moving kernel code to kernel/
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@@ -0,0 +1,168 @@
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const std = @import("std");
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const danos = @import("danos");
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const arch = @import("arch");
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const console = @import("console.zig");
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const pmm = @import("pmm.zig");
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const heap = @import("heap.zig");
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const sched = @import("sched.zig");
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const tests = @import("tests.zig");
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const build_options = @import("build_options");
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const BootInfo = danos.BootInfo;
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/// The calling convention used to enter the kernel. Pinned to SysV explicitly:
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/// the bootloader is built for the UEFI target, whose C convention is Microsoft
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/// x64 (first argument in RCX), while the kernel is SysV (first argument in
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/// RDI). Both sides reference this so the `boot_info` pointer lands in the
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/// register the other expects. `danos.kernel_abi` re-exports it to the loader.
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pub const kernel_abi = danos.kernel_abi;
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/// The system console, valid once `kmain` has initialised it. Global so the
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/// panic handler can reach it too.
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var con: console.Console = undefined;
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var con_ready = false;
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/// Kernel entry point. The bootloader jumps here after `ExitBootServices` with a
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/// pointer to the handoff data. There is no runtime, no stack unwinding, and no
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/// caller to return to, so this never returns.
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export fn _start(boot_info: *const BootInfo) callconv(kernel_abi) noreturn {
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kmain(boot_info);
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}
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fn kmain(boot_info: *const BootInfo) noreturn {
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arch.serialInit(); // machine-readable log; console mirrors to it
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const fb = boot_info.framebuffer;
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const serial0 = console.SerialConsole;
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con = console.Console.init(fb);
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con.clear();
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con_ready = true;
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// Catch CPU exceptions before doing anything that might fault: install our
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// reporter, then bring up the GDT + IDT.
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arch.setFaultHandler(onException);
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arch.init();
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con.write("danos: initalizing kernel...");
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serial0.debugWrite("danos: framebuffer console online\n");
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serial0.debugWrite("danos: cpu tables online (GDT, IDT, TSS)\n");
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serial0.debugPrint(" resolution : {d}x{d}\n", .{ fb.width, fb.height });
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serial0.debugPrint(" pitch : {d} bytes\n", .{fb.pitch});
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serial0.debugPrint(" format : {s}\n", .{@tagName(fb.format)});
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serial0.debugPrint(" framebuffer: 0x{x:0>16}\n", .{fb.base});
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serial0.debugPrint (" footdebugPrint : {d} MiB\n", .{(fb.pitch * fb.height) / (1024 * 1024)});
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// Summarise the physical memory the loader handed us. The array is danos's
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// own MemoryRegion, so this is a plain slice — no firmware layout in sight.
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const regions = @as([*]const danos.MemoryRegion, @ptrFromInt(boot_info.memory_map.regions))[0..boot_info.memory_map.len];
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var usable_pages: u64 = 0;
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var reserved_pages: u64 = 0; // reserved RAM only — MMIO is device space, not RAM
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for (regions) |r| {
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switch (r.kind) {
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.usable => usable_pages += r.pages,
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.reserved, .acpi_tables, .acpi_nvs => reserved_pages += r.pages,
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.mmio => {},
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}
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}
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const total_pages = usable_pages + reserved_pages;
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const total_bytes = total_pages * danos.page_size;
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const gib = 1 << 30;
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serial0.debugWrite("\ndanos: physical memory\n");
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serial0.debugPrint(" total RAM : {d}.{d:0>2} GiB ({d} MiB) - RAM the firmware reported\n", .{ total_bytes / gib, (total_bytes % gib) * 100 / gib, mib(total_pages) });
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serial0.debugPrint(" usable : {d} MiB - free RAM (incl. reclaimed boot-services memory)\n", .{mib(usable_pages)});
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serial0.debugPrint(" reserved : {d} MiB - kernel image, boot stack, ACPI, runtime services\n", .{mib(reserved_pages)});
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serial0.debugPrint(" regions : {d} - entries in the firmware memory map\n", .{regions.len});
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// Bring up the physical frame allocator over that map, and prove it works:
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// allocate three frames, then hand them back.
