bump allocator implemented

README.md

@@ -9,20 +9,21 @@ slowly porting from rust.
  - interrupts
  - terminal console
  - lspci
- - todo: memory mapping
- - todo: cfs scheduler
- - todo: smp
 
 ### dependencies
 
-`ziglang` compiler
+`zig` compiler
 
 ### compile
 
-`zig build` compile and links a multiboot kernel, without a bootloader.
+`zig build` compiles and links the multiboot kernel, without a bootloader.
 
 ### test
 
-`./run.sh qemu start`
-`./run.sh qemu monitor`
-`./run.sh gdb`
+`./qemu.sh start`  
+`./qemu.sh monitor`  
+`./qemu.sh gdb`  
+
+### todo
+
+- recycling allocator that wraps the bump allocator

qemu.sh

@@ -9,8 +9,10 @@ start() {
         -gdb tcp::${QEMU_GDB_PORT} \
         -monitor unix:${QEMU_SOCKET},server,nowait \
         -enable-kvm \
-        -m 547M \
+        -m 1337M \
         -display curses \
+        -serial mon:stdio \
+        -append "Hello" \
         -device virtio-net,netdev=network0 -netdev tap,id=network0,ifname=tap0,script=no,downscript=no \
         -kernel ${KERNEL}
 	# build/kernel.iso

src/arch/x86/main.zig

@@ -5,12 +5,14 @@ const mem = @import("mem.zig");
 const gdt = @import("gdt.zig");
 const x86 = @import("lib/index.zig");
 const console = @import("../console.zig");
+const printf = @import("../../vga.zig").printf;
 
 /// x86 specific intialization
 /// first entry point (see linker.ld)
 pub fn x86_main(info: *const MultibootInfo) void {
-    mem.initialize(info);
+    var allocator = mem.initialize(info);
+
     // gdt.initialize();
     idt.initialize();
-    // x86.sti();
+    x86.sti();
 }

src/arch/x86/mem.zig

@@ -1,30 +1,157 @@
 usingnamespace @import("kernel").multiboot;
 const assert = @import("std").debug.assert;
 const vga = @import("../../vga.zig");
+const std = @import("std");
+const printf = @import("../../vga.zig").printf;
 
-pub fn initialize(info: *const MultibootInfo) void {
+pub fn initialize(info: *const MultibootInfo) bumpAllocator {
     assert((info.flags & MULTIBOOT_INFO_MEMORY) != 0);
     assert((info.flags & MULTIBOOT_INFO_MEM_MAP) != 0);
 
+    format_multibootinfo(info);
+    return bumpAllocator.new(info);
+}
+
+pub fn format_multibootentry(entry: *MultibootMMapEntry) void {
+    if (entry.type == MULTIBOOT_MEMORY_AVAILABLE) {
+        vga.printf("AVAILABLE: ");
+    } else {
+        vga.printf("NOT AVAILABLE: ");
+    }
+    vga.printf("{x} ", entry.addr);
+    if (entry.len / (1024 * 1024) > 0) {
+        vga.printf("({} MB)\n", entry.len / (1024 * 1024));
+    } else {
+        vga.printf("({} kB)\n", entry.len / (1024));
+    }
+}
+
+pub fn format_multibootinfo(info: *const MultibootInfo) void {
+    var cmdline_ptr = @intToPtr([*c]const u8, info.cmdline);
+    var cmdline = @ptrCast([*c]const u8, cmdline_ptr);
+    // var cmdline = std.cstr.toSliceConst(info.cmdline);
     vga.printf("lower: {x}\n", info.mem_lower);
     vga.printf("upper: {x}\n", info.mem_upper);
     vga.printf("mmap_l: {}\n", info.mmap_length);
     vga.printf("mmap_a: {x}\n", info.mmap_addr);
+    vga.printf("cmdline: {x}\n", cmdline_ptr);
+    vga.printf("cmdline: {}\n", cmdline);
 
