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@@ -0,0 +1,75 @@
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+#![no_std]
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+#![no_main]
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+
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+// TODO: RustSBI EFI module
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+#[no_mangle]
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+extern "C" fn rust_main(_hart_id: usize, _opaque: usize) {
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+ // TODO
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+}
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+
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+#[no_mangle]
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+extern "C" fn rust_sbi_exit() -> ! {
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+ sbi_rt::system_reset(sbi_rt::Shutdown, sbi_rt::NoReason);
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+ loop {
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+ core::hint::spin_loop();
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+ }
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+}
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+
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+#[panic_handler]
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+fn panic(_info: &core::panic::PanicInfo) -> ! {
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+ // TODO panic handler
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+ loop {
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+ core::hint::spin_loop();
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+ }
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+}
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+
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+const LEN_STACK_PER_HART: usize = 16 * 1024;
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+pub const NUM_HART_MAX: usize = 8;
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+#[link_section = ".bss.uninit"]
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+static mut STACK: [u8; NUM_HART_MAX * LEN_STACK_PER_HART] = [0; NUM_HART_MAX * LEN_STACK_PER_HART];
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+
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+// If booted with RISC-V SBI, a0 must include hart ID, while a1 must be an opaque register
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+#[naked_function::naked]
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+#[link_section = ".text.entry"]
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+#[export_name = "_start"]
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+unsafe extern "C" fn start() -> ! {
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+ asm!(
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+ // 1. Turn off interrupt
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+ " csrw sie, zero",
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+ // 2. Initialize programming langauge runtime
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+ // only initialize if it is boot hart (hart ID 0)
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+ " bnez a0, 3f",
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+ // clear bss segment
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+ " la t0, sbss
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+ la t1, ebss
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+ 2: bgeu t0, t1, 2f
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+ sd zero, 0(t0)
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+ addi t0, t0, 8
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+ j 2b",
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+ // prepare data segment
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+ " la t3, sidata
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+ la t4, sdata
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+ la t5, edata
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+ 2: bgeu t4, t5, 2f
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+ ld t6, 0(t3)
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+ sd t6, 0(t4)
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+ addi t3, t3, 8
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+ addi t4, t4, 8
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+ j 2b",
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+ "3:",
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+ // 3. Prepare stack for each hart
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+ " la sp, {stack}
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+ li t1, {per_hart_stack_size}
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+ addi t2, a0, 1
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+ 2: add sp, sp, t1
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+ addi t2, t2, -1
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+ bnez t2, 2b",
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+ // 4. Start main function
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+ " call {main}",
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+ " call {exit}",
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+ stack = sym STACK,
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+ per_hart_stack_size = const LEN_STACK_PER_HART,
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+ main = sym rust_main,
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+ exit = sym rust_sbi_exit
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+ )
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+}
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guttatus