refactor(aarch64,riscv64): Remove use of linker script

build.rs

@@ -11,8 +11,6 @@ fn set_linker_script() {
 	let cfg_feature = env::var("CARGO_CFG_FEATURE").unwrap();
 
 	let linker_script = match cfg_target_arch.as_str() {
-		"aarch64" if cfg_feature.contains("elf") => "link.ld",
-		"riscv64" if cfg_feature.contains("sbi") => "link.ld",
 		"x86_64" if cfg_feature.contains("multiboot") => "platform/multiboot/link.ld",
 		_ => return,
 	};

src/arch/aarch64/entry.rs

@@ -8,11 +8,14 @@ use aarch64_cpu::registers::{
 use log::info;
 use tock_registers::fields::{FieldValue, TryFromValue};
 
+use crate::stack::STACK;
+
 /// Number of virtual address bits for 4KB page
 const VA_BITS: u64 = 48;
 
 global_asm!(
 	include_str!("entry.s"),
+	BOOT_STACK = sym STACK,
 	start_rust = sym start_rust,
 );
 

src/arch/aarch64/entry.s

@@ -16,8 +16,8 @@ _start:
 
 	// This loads the physical address of the stack end. For details see
 	// https://github.com/rust-embedded/rust-raspberrypi-OS-tutorials/blob/master/16_virtual_mem_part4_higher_half_kernel/src/bsp/raspberrypi/link.ld
-	adrp	x4, __boot_core_stack_end_exclusive
-	add		x4, x4, #:lo12:__boot_core_stack_end_exclusive
+	adrp	x4, {BOOT_STACK}
+	add		x4, x4, #:lo12:{BOOT_STACK}
 	mov		sp, x4
 
 	// Set correct Exception level!

src/arch/aarch64/mod.rs

@@ -17,15 +17,13 @@ use hermit_entry::boot_info::{BootInfo, HardwareInfo, PlatformInfo, RawBootInfo,
 use hermit_entry::elf::LoadedKernel;
 use log::info;
 
-use crate::BootInfoExt;
 use crate::arch::paging::*;
 use crate::fdt_ext::FdtExt;
 use crate::os::CONSOLE;
+use crate::{BootInfoExt, stack};
 
 /// start address of the RAM at Qemu's virt emulation
 const RAM_START: u64 = 0x40000000;
-/// Default stack size of the kernel
-const KERNEL_STACK_SIZE: usize = 32_768;
 /// Qemu assumes for ELF kernel that the fdt is located at
 /// start of RAM (0x4000_0000)
 /// see <https://qemu.readthedocs.io/en/latest/system/arm/virt.html>
@@ -102,8 +100,7 @@ pub unsafe fn boot_kernel(kernel_info: LoadedKernel) -> ! {
 		platform_info: PlatformInfo::LinuxBoot,
 	};
 
-	let stack = boot_info.load_info.kernel_image_addr_range.start as usize - KERNEL_STACK_SIZE;
-	let stack = ptr::with_exposed_provenance_mut(stack);
+	let stack = stack::get_stack_ptr();
 	let entry = ptr::with_exposed_provenance(entry_point.try_into().unwrap());
 	let raw_boot_info = boot_info.write();
 

src/arch/riscv64/mod.rs

@@ -14,8 +14,8 @@ use hermit_entry::boot_info::{
 use hermit_entry::elf::LoadedKernel;
 use log::info;
 
-use crate::BootInfoExt;
 use crate::fdt_ext::FdtExt;
+use crate::{BootInfoExt, stack};
 
 pub fn find_kernel() -> &'static [u8] {
 	let fdt = start::get_fdt();
@@ -92,7 +92,7 @@ pub unsafe fn boot_kernel(kernel_info: LoadedKernel) -> ! {
 		platform_info: PlatformInfo::LinuxBoot,
 	};
 
