init: Add basic virtual memory code

Some thread variables don't need to be set manually,
since they are updated whenever needed by some functions.
Add comments to make that clear.

core/src/arch/cpu.zig

@@ -20,7 +20,8 @@ pub fn setupCore(allocator: *pmm.FrameAllocator) !void {
 
     const core: *arch.Core = @ptrFromInt(frame.virtualAddress(vmm.PHYSICAL_MAPPING_BASE));
     core.id = 0; // FIXME: Actually check core id
-    core.thread_list = .{};
+    core.active_thread_list = .{};
+    core.sleeping_thread_list = .{};
 
     const idle_thread = &core.idle_thread.data;
 

core/src/arch/x86_64/cpu.zig

@@ -1,3 +1,3 @@
 const thread = @import("../../thread.zig");
 
-pub const Core = struct { id: u32, thread_list: thread.ThreadList, current_thread: *thread.ThreadControlBlock, idle_thread: thread.ThreadList.Node };
+pub const Core = struct { id: u32, active_thread_list: thread.ThreadList, sleeping_thread_list: thread.ThreadList, current_thread: *thread.ThreadControlBlock, idle_thread: thread.ThreadList.Node };

core/src/arch/x86_64/thread.zig

@@ -51,8 +51,9 @@ pub fn setAddress(regs: *interrupts.InterruptStackFrame, address: u64) void {
     regs.rip = address;
 }
 
-pub fn setArgument(regs: *interrupts.InterruptStackFrame, argument: u64) void {
-    regs.rdi = argument;
+pub fn setArguments(regs: *interrupts.InterruptStackFrame, arg0: u64, arg1: u64) void {
+    regs.rdi = arg0;
+    regs.rsi = arg1;
 }
 
 pub fn setStack(regs: *interrupts.InterruptStackFrame, stack: u64) void {

core/src/arch/x86_64/vmm.zig

@@ -23,11 +23,11 @@ pub const PageTableEntry = packed struct {
     available2: u3,
     no_execute: u1,
 
-    pub fn set_address(self: *PageTableEntry, address: u64) void {
+    pub fn setAddress(self: *PageTableEntry, address: u64) void {
         self.address = @intCast(address >> 12);
     }
 
-    pub fn get_address(self: *PageTableEntry) u64 {
+    pub fn getAddress(self: *PageTableEntry) u64 {
         return self.address << 12;
     }
 
@@ -86,7 +86,7 @@ fn updatePageTableEntry(entry: *PageTableEntry, phys: pmm.PhysFrame, flags: u32)
     entry.cache_disabled = hasFlag(flags, Flags.CacheDisable);
     entry.no_execute = hasFlag(flags, Flags.NoExecute);
     entry.global = hasFlag(flags, Flags.Global);
-    entry.set_address(phys.address);
+    entry.setAddress(phys.address);
 }
 
 fn setUpParentPageTableEntry(allocator: *pmm.FrameAllocator, pte: *PageTableEntry, flags: u32, base: usize) !void {
@@ -94,7 +94,7 @@ fn setUpParentPageTableEntry(allocator: *pmm.FrameAllocator, pte: *PageTableEntr
         pte.clear();
         const frame = try pmm.allocFrame(allocator);
         pte.present = 1;
-        pte.set_address(frame.address);
+        pte.setAddress(frame.address);
         getTable(pte, base).* = std.mem.zeroes(PageDirectory);
     }
     if (hasFlag(flags, Flags.ReadWrite) == 1) pte.read_write = 1;
@@ -102,7 +102,7 @@ fn setUpParentPageTableEntry(allocator: *pmm.FrameAllocator, pte: *PageTableEntr
 }
 
 fn getTable(pte: *PageTableEntry, base: usize) *allowzero PageDirectory {
-    const frame = pmm.PhysFrame{ .address = pte.get_address() };
+    const frame = pmm.PhysFrame{ .address = pte.getAddress() };
     return @ptrFromInt(frame.virtualAddress(base));
 }
 
