Merge pull request #17 from SamTebbs33/feature/architecture-separation

This patch separates the architecture-specific and core code from each other, with the arch code moved to its own directory under src/kernel/arch. The architecture and core code are built to objects, then linked togetherm, and an interface is added in src/kernel/arch.zig which each architecture must implement. Closes #16

build.zig

@@ -8,7 +8,7 @@ const ArrayList = std.ArrayList;
 const warn = std.debug.warn;
 const mem = std.mem;
 
-const src_files = [][]const u8{"kernel/kmain"};
+var src_files: ArrayList([]const u8) = undefined;
 
 fn concat(allocator: *std.mem.Allocator, str: []const u8, str2: []const u8) !std.Buffer {
     var b = try std.Buffer.init(allocator, str);
@@ -17,6 +17,7 @@ fn concat(allocator: *std.mem.Allocator, str: []const u8, str2: []const u8) !std
 }
 
 pub fn build(b: *Builder) void {
+    src_files = ArrayList([]const u8).init(b.allocator);
     const debug = b.option(bool, "debug", "build with debug symbols / make qemu wait for a debug connection") orelse false;
     var build_path = b.option([]const u8, "build-path", "path to build to") orelse "bin";
     var src_path = b.option([]const u8, "source-path", "path to source") orelse "src";
@@ -25,6 +26,13 @@ pub fn build(b: *Builder) void {
 
     const iso_path = concat(b.allocator, build_path, "/pluto.iso") catch unreachable;
 
+    src_files.append("kernel/kmain") catch unreachable;
+
+    // Add the architecture init file to the source files
+    var arch_init = concat(b.allocator, "kernel/arch/", target) catch unreachable;
+    arch_init.append("/arch") catch unreachable;
+    src_files.append(arch_init.toSlice()) catch unreachable;
+
     var objects_steps = buildObjects(b, builtin_target, build_path, src_path);
     var link_step = buildLink(b, builtin_target, build_path);
     const iso_step = buildISO(b, build_path, iso_path.toSlice());
@@ -41,7 +49,7 @@ pub fn build(b: *Builder) void {
 fn buildTest(b: *Builder, src_path: []const u8) void {
     const step = b.step("test", "Run all tests");
     const src_path2 = concat(b.allocator, src_path, "/") catch unreachable;
-    for (src_files) |file| {
+    for (src_files.toSlice()) |file| {
         var file_src = concat(b.allocator, src_path2.toSlice(), file) catch unreachable;
         file_src.append(".zig") catch unreachable;
         const tst = b.addTest(file_src.toSlice());
@@ -100,7 +108,7 @@ fn buildLink(b: *Builder, target: builtin.Arch, build_path: []const u8) *Step {
     exec.setOutputDir(elf_path.toSlice());
     exec.setLinkerScriptPath("link.ld");
     exec.setTarget(target, builtin.Os.freestanding, builtin.Abi.gnu);
-    for (src_files) |file| {
+    for (src_files.toSlice()) |file| {
         var file_obj = concat(b.allocator, build_path, "/") catch unreachable;
         file_obj.append(file) catch unreachable;
         file_obj.append(".o") catch unreachable;
@@ -112,7 +120,7 @@ fn buildLink(b: *Builder, target: builtin.Arch, build_path: []const u8) *Step {
 fn buildObjects(b: *Builder, target: builtin.Arch, build_path: []const u8, src_path: []const u8) ArrayList(*Step) {
     var objects = ArrayList(*Step).init(b.allocator);
     const src_path2 = concat(b.allocator, src_path, "/") catch unreachable;
-    for (src_files) |file| {
+    for (src_files.toSlice()) |file| {
         var file_src = concat(b.allocator, src_path2.toSlice(), file) catch unreachable;
         file_src.append(".zig") catch unreachable;
         const obj = b.addObject(file, file_src.toSlice());

src/kernel/arch.zig

@@ -0,0 +1,2 @@
+/// Initialise the architecture
+pub extern fn init() void;

