From c6e63ed2bfc30fa48f45a689d6c448cc10623743 Mon Sep 17 00:00:00 2001
From: iretq <me@iretq.dev>
Date: Sat, 28 Mar 2026 19:14:17 +0100
Subject: [PATCH] feat(pl/ke): initial amd64 support

---
 build.zig                       |  14 +--
 build/config.zig                |  28 +++++-
 build/image.zig                 |   1 +
 build/linker-scripts/x86_64.lds |  12 +++
 build/run.zig                   |   1 -
 src/kern/amd64/impl.zig         | 148 ++++++++++++++++++++++++++++++++
 src/kern/init.zig               |  15 +++-
 src/kern/ipl.zig                |   4 +-
 src/kern/panic.zig              |  11 ++-
 src/kern/um/impl.zig            |   6 +-
 src/main.zig                    |  58 -------------
 src/platform/amd64/entry.zig    |   3 -
 src/platform/amd64/impl.zig     |  23 ++++-
 src/platform/limine/entry.zig   |  31 +++++++
 src/platform/root.zig           |   4 +
 src/platform/um/entry.zig       |   1 +
 src/platform/um/timer.zig       |   4 +-
 src/root.zig                    |   2 +
 18 files changed, 279 insertions(+), 87 deletions(-)
 delete mode 100644 src/main.zig
 delete mode 100644 src/platform/amd64/entry.zig
 create mode 100644 src/platform/limine/entry.zig

diff --git a/build.zig b/build.zig
index 6613c21..ec943d5 100644
--- a/build.zig
+++ b/build.zig
@@ -150,6 +150,7 @@ fn targetQueryForPlatform(plat: config.Platform) std.Target.Query {
         switch (plat.arch) {
             .x86_64 => {
                 const f = std.Target.Cpu.Feature.FeatureSetFns(std.Target.x86.Feature);
+                q.cpu_features_add = f.featureSet(&.{.soft_float});
                 q.cpu_features_sub = f.featureSet(&.{ .x87, .mmx, .sse, .sse2 });
             },
             .aarch64 => {
@@ -169,7 +170,14 @@ fn addKernel(b: *std.Build, plat: config.Platform, optimize: std.builtin.Optimiz
 
     const name = b.fmt("kernel-{s}", .{@tagName(plat.arch)});
 
-    const root_source_file = if (plat.os == .freestanding) "src/main.zig" else "src/platform/um/entry.zig";
+    const platform_name = if (plat.bootloader) |bl|
+        switch (bl) {
+            .Limine => "limine",
+        }
+    else
+        @tagName(plat.arch);
+
+    const root_source_file = b.fmt("src/platform/{s}/entry.zig", .{platform_name});
 
     const kernel = b.addExecutable(.{
         .name = name,
@@ -191,12 +199,8 @@ fn addKernel(b: *std.Build, plat: config.Platform, optimize: std.builtin.Optimiz
     if (plat.os == .freestanding) {
         kernel.linkage = .static;
         kernel.pie = false;
-        kernel.bundle_compiler_rt = false;
-        kernel.bundle_ubsan_rt = false;
 
-        kernel.root_module.link_libc = false;
         kernel.root_module.pic = false;
-        kernel.root_module.single_threaded = true;
         kernel.root_module.strip = false;
         kernel.root_module.stack_check = false;
         kernel.root_module.stack_protector = false;
diff --git a/build/config.zig b/build/config.zig
index ea25810..ae505c0 100644
--- a/build/config.zig
+++ b/build/config.zig
@@ -3,9 +3,15 @@ const builtin = @import("builtin");
 
 pub const Config = std.StringHashMap([]const u8);
 
+pub const Bootloader = enum {
+    Limine,
+};
+
 pub const Platform = struct {
     arch: std.Target.Cpu.Arch,
     os: std.Target.Os.Tag,
+
+    bootloader: ?Bootloader = null,
 };
 
 pub fn parseConfig(b: *std.Build) !Config {
@@ -73,11 +79,25 @@ pub fn getPlatform(config: Config) !Platform {
         .{ "CONFIG_ARCH_UM", Platform{ .arch = builtin.cpu.arch, .os = .linux } },
     };
 