@@ -160,7 +160,7 @@ pub fn copyToUser(mapper: MemoryMapper, base: usize, user: usize, kernel: [*]con
 
     if (user_address != user_page) {
         const pte = getEntry(mapper, base, user_page) orelse return error.MemoryNotInUse;
-        const frame = pmm.PhysFrame{ .address = pte.get_address() };
+        const frame = pmm.PhysFrame{ .address = pte.getAddress() };
         const amount: usize = @min((platform.PAGE_SIZE - remainder), count);
         const virt = frame.virtualAddress(base) + remainder;
 
@@ -173,7 +173,7 @@ pub fn copyToUser(mapper: MemoryMapper, base: usize, user: usize, kernel: [*]con
 
     while (count > 0) {
         const pte = getEntry(mapper, base, user_address) orelse return error.MemoryNotInUse;
-        const frame = pmm.PhysFrame{ .address = pte.get_address() };
+        const frame = pmm.PhysFrame{ .address = pte.getAddress() };
         const amount: usize = @min(platform.PAGE_SIZE, count);
         const virt = frame.virtualAddress(base);
 
@@ -196,7 +196,7 @@ pub fn memsetUser(mapper: MemoryMapper, base: usize, user: usize, elem: u8, size
 
     if (user_address != user_page) {
         const pte = getEntry(mapper, base, user_page) orelse return error.MemoryNotInUse;
-        const frame = pmm.PhysFrame{ .address = pte.get_address() };
+        const frame = pmm.PhysFrame{ .address = pte.getAddress() };
         const amount: usize = @min((platform.PAGE_SIZE - remainder), count);
         const virt = frame.virtualAddress(base) + remainder;
 
@@ -208,7 +208,7 @@ pub fn memsetUser(mapper: MemoryMapper, base: usize, user: usize, elem: u8, size
 
     while (count > 0) {
         const pte = getEntry(mapper, base, user_address) orelse return error.MemoryNotInUse;
-        const frame = pmm.PhysFrame{ .address = pte.get_address() };
+        const frame = pmm.PhysFrame{ .address = pte.getAddress() };
         const amount: usize = @min(platform.PAGE_SIZE, count);
         const virt = frame.virtualAddress(base);
 
@@ -251,9 +251,9 @@ fn lockPageDirectoryFrames(allocator: *pmm.FrameAllocator, directory: *PageDirec
             if (pte.present == 0) continue;
             if ((index < 4) and (pte.larger_pages == 1)) continue;
 
-            try pmm.lockFrame(allocator, pte.get_address());
+            try pmm.lockFrame(allocator, pte.getAddress());
 
-            const child_table: *PageDirectory = @ptrFromInt(pte.get_address());
+            const child_table: *PageDirectory = @ptrFromInt(pte.getAddress());
 
             try lockPageDirectoryFrames(allocator, child_table, index - 1);
         }

core/src/main.zig

@@ -71,9 +71,7 @@ export fn _start(magic: u32, info: MultibootInfo) callconv(.C) noreturn {
     init.mapper = mapper;
     init.user_priority = 255;
     thread.arch.initUserRegisters(&init.regs);
-    thread.arch.setArgument(&init.regs, base);
-
-    thread.addThreadToScheduler(cpu.thisCore(), init);
+    thread.arch.setArguments(&init.regs, base, mapper.phys.address);
 
     const ctx = Context{ .allocator = &allocator, .mapper = mapper, .regs = &init.regs };
 

core/src/sys/sched.zig

@@ -19,3 +19,7 @@ pub fn getPriority(_: *interrupts.InterruptStackFrame, _: *sys.Arguments, retval
     const core = cpu.thisCore();
     retval.* = core.current_thread.user_priority;
 }
+
+pub fn sleep(regs: *interrupts.InterruptStackFrame, args: *sys.Arguments, _: *isize) anyerror!void {
+    _ = thread.startSleep(regs, args.arg0);
+}

core/src/sys/syscall.zig

@@ -15,7 +15,7 @@ pub const Arguments = struct {
 
 const SystemCall = *const fn (frame: *interrupts.InterruptStackFrame, args: *Arguments, retval: *isize) anyerror!void;
 
