Merge pull request #224 from joergroedel/mutable-static

Get rid of some mutable global statics

src/cpu/gdt.rs

@@ -4,98 +4,140 @@
 //
 // Author: Joerg Roedel <[email protected]>
 
-use super::tss::{X86Tss, TSS_LIMIT};
+use super::tss::X86Tss;
 use crate::address::VirtAddr;
+use crate::locking::{RWLock, ReadLockGuard, WriteLockGuard};
 use crate::types::{SVSM_CS, SVSM_DS, SVSM_TSS};
 use core::arch::asm;
 use core::mem;
 
 #[repr(C, packed(2))]
 #[derive(Clone, Copy, Debug)]
-pub struct GdtDesc {
+struct GDTDesc {
     size: u16,
     addr: VirtAddr,
 }
 
-const GDT_SIZE: u16 = 8;
-
-static mut GDT: [u64; GDT_SIZE as usize] = [
-    0,
-    0x00af9a000000ffff, // 64-bit code segment
-    0x00cf92000000ffff, // 64-bit data segment
-    0,                  // Reserved for User code
-    0,                  // Reserver for User data
-    0,                  // Reverved
-    0,                  // TSS
-    0,                  // TSS continued
-];
+#[derive(Copy, Clone, Debug)]
+pub struct GDTEntry(u64);
 
-pub fn load_tss(tss: &X86Tss) {
-    let addr = (tss as *const X86Tss) as u64;
+impl GDTEntry {
+    pub const fn from_raw(entry: u64) -> Self {
+        Self(entry)
+    }
 
-    let mut desc0: u64 = 0;
-    let mut desc1: u64 = 0;
+    pub fn to_raw(&self) -> u64 {
+        self.0
+    }
 
-    // Limit
-    desc0 |= TSS_LIMIT & 0xffffu64;
-    desc0 |= ((TSS_LIMIT >> 16) & 0xfu64) << 48;
+    pub const fn null() -> Self {
+        Self(0u64)
+    }
 
-    // Address
-    desc0 |= (addr & 0x00ff_ffffu64) << 16;
-    desc0 |= (addr & 0xff00_0000u64) << 32;
-    desc1 |= addr >> 32;
+    pub const fn code_64_kernel() -> Self {
+        Self(0x00af9a000000ffffu64)
+    }
 
-    // Present
-    desc0 |= 1u64 << 47;
+    pub const fn data_64_kernel() -> Self {
+        Self(0x00cf92000000ffffu64)
+    }
+}
 
-    // Type
-    desc0 |= 0x9u64 << 40;
+const GDT_SIZE: u16 = 8;
 
-    unsafe {
-        let idx = (SVSM_TSS / 8) as usize;
-        GDT[idx] = desc0;
-        GDT[idx + 1] = desc1;
+#[derive(Copy, Clone, Debug)]
+pub struct GDT {
+    entries: [GDTEntry; GDT_SIZE as usize],
+}
 
-        asm!("ltr %ax", in("ax") SVSM_TSS, options(att_syntax));
+impl GDT {
+    pub const fn new() -> Self {
+        GDT {
+            entries: [
+                GDTEntry::null(),
+                GDTEntry::code_64_kernel(),
+                GDTEntry::data_64_kernel(),
+                GDTEntry::null(),
+                GDTEntry::null(),
+                GDTEntry::null(),
+                GDTEntry::null(),
+                GDTEntry::null(),
+            ],
+        }
     }
-}
 
-pub fn gdt_base_limit() -> (u64, u32) {
-    unsafe {
+    pub fn base_limit(&self) -> (u64, u32) {
         let gdt_entries = GDT_SIZE as usize;
-        let base = (&GDT as *const [u64; GDT_SIZE as usize]) as u64;
+        let base = (self as *const GDT) as u64;
         let limit = ((mem::size_of::<u64>() * gdt_entries) - 1) as u32;
         (base, limit)
     }
-}
 