-    inline for (keys) |entry| {
-        if (config.get(entry[0])) |val| {
-            if (std.mem.eql(u8, val, "y")) return entry[1];
+    var ret = blk: {
+        inline for (keys) |entry| {
+            if (config.get(entry[0])) |val| {
+                if (std.mem.eql(u8, val, "y")) break :blk entry[1];
+            }
         }
+
+        return error.NoArchConfigured;
+    };
+
+    if (ret.arch == .x86_64 or ret.arch == .aarch64) {
+        ret.bootloader = blk: {
+            if (config.get("CONFIG_BOOT_LIMINE")) |val| {
+                if (std.mem.eql(u8, val, "y")) break :blk .Limine;
+            }
+
+            return error.NoBootloaderConfigured;
+        };
     }
 
-    return error.NoArchConfigured;
+    return ret;
 }
diff --git a/build/image.zig b/build/image.zig
index 29e21b1..80e2f69 100644
--- a/build/image.zig
+++ b/build/image.zig
@@ -94,6 +94,7 @@ pub fn addIso(
     mkiso.addArg("-o");
     const iso_out = mkiso.addOutputFileArg(b.fmt("{s}.iso", .{image_name}));
     mkiso.step.dependOn(&prep.step);
+    _ = mkiso.captureStdErr(.{});
 
     if (arch == .x86_64) {
         const bios_install = b.addRunArtifact(limine_tool);
diff --git a/build/linker-scripts/x86_64.lds b/build/linker-scripts/x86_64.lds
index 0f0da9d..b5df9b5 100644
--- a/build/linker-scripts/x86_64.lds
+++ b/build/linker-scripts/x86_64.lds
@@ -44,6 +44,12 @@ SECTIONS
         *(.rodata .rodata.*)
     } :rodata
 
+    .percpu_init_array : {
+        __init_array_percpu_start = .;
+        KEEP(*(.percpu_init_array))
+        __init_array_percpu_end = .;
+    } :rodata
+
     /* Add a .note.gnu.build-id output section in case a build ID flag is added to the */
     /* linker command. */
     .note.gnu.build-id : {
@@ -57,6 +63,12 @@ SECTIONS
         *(.data .data.*)
     } :data
 
+    .data.percpu : {
+        __percpu_start = .;
+        *(.data.percpu)
+        __percpu_end = .;
+    } :data
+
     /* NOTE: .bss needs to be the last thing mapped to :data, otherwise lots of */
     /* unnecessary zeros will be written to the binary. */
     /* If you need, for example, .init_array and .fini_array, those should be placed */
diff --git a/build/run.zig b/build/run.zig
index 9cf68ab..05fedcc 100644
--- a/build/run.zig
+++ b/build/run.zig
@@ -44,7 +44,6 @@ pub fn addRun(b: *std.Build, kernel: *std.Build.Step.Compile, plat: config.Platf
 
