refactor(x86_64): extract boot stack to Rust

src/arch/x86_64/mod.rs

@@ -6,6 +6,8 @@ mod paging;
 #[cfg(target_os = "none")]
 mod physicalmem;
 mod platform;
+#[cfg(target_os = "none")]
+mod stack;
 
 pub use console::Console;
 

src/arch/x86_64/platform/linux/entry.s

@@ -3,8 +3,6 @@
 
 .code64
 
-.set BOOT_STACK_SIZE, 4096
-
 .extern loader_start		# defined in linker script
 .extern loader_end
 
@@ -16,8 +14,8 @@ _start:
     cli # avoid any interrupt
 
     # Initialize stack pointer
-    movabs rsp, OFFSET boot_stack
-    add rsp, BOOT_STACK_SIZE - 16
+    movabs rsp, OFFSET {stack}
+    add rsp, {stack_top_offset}
 
     mov [boot_params], rsi
 
@@ -67,8 +65,8 @@ start64:
     mov gs, ax
     cld
     # set default stack pointer
-    movabs rsp, OFFSET boot_stack
-    add rsp, BOOT_STACK_SIZE-16
+    movabs rsp, OFFSET {stack}
+    add rsp, {stack_top_offset}
 
     # jump to the boot processors's C code
     jmp {loader_main}
@@ -81,11 +79,6 @@ invalid:
 boot_params:
     .8byte 0
 
-.align 4096
-.global boot_stack
-boot_stack:
-    .fill BOOT_STACK_SIZE, 1, 0xcd
-
 # Bootstrap page tables are used during the initialization.
 .align 4096
 boot_pml4:

src/arch/x86_64/platform/linux/mod.rs

@@ -26,6 +26,8 @@ mod entry {
 	core::arch::global_asm!(
 		include_str!("entry.s"),
 		loader_main = sym crate::os::loader_main,
+		stack = sym crate::arch::x86_64::stack::STACK,
+		stack_top_offset = const crate::arch::x86_64::stack::Stack::top_offset(),
 		gdt_ptr = sym crate::arch::x86_64::gdt::GDT_PTR,
 		kernel_code_selector = const crate::arch::x86_64::gdt::Gdt::kernel_code_selector().0,
 		kernel_data_selector = const crate::arch::x86_64::gdt::Gdt::kernel_data_selector().0,

src/arch/x86_64/platform/multiboot/entry.s

@@ -5,8 +5,6 @@
 
 .code32
 
-.set BOOT_STACK_SIZE, 4096
-
 .extern loader_start		# defined in linker script
 .extern loader_end
 
@@ -37,8 +35,8 @@ _start:
     cli # avoid any interrupt
 
     # Initialize stack pointer
-    mov esp, OFFSET boot_stack
-    add esp, BOOT_STACK_SIZE - 16
+    mov esp, OFFSET {stack}
+    add esp, {stack_top_offset}
 
     # Interpret multiboot information
     mov [mb_info], ebx
@@ -155,8 +153,8 @@ start64:
     mov gs, eax
     cld
     # set default stack pointer
-    movabs rsp, OFFSET boot_stack
-    add rsp, BOOT_STACK_SIZE-16
+    movabs rsp, OFFSET {stack}
+    add rsp, {stack_top_offset}
 
     # jump to the boot processors's C code
     jmp {loader_main}
@@ -168,11 +166,6 @@ start64:
 mb_info:
     .8byte 0
 
-.align 4096
-.global boot_stack
-boot_stack:
-    .fill BOOT_STACK_SIZE, 1, 0xcd
-
 # Bootstrap page tables are used during the initialization.
 .align 4096
 boot_pml4:

src/arch/x86_64/platform/multiboot/mod.rs

@@ -27,6 +27,8 @@ mod entry {
 	core::arch::global_asm!(
 		include_str!("entry.s"),
 		loader_main = sym crate::os::loader_main,
+		stack = sym crate::arch::x86_64::stack::STACK,
+		stack_top_offset = const crate::arch::x86_64::stack::Stack::top_offset(),
 		gdt_ptr = sym crate::arch::x86_64::gdt::GDT_PTR,
 		kernel_code_selector = const crate::arch::x86_64::gdt::Gdt::kernel_code_selector().0,
 		kernel_data_selector = const crate::arch::x86_64::gdt::Gdt::kernel_data_selector().0,

src/arch/x86_64/stack.rs

@@ -0,0 +1,24 @@
+use core::cell::UnsafeCell;
+use core::mem::{self, MaybeUninit};
+
+#[repr(C, align(0x1000))]
+pub struct Stack(UnsafeCell<[MaybeUninit<u8>; 0x1000]>);
+
+unsafe impl Sync for Stack {}
+
+impl Stack {
+	const fn new() -> Self {
+		let fill = if cfg!(debug_assertions) {
+			MaybeUninit::new(0xcd)
+		} else {
+			MaybeUninit::uninit()
+		};
+		Self(UnsafeCell::new([fill; _]))
+	}
+
+	pub const fn top_offset() -> u16 {
+		mem::size_of::<Self>() as u16 - 0x10
+	}
+}
+
+pub static STACK: Stack = Stack::new();