-pub fn load_gdt() {
-    unsafe {
-        let gdt_desc: GdtDesc = GdtDesc {
+    fn descriptor(&self) -> GDTDesc {
+        GDTDesc {
             size: (GDT_SIZE * 8) - 1,
-            addr: VirtAddr::from(GDT.as_ptr()),
-        };
-
-        asm!(r#" /* Load GDT */
-             lgdt   (%rax)
-
-             /* Reload data segments */
-             movw   %cx, %ds
-             movw   %cx, %es
-             movw   %cx, %fs
-             movw   %cx, %gs
-             movw   %cx, %ss
-
-             /* Reload code segment */
-             pushq  %rdx
-             leaq   1f(%rip), %rax
-             pushq  %rax
-             lretq
-        1:
-             "#,
-            in("rax") &gdt_desc,
-            in("rdx") SVSM_CS,
-            in("rcx") SVSM_DS,
-            options(att_syntax));
+            addr: VirtAddr::from(self.entries.as_ptr()),
+        }
+    }
+
+    pub fn load(&self) {
+        let gdt_desc = self.descriptor();
+        unsafe {
+            asm!(r#" /* Load GDT */
+                 lgdt   (%rax)
+
+                 /* Reload data segments */
+                 movw   %cx, %ds
+                 movw   %cx, %es
+                 movw   %cx, %fs
+                 movw   %cx, %gs
+                 movw   %cx, %ss
+
+                 /* Reload code segment */
+                 pushq  %rdx
+                 leaq   1f(%rip), %rax
+                 pushq  %rax
+                 lretq
+            1:
+                 "#,
+                in("rax") &gdt_desc,
+                in("rdx") SVSM_CS,
+                in("rcx") SVSM_DS,
+                options(att_syntax));
+        }
     }
+
+    fn set_tss_entry(&mut self, desc0: GDTEntry, desc1: GDTEntry) {
+        let idx = (SVSM_TSS / 8) as usize;
+
+        self.entries[idx] = desc0;
+        self.entries[idx + 1] = desc1;
+    }
+
+    fn clear_tss_entry(&mut self) {
+        let idx = (SVSM_TSS / 8) as usize;
+
+        self.entries[idx] = GDTEntry::null();
+        self.entries[idx + 1] = GDTEntry::null();
+    }
+
+    pub fn load_tss(&mut self, tss: &X86Tss) {
+        let (desc0, desc1) = tss.to_gdt_entry();
+
+        self.set_tss_entry(desc0, desc1);
+        unsafe {
+            asm!("ltr %ax", in("ax") SVSM_TSS, options(att_syntax));
+        }
+        self.clear_tss_entry()
+    }
+}
+
+static GDT: RWLock<GDT> = RWLock::new(GDT::new());
+
+pub fn gdt() -> ReadLockGuard<'static, GDT> {
+    GDT.lock_read()
+}
+
+pub fn gdt_mut() -> WriteLockGuard<'static, GDT> {
+    GDT.lock_write()
 }

src/cpu/idt/common.rs

@@ -6,6 +6,7 @@
 
 use crate::address::{Address, VirtAddr};
 use crate::cpu::registers::{X86GeneralRegs, X86InterruptFrame};
+use crate::locking::{RWLock, ReadLockGuard, WriteLockGuard};
 use crate::types::SVSM_CS;
 use core::arch::{asm, global_asm};
 use core::mem;
@@ -104,27 +105,63 @@ struct IdtDesc {
     address: VirtAddr,
 }
 
-pub type Idt = [IdtEntry; IDT_ENTRIES];
+#[derive(Copy, Clone, Debug)]
+pub struct IDT {
+    entries: [IdtEntry; IDT_ENTRIES],
+}
 
-pub static mut GLOBAL_IDT: Idt = [IdtEntry::no_handler(); IDT_ENTRIES];
+impl IDT {
+    pub const fn new() -> Self {
+        IDT {
+            entries: [IdtEntry::no_handler(); IDT_ENTRIES],
+        }
+    }
 
-pub fn idt_base_limit() -> (u64, u32) {
-    unsafe {
-        let base = (&GLOBAL_IDT as *const Idt) as u64;
+    pub fn init(&mut self, handler_array: *const u8, size: usize) -> &mut Self {
+        // Set IDT handlers
+        let handlers = VirtAddr::from(handler_array);
+
+        for idx in 0..size {
+            self.set_entry(idx, IdtEntry::entry(handlers + (32 * idx)));
+        }
+
+        self
+    }
+
+    pub fn set_entry(&mut self, idx: usize, entry: IdtEntry) -> &mut Self {
+        self.entries[idx] = entry;
+
+        self
+    }
+
+    pub fn load(&self) -> &Self {
+        let desc: IdtDesc = IdtDesc {
+            size: (IDT_ENTRIES * 16) as u16,
+            address: VirtAddr::from(self.entries.as_ptr()),
+        };
+
+        unsafe {
+            asm!("lidt (%rax)", in("rax") &desc, options(att_syntax));
+        }
+
+        self
+    }
+
+    pub fn base_limit(&self) -> (u64, u32) {
+        let base = (self as *const IDT) as u64;
         let limit = (IDT_ENTRIES * mem::size_of::<IdtEntry>()) as u32;
         (base, limit)
     }
 }
 
-pub fn load_idt(idt: &Idt) {
-    let desc: IdtDesc = IdtDesc {
-        size: (IDT_ENTRIES * 16) as u16,
-        address: VirtAddr::from(idt.as_ptr()),
-    };
+static IDT: RWLock<IDT> = RWLock::new(IDT::new());
 