         if (debug) {
             qemu.addArgs(&.{
-                "-serial",    "stdio",
                 "-d",         "int",
                 "-D",         "qemu.log",
                 "-no-reboot", "-no-shutdown",
diff --git a/src/kern/amd64/impl.zig b/src/kern/amd64/impl.zig
index e69de29..014e27d 100644
--- a/src/kern/amd64/impl.zig
+++ b/src/kern/amd64/impl.zig
@@ -0,0 +1,148 @@
+const b = @import("base");
+const ke = b.ke;
+
+const std = @import("std");
+
+pub const Cpu = struct {
+    self_ptr: *Cpu,
+    percpu_offset: usize,
+};
+
+pub const ThreadContext = struct {
+    rdi: u64,
+    rsi: u64,
+    rbx: u64,
+    rsp: u64,
+    rbp: u64,
+    r12: u64,
+    r13: u64,
+    r14: u64,
+    r15: u64,
+
+    fn thread_trampoline(entry: usize, arg: usize) callconv(.c) void {
+        const entry_fn: *const fn (?*anyopaque) void = @ptrFromInt(entry);
+        entry_fn(@ptrFromInt(arg));
+        // TODO: This shouldn't be reached!!!
+    }
+
+    pub fn init(stack: b.VAddr, stack_size: usize, entry: *const fn (?*anyopaque) void, arg: ?*anyopaque) @This() {
+        var ctx: @This() = undefined;
+        ctx.rdi = @intFromPtr(entry);
+        ctx.rsi = @intFromPtr(arg);
+
+        var sp = stack + stack_size;
+        {
+            sp -= @sizeOf(usize);
+            @as(*usize, @ptrFromInt(sp)).* = 0;
+
+            sp -= @sizeOf(usize);
+            @as(*usize, @ptrFromInt(sp)).* = @intFromPtr(&thread_trampoline);
+        }
+        ctx.rsp = sp;
+
+        return ctx;
+    }
+
+    export fn do_switch_to() callconv(.naked) void {
+        const asm_template = std.fmt.comptimePrint(
+            \\movq %%rbx, {d}(%%rdi)
+            \\movq %%rsp, {d}(%%rdi)
+            \\movq %%rbp, {d}(%%rdi)
+            \\movq %%r12, {d}(%%rdi)
+            \\movq %%r13, {d}(%%rdi)
+            \\movq %%r14, {d}(%%rdi)
+            \\movq %%r15, {d}(%%rdi)
+            \\
+            \\movq {d}(%%rsi), %%rbx
+            \\movq {d}(%%rsi), %%rsp
+            \\movq {d}(%%rsi), %%rbp
+            \\movq {d}(%%rsi), %%r12
+            \\movq {d}(%%rsi), %%r13
+            \\movq {d}(%%rsi), %%r14
+            \\movq {d}(%%rsi), %%r15
+            \\movq {d}(%%rsi), %%rdi
+            \\movq {d}(%%rsi), %%rsi
+            \\
+            \\ret
+        , .{
+            @offsetOf(ThreadContext, "rbx"),
+            @offsetOf(ThreadContext, "rsp"),
+            @offsetOf(ThreadContext, "rbp"),
+            @offsetOf(ThreadContext, "r12"),
+            @offsetOf(ThreadContext, "r13"),
+            @offsetOf(ThreadContext, "r14"),
+            @offsetOf(ThreadContext, "r15"),
+
+            @offsetOf(ThreadContext, "rbx"),
+            @offsetOf(ThreadContext, "rsp"),
+            @offsetOf(ThreadContext, "rbp"),
+            @offsetOf(ThreadContext, "r12"),
+            @offsetOf(ThreadContext, "r13"),
+            @offsetOf(ThreadContext, "r14"),
+            @offsetOf(ThreadContext, "r15"),
+            @offsetOf(ThreadContext, "rdi"),
+            @offsetOf(ThreadContext, "rsi"),
+        });
+
+        asm volatile (asm_template);
+    }
+
+    pub fn switch_to(self: *ThreadContext, new: *ThreadContext) callconv(.c) void {
+        asm volatile (
+            \\call do_switch_to
+            :
+            : [_] "{rdi}" (self),
+              [_] "{rsi}" (new),
+        );
+    }
+};
+
+pub fn curcpu() *ke.Cpu {
+    const asm_template = std.fmt.comptimePrint("movq %%gs:{d}, %[ret]", .{@offsetOf(Cpu, "self_ptr")});
+    const impl_cpu = asm volatile (asm_template
+        : [ret] "=r" (-> *Cpu),
+    );
+
+    return @fieldParentPtr("impl", impl_cpu);
+}
+
+inline fn percpu_ptr_for(variable: anytype, cpu: *ke.Cpu) @TypeOf(variable) {
+    return @ptrFromInt(@intFromPtr(variable) +% cpu.impl.percpu_offset);
+}
+
+pub inline fn percpu_ptr_other(variable: anytype, id: usize) @TypeOf(variable) {
+    return percpu_ptr_for(variable, ke.cpus[id]);
+}
+
+pub inline fn percpu_ptr(variable: anytype) @TypeOf(variable) {
+    return percpu_ptr_for(variable, curcpu());
+}
+
+pub inline fn set_hardware_ipl(_: ke.Ipl) void {}
+
+pub inline fn enable_interrupts() void {
+    asm volatile ("sti");
+}
+
+pub inline fn disable_interrupts() bool {
+    const rflags = asm volatile (
+        \\cli
+        \\pushfq
+        \\popq %[rflags]
+        : [rflags] "=r" (-> usize),
+    );
+
+    return rflags & (1 << 9) != 0;
+}
+
+pub inline fn restore_interrupts(state: bool) void {
+    if (state) {
+        enable_interrupts();
+    } else {
+        _ = disable_interrupts();
+    }
+}
+
+pub inline fn send_resched_ipi(_: *ke.Cpu) void {
+    @panic("TODO send_resched_ipi");
+}
diff --git a/src/kern/init.zig b/src/kern/init.zig
index 47d3626..2c10e6f 100644
--- a/src/kern/init.zig
+++ b/src/kern/init.zig
@@ -14,8 +14,17 @@ fn handler(_: ?*anyopaque) void {
     while (true) {}
 }
 