     var map: usize = info.mmap_addr;
     while (map < info.mmap_addr + info.mmap_length) {
         var entry = @intToPtr(*MultibootMMapEntry, map);
-        if (entry.type == MULTIBOOT_MEMORY_AVAILABLE) {
-            vga.printf("AVAILABLE: ");
-        } else {
-            vga.printf("NOT AVAILABLE: ");
-        }
-        vga.printf("{x} ", entry.addr);
-        if (entry.len / (1024 * 1024) > 0) {
-            vga.printf("({} MB)\n", entry.len / (1024 * 1024));
-        } else {
-            vga.printf("({} kB)\n", entry.len / (1024));
-        }
+        format_multibootentry(entry);
         map += entry.size + @sizeOf(@typeOf(entry.size));
     }
 }
+
+// returns each available physical frame one by one in order
+pub const bumpAllocator = struct {
+    next_free_frame: physFrame,
+    current_area: ?*MultibootMMapEntry,
+    info: *const MultibootInfo,
+
+    pub fn new(info: *const MultibootInfo) bumpAllocator {
+        const first_area = @intToPtr(*MultibootMMapEntry, info.mmap_addr);
+        var allocator = bumpAllocator{
+            .current_area = first_area,
+            .next_free_frame = physFrame.from_addr(first_area.addr),
+            .info = info,
+        };
+        // allocator.choose_next_area();
+        return allocator;
+    }
+
+    pub fn allocate(self: var, count: u64) ?physFrame {
+        if (count == 0) {
+            return null;
+        }
+        if (self.current_area == null) {
+            return null;
+        }
+        if (self.current_area.?.type != MULTIBOOT_MEMORY_AVAILABLE) {
+            self.choose_next_area();
+            return self.allocate(count);
+        }
+
+        const start_frame = self.next_free_frame;
+        const end_frame = self.next_free_frame.add(count - 1);
+        const current_area_last_frame = physFrame.from_addr(self.current_area.?.addr + self.current_area.?.len);
+        if (end_frame.number > current_area_last_frame.number) {
+            self.choose_next_area();
+            return self.allocate(count);
+        }
+        self.next_free_frame.number += count;
+        return start_frame;
+    }
+
+    pub fn choose_next_area(self: var) void {
+        printf("choosing next area\n");
+        const current = self.current_area.?;
+        var next_area = @ptrToInt(current) + current.size + @sizeOf(@typeOf(current));
+        if (next_area >= self.info.mmap_addr + self.info.mmap_length) {
+            self.current_area = null;
+        } else {
+            format_multibootentry(self.current_area.?);
+            self.current_area = @intToPtr(*MultibootMMapEntry, next_area);
+            format_multibootentry(self.current_area.?);
+            self.next_free_frame = physFrame.from_addr(self.current_area.?.addr);
+        }
+    }
+};
+
+pub const PAGE_SIZE = 4096;
+
+pub const physFrame = struct {
+    number: u64,
+
+    pub fn from_addr(addr: u64) physFrame {
+        return physFrame{ .number = @divTrunc(addr, PAGE_SIZE) };
+    }
+
+    pub fn add(self: physFrame, count: u64) physFrame {
+        return physFrame{ .number = self.number + count };
+    }
+
+    pub fn start_addr(self: physFrame) u64 {
+        return (self.number * PAGE_SIZE);
+    }
+};
+
+const PageDirectory = packed struct {
+    entries: [1024]PageDirectoryEntry,
+};
+
+const PageDirectoryEntry = packed struct {
+    address: u21,
+    available: u2,
+    ignored: u1,
+    size: u1,
+    zero: u1,
+    accessed: u1,
+    cache_disabled: u1,
+    write_through: u1,
+    user: u1,
+    writeable: u1,
+    present: u1,
+};
+
+const PageTable = packed struct {
+    entries: [1024]PageTableEntry,
+};
+
+const PageTableEntry = packed struct {
+    address: u21,
+    available: u2,
+    global: u1,
+    zero: u1,
+    dirty: u1,
+    accessed: u1,
+    cache_disabled: u1,
+    write_through: u1,
+    user: u1,
+    writeable: u1,
+    present: u1,
+};
+
+// assert(@sizeOf(PageTableEntry) == 32);

src/main.zig

@@ -1,8 +1,8 @@
 usingnamespace @import("multiboot.zig");
+usingnamespace @import("vga.zig");
 const pci = @import("pci.zig");
 const arch = @import("arch/x86/lib/index.zig");
 const console = @import("console.zig");
-const vga = @import("vga.zig");
 const x86 = @import("arch/x86/main.zig");
 const assert = @import("std").debug.assert;
 
@@ -11,11 +11,23 @@ export fn kmain(magic: u32, info: *const MultibootInfo) noreturn {
     assert(magic == MULTIBOOT_BOOTLOADER_MAGIC);
     console.initialize();
 
-    vga.printf("--- x86_main ---\n");
+    printf("--- hello x86_main ---\n");
 
     x86.x86_main(info);
 
-    vga.printf("--- arch indepent boot ---\n");
+    // pagefault_test(0xfeffc000);
+
+    printf("\n--- arch indepent boot ---\n");
 
     while (true) {}
 }
+
+fn pagefault_test(addr: u32) void {
+    const ptr = @intToPtr(*volatile u8, addr);
+    var a: u8 = ptr.*;
+    printf("a = {}\n", a);
+
+    ptr.* += 1;
+
+    printf("a = {}\n", ptr.*);
+}

src/multiboot.zig

@@ -1,3 +1,6 @@
+// MULTIBOOT1
+// https://www.gnu.org/software/grub/manual/multiboot/multiboot.html
+
 // zig fmt: off
 const tty = @import("tty.zig");
 const cstr = @import("std").cstr;
@@ -117,7 +120,8 @@ export const multiboot_header align(4) linksection(".multiboot") = multiboot: {
     const MAGIC   = u32(0x1BADB002);  // multiboot magic
     const ALIGN   = u32(1 << 0);      // Align loaded modules.
     const MEMINFO = u32(1 << 1);      // Receive a memory map from the bootloader.
-    const FLAGS   = ALIGN | MEMINFO;  // Combine the flags.
+    const CMDLINE = u32(1 << 2);      // Receive a cmdline from the bootloader
+    const FLAGS   = ALIGN | MEMINFO | CMDLINE;  // Combine the flags.
 
     break :multiboot MultibootHeader {
         .magic    = MAGIC,