-	let stack = start::get_stack_ptr();
+	let stack = stack::get_stack_ptr();
 	let entry = ptr::with_exposed_provenance(entry_point.try_into().unwrap());
 	let hart_id = start::get_hart_id();
 	let raw_boot_info = boot_info.write();

src/arch/riscv64/start.rs

@@ -3,7 +3,8 @@ use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 
 use fdt::Fdt;
 
-static mut STACK: Stack = Stack::new();
+use crate::stack::{STACK, Stack};
+
 static HART_ID: AtomicUsize = AtomicUsize::new(0);
 static FDT: AtomicPtr<u8> = AtomicPtr::new(ptr::null_mut());
 
@@ -20,29 +21,24 @@ pub fn get_fdt() -> Fdt<'static> {
 	unsafe { Fdt::from_ptr(get_fdt_ptr()).unwrap() }
 }
 
-pub fn get_stack_ptr() -> *mut u8 {
-	let stack_top = &raw mut STACK;
-	// SAFETY: Pointing directly past the object is allowed
-	let stack_bottom = unsafe { stack_top.add(1) };
-	stack_bottom.cast::<u8>()
-}
-
 // TODO: Migrate to Constrained Naked Functions once stabilized
 // https://github.com/rust-lang/rust/issues/90957
 // TODO: Migrate to asm_const for Stack::SIZE once stabilized
 // https://github.com/rust-lang/rust/issues/93332
 #[no_mangle]
 #[naked_function::naked]
+#[link_section = ".init"]
 pub unsafe extern "C" fn _start(hart_id: usize, fdt: *const u8) -> ! {
 	asm!(
 		// Initialize stack
 		"la      sp, {BOOT_STACK}",
-		"li      t0, 0x8000",
+		"li      t0, {STACK_SIZE}",
 		"add     sp, sp, t0",
 
 		"j       {start}",
 
 		BOOT_STACK = sym STACK,
+		STACK_SIZE = const Stack::SIZE,
 		start = sym start,
 	)
 }
@@ -54,15 +50,3 @@ extern "C" fn start(hart_id: usize, fdt: *const u8) -> ! {
 
 	unsafe { crate::os::loader_main() }
 }
-
-// Align to page size
-#[repr(C, align(0x1000))]
-pub struct Stack([u8; Self::SIZE]);
-
-impl Stack {
-	const SIZE: usize = 0x8000;
-
-	pub const fn new() -> Self {
-		Self([0; Self::SIZE])
-	}
-}

src/main.rs

@@ -19,6 +19,8 @@ mod fdt;
 mod fdt_ext;
 mod log;
 mod os;
+#[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
+mod stack;
 
 #[cfg(any(target_os = "uefi", all(target_arch = "x86_64", target_os = "none")))]
 extern crate alloc;

src/stack.rs

@@ -0,0 +1,20 @@
+pub static mut STACK: Stack = Stack::new();
+
+// Align to page size
+#[repr(C, align(0x1000))]
+pub struct Stack([u8; Self::SIZE]);
+
+impl Stack {
+	pub const SIZE: usize = 0x8000;
+
+	pub const fn new() -> Self {
+		Self([0; Self::SIZE])
+	}
+}
+
+pub fn get_stack_ptr() -> *mut u8 {
+	let stack_top = &raw mut STACK;
+	// SAFETY: Pointing directly past the object is allowed
+	let stack_bottom = unsafe { stack_top.add(1) };
+	stack_bottom.cast::<u8>()
+}

xtask/src/target.rs

@@ -75,6 +75,15 @@ impl Target {
 
 	pub fn rustflags(&self) -> &'static [&'static str] {
 		match self {
+			Self::Aarch64Elf | Self::Aarch64BeElf => &[
+				"-Crelocation-model=static",
+				"-Clink-arg=--image-base=0x40400000",
+			],
+			Self::Riscv64Sbi => &[
+				"-Crelocation-model=static",
+				"-Clink-arg=--image-base=0x801ffe00",
+				"-Clink-arg=--section-start=.init=0x80200000",
+			],
 			Self::X86_64Linux | Self::X86_64Multiboot => &["-Crelocation-model=static"],
 			_ => &[],
 		}