+var temp_stack1: [8192]u8 align(16) = undefined;
+var temp_stack2: [8192]u8 align(16) = undefined;
+var temp_stack3: [8192]u8 align(16) = undefined;
+
+var stacks: []const []u8 = &.{&temp_stack1, &temp_stack2, &temp_stack3};
+var which_stack: usize = 0;
+
 fn make_thread(entry: *const fn (?*anyopaque) void, td: *ke.Thread, arg: ?*anyopaque) void {
-    const _stack = std.heap.page_allocator.alloc(u8, 16384) catch @panic("wtf");
+    std.debug.assert(which_stack < 3);
+    const _stack = stacks[which_stack];
+    which_stack += 1;
 
     td.init(@intFromPtr(_stack.ptr), 16384, entry, arg);
 }
@@ -49,8 +58,8 @@ pub fn init(boot_info: *pl.BootInfo) linksection(b.init) void {
 
         ke.ipl.lower(ipl);
     } else {
-        make_thread(&b.ex.fireworks.start, &threads[0], boot_info);
-        ke.sched.enqueue(&threads[0]);
+        // make_thread(&b.ex.fireworks.start, &threads[0], boot_info);
+        // ke.sched.enqueue(&threads[0]);
     }
 
     while (true) {}
diff --git a/src/kern/ipl.zig b/src/kern/ipl.zig
index d0bd87b..9ee6631 100644
--- a/src/kern/ipl.zig
+++ b/src/kern/ipl.zig
@@ -31,7 +31,7 @@ pub fn raise(new: Ipl) Ipl {
     const old = cpu.ipl;
 
     if (@intFromEnum(new) < @intFromEnum(old)) {
-        ke.panic("ke.ipl.raise(): Target IPL ({}) is lower than current IPL ({})\n", .{ new, old });
+        std.debug.panic("ke.ipl.raise(): Target IPL ({}) is lower than current IPL ({})", .{ new, old });
     }
 
     if (@intFromEnum(new) > @intFromEnum(Ipl.get_max_software())) {
@@ -53,7 +53,7 @@ pub fn lower(new: Ipl) void {
     const old = cpu.ipl;
 
     if (@intFromEnum(new) > @intFromEnum(old)) {
-        ke.panic("ke.ipl.lower(): Target IPL ({}) is higher than current IPL ({})\n", .{ new, old });
+        std.debug.panic("ke.ipl.lower(): Target IPL ({}) is higher than current IPL ({})", .{ new, old });
     }
 
     if (@intFromEnum(new) <= @intFromEnum(Ipl.get_max_software()) and @intFromEnum(old) > @intFromEnum(Ipl.get_max_software())) {
diff --git a/src/kern/panic.zig b/src/kern/panic.zig
index 6cfa23b..4e06fb3 100644
--- a/src/kern/panic.zig
+++ b/src/kern/panic.zig
@@ -3,10 +3,13 @@ const b = @import("base");
 const ke = b.ke;
 const ki = ke.private;
 
