Refactor and use the Multiboot info struct

src/main.zig

@@ -1,21 +1,23 @@
 const lazy = @import("utils/Lazy.zig").lazy;
 const Console = @import("Console.zig");
+const MultibootInfo = @import("multiboot.zig").Info;
+
+const MultibootHeader = packed struct {
+    magic: i32,
+    flags: i32,
+    checksum: i32,
+    padding: u32,
+};
 
 const ALIGN = 1 << 0;
 const MEMINFO = 1 << 1;
 const MAGIC = 0x1BADB002;
 const FLAGS = ALIGN | MEMINFO;
-
-const MultibootHeader = packed struct {
-    magic: i32 = MAGIC,
-    flags: i32,
-    checksum: i32,
-    padding: u32 = 0,
-};
-
 export var mutliboot: MultibootHeader align(4) linksection(".multiboot") = .{
+    .magic = MAGIC,
     .flags = FLAGS,
     .checksum = -(MAGIC + FLAGS),
+    .padding = 0,
 };
 
 var stack_bytes: [16 * 1024]u8 align(16) linksection(".bss") = undefined;
@@ -24,6 +26,8 @@ export fn _start() callconv(.naked) noreturn {
     asm volatile (
         \\ movl %[stack_top], %%esp
         \\ movl %%esp, %%ebp
+        \\ push %%ebx
+        \\ push %%eax
         \\ call %[kmain:P]
         :
         : [stack_top] "i" (@as([*]align(16) u8, @ptrCast(&stack_bytes)) + @sizeOf(@TypeOf(stack_bytes))),
@@ -33,13 +37,23 @@ export fn _start() callconv(.naked) noreturn {
 
 var console = lazy(Console, .init);
 
-fn kmain() callconv(.C) void {
-    std.log.info("This is an info message", .{});
-    std.log.debug("This is a debug message!", .{});
-    std.log.warn("This is a warning message!", .{});
-    std.log.err("This is an error message!", .{});
+fn kmain(magic: u32, info: *const MultibootInfo) callconv(.c) void {
+    std.debug.assert(magic == MAGIC);
 
-    @panic("Uh oh");
+    std.log.info("{any}", .{info});
+
+    if (info.isValid(.boot_loader_name)) {
+        std.log.info("Booted by {s}", .{info.boot_loader_name});
+    }
+    if (info.isValid(.cmdline)) {
+        std.log.info("Booted with cmdline \"{s}\"", .{info.cmdline});
+    }
+
+    hang();
+}
+
+fn hang() noreturn {
+    while (true) asm volatile ("hlt");
 }
 
 const std = @import("std");
@@ -51,7 +65,7 @@ fn kpanic(msg: []const u8, first_trace_addr: ?usize) noreturn {
 
     std.log.err("PANIC: {s}", .{msg});
 
-    while (true) {}
+    hang();
 }
 
 pub const std_options = std.Options{

src/multiboot.zig

@@ -0,0 +1,96 @@
+const std = @import("std");
+
+const BootModule = packed struct {
+    start: u32,
+    end: u32,
+    string: ?[*:0]u8,
+    reserved: u32,
+};
+
+pub const Info = packed struct {
+    flags: std.bit_set.IntegerBitSet(32),
+    mem_lower: u32,
+    mem_upper: u32,
+    boot_device: packed struct {
+        part3: u8,
+        part2: u8,
+        part1: u8,
+        drive: u8,
+    },
+    cmdline: [*:0]u8,
+    mods_count: u32,
+    mods_addr: [*]BootModule,
+    u: packed union {
+        aout_sym: packed struct {
+            tabsize: u32,
+            strsize: u32,
+            addr: u32,
+            reserved: u32,
+        },
+        elf_sec: packed struct {
+            num: u32,
+            size: u32,
+            addr: u32,
+            shndx: u32,
+        },
+    },
+    mmap_length: u32,
+    mmap_addr: u32,
+    drives_length: u32,
+    drives_addr: u32,
+    config_table: u32,
+    boot_loader_name: [*:0]u8,
+    apm_table: u32,
+    vbe: packed struct {
+        control_info: u32,
+        move_info: u32,
+        mode: u16,
+        interface_seg: u16,
+        interface_off: u16,
+        interface_len: u16,
+    },
+    framebuffer: packed struct {
+        addr: u64,
+        pitch: u32,
+        width: u32,
+        height: u32,
+        bpp: u8,
+        type: u8,
+        color_info: packed union {
+            indexed_color: packed struct {
+                framebuffer_palette_addr: u32,
+                framebuffer_palette_num_colors: u16,
+            },
+            rgb_color: packed struct {
+                framebuffer_red_field_position: u8,
+                framebuffer_red_mask_size: u8,
+                framebuffer_green_field_position: u8,
+                framebuffer_green_mask_size: u8,
+                framebuffer_blue_field_position: u8,
+                framebuffer_blue_mask_size: u8,
+            },
+        },
+    },
+
+    const Self = @This();
+
+    pub fn isValid(self: *const Self, comptime field: std.meta.FieldEnum(Self)) bool {
+        return switch (field) {
+            .flags => true,
+            .mem_lower, .mem_upper => self.flags.isSet(0),
+            .boot_device => self.flags.isSet(1),
+            .cmdline => self.flags.isSet(2),
+            .mods_count, .mods_addr => self.flags.isSet(3),
+            // TODO: .u => either 4 or 5
+            .mmap_length, .mmap_addr => self.flags.isSet(6),
+            .drives_length, .drives_addr => self.flags.isSet(7),
+            .config_table => self.flags.isSet(8),
+            .boot_loader_name => self.flags.isSet(9),
+            .apm_table => self.flags.isSet(10),
+            .vbe => self.flags.isSet(11),
+            .framebuffer => self.flags.isSet(12),
+            else => false,
+        };
+    }
+};
+