-const syscalls = [_]SystemCall{ print, mem.allocFrame, mem.lockFrame, mem.freeFrame, sched.yield, sched.setPriority, sched.getPriority };
+const syscalls = [_]SystemCall{ print, mem.allocFrame, mem.lockFrame, mem.freeFrame, sched.yield, sched.setPriority, sched.getPriority, sched.sleep };
 
 pub fn invokeSyscall(number: usize, frame: *interrupts.InterruptStackFrame, args: *Arguments, retval: *isize) void {
     if (number >= syscalls.len) {

core/src/thread.zig

@@ -9,6 +9,7 @@ pub const ThreadState = enum {
     Inactive,
     Running,
     Blocked,
+    Sleeping,
 };
 
 pub const ThreadControlBlock = struct {
@@ -16,11 +17,14 @@ pub const ThreadControlBlock = struct {
     mapper: ?vmm.MemoryMapper,
     regs: interrupts.InterruptStackFrame,
     state: ThreadState,
-
-    ticks: u64,
-
     user_priority: u8,
+
+    // Managed by scheduleNewTask(), no need to set manually.
+    ticks: u64,
+    // Managed by addThreadToPriorityQueue(), no need to set manually.
     current_priority: u32,
+    // Managed by startSleep(), no need to set manually.
+    sleep_ticks: u64,
 };
 
 pub const ThreadList = std.DoublyLinkedList(ThreadControlBlock);
@@ -41,7 +45,7 @@ pub fn enterTask(task: *ThreadControlBlock) noreturn {
     arch.enterTask(&task.regs, vmm.PHYSICAL_MAPPING_BASE, directory.address);
 }
 
-pub fn switchTask(regs: *interrupts.InterruptStackFrame, new_task: *ThreadControlBlock) void {
+fn switchTask(regs: *interrupts.InterruptStackFrame, new_task: *ThreadControlBlock) void {
     const core = cpu.thisCore();
 
     core.current_thread.regs = regs.*;
@@ -57,7 +61,7 @@ pub fn switchTask(regs: *interrupts.InterruptStackFrame, new_task: *ThreadContro
 }
 
 pub fn fetchNewTask(core: *cpu.arch.Core, should_idle_if_not_found: bool) ?*ThreadControlBlock {
-    const last = core.thread_list.last orelse {
+    const last = core.active_thread_list.last orelse {
         if (should_idle_if_not_found) {
             return &core.idle_thread.data;
         } else return null;
@@ -71,7 +75,7 @@ pub fn fetchNewTask(core: *cpu.arch.Core, should_idle_if_not_found: bool) ?*Thre
 }
 
 pub fn scheduleNewTask(core: *cpu.arch.Core, regs: *interrupts.InterruptStackFrame, new_thread: *ThreadControlBlock) *ThreadControlBlock {
-    if (core.thread_list.first) |first| {
+    if (core.active_thread_list.first) |first| {
         first.data.current_priority +|= 4;
     }
 
@@ -85,6 +89,11 @@ pub fn scheduleNewTask(core: *cpu.arch.Core, regs: *interrupts.InterruptStackFra
 pub fn preempt(regs: *interrupts.InterruptStackFrame) void {
     const core = cpu.thisCore();
 
+    updateSleepQueue(core);
+    while (popSleepQueue(core)) |thread| {
+        reviveThread(core, thread);
+    }
+
     core.current_thread.ticks -|= 1;
     if (core.current_thread.ticks == 0) {
         const new_thread = fetchNewTask(core, false) orelse return;
@@ -93,12 +102,81 @@ pub fn preempt(regs: *interrupts.InterruptStackFrame) void {
     }
 }
 
-var next_id: std.atomic.Value(u64) = std.atomic.Value(u64).init(1);
+pub fn block(regs: *interrupts.InterruptStackFrame) *ThreadControlBlock {
+    const core = cpu.thisCore();
 