-/// Panics!
-pub fn panic(comptime fmt: []const u8, args: anytype) noreturn {
-    // FIXME: this is probably broken.
-    std.log.err("KERNEL PANIC: " ++ fmt, args);
+pub fn panic(
+    msg: []const u8,
+    first_trace_addr: ?usize,
+) noreturn {
+    _ = first_trace_addr;
+
+    std.log.err("KERNEL PANIC: {s}", .{msg});
 
     while (true) {}
 }
diff --git a/src/kern/um/impl.zig b/src/kern/um/impl.zig
index bd5661e..fda9811 100644
--- a/src/kern/um/impl.zig
+++ b/src/kern/um/impl.zig
@@ -20,7 +20,7 @@ fn set_signals(enabled: bool) bool {
     const how = if (enabled) c.SIG_UNBLOCK else c.SIG_BLOCK;
 
     if (c.pthread_sigmask(how, &newmask, &oldmask) != 0) {
-        ke.panic("pthread_sigmask failed", .{});
+        @panic("pthread_sigmask failed");
     }
 
     return c.sigismember(&oldmask, c.SIGUSR1) == 0;
@@ -67,7 +67,7 @@ pub const ThreadContext = struct {
         var new: ThreadContext = .{ .ucontext = undefined };
 
         if (c.getcontext(&new.ucontext) == -1) {
-            ke.panic("getcontext() failed", .{});
+            @panic("getcontext() failed");
         }
 
         new.ucontext.uc_stack.ss_sp = @ptrFromInt(stack);
@@ -99,7 +99,7 @@ pub const ThreadContext = struct {
         thread.lock.release_no_ipl();
 
         if (c.swapcontext(&self.ucontext, &new.ucontext) == -1) {
-            ke.panic("swapcontext() failed", .{});
+            @panic("swapcontext() failed");
         }
     }
 };
diff --git a/src/main.zig b/src/main.zig
deleted file mode 100644
index 9193797..0000000
--- a/src/main.zig
+++ /dev/null
@@ -1,58 +0,0 @@
-const std = @import("std");
-const ksyms = @import("ksyms");
-const pl = @import("base").pl;
-pub const rtl = @import("rtl");
-
-const DebugWriter = struct {
-    pub const Error = error{};
-    pub const Writer = std.io.GenericWriter(*DebugWriter, Error, write);
-
-    fn write(self: *DebugWriter, bytes: []const u8) Error!usize {
-        _ = self;
-        for (bytes) |c| pl.debug_write(c);
-        return bytes.len;
-    }
-
-    fn writer(self: *DebugWriter) Writer {
-        return .{ .context = self };
-    }
-};
-
-var debug_writer = DebugWriter{};
-
-export fn kmain() callconv(.c) void {
-    print("hello from kernel!\n", .{});
-
-    for (ksyms.ksyms) |sym| {
-        print("  0x{x:0>16} {s}\n", .{ sym.addr, sym.name });
-    }
-
-    pl.first_init();
-
-    while (true) {
-        asm volatile ("hlt");
-    }
-}
-
-export fn memset(dest: [*]u8, c: u8, n: usize) [*]u8 {
-    for (dest[0..n]) |*b| b.* = c;
-    return dest;
-}
-
-export fn memcpy(dest: [*]u8, src: [*]const u8, n: usize) [*]u8 {
-    for (0..n) |i| dest[i] = src[i];
-    return dest;
-}
-
-export fn memmove(dest: [*]u8, src: [*]const u8, n: usize) [*]u8 {
-    if (@intFromPtr(dest) < @intFromPtr(src)) {
-        for (0..n) |i| dest[i] = src[i];
-    } else {
-        var i = n;
-        while (i > 0) {
-            i -= 1;
-            dest[i] = src[i];
-        }
-    }
-    return dest;
-}
diff --git a/src/platform/amd64/entry.zig b/src/platform/amd64/entry.zig
deleted file mode 100644
index 534a03b..0000000
--- a/src/platform/amd64/entry.zig
+++ /dev/null
@@ -1,3 +0,0 @@
-const b = @import("base");
-
-pub fn first_init() linksection(b.init) void {}
diff --git a/src/platform/amd64/impl.zig b/src/platform/amd64/impl.zig
index f77b5ac..58f1316 100644
--- a/src/platform/amd64/impl.zig
+++ b/src/platform/amd64/impl.zig
@@ -1,6 +1,25 @@
-const entry = @import("entry.zig");
+const b = @import("base");
+const ki = b.ke.private;
 
