From f62b05c93c6c539d899d2656c0638d404a036f1a Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 24 Jul 2025 12:28:23 +0000
Subject: x86_64: implement robust C++ global initialization

Implement a comprehensive mechanism to ensure correct C++ runtime
initialization before the kernel main function is called. This replaces
the previous, incomplete reliance on an `_init` function.

The new design robustly handles both legacy `.ctors` and modern
`.init_array` initialization schemes used by the GNU toolchain. A single
C++ function, `invoke_global_constructors`, now iterates through both
arrays of function pointers to ensure all types of global initializers
are executed.
---
 arch/x86_64/src/boot/crti.s                 | 13 -------------
 arch/x86_64/src/boot/crtn.s                 |  9 ---------
 arch/x86_64/src/boot/entry64.s              |  4 ++--
 arch/x86_64/src/boot/initialize_runtime.cpp | 24 ++++++++++++++++++++++++
 4 files changed, 26 insertions(+), 24 deletions(-)
 delete mode 100644 arch/x86_64/src/boot/crti.s
 delete mode 100644 arch/x86_64/src/boot/crtn.s
 create mode 100644 arch/x86_64/src/boot/initialize_runtime.cpp

(limited to 'arch/x86_64/src')

diff --git a/arch/x86_64/src/boot/crti.s b/arch/x86_64/src/boot/crti.s
deleted file mode 100644
index 26878fe..0000000
--- a/arch/x86_64/src/boot/crti.s
+++ /dev/null
@@ -1,13 +0,0 @@
-.code64
-
-.section .init
-.global _init
-_init:
-    push %rbp
-    movq %rsp, %rbp
-
-.section .fini
-.global _fini
-_fini:
-    push %rbp
-    movq %rsp, %rbp
diff --git a/arch/x86_64/src/boot/crtn.s b/arch/x86_64/src/boot/crtn.s
deleted file mode 100644
index 06fb7ce..0000000
--- a/arch/x86_64/src/boot/crtn.s
+++ /dev/null
@@ -1,9 +0,0 @@
-.code64
-
-.section .init
-    popq %rbp
-    ret
-
-.section .fini
-    popq %rbp
-    ret
diff --git a/arch/x86_64/src/boot/entry64.s b/arch/x86_64/src/boot/entry64.s
index f575c50..110ced8 100644
--- a/arch/x86_64/src/boot/entry64.s
+++ b/arch/x86_64/src/boot/entry64.s
@@ -12,8 +12,8 @@ _entry64:
 
     xor %rax, %rax
 
-    call _init
-
+    call invoke_global_constructors
+    
     call main
 
 1:
diff --git a/arch/x86_64/src/boot/initialize_runtime.cpp b/arch/x86_64/src/boot/initialize_runtime.cpp
new file mode 100644
index 0000000..9a3df0e
--- /dev/null
+++ b/arch/x86_64/src/boot/initialize_runtime.cpp
@@ -0,0 +1,24 @@
+#include <algorithm>
+#include <functional>
+#include <span>
+
+extern "C"
+{
+  using global_initializer = auto (*)() -> void;
+
+  extern global_initializer __ctors_start;
+  extern global_initializer __ctors_end;
+  extern global_initializer __init_array_start;
+  extern global_initializer __init_array_end;
+
+  auto invoke_global_constructors() -> void
+  {
+    auto constructors = std::span{&__ctors_start, &__ctors_end};
+    auto initializers = std::span{&__init_array_start, &__init_array_end};
+
+    auto apply_invoke = [](auto invokable) { return std::invoke(invokable); };
+
+    std::ranges::for_each(constructors, apply_invoke);
+    std::ranges::for_each(initializers, apply_invoke);
+  }
+}
-- 
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