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pmm.init(boot_info.memory_map);
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const s1 = pmm.stats();
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serial0.debugPrint("\ndanos: frame allocator online\n", .{});
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serial0.debugPrint(" free frames: {d} ({d} MiB)\n", .{ s1.free_frames, mib(s1.free_frames) });
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const f0 = pmm.alloc();
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const f1 = pmm.alloc();
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const f2 = pmm.alloc();
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serial0.debugPrint(" alloc x3 : 0x{x} 0x{x} 0x{x}\n", .{ f0 orelse 0, f1 orelse 0, f2 orelse 0 });
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if (f0) |p| pmm.free(p);
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if (f1) |p| pmm.free(p);
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if (f2) |p| pmm.free(p);
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serial0.debugPrint(" after free : {d} frames free\n", .{pmm.stats().free_frames});
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// Switch off the firmware's page tables onto our own (with real permissions).
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arch.enablePaging(pmm.alloc, boot_info);
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serial0.debugPrint("\ndanos: paging enabled\n", .{});
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serial0.debugPrint(" page tables: CR3 = 0x{x:0>16}\n", .{arch.readCr3()});
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serial0.debugPrint(" kernel segs: {d} (mapped with W^X permissions)\n", .{boot_info.kernel_segment_count});
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// Bring up the kernel heap (dynamic allocation), built on the VMM.
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heap.init();
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serial0.debugWrite("\ndanos: kernel heap online\n");
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// Measure the amount of resources the kernel is actually using
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const s2 = pmm.stats();
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serial0.debugPrint(" Kernel FootdebugPrint: {d} KiB\n", .{kib(s1.free_frames - s2.free_frames)});
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// Register the current context as the first task before enabling preemption.
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sched.init(4);
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serial0.debugWrite("\ndanos: scheduler online\n");
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// Start the timer and unmask interrupts — the kernel now has a heartbeat, and
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// the timer preempts among tasks.
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arch.startTimer();
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arch.enableInterrupts();
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serial0.debugPrint("danos: timer online ({d} Hz tick; LAPIC {d} MHz, TSC {d} MHz measured)\n", .{ arch.timer_hz, arch.lapicHz() / 1_000_000, arch.tscHz() / 1_000_000 });
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// In a test build (`zig build -Dtest-case=<name>`), run that case and stop.
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// Normal builds fall through to the idle halt.
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if (build_options.test_case) |case| {
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tests.run(case, boot_info);
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arch.halt();
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}
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con.write("kernel initialised.\n");
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// TODO: init process
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con.write("\nnothing left to do; halting CPU.\n");
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arch.halt();
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}
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/// Frames (4 KiB pages) to whole MiB.
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fn mib(pages: u64) u64 {
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return pages * danos.page_size / (1024 * 1024);
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}
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fn kib(frames: u64) u64 {
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return frames * danos.page_size / (1024);
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}
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/// Report a CPU exception in red and halt. There's no fault recovery yet, so any
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/// exception is terminal — but now it debugPrints what and where instead of silently
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/// resetting the machine.
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fn onException(state: *const arch.CpuState) noreturn {
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if (con_ready) {
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con.fg = 0x00ff_5555;
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con.print("\nCPU EXCEPTION: {s} (vector {d})\n", .{ arch.vectorName(state.vector), state.vector });
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con.print(" error code : 0x{x}\n", .{state.error_code});
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con.print(" RIP : 0x{x:0>16}\n", .{state.rip});
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con.print(" RSP : 0x{x:0>16}\n", .{state.rsp});
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if (state.vector == 14) con.print(" CR2 (addr) : 0x{x:0>16}\n", .{arch.readCr2()});
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}
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arch.halt();
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}
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/// Freestanding has no OS to receive a panic. debugPrint it to the console (if it is
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/// up yet) in red, then halt.
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pub const panic = std.debug.FullPanic(struct {
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fn panic(msg: []const u8, first_trace_addr: ?usize) noreturn {
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_ = first_trace_addr;
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if (con_ready) {
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con.fg = 0x00ff_5555;
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con.write("\nKERNEL PANIC: ");
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con.write(msg);
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con.write("\n");
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}
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arch.halt();
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}
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}.panic);
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