-pub const first_init = entry.first_init;
+pub const name = "AMD64";
+
+pub fn first_init() void {}
+
+pub fn early_init() void {
+    const impl_cpu = &ki.bootstrap_cpu.impl;
+    impl_cpu.self_ptr = impl_cpu;
+    impl_cpu.percpu_offset = 0;
+
+    const impl_cpu_ptr = @intFromPtr(impl_cpu);
+    asm volatile ("wrmsr"
+        :
+        : [_] "{eax}" (@as(u32, @intCast(impl_cpu_ptr & 0xFFFFFFFF))),
+          [_] "{edx}" (@as(u32, @truncate(impl_cpu_ptr >> 32))),
+          [_] "{ecx}" (0xC000_0101),
+    );
+}
+
+pub fn late_init() void {}
 
 pub fn devices_init() void {}
 
diff --git a/src/platform/limine/entry.zig b/src/platform/limine/entry.zig
new file mode 100644
index 0000000..888a4b8
--- /dev/null
+++ b/src/platform/limine/entry.zig
@@ -0,0 +1,31 @@
+const b = @import("base");
+const ksyms = @import("ksyms");
+
+const pl = b.pl;
+const ke = b.ke;
+
+pub const std_options = b.std_options;
+pub const panic = b.panic;
+
+pub const rtl = @import("rtl");
+
+const std = @import("std");
+
+var boot_info: pl.BootInfo = undefined;
+
+export fn kmain() callconv(.c) void {
+    std.log.info("hello from kernel!", .{});
+
+    for (ksyms.ksyms) |sym| {
+        std.log.info("  0x{x:0>16} {s}", .{ sym.addr, sym.name });
+    }
+
+    boot_info.memory_map.entry_count = 0;
+
+    var cpus: [1]*ke.Cpu = .{&ke.private.bootstrap_cpu};
+
+    ke.ncpus = 1;
+    ke.cpus = &cpus;
+
+    ke.private.init(&boot_info);
+}
diff --git a/src/platform/root.zig b/src/platform/root.zig
index bd24b9d..85c1cda 100644
--- a/src/platform/root.zig
+++ b/src/platform/root.zig
@@ -10,6 +10,10 @@ else if (@hasDecl(config, "CONFIG_ARCH_UM"))
 else
     @compileError("unsupported architecture");
 
+pub inline fn first_init() void {
+    return impl.first_init();
+}
+
 /// Early platform-specific initialization, called before anything else.
 pub inline fn early_init() void {
     return impl.early_init();
diff --git a/src/platform/um/entry.zig b/src/platform/um/entry.zig
index 6c50e1e..fec2269 100644
--- a/src/platform/um/entry.zig
+++ b/src/platform/um/entry.zig
@@ -1,6 +1,7 @@
 const b = @import("base");
 
 pub const std_options = b.std_options;
+pub const panic = b.panic;
 
 pub const rtl = @import("rtl");
 
diff --git a/src/platform/um/timer.zig b/src/platform/um/timer.zig
index 4abc321..5330b94 100644
--- a/src/platform/um/timer.zig
+++ b/src/platform/um/timer.zig
@@ -27,7 +27,7 @@ pub fn arm_timer(ns: b.Nanoseconds) void {
     }, .it_interval = .{ .tv_sec = 0, .tv_nsec = 0 } };
 
     if (c.timer_settime(timerid, 0, &value, null) == -1) {
-        ke.panic("timer_settime failed", .{});
+        @panic("timer_settime failed");
     }
 }
 
@@ -68,6 +68,6 @@ pub fn init_cpu() void {
     sev._sigev_un._tid = linux.gettid();
 
     if (c.timer_create(c.CLOCK_MONOTONIC, &sev, &timerid) == -1) {
-        ke.panic("timer_create failed", .{});
+        @panic("timer_create failed");
     }
 }
diff --git a/src/root.zig b/src/root.zig
index 150ff8b..0ca3bc5 100644
--- a/src/root.zig
+++ b/src/root.zig
@@ -40,3 +40,5 @@ pub fn tib(comptime N: u32) usize {
 pub const std_options = std.Options{
     .logFn = ke.log.log,
 };
+
+pub const panic = std.debug.FullPanic(ke.panic);