Prepare for syscalls

Cargo.lock

@@ -221,6 +221,7 @@ dependencies = [
  "kernel-common",
  "lock_api",
  "log",
+ "raw-cpuid",
 ]
 
 [[package]]

kernel/Cargo.toml

@@ -15,6 +15,7 @@ embedded-graphics = "0.8.1"
 kernel-common = {path = "../lib/kernel-common"}
 lock_api = "0.4.12"
 log = "0.4.22"
+raw-cpuid = "11.2.0"
 
 [lints.clippy]
 missing_safety_doc = "allow"

kernel/src/cpu/cpu.rs

@@ -1,6 +1,7 @@
-use core::arch::asm;
+use core::arch::{asm, global_asm};
 
 use kernel_common::instructions::sti;
+use raw_cpuid::CpuId;
 
 use crate::{
     cpu::{gdt::setup_gdt, idt::setup_idt},
@@ -10,6 +11,12 @@ use crate::{
     },
 };
 
+global_asm!(include_str!("syscall.s"), options(att_syntax));
+
+extern "C" {
+    fn syscall();
+}
+
 #[no_mangle]
 extern "C" fn ap_main() -> ! {
     setup_gdt();
@@ -25,9 +32,24 @@ extern "C" fn ap_main() -> ! {
     panic!("Yielding to idle task failed");
 }
 pub fn set_cpu_flags() {
+    let cpuid = CpuId::new();
+    let features = cpuid.get_feature_info().unwrap();
+    let extended_features = cpuid.get_extended_feature_info().unwrap();
     unsafe {
-        // SMAP and SMEP
+        // Time Stamp Disable, SMEP and SMAP
-        asm!("mov rax, cr4; bts rax, 20; bts rax, 21; mov cr4, rax", out("rax") _);
+        asm!("mov rax, cr4; bts rax, 2; bts rax, 20; bts rax, 21; mov cr4, rax", out("rax") _);
+        if features.has_mce() {
+            asm!("mov rax, cr4; bts rax, 6; mov cr4, rax", out("rax") _);
+        }
+        if extended_features.has_umip() {
+            asm!("mov rax, cr4; bts rax, 11; mov cr4, rax", out("rax") _);
+        }
+        // System Call Extensions
+        asm!("rdmsr; bts rax, 0; wrmsr", in("rcx") 0xc0000080_u64, out("rax") _, out("rdx") _);
+        asm!("wrmsr", in("rcx") 0xc0000081_u64, in("rax") 0, in("rdx") 8 | 16 << 16);
+        asm!("wrmsr", in("rcx") 0xc0000082_u64, in("rax") syscall, in("rdx") syscall as u64 >> 32);
+        // Clear IF and DF
+        asm!("wrmsr", in("rcx") 0xc0000084_u64, in("rax") 1 << 9 | 1 << 10, in("rdx") 0);
     }
 }
 pub fn enable_user_memory_access() {

kernel/src/cpu/gdt.rs

@@ -58,6 +58,7 @@ pub fn setup_gdt() {
     tss.rsp[0] = allocate_stack();
     tss.ist[0] = allocate_stack();
     tss.ist[1] = allocate_stack();
+    tss.ist[2] = allocate_stack();
     let gdt = Box::leak(Box::new(GDT {
         entries: [
             GDTEntry {
@@ -88,16 +89,16 @@ pub fn setup_gdt() {
                 limit_low: 0,
                 base_low: 0,
                 base_middle: 0,
-                access: 0xfa,
+                access: 0xf2,
-                flags: 0x20,
+                flags: 0,
                 base_high: 0,
             },
             GDTEntry {
                 limit_low: 0,
                 base_low: 0,
                 base_middle: 0,
-                access: 0xf2,
+                access: 0xfa,
-                flags: 0,
+                flags: 0x20,
                 base_high: 0,
             },
         ],

kernel/src/cpu/idt.rs

@@ -325,4 +325,5 @@ pub fn setup_idt() {
     }
     idt.entries[2].ist = 1; // NMI
     idt.entries[8].ist = 2; // Double fault
+    idt.entries[18].ist = 3; // Machine Check
 }

kernel/src/cpu/isr.rs

@@ -111,7 +111,7 @@ extern "C" fn isr_handler(state: &mut ISRState) {
     let lapic_id = get_current_lapic_id();
     IN_ISR_HANDLER[lapic_id].store(true, Ordering::SeqCst);
     if state.isr < 32 {
-        if state.cs == 0x1b && state.isr != 2 && state.isr != 8 {
+        if state.cs == 0x23 && state.isr != 2 && state.isr != 8 && state.isr != 18 {
             warn!("Exception in usermode: {}", EXCEPTIONS[state.isr as usize]);
             terminate_current_task();
             state.isr = ISR_SCHEDULER;

kernel/src/cpu/syscall.s

@@ -0,0 +1,5 @@
+.text
+
+.global syscall
+syscall:
+  jmp .

kernel/src/cpu/usermode.s

@@ -2,15 +2,15 @@
 
 .global jump_usermode
 jump_usermode:
-  mov $0x23, %ax
+  mov $0x1b, %ax
   mov %ax, %ds
   mov %ax, %es
   mov %ax, %fs
   mov %ax, %gs
-  push $0x23
+  push $0x1b
   push $0
   pushf
-  push $0x1b
+  push $0x23
   push %rdi
 
   xor %rax, %rax

loader/src/main.rs

@@ -54,6 +54,7 @@ fn main() -> Status {
     uefi::helpers::init().unwrap();
     BOOT_SERVICES_ACTIVE.store(true, Ordering::SeqCst);
     assert!(features.has_rdrand());
+    assert!(features.has_tsc());
     let extended_features = cpuid.get_extended_feature_info().unwrap();
     assert!(extended_features.has_smap());
     assert!(extended_features.has_smep());

qemu.sh

@@ -2,4 +2,4 @@
 # shellcheck disable=SC2068
 set -euo pipefail
 ./build.sh
-qemu-system-x86_64 -M q35 -accel kvm -cpu qemu64,rdrand,smap,smep -smp 4 -m 256M -L /usr/share/OVMF -bios OVMF_CODE.fd -drive file=img/os.img,format=raw $@
+qemu-system-x86_64 -M q35 -accel kvm -cpu qemu64,rdrand,smap,smep,umip -smp 4 -m 256M -L /usr/share/OVMF -bios OVMF_CODE.fd -drive file=img/os.img,format=raw $@