src/kernel/arch/x86/arch.zig

@@ -0,0 +1,103 @@
+extern fn kmain() void;
+
+const MultiBoot = packed struct {
+    magic: i32,
+    flags: i32,
+    checksum: i32,
+};
+
+const ALIGN = 1 << 0;
+const MEMINFO = 1 << 1;
+const MAGIC = 0x1BADB002;
+const FLAGS = ALIGN | MEMINFO;
+
+export var multiboot align(4) linksection(".rodata.boot") = MultiBoot{
+    .magic = MAGIC,
+    .flags = FLAGS,
+    .checksum = -(MAGIC + FLAGS),
+};
+
+const KERNEL_ADDR_OFFSET = 0xC0000000;
+const KERNEL_PAGE_NUMBER = KERNEL_ADDR_OFFSET >> 22;
+// The number of pages occupied by the kernel, will need to be increased as we add a heap etc.
+const KERNEL_NUM_PAGES = 1;
+
+// The initial page directory used for booting into the higher half. Should be overwritten later
+export var boot_page_directory: [1024]u32 align(4096) linksection(".rodata.boot") = init: {
+    // Increase max number of branches done by comptime evaluator
+    @setEvalBranchQuota(1024);
+    // Temp value
+    var dir: [1024]u32 = undefined;
+
+    // Page for 0 -> 4 MiB. Gets unmapped later
+    dir[0] = 0x00000083;
+
+    var i = 0;
+    var idx = 1;
+
+    // Fill preceding pages with zeroes. May be unecessary but incurs no runtime cost
+    while (i < KERNEL_PAGE_NUMBER - 1) : ({
+        i += 1;
+        idx += 1;
+    }) {
+        dir[idx] = 0;
+    }
+
+    // Map the kernel's higher half pages increasing by 4 MiB every time
+    i = 0;
+    while (i < KERNEL_NUM_PAGES) : ({
+        i += 1;
+        idx += 1;
+    }) {
+        dir[idx] = 0x00000083 | (i << 22);
+    }
+    // Fill suceeding pages with zeroes. May be unecessary but incurs no runtime cost
+    i = 0;
+    while (i < 1024 - KERNEL_PAGE_NUMBER - KERNEL_NUM_PAGES) : ({
+        i += 1;
+        idx += 1;
+    }) {
+        dir[idx] = 0;
+    }
+    break :init dir;
+};
+
+export var kernel_stack: [16 * 1024]u8 align(16) linksection(".bss.stack") = undefined;
+
+export nakedcc fn _start() align(16) linksection(".text.boot") noreturn {
+    // Seth the page directory to the boot directory
+    asm volatile (
+        \\.extern boot_page_directory
+        \\mov $boot_page_directory, %%ecx
+        \\mov %%ecx, %%cr3
+    );
+    // Enable 4 MiB pages
+    asm volatile (
+        \\mov %%cr4, %%ecx
+        \\or $0x00000010, %%ecx
+        \\mov %%ecx, %%cr4
+    );
+    // Enable paging
+    asm volatile (
+        \\mov %%cr0, %%ecx
+        \\or $0x80000000, %%ecx
+        \\mov %%ecx, %%cr0
+    );
+    asm volatile ("jmp start_higher_half");
+    while (true) {}
+}
+
+export nakedcc fn start_higher_half() noreturn {
+    // Invalidate the page for the first 4MiB as it's no longer needed
+    asm volatile ("invlpg (0)");
+    // Setup the stack
+    asm volatile (
+        \\.extern KERNEL_STACK_END
+        \\mov $KERNEL_STACK_END, %%esp
+        \\mov %%esp, %%ebp
+    );
+    kmain();
+    while (true) {}
+}
+
+export fn init() void {}

