rtl: add LinkerSet

build/linker-scripts/x86_64.lds

@@ -52,12 +52,6 @@ SECTIONS
     } :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 : {

src/ex/init.zig

@@ -6,6 +6,7 @@ const mm = r.mm;
 const ex = r.ex;
 const ps = r.ps;
 const exp = ex.private;
+const rtl = @import("rtl");
 
 // XXX
 const fbconsole = @import("../dev/fbconsole.zig");

src/kern/cpu.zig

@@ -5,22 +5,16 @@ const r = @import("root");
 const ke = r.ke;
 const ki = r.ke.private;
 
-extern var __init_array_percpu_start: u8;
-extern var __init_array_percpu_end: u8;
-
 const id = CpuLocal(u32, 0);
 
 /// Initialize a CPU. Must be called on all CPUs.
 pub fn init_cpu(cpu_id: u32) void {
-    const start = @intFromPtr(&__init_array_percpu_start);
-    const end = @intFromPtr(&__init_array_percpu_end);
-    const count = (end - start) / @sizeOf(*const fn () void);
-    const funcs: [*]const *const fn () callconv(.c) void = @ptrFromInt(start);
+    const elems = r.percpu_init_set.elems();
 
     id.local().* = cpu_id;
 
-    for (0..count) |i| {
-        funcs[i]();
+    for (elems) |func| {
+        func();
     }
 }
 

src/kern/dpc.zig

@@ -40,12 +40,14 @@ const pcpu = ke.CpuLocal(PerCpu, .{
     .queue = undefined,
 });
 
-export const dpc_percpu_init linksection(r.percpu_init) = &pcpu_init;
-
-fn pcpu_init() linksection(r.init) callconv(.c) void {
+fn pcpu_init() linksection(r.init) void {
     pcpu.local().queue.init();
 }
 
+comptime {
+    _ = r.percpu_init_set.insert(&pcpu_init);
+}
+
 /// Enqueue a DPC.
 /// If the DPC is already enqueued, this function is a no-op.
 pub fn enqueue(dpc: *Dpc, arg: ?*anyopaque) void {

src/kern/sched.zig

@@ -384,10 +384,8 @@ pub fn update_priority_locked(td: *ke.Thread, new_prio: u8) void {
 
 }
 
-export const sched_percpu_init linksection(r.percpu_init) = &init_cpu;
-
 /// Initialize a CPU for use by the scheduler.
-fn init_cpu() linksection(r.init) callconv(.c) void {
+fn init_cpu() linksection(r.init) void {
     var cpu = percpu.local();
 
     cpu.* = .{
@@ -421,6 +419,10 @@ fn init_cpu() linksection(r.init) callconv(.c) void {
     }
 }
 
+comptime {
+    _ = r.percpu_init_set.insert(&init_cpu);
+}
+
 /// Called on CPU 0 to initialize load balancing mechanisms.
 pub fn late_init() linksection(r.init) void {
     balance_timer.init();

src/kern/shootdown.zig

@@ -49,9 +49,7 @@ var sync_addr: r.VAddr = 0;
 var sync_count: usize = 0;
 var shootdown_lock: ke.SpinLock = .init();
 
-export const tlb_percpu_init linksection(r.percpu_init) = &pcpu_init;
-
-fn pcpu_init() linksection(r.init) callconv(.c) void {
+fn pcpu_init() linksection(r.init) void {
     const local = percpu.local();
 
     local.valid_states = @splat(.init(0));
@@ -59,6 +57,10 @@ fn pcpu_init() linksection(r.init) callconv(.c) void {
     local.states = @splat(.{ .base = 0, .npages = 0, .state = .init(slot_free), .payload = undefined, .link = undefined });
 }
 
+comptime {
+    _ = r.percpu_init_set.insert(&pcpu_init);
+}
+
 /// Allocate an invalidation state slot on this CPU.
 /// O(N) algorithm but N is tiny.
 fn allocate_slot(cpu: *PerCpu) ?usize {

src/kern/spinlock.zig

@@ -124,10 +124,8 @@ const PerCpu = struct {
 
 const pcpu = ke.CpuLocal(PerCpu, undefined);
 
-export const qspinlock_percpu_init linksection(r.percpu_init) = &init_cpu;
-
 /// Initialize a CPU's MCS nodes.
-fn init_cpu() linksection(r.init) callconv(.c) void {
+fn init_cpu() linksection(r.init) void {
     var cpu = pcpu.local();
     cpu.curr_idx = 0;
 
@@ -137,6 +135,10 @@ fn init_cpu() linksection(r.init) callconv(.c) void {
     }
 }
 
+comptime {
+    _ = r.percpu_init_set.insert(&init_cpu);
+}
+
 /// Queued spin lock implementation.
 /// See https://rdmsr.github.io/writing/qspinlocks
 pub const QSpinLock = LockTemplate(struct {

src/kern/tunable.zig

@@ -5,6 +5,8 @@ const rtl = @import("rtl");
 const r = @import("root");
 const pl = r.pl;
 
+const set = rtl.LinkerSet("tunables", *const Entry);
+
 const Entry = struct {
     name: []const u8,
     address: *anyopaque,
@@ -18,7 +20,7 @@ pub fn Tunable(comptime T: type, comptime default: T, comptime name: []const u8)
     return struct {
         var storage: T = default;
 
-        const metadata: Entry linksection(".data.tunable") =
+        const metadata: Entry =
             .{
                 .name = name,
                 .address = &storage,
@@ -30,33 +32,32 @@ pub fn Tunable(comptime T: type, comptime default: T, comptime name: []const u8)
                 },
             };
 
+        comptime {
+            _ = set.insert(&metadata);
+        }
+
         pub fn load() T {
-            _ = metadata;
             return storage;
         }
     };
 }
 