-pub fn addThreadToScheduler(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
+    // fetchNewTask() always returns a thread if should_idle_if_not_found is set to true.
+    const new_thread = fetchNewTask(core, true) orelse unreachable;
+    const current_thread = scheduleNewTask(core, regs, new_thread);
+    current_thread.state = .Blocked;
+
+    return current_thread;
+}
+
+pub fn startSleep(regs: *interrupts.InterruptStackFrame, ticks: u64) *ThreadControlBlock {
+    const core = cpu.thisCore();
+
+    // fetchNewTask() always returns a thread if should_idle_if_not_found is set to true.
+    const new_thread = fetchNewTask(core, true) orelse unreachable;
+    const current_thread = scheduleNewTask(core, regs, new_thread);
+    current_thread.state = .Sleeping;
+    addThreadToSleepQueue(core, current_thread, ticks);
+
+    return current_thread;
+}
+
+fn addThreadToSleepQueue(core: *cpu.arch.Core, thread: *ThreadControlBlock, ticks: u64) void {
+    thread.sleep_ticks = ticks;
+
+    var it: ?*ThreadList.Node = core.sleeping_thread_list.first;
+    while (it) |n| : (it = n.next) {
+        if (thread.sleep_ticks <= n.data.sleep_ticks) {
+            n.data.sleep_ticks -|= thread.sleep_ticks;
+            core.sleeping_thread_list.insertBefore(n, @fieldParentPtr("data", thread));
+            return;
+        }
+        thread.sleep_ticks -|= n.data.sleep_ticks;
+    }
+
+    core.sleeping_thread_list.append(@fieldParentPtr("data", thread));
+}
+
+pub fn removeThreadFromSleepQueue(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
+    const node: *ThreadList.Node = @fieldParentPtr("data", thread);
+
+    if (node.next) |n| {
+        n.data.sleep_ticks +|= thread.sleep_ticks;
+    }
+
+    core.sleeping_thread_list.remove(node);
+
+    reviveThread(core, thread);
+}
+
+fn updateSleepQueue(core: *cpu.arch.Core) void {
+    const first = core.sleeping_thread_list.first orelse return;
+
+    first.data.sleep_ticks -|= 1;
+}
+
+fn popSleepQueue(core: *cpu.arch.Core) ?*ThreadControlBlock {
+    const first = core.sleeping_thread_list.first orelse return null;
+
+    if (first.data.sleep_ticks == 0) {
+        core.sleeping_thread_list.remove(first);
+        return &first.data;
+    }
+
+    return null;
+}
+
+pub fn reviveThread(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
+    thread.state = .Running;
     addThreadToPriorityQueue(core, thread);
 }
 
+var next_id: std.atomic.Value(u64) = std.atomic.Value(u64).init(1);
+
 pub fn createThreadControlBlock(allocator: *pmm.FrameAllocator) !*ThreadControlBlock {
     const frame = try pmm.allocFrame(allocator);
 
@@ -116,25 +194,25 @@ pub fn createThreadControlBlock(allocator: *pmm.FrameAllocator) !*ThreadControlB
 pub fn addThreadToPriorityQueue(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
     thread.current_priority = thread.user_priority;
 
-    var it: ?*ThreadList.Node = core.thread_list.first;
+    var it: ?*ThreadList.Node = core.active_thread_list.first;
     while (it) |n| : (it = n.next) {
         if (thread.current_priority <= n.data.current_priority) {
             n.data.current_priority -|= thread.current_priority;
-            core.thread_list.insertBefore(n, @fieldParentPtr("data", thread));
+            core.active_thread_list.insertBefore(n, @fieldParentPtr("data", thread));
             return;
         }
         thread.current_priority -|= n.data.current_priority;
     }
 
-    core.thread_list.append(@fieldParentPtr("data", thread));
+    core.active_thread_list.append(@fieldParentPtr("data", thread));
 }
 
-pub fn removeThreadFromPriorityQueue(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
+fn removeThreadFromPriorityQueue(core: *cpu.arch.Core, thread: *ThreadControlBlock) void {
     const node: *ThreadList.Node = @fieldParentPtr("data", thread);
 
     if (node.next) |n| {
         n.data.current_priority +|= thread.current_priority;
     }
 
-    core.thread_list.remove(node);
+    core.active_thread_list.remove(node);
 }

system/init/arch/vm.zig

@@ -0,0 +1,9 @@
+const std = @import("std");
+const target = @import("builtin").target;
+
+pub const arch = switch (target.cpu.arch) {
+    .x86_64 => @import("x86_64/vm.zig"),
+    else => {
+        @compileError("unsupported architecture");
+    },
+};