-    unsafe {
-        asm!("lidt (%rax)", in("rax") &desc, options(att_syntax));
-    }
+pub fn idt() -> ReadLockGuard<'static, IDT> {
+    IDT.lock_read()
+}
+
+pub fn idt_mut() -> WriteLockGuard<'static, IDT> {
+    IDT.lock_write()
 }
 
 pub fn triple_fault() {

src/cpu/idt/mod.rs

@@ -7,3 +7,5 @@
 pub mod common;
 pub mod stage2;
 pub mod svsm;
+
+pub use common::{idt, idt_mut};

src/cpu/idt/stage2.rs

@@ -4,35 +4,25 @@
 //
 // Author: Joerg Roedel <[email protected]>
 
-use super::common::{load_idt, Idt, IdtEntry, DF_VECTOR, GLOBAL_IDT, HV_VECTOR, VC_VECTOR};
-use crate::address::VirtAddr;
+use super::common::{idt_mut, DF_VECTOR, HV_VECTOR, VC_VECTOR};
 use crate::cpu::control_regs::read_cr2;
 use crate::cpu::vc::{stage2_handle_vc_exception, stage2_handle_vc_exception_no_ghcb};
 use crate::cpu::X86ExceptionContext;
 use core::arch::global_asm;
 
-fn init_idt(idt: &mut Idt, handler_array: *const u8) {
-    // Set IDT handlers
-    let handlers = VirtAddr::from(handler_array);
-    for (i, entry) in idt.iter_mut().enumerate() {
-        *entry = IdtEntry::entry(handlers + (32 * i));
-    }
-}
-
 pub fn early_idt_init_no_ghcb() {
     unsafe {
-        init_idt(
-            &mut GLOBAL_IDT,
-            &stage2_idt_handler_array_no_ghcb as *const u8,
-        );
-        load_idt(&GLOBAL_IDT);
+        idt_mut()
+            .init(&stage2_idt_handler_array_no_ghcb as *const u8, 32)
+            .load();
     }
 }
 
 pub fn early_idt_init() {
     unsafe {
-        init_idt(&mut GLOBAL_IDT, &stage2_idt_handler_array as *const u8);
-        load_idt(&GLOBAL_IDT);
+        idt_mut()
+            .init(&stage2_idt_handler_array as *const u8, 32)
+            .load();
     }
 }
 

src/cpu/idt/svsm.rs

@@ -11,39 +11,34 @@ use super::super::tss::IST_DF;
 use super::super::vc::handle_vc_exception;
 use super::common::PF_ERROR_WRITE;
 use super::common::{
-    load_idt, Idt, IdtEntry, BP_VECTOR, DF_VECTOR, GLOBAL_IDT, GP_VECTOR, HV_VECTOR, PF_VECTOR,
-    VC_VECTOR,
+    idt_mut, IdtEntry, BP_VECTOR, DF_VECTOR, GP_VECTOR, HV_VECTOR, PF_VECTOR, VC_VECTOR,
 };
 use crate::address::VirtAddr;
 use crate::cpu::X86ExceptionContext;
 use crate::debug::gdbstub::svsm_gdbstub::handle_debug_exception;
 use core::arch::global_asm;
 
-fn init_idt(idt: &mut Idt) {
-    // Set IDT handlers
-    let handlers = unsafe { VirtAddr::from(&svsm_idt_handler_array as *const u8) };
-    for (i, entry) in idt.iter_mut().enumerate() {
-        *entry = IdtEntry::entry(handlers + (32 * i));
+fn init_ist_vectors() {
+    unsafe {
+        let handler = VirtAddr::from(&svsm_idt_handler_array as *const u8) + (32 * DF_VECTOR);
+        idt_mut().set_entry(
+            DF_VECTOR,
+            IdtEntry::ist_entry(handler, IST_DF.try_into().unwrap()),
+        );
     }
 }
 
-unsafe fn init_ist_vectors(idt: &mut Idt) {
-    let handler = VirtAddr::from(&svsm_idt_handler_array as *const u8) + (32 * DF_VECTOR);
-    idt[DF_VECTOR] = IdtEntry::ist_entry(handler, IST_DF.try_into().unwrap());
-}
-
 pub fn early_idt_init() {
     unsafe {
-        init_idt(&mut GLOBAL_IDT);
-        load_idt(&GLOBAL_IDT);
+        idt_mut()
+            .init(&svsm_idt_handler_array as *const u8, 32)
+            .load();
     }
 }
 
 pub fn idt_init() {
     // Set IST vectors
-    unsafe {
-        init_ist_vectors(&mut GLOBAL_IDT);
-    }
+    init_ist_vectors();
 }
 
 #[no_mangle]