-extern var __tunables_start: u8;
-extern var __tunables_end: u8;
-
 pub fn init(boot_info: *pl.BootInfo) void {
     const cmdline = boot_info.cmdline orelse return;
 
-    const start = @intFromPtr(&__tunables_start);
-    const end = @intFromPtr(&__tunables_end);
-    const count = (end - start) / @sizeOf(Entry);
-    const entries: [*]Entry = @ptrFromInt(start);
+    const elems = set.elems();
 
-    for (0..count) |i| {
-        switch (entries[i].type) {
+    for (elems) |entry| {
+        switch (entry.type) {
             .num => |info| {
-                const a = entries[i].address;
+                const a = entry.address;
 
                 switch (info.signedness) {
                     .unsigned => {
-                        const value = rtl.cmdline.get_number(u64, cmdline, entries[i].name) orelse {
-                            std.log.warn("Invalid number value for '{s}', falling back.", .{entries[i].name});
+                        const value = rtl.cmdline.get_number(u64, cmdline, entry.name) catch |e| {
+                            if (e == error.Format) {
+                                std.log.warn("Invalid number value for '{s}', falling back.", .{entry.name});
+                            }
                             continue;
                         };
 
@@ -70,8 +71,11 @@ pub fn init(boot_info: *pl.BootInfo) void {
                     },
 
                     .signed => {
-                        const value = rtl.cmdline.get_number(i64, cmdline, entries[i].name) orelse {
-                            std.log.warn("Invalid number value for '{s}', falling back.", .{entries[i].name});
+                        const value = rtl.cmdline.get_number(i64, cmdline, entry.name) catch |e| {
+                            if (e == error.Format) {
+                                std.log.warn("Invalid number value for '{s}', falling back.", .{entry.name});
+                            }
+
                             continue;
                         };
 
@@ -87,15 +91,15 @@ pub fn init(boot_info: *pl.BootInfo) void {
             },
 
             .bool => {
-                const value = rtl.cmdline.get_string(cmdline, entries[i].name) orelse continue;
-                const ptr: *bool = @ptrCast(@alignCast(entries[i].address));
+                const value = rtl.cmdline.get_string(cmdline, entry.name) orelse continue;
+                const ptr: *bool = @ptrCast(@alignCast(entry.address));
 
                 if (std.mem.eql(u8, value, "true")) {
                     ptr.* = true;
                 } else if (std.mem.eql(u8, value, "false")) {
                     ptr.* = false;
                 } else {
-                    std.log.warn("Invalid cmdline boolean value for tunable '{s}'", .{entries[i].name});
+                    std.log.warn("Invalid cmdline boolean value for tunable '{s}'", .{entry.name});
                 }
             },
         }

src/root.zig

@@ -11,7 +11,8 @@ pub const ps = @import("proc/root.zig");
 const config = @import("config");
 
 pub const init = ".text.init";
-pub const percpu_init = ".percpu_init_array";
+
+pub const percpu_init_set = rtl.LinkerSet("percpu_init", *const fn () void);
 pub const percpu = ".data.percpu";
 
 pub const VAddr = usize;

src/rtl/cmdline.zig

@@ -17,13 +17,13 @@ pub fn get_string(cmdline: []const u8, key: []const u8) ?[]const u8 {
 }
 
 /// Get the number value of `key` in `cmdline`.
-pub fn get_number(comptime T: type, cmdline: []const u8, key: []const u8) ?T {
+pub fn get_number(comptime T: type, cmdline: []const u8, key: []const u8) !T {
     const str = get_string(cmdline, key);
     if (str) |s| {
-        const res = std.fmt.parseInt(T, s, 10) catch return null;
+        const res = std.fmt.parseInt(T, s, 10) catch return error.Format;
         return res;
     }
-    return null;
+    return error.NotPresent;
 }
 
 test "get_string() should return the value of a key" {

src/rtl/linker_set.zig

@@ -0,0 +1,41 @@
+const std = @import("std");
+
+/// Used for declaring global objects that get collected by the linker
+/// into a `LinkerSet`. This works by declaring each set its own section
+/// and abusing linker-generated `__start_<name>` and `__stop_<name>` symbols.
+/// Each set stores pointers to objects, so `T` must be a pointer type.
+pub fn LinkerSet(name: []const u8, comptime T: type) type {
+    if (@typeInfo(T) != .pointer) {
+        @compileError("LinkerSet type must be a pointer type");
+    }
+
+    return struct {
+        const start = @extern(*u8, .{ .name = "__start_set_" ++ name });
+        const end = @extern(*u8, .{ .name = "__stop_set_" ++ name });
+
+        const Self = @This();
+
+        pub fn count() usize {
+            return (@intFromPtr(end) - @intFromPtr(start)) / @sizeOf(T);
+        }
+
+        pub fn elems() []T {
+            const n = count();
+            const arr: [*]T = @ptrCast(@alignCast(start));
+
+            return arr[0..n];
+        }
+
+        pub fn insert(elem: T) type {
+            const U = struct {
+                var storage: T linksection("set_" ++ name) = elem;
+
+                comptime {
+                    _ = &storage;
+                }
+            };
+
+            return U;
+        }
+    };
+}

src/rtl/root.zig

@@ -14,6 +14,7 @@ pub const AVLTree = @import("avl.zig").AVLTree;
 pub const BitMap = @import("bitmap.zig").BitMap;
 pub const AtomicBitMap = @import("bitmap.zig").AtomicBitMap;
 pub const HandoffList = @import("handoff.zig").HandoffList;
+pub const LinkerSet = @import("linker_set.zig").LinkerSet;
 
 /// Asserts that a given type `T` matches the schema declared by `I`.
 /// This includes public methods and fields.