implement panic handler (#70)

src/main.zig

@@ -7,6 +7,7 @@ const log = @import("log.zig");
 const fs = @import("fs.zig");
 const heap = @import("heap.zig");
 const mem = @import("mem.zig");
+const mewz_panic = @import("panic.zig");
 const uart = @import("uart.zig");
 const param = @import("param.zig");
 const pci = @import("pci.zig");
@@ -23,6 +24,8 @@ const wasi = @import("wasi.zig");
 
 extern fn wasker_main() void;
 
+pub const panic = mewz_panic.panic;
+
 export fn bspEarlyInit(boot_magic: u32, boot_params: u32) align(16) callconv(.C) void {
     const bootinfo = @as(*multiboot.BootInfo, @ptrFromInt(boot_params));
     const cmdline = util.getString(bootinfo.cmdline);
@@ -43,6 +46,7 @@ export fn bspEarlyInit(boot_magic: u32, boot_params: u32) align(16) callconv(.C)
     if (param.params.isNetworkEnabled()) {
         virtio_net.init();
     }
+
     mem.init2();
     if (param.params.isNetworkEnabled()) {
         tcpip.init(param.params.addr.?, param.params.subnetmask.?, param.params.gateway.?, &virtio_net.virtio_net.mac_addr);

src/panic.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+const log = @import("log.zig");
+
+var panicked = false;
+
+pub fn panic(msg: []const u8, _: ?*std.builtin.StackTrace, _: ?usize) noreturn {
+    log.fatal.printf("=== PANIC ===\n", .{});
+    log.fatal.printf("Message: {s}\n", .{msg});
+    asm volatile ("cli");
+
+    if (panicked) {
+        log.fatal.print("Double Panic\n");
+        asm volatile ("hlt");
+    }
+    panicked = true;
+
+    var it = std.debug.StackIterator.init(@returnAddress(), null);
+    var ix: usize = 0;
+    log.fatal.printf("Stack Trace:\n", .{});
+    while (it.next()) |frame| : (ix += 1) {
+        log.fatal.printf("#{d:0>2}: 0x{X:0>16}\n", .{ ix, frame });
+    }
+
+    asm volatile ("hlt");
+
+    unreachable;
+}