 2,
@ -68,6 +69,7 @@ fn hasFlag(flags: u32, flag: Flags) u1 {
}
fn updatePageTableEntry(entry: *PageTableEntry, phys: pmm.PhysFrame, flags: u32) void {
entry.clear();
entry.present = 1;
entry.read_write = hasFlag(flags, Flags.ReadWrite);
entry.user = hasFlag(flags, Flags.User);
@ -80,6 +82,7 @@ fn updatePageTableEntry(entry: *PageTableEntry, phys: pmm.PhysFrame, flags: u32)
fn setUpParentPageTableEntry(allocator: *pmm.FrameAllocator, pte: *PageTableEntry, flags: u32, base: usize) !void {
if (pte.present == 0) {
pte.clear();
const frame = try pmm.allocFrame(allocator);
pte.present = 1;
pte.set_address(frame.address);
@ -107,8 +110,8 @@ pub fn map(allocator: *pmm.FrameAllocator, directory: *PageDirectory, base: usiz
if (l2.larger_pages == 1) return error.MemoryAlreadyInUse;
if (use_huge_pages) {
l2.larger_pages = 1;
updatePageTableEntry(l2, phys, flags);
l2.larger_pages = 1;
return;
}
@ -119,6 +122,108 @@ pub fn map(allocator: *pmm.FrameAllocator, directory: *PageDirectory, base: usiz
updatePageTableEntry(l1, phys, flags);
}
pub fn getEntry(directory: *PageDirectory, base: usize, virt_address: u64) ?*PageTableEntry {
const indexes = calculatePageTableIndexes(virt_address);
const l4 = &directory.entries[indexes.level4];
if (l4.present == 0) return null;
const l3 = &getTable(l4, base).entries[indexes.level3];
if (l3.present == 0) return null;
if (l3.larger_pages == 1) return l3;
const l2 = &getTable(l3, base).entries[indexes.level2];
if (l2.present == 0) return null;
if (l2.larger_pages == 1) return l2;
const l1 = &getTable(l2, base).entries[indexes.level1];
if (l1.present == 0) return null;
return l1;
}
pub fn copyToUser(directory: *PageDirectory, base: usize, user: usize, kernel: [*]const u8, size: usize) !void {
const remainder: usize = @rem(user, platform.PAGE_SIZE);
const user_page = user - remainder;
var user_address = user;
var kernel_ptr = kernel;
var count = size;
if (user_address != user_page) {
const pte = getEntry(directory, base, user_page) orelse return error.MemoryNotInUse;
const frame = pmm.PhysFrame{ .address = pte.get_address() };
const amount: usize = @min((platform.PAGE_SIZE - remainder), count);
const virt = frame.virtualAddress(base) + remainder;
@memcpy(@as([*]u8, @ptrFromInt(virt))[0..amount], kernel_ptr[0..amount]);
kernel_ptr += amount;
user_address += amount;
count -= amount;
}
while (count > 0) {
const pte = getEntry(directory, base, user_address) orelse return error.MemoryNotInUse;
const frame = pmm.PhysFrame{ .address = pte.get_address() };
const amount: usize = @min(platform.PAGE_SIZE, count);
const virt = frame.virtualAddress(base);
@memcpy(@as([*]u8, @ptrFromInt(virt))[0..amount], kernel_ptr[0..amount]);
kernel_ptr += amount;
user_address += amount;
count -= amount;
}
return;
}
pub fn memsetUser(directory: *PageDirectory, base: usize, user: usize, elem: u8, size: usize) !void {
const remainder: usize = @rem(user, platform.PAGE_SIZE);
const user_page = user - remainder;
var user_address = user;
var count = size;
if (user_address != user_page) {
const pte = getEntry(directory, base, user_page) orelse return error.MemoryNotInUse;
const frame = pmm.PhysFrame{ .address = pte.get_address() };
const amount: usize = @min((platform.PAGE_SIZE - remainder), count);
const virt = frame.virtualAddress(base) + remainder;
@memset(@as([*]u8, @ptrFromInt(virt))[0..amount], elem);
user_address += amount;
count -= amount;
}
while (count > 0) {
const pte = getEntry(directory, base, user_address) orelse return error.MemoryNotInUse;
const frame = pmm.PhysFrame{ .address = pte.get_address() };
const amount: usize = @min(platform.PAGE_SIZE, count);
const virt = frame.virtualAddress(base);
@memset(@as([*]u8, @ptrFromInt(virt))[0..amount], elem);
user_address += amount;
count -= amount;
}
return;
}
pub fn allocAndMap(allocator: *pmm.FrameAllocator, directory: *PageDirectory, base: u64, pages: usize, flags: u32) !void {
var virt = base;
var i: usize = 0;
while (i < pages) {
const frame = try pmm.allocFrame(allocator);
try map(allocator, directory, PHYSICAL_MAPPING_BASE, virt, frame, flags, false);
virt += platform.PAGE_SIZE;
i += 1;
}
}
fn mapPhysicalMemory(allocator: *pmm.FrameAllocator, tag: *easyboot.multiboot_tag_mmap_t, directory: *PageDirectory, base: usize, flags: u32) !void {
const address_space_size = mmap.getAddressSpaceSize(tag) orelse return error.InvalidMemoryMap;
const address_space_pages = address_space_size / HUGE_PAGE_SIZE;
@ -195,6 +300,10 @@ pub fn readPageDirectory() *PageDirectory {
return directory;
}
pub fn getPhysicalPageDirectory(directory: *PageDirectory) *PageDirectory {
return @ptrFromInt(@intFromPtr(directory) - @as(usize, PHYSICAL_MAPPING_BASE));
}
pub fn setPageDirectory(directory: *PageDirectory) void {
asm volatile ("mov %[dir], %%cr3"
: