move stack and bss initialization to start.rs

.cargo/config.toml

@@ -7,7 +7,7 @@ target = "x86_64-eduos.json"
 
 [target.i686-eduos]
 rustflags = [
-  "-C", "link-arg=-Tsrc/arch/x86/link_i686.ld", "-C", "relocation-model=static"
+  "-C", "link-arg=-Tsrc/arch/x86/kernel/link_i686.ld", "-C", "relocation-model=static"
 ]
 runner = "qemu-system-x86_64 -display none -serial stdio -smp 1 -m 256M -device isa-debug-exit,iobase=0xf4,iosize=0x04 -kernel"
 

src/arch/mod.rs

@@ -1,13 +1,17 @@
+// Implementations for x86.
+#[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
+pub mod x86;
+
 // Export our platform-specific modules.
 #[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
-pub use self::x86::{init, processor};
+pub use self::x86::kernel::{init, processor};
 
-#[cfg(all(target_arch = "x86", feature = "vga"))]
-pub use self::x86::vga;
+#[cfg(feature = "vga")]
+pub use self::x86::kernel::vga;
 
-#[cfg(not(all(target_arch = "x86", feature = "vga")))]
-pub use self::x86::serial;
+#[cfg(not(feature = "vga"))]
+pub use self::x86::kernel::serial;
 
-// Implementations for x86.
+// Export our platform-specific modules.
 #[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
-pub mod x86;
+pub use self::x86::mm;

src/arch/x86/entry.s → src/arch/x86/kernel/entry.s

@@ -1,12 +1,8 @@
-# This is the kernel's entry point. We could either call main here,
-# or we can use this to setup the stack or other nice stuff, like
-# perhaps setting up the GDT and segments. Please note that interrupts
-# are disabled at this point: More on interrupts later!
+# Muktiboot header, which is used by the loader to detect
+# a multiboot kernel
 
 .code32
 
-.set BOOT_STACK_SIZE, 4096
-
 # We use a special name to map this section at the begin of our kernel
 # =>  Multiboot expects its magic number at the beginning of the kernel.
 .section .mboot, "a"
@@ -26,30 +22,4 @@ mboot:
     .4byte MULTIBOOT_HEADER_MAGIC
     .4byte MULTIBOOT_HEADER_FLAGS
     .4byte MULTIBOOT_CHECKSUM
-    .4byte 0, 0, 0, 0, 0 # address fields
-
-.section .text
-.align 4
-.extern main
-.extern shutdown
-.global _start
-_start:
-    cli # avoid any interrupt
-
-    # Initialize stack pointer
-    mov esp, OFFSET boot_stack
-    add esp, BOOT_STACK_SIZE - 16
-
-    call main
-    # eax has the return value of main
-    push eax
-    call shutdown
-L0:
-    hlt
-    jmp L0
-
-.section .data
-.align 4096
-.global boot_stack
-boot_stack:
-    .fill BOOT_STACK_SIZE, 1, 0xcd
+    .4byte 0, 0, 0, 0, 0 # address fields

src/arch/x86/link_i686.ld → src/arch/x86/kernel/link_i686.ld

@@ -4,24 +4,26 @@ phys = 0x000000100000;
 SECTIONS
 {
   kernel_start = phys;
-  .mboot phys : AT(ADDR(.mboot)) {
+  .mboot phys : {
     KEEP(*(.mboot))
     KEEP(*(.mboot.*))
   }
-  .text ALIGN(4096) : AT(ADDR(.text)) {
+  .text ALIGN(4) : {
     *(.text)
     *(.text.*)
   }
-  .rodata ALIGN(4096) : AT(ADDR(.rodata)) {
+  .rodata ALIGN(4) : {
     *(.rodata)
     *(.rodata.*)
   }
-  .data ALIGN(4096) : AT(ADDR(.data)) {
+  .data ALIGN(4) : {
     *(.data)
     *(.data.*)
   }
-  .bss ALIGN(4096) : AT(ADDR(.bss)) {
+  .bss ALIGN(4) : {
+    __bss_start = .;
     *(.bss)
     *(.bss.*)
+    __bss_end = .;
   }
 }

src/arch/x86/kernel/mod.rs

@@ -0,0 +1,16 @@
+pub mod processor;
+#[cfg(not(feature = "vga"))]
+pub mod serial;
+pub mod start;
+#[cfg(feature = "vga")]
+pub mod vga;
+
+#[cfg(target_arch = "x86")]
+core::arch::global_asm!(include_str!("entry.s"));
+
+pub fn init() {
+	processor::cpu_init();
+
+	#[cfg(all(target_arch = "x86", feature = "vga"))]
+	vga::init();
+}

src/arch/x86/kernel/start.rs

@@ -0,0 +1,68 @@
+use crate::arch;
+use crate::arch::x86::kernel::processor::shutdown;
+
+extern "C" {
+	pub fn main() -> i32;
+}
+
+#[cfg(target_arch = "x86")]
+extern "C" {
+	static mut __bss_start: u8;
+	static __bss_end: u8;
+}
+
+/// initialize bss section
+#[cfg(target_arch = "x86")]
+unsafe fn bss_init() {
+	core::ptr::write_bytes(
+		core::ptr::addr_of_mut!(__bss_start),
+		0,
+		core::ptr::addr_of!(__bss_end) as usize - core::ptr::addr_of!(__bss_start) as usize,
+	);
+}
+
+#[cfg(not(test))]
+unsafe extern "C" fn entry() -> ! {
+	arch::init();
+
+	#[cfg(target_arch = "x86")]
+	bss_init();
+
+	let ret = main();
+
+	shutdown(ret)
+}
+
+#[cfg(not(test))]
+#[cfg(target_arch = "x86_64")]
+#[no_mangle]
+/// # Safety
+///
+/// This function is the entry point of the kernel.
+/// The kernel itself should not call this function.
+pub unsafe extern "C" fn _start() -> ! {
+	entry();
+}
+
+#[cfg(not(test))]
+#[cfg(target_arch = "x86")]
+#[no_mangle]
+#[naked]
+/// # Safety
+///
+/// This function is the entry point of the kernel.
+/// The kernel itself should not call this function.
+pub unsafe extern "C" fn _start() -> ! {
+	use crate::arch::mm::{BOOT_STACK, BOOT_STACK_SIZE};
+	use core::arch::naked_asm;
+
+	naked_asm!(
+		"lea esp, {stack}",
+		"add esp, {offset}",
+		"jmp {entry}",
+		stack = sym BOOT_STACK,
+		offset = const BOOT_STACK_SIZE - 16,
+		entry = sym entry,
+		options(noreturn)
+	);
+}

src/arch/x86/mm/mod.rs

@@ -0,0 +1,18 @@
+#[cfg(target_arch = "x86")]
+#[repr(C, align(64))]
+pub(crate) struct Aligned<T>(T);
+
+#[cfg(target_arch = "x86")]
+impl<T> Aligned<T> {
+	/// Constructor.
+	pub const fn new(t: T) -> Self {
+		Self(t)
+	}
+}
+
+#[cfg(target_arch = "x86")]
+pub(crate) const BOOT_STACK_SIZE: usize = 0x3000;
+#[cfg(target_arch = "x86")]
+#[link_section = ".data"]
+pub(crate) static mut BOOT_STACK: Aligned<[u8; BOOT_STACK_SIZE]> =
+	Aligned::new([0; BOOT_STACK_SIZE]);

src/arch/x86/mod.rs

@@ -1,17 +1,2 @@
-pub mod processor;
-#[cfg(not(all(target_arch = "x86", feature = "vga")))]
-pub mod serial;
-#[cfg(target_arch = "x86_64")]
-pub mod start;
-#[cfg(all(target_arch = "x86", feature = "vga"))]
-pub mod vga;
-
-#[cfg(target_arch = "x86")]
-core::arch::global_asm!(include_str!("entry.s"));
-
-pub fn init() {
-	processor::cpu_init();
-
-	#[cfg(all(target_arch = "x86", feature = "vga"))]
-	vga::init();
-}
+pub mod kernel;
+pub mod mm;