src/kernel/kmain.zig

@@ -5,106 +5,7 @@
 // Date: 2019-03-30
 //
 const builtin = @import("builtin");
-
+const arch = @import("arch.zig");
-const MultiBoot = packed struct {
-    magic: i32,
-    flags: i32,
-    checksum: i32,
-};
-
-const ALIGN = 1 << 0;
-const MEMINFO = 1 << 1;
-const MAGIC = 0x1BADB002;
-const FLAGS = ALIGN | MEMINFO;
-
-export var multiboot align(4) linksection(".rodata.boot") = MultiBoot{
-    .magic = MAGIC,
-    .flags = FLAGS,
-    .checksum = -(MAGIC + FLAGS),
-};
-
-const KERNEL_ADDR_OFFSET = 0xC0000000;
-const KERNEL_PAGE_NUMBER = KERNEL_ADDR_OFFSET >> 22;
-// The number of pages occupied by the kernel, will need to be increased as we add a heap etc.
-const KERNEL_NUM_PAGES = 1;
-
-// The initial page directory used for booting into the higher half. Should be overwritten later
-export var boot_page_directory: [1024]u32 align(4096) linksection(".rodata.boot") = init: {
-    // Increase max number of branches done by comptime evaluator
-    @setEvalBranchQuota(1024);
-    // Temp value
-    var dir: [1024]u32 = undefined;
-
-    // Page for 0 -> 4 MiB. Gets unmapped later
-    dir[0] = 0x00000083;
-
-    var i = 0;
-    var idx = 1;
-
-    // Fill preceding pages with zeroes. May be unecessary but incurs no runtime cost
-    while (i < KERNEL_PAGE_NUMBER - 1) : ({
-        i += 1;
-        idx += 1;
-    }) {
-        dir[idx] = 0;
-    }
-
-    // Map the kernel's higher half pages increasing by 4 MiB every time
-    i = 0;
-    while (i < KERNEL_NUM_PAGES) : ({
-        i += 1;
-        idx += 1;
-    }) {
-        dir[idx] = 0x00000083 | (i << 22);
-    }
-    // Fill suceeding pages with zeroes. May be unecessary but incurs no runtime cost
-    i = 0;
-    while (i < 1024 - KERNEL_PAGE_NUMBER - KERNEL_NUM_PAGES) : ({
-        i += 1;
-        idx += 1;
-    }) {
-        dir[idx] = 0;
-    }
-    break :init dir;
-};
-
-export var kernel_stack: [16 * 1024]u8 align(16) linksection(".bss.stack") = undefined;
-
-export nakedcc fn _start() align(16) linksection(".text.boot") noreturn {
-    // Seth the page directory to the boot directory
-    asm volatile (
-        \\.extern boot_page_directory
-        \\mov $boot_page_directory, %%ecx
-        \\mov %%ecx, %%cr3
-    );
-    // Enable 4 MiB pages
-    asm volatile (
-        \\mov %%cr4, %%ecx
-        \\or $0x00000010, %%ecx
-        \\mov %%ecx, %%cr4
-    );
-    // Enable paging
-    asm volatile (
-        \\mov %%cr0, %%ecx
-        \\or $0x80000000, %%ecx
-        \\mov %%ecx, %%cr0
-    );
-    asm volatile ("jmp start_higher_half");
-    while (true) {}
-}
-
-export nakedcc fn start_higher_half() noreturn {
-    // Invalidate the page for the first 4MiB as it's no longer needed
-    asm volatile ("invlpg (0)");
-    // Setup the stack
-    asm volatile (
-        \\.extern KERNEL_STACK_END
-        \\mov $KERNEL_STACK_END, %%esp
-        \\mov %%esp, %%ebp
-    );
-    kmain();
-    while (true) {}
-}
 
 pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn {
     @setCold(true);
@@ -113,7 +14,8 @@ pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn
     while (true) {}
 }
 
-fn kmain() void {
+pub export fn kmain() void {
+    arch.init();
     terminal.initialize();
     terminal.write("Hello, kernel World!");
 }