td-exception: use global asm to replace naked interrupt handler

An interrupt handler table is used to handle all 256 interrupts. They
share common handler that saves the interrupt vector and context. If the
interrupt is not an error, a zero is pushed to the stack to align with
the error one.

Function `generic_interrupt_handler` is called to find and call the
corresponding callback in the `CALLBACK_TABLE`.

For virtualization exception, when the CET shadow stack is enabled, we
need to update the LIP value in the shadow stack. As shadow stack saves
the latest two return address after interrupt entry and the SSP, the
position of saved LIP value is the top address of shadow stack minus
0x18 bytes.

Signed-off-by: Jiaqi Gao <[email protected]>

td-exception/src/asm/handler.asm

@@ -0,0 +1,60 @@
+# Copyright (c) 2024 Intel Corporation
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+
+.section .text
+interrupt_handler_entry:
+        push rax
+        push rcx
+        push rdx
+        push rdi
+        push rsi
+        push r8
+        push r9
+        push r10
+        push r11
+        push rbx
+        push rbp
+        push r12
+        push r13
+        push r14
+        push r15
+
+        mov rdi, rsp
+        call generic_interrupt_handler
+
+        pop r15
+        pop r14
+        pop r13
+        pop r12
+        pop rbp
+        pop rbx
+        pop r11
+        pop r10
+        pop r9
+        pop r8
+        pop rsi
+        pop rdi
+        pop rdx
+        pop rcx
+        pop rax
+
+        # vector number and error code
+        add rsp, 16
+
+        iretq
+
+.align 32
+.global interrupt_handler_table
+interrupt_handler_table:
+        i = 0
+        .rept 256
+        .align 32
+        .if ((0x20027d00 >> i) & 1) == 0
+        push 0
+        .endif
+        push i
+        jmp interrupt_handler_entry
+        i = i + 1
+        .endr
+
+        ret

td-exception/src/asm/mod.rs

@@ -0,0 +1,7 @@
+use core::arch::global_asm;
+
+global_asm!(include_str!("handler.asm"));
+
+extern "C" {
+    pub(crate) static interrupt_handler_table: u8;
+}

td-exception/src/idt.rs

@@ -22,9 +22,10 @@ use x86_64::{
     VirtAddr,
 };
 
-use crate::interrupt;
+use crate::asm::interrupt_handler_table;
+use crate::interrupt::init_interrupt_callbacks;
 
-const IDT_ENTRY_COUNT: usize = 256;
+pub(crate) const IDT_ENTRY_COUNT: usize = 256;
 
 lazy_static! {
     static ref INIT_IDT: Mutex<Idt> = Mutex::new(Idt::new());
@@ -71,44 +72,13 @@ impl Idt {
 
     pub fn init(&mut self) {
         let current_idt = &mut self.entries;
+        let handler_table = unsafe { &interrupt_handler_table as *const u8 as usize };
 
-        // Set up exceptions handler according to Intel64 & IA32 Software Developer Manual
-        // Reference: https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html
-        current_idt[0].set_func(interrupt::divide_by_zero as usize);
-        current_idt[1].set_func(interrupt::debug as usize);
-        current_idt[2].set_func(interrupt::non_maskable as usize);
-        current_idt[3].set_func(interrupt::breakpoint as usize);
-        current_idt[4].set_func(interrupt::overflow as usize);
-        current_idt[5].set_func(interrupt::bound_range as usize);
-        current_idt[6].set_func(interrupt::invalid_opcode as usize);
-        current_idt[7].set_func(interrupt::device_not_available as usize);
-        current_idt[8].set_func(interrupt::double_fault as usize);
-        // 9 no longer available
-        current_idt[9].set_func(interrupt::default_exception as usize);
-        current_idt[10].set_func(interrupt::invalid_tss as usize);
-        current_idt[11].set_func(interrupt::segment_not_present as usize);
-        current_idt[12].set_func(interrupt::stack_segment as usize);
-        current_idt[13].set_func(interrupt::protection as usize);
-        current_idt[14].set_func(interrupt::page as usize);
-        // 15 reserved
-        current_idt[15].set_func(interrupt::default_exception as usize);
-        current_idt[16].set_func(interrupt::fpu as usize);
-        current_idt[17].set_func(interrupt::alignment_check as usize);
-        current_idt[18].set_func(interrupt::machine_check as usize);
-        current_idt[19].set_func(interrupt::simd as usize);
-        #[cfg(feature = "tdx")]
-        current_idt[20].set_func(interrupt::virtualization as usize);
-        #[cfg(not(feature = "tdx"))]
-        current_idt[20].set_func(interrupt::default_exception as usize);
-        current_idt[21].set_func(interrupt::control_flow as usize);
-        // reset exception reserved
-        for idt in current_idt.iter_mut().take(32).skip(22) {
-            idt.set_func(interrupt::default_exception as usize);
-        }
-        // Setup reset potential interrupt handler.
-        for idt in current_idt.iter_mut().take(IDT_ENTRY_COUNT).skip(32) {
-            idt.set_func(interrupt::default_interrupt as usize);
+        for (idx, idt) in current_idt.iter_mut().enumerate() {
+            idt.set_func(handler_table + idx * 32);
         }
+
+        init_interrupt_callbacks();
     }
 
     // Construct the Interrupt Descriptor Table Pointer (IDTR) based