system/init/arch/x86_64/vm.zig

@@ -0,0 +1,182 @@
+const std = @import("std");
+const kernel = @import("../../kernel.zig");
+
+const MapError = error{
+    MemoryAlreadyInUse,
+    MemoryNotInUse,
+    OutOfMemory,
+};
+
+const PhysFrame = struct {
+    address: u64,
+
+    pub fn virtualAddress(self: *const PhysFrame, base: usize) usize {
+        return base + self.address;
+    }
+
+    pub fn virtualPointer(self: *const PhysFrame, comptime T: type, base: usize) *T {
+        return @ptrFromInt(self.virtualAddress(base));
+    }
+};
+
+const PageTableEntry = packed struct {
+    present: u1,
+    read_write: u1,
+    user: u1,
+    write_through: u1,
+    cache_disabled: u1,
+    accessed: u1,
+    reserved: u1,
+    larger_pages: u1,
+    global: u1,
+    available: u3,
+    address: u48,
+    available2: u3,
+    no_execute: u1,
+
+    pub fn setAddress(self: *PageTableEntry, address: u64) void {
+        self.address = @intCast(address >> 12);
+    }
+
+    pub fn getAddress(self: *PageTableEntry) u64 {
+        return self.address << 12;
+    }
+
+    pub fn clear(self: *PageTableEntry) void {
+        self.* = std.mem.zeroes(PageTableEntry);
+    }
+};
+
+const PageDirectory = struct {
+    entries: [512]PageTableEntry,
+};
+
+pub const Flags = enum(u32) {
+    None = 0,
+    ReadWrite = 1,
+    User = 2,
+    NoExecute = 4,
+    WriteThrough = 8,
+    CacheDisable = 16,
+    Global = 32,
+};
+
+const PageTableIndexes = struct {
+    level4: u24,
+    level3: u24,
+    level2: u24,
+    level1: u24,
+};
+
+pub const MemoryMapper = struct {
+    cr3: PhysFrame,
+    directory: *PageDirectory,
+    base: u64,
+
+    pub fn create(frame: PhysFrame, base: usize) MemoryMapper {
+        return .{ .cr3 = frame, .directory = frame.virtualPointer(PageDirectory, base), .base = base };
+    }
+};
+
+fn calculatePageTableIndexes(address: usize) PageTableIndexes {
+    return .{ .level4 = @intCast((address >> 39) & 0o777), .level3 = @intCast((address >> 30) & 0o777), .level2 = @intCast((address >> 21) & 0o777), .level1 = @intCast((address >> 12) & 0o777) };
+}
+
+fn hasFlag(flags: u32, flag: Flags) u1 {
+    return switch ((flags & @intFromEnum(flag)) > 0) {
+        true => 1,
+        false => 0,
+    };
+}
+
+fn updatePageTableEntry(entry: *PageTableEntry, phys: PhysFrame, flags: u32) void {
+    entry.clear();
+    entry.present = 1;
+    entry.read_write = hasFlag(flags, Flags.ReadWrite);
+    entry.user = hasFlag(flags, Flags.User);
+    entry.write_through = hasFlag(flags, Flags.WriteThrough);
+    entry.cache_disabled = hasFlag(flags, Flags.CacheDisable);
+    entry.no_execute = hasFlag(flags, Flags.NoExecute);
+    entry.global = hasFlag(flags, Flags.Global);
+    entry.setAddress(phys.address);
+}
+
+fn setUpParentPageTableEntry(mapper: *const MemoryMapper, pte: *PageTableEntry, flags: u32) !void {
+    if (pte.present == 0) {
+        pte.clear();
+        const frame = PhysFrame{ .address = try kernel.allocFrame() };
+        pte.present = 1;
+        pte.setAddress(frame.address);
+        getTable(pte, mapper.base).* = std.mem.zeroes(PageDirectory);
+    }
+    if (hasFlag(flags, Flags.ReadWrite) == 1) pte.read_write = 1;
+    if (hasFlag(flags, Flags.User) == 1) pte.user = 1;
+}
+
+fn getTable(mapper: *const MemoryMapper, pte: *PageTableEntry) *PageDirectory {
+    const frame = PhysFrame{ .address = pte.getAddress() };
+    return frame.virtualPointer(PageDirectory, mapper.base);
+}
+
+pub fn map(mapper: *const MemoryMapper, virt_address: u64, phys: PhysFrame, flags: u32) !void {
+    const indexes = calculatePageTableIndexes(virt_address);
+    const l4 = &mapper.directory.entries[indexes.level4];
+    try setUpParentPageTableEntry(mapper, l4, flags);
+
+    const l3 = &getTable(mapper, l4).entries[indexes.level3];
+    if (l3.larger_pages == 1) return error.MemoryAlreadyInUse;
+    try setUpParentPageTableEntry(mapper, l3, flags);
+
+    const l2 = &getTable(mapper, l3).entries[indexes.level2];
+    if (l2.larger_pages == 1) return error.MemoryAlreadyInUse;
+    try setUpParentPageTableEntry(mapper, l2, flags);
+
+    const l1 = &getTable(mapper, l2).entries[indexes.level1];
+    if (l1.present == 1) return error.MemoryAlreadyInUse;
+    updatePageTableEntry(l1, phys, flags);
+}
+
+pub fn remap(mapper: *const MemoryMapper, virt_address: u64, phys: ?PhysFrame, flags: u32) !PhysFrame {
+    const entry = getEntry(mapper, virt_address) orelse return error.MemoryNotInUse;
+    const old_frame = PhysFrame{ .address = entry.getAddress() };
+    const frame = phys orelse old_frame;
+
+    updatePageTableEntry(entry, frame, flags);
+
+    return old_frame;
+}
+
+pub fn unmap(mapper: *const MemoryMapper, virt_address: u64) !PhysFrame {
+    const entry = getEntry(mapper, virt_address) orelse return error.MemoryNotInUse;
+
+    const frame = PhysFrame{ .address = entry.getAddress() };
+
+    entry.clear();
+
+    return frame;
+}
+
+pub fn getEntry(mapper: MemoryMapper, virt_address: u64) ?*PageTableEntry {
+    const indexes = calculatePageTableIndexes(virt_address);
+    const l4 = &mapper.directory.entries[indexes.level4];
+    if (l4.present == 0) return null;
+
+    const l3 = &getTable(mapper, l4).entries[indexes.level3];
+    if (l3.present == 0) return null;
+    if (l3.larger_pages == 1) return l3;
+
+    const l2 = &getTable(mapper, l3).entries[indexes.level2];
+    if (l2.present == 0) return null;
+    if (l2.larger_pages == 1) return l2;
+
+    const l1 = &getTable(mapper, l2).entries[indexes.level1];
+    if (l1.present == 0) return null;
+
+    return l1;
+}
+
+pub fn getPhysical(mapper: MemoryMapper, virt_address: u64) ?PhysFrame {
+    const entry = getEntry(mapper, virt_address) orelse return null;
+
+    return PhysFrame{ .address = entry.getAddress() };
+}

system/init/kernel.zig

@@ -6,6 +6,7 @@ const SystemCall = enum(u64) {
     Yield,
     SetPriority,
     GetPriority,
+    Sleep,
 };
 
 const SystemError = error{
@@ -49,3 +50,7 @@ pub fn setPriority(priority: u8) void {
 pub fn getPriority() u8 {
     return @truncate(@as(u64, @bitCast(syscall(.GetPriority, 0))));
 }
+
+pub fn sleep(ms: u64) void {
+    _ = syscall(.Sleep, ms);
+}

system/init/main.zig

@@ -1,13 +1,19 @@
 const kernel = @import("kernel.zig");
+const vm = @import("arch/vm.zig").arch;
+
+export fn _start(base: u64, address: u64) callconv(.C) noreturn {
+    const mapper = vm.MemoryMapper.create(.{ .address = address }, base);
 
-export fn _start(base: u64) callconv(.C) noreturn {
     kernel.print(base);
-    kernel.print(kernel.getPriority());
+    kernel.print(address);
+    kernel.print(@intFromPtr(mapper.directory));
 
-    kernel.setPriority(128);
-    kernel.print(kernel.getPriority());
+    vm.map(&mapper, 0x6000000, kernel.allocFrame(), @intFromEnum(vm.Flags.ReadWrite) | @intFromEnum(vm.Flags.User));
 
-    while (true) {
-        kernel.yield();
+    var counter: u64 = 0;
+
+    while (true) : (counter += 4) {
+        kernel.sleep(1000);
+        kernel.print(counter);
     }
 }