Remove rd/wrfsbase

arch/x86_64/src/gdt.rs

@@ -11,8 +11,9 @@ pub const GDT_KERNEL_DATA: usize = 2;
 pub const GDT_KERNEL_TLS: usize = 3;
 pub const GDT_USER_CODE: usize = 4;
 pub const GDT_USER_DATA: usize = 5;
-pub const GDT_TSS: usize = 6;
-pub const GDT_TSS_HIGH: usize = 7;
+pub const GDT_USER_TLS: usize = 6;
+pub const GDT_TSS: usize = 7;
+pub const GDT_TSS_HIGH: usize = 8;
 
 pub const GDT_A_PRESENT: u8 = 1 << 7;
 pub const GDT_A_RING_0: u8 = 0 << 5;
@@ -55,7 +56,7 @@ pub static mut GDTR: DescriptorTablePointer = DescriptorTablePointer {
 };
 
 #[thread_local]
-pub static mut GDT: [GdtEntry; 8] = [
+pub static mut GDT: [GdtEntry; 9] = [
     // Null
     GdtEntry::new(0, 0, 0, 0),
     // Kernel code
@@ -68,6 +69,8 @@ pub static mut GDT: [GdtEntry; 8] = [
     GdtEntry::new(0, 0, GDT_A_PRESENT | GDT_A_RING_3 | GDT_A_SYSTEM | GDT_A_EXECUTABLE | GDT_A_PRIVILEGE, GDT_F_LONG_MODE),
     // User data
     GdtEntry::new(0, 0, GDT_A_PRESENT | GDT_A_RING_3 | GDT_A_SYSTEM | GDT_A_PRIVILEGE, GDT_F_LONG_MODE),
+    // User TLS
+    GdtEntry::new(0, 0, GDT_A_PRESENT | GDT_A_RING_3 | GDT_A_SYSTEM | GDT_A_PRIVILEGE, GDT_F_LONG_MODE),
     // TSS
     GdtEntry::new(0, 0, GDT_A_PRESENT | GDT_A_RING_3 | GDT_A_TSS_AVAIL, 0),
     // TSS must be 16 bytes long, twice the normal size
@@ -113,6 +116,9 @@ pub unsafe fn init(tcb_offset: usize, stack_offset: usize) {
     // Set the TLS segment to the offset of the Thread Control Block
     GDT[GDT_KERNEL_TLS].set_offset(tcb_offset as u32);
 
+    // Set the User TLS segment to the offset of the user TCB
+    GDT[GDT_USER_TLS].set_offset(::USER_TCB_OFFSET as u32);
+
     // We can now access our TSS, which is a thread local
     GDT[GDT_TSS].set_offset(&TSS as *const _ as u32);
     GDT[GDT_TSS].set_limit(mem::size_of::<TaskStateSegment>() as u32);

arch/x86_64/src/interrupt/syscall.rs

@@ -24,8 +24,6 @@ pub unsafe extern fn syscall() {
     }
 
     asm!("push r15
-        rdfsbase r15
-        push r15
         push fs
         mov r15, 0x18
         mov fs, r15"
@@ -35,8 +33,6 @@ pub unsafe extern fn syscall() {
 
     // Interrupt return
     asm!("pop fs
-        pop r15
-        wrfsbase r15
         pop r15
         iretq"
         : : : : "intel", "volatile");

arch/x86_64/src/lib.rs

@@ -48,6 +48,9 @@ pub extern crate x86;
     /// Offset to user image
     pub const USER_OFFSET: usize = 0;
 
+    /// Offset to user TCB
+    pub const USER_TCB_OFFSET: usize = 0xB000_0000;
+
     /// Offset to user arguments
     pub const USER_ARG_OFFSET: usize = USER_OFFSET + PML4_SIZE/2;
 
@@ -118,8 +121,6 @@ macro_rules! interrupt {
                 push r9
                 push r10
                 push r11
-                rdfsbase rax
-                push rax
                 push fs
                 mov rax, 0x18
                 mov fs, ax"
@@ -130,8 +131,6 @@ macro_rules! interrupt {
 
             // Pop scratch registers and return
             asm!("pop fs
-                pop rax
-                wrfsbase rax
                 pop r11
                 pop r10
                 pop r9
@@ -184,8 +183,6 @@ macro_rules! interrupt_stack {
                 push r9
                 push r10
                 push r11
-                rdfsbase rax
-                push rax
                 push fs
                 mov rax, 0x18
                 mov fs, ax"
@@ -200,8 +197,6 @@ macro_rules! interrupt_stack {
 
             // Pop scratch registers and return
             asm!("pop fs
-                pop rax
-                wrfsbase rax
                 pop r11
                 pop r10
                 pop r9

arch/x86_64/src/start.rs

@@ -158,14 +158,13 @@ pub unsafe extern fn kstart_ap(cpu_id: usize, bsp_table: usize, stack_start: usi
     kmain_ap(cpu_id);
 }
 
-pub unsafe fn usermode(ip: usize, sp: usize, fs: usize) -> ! {
+pub unsafe fn usermode(ip: usize, sp: usize) -> ! {
     // Go to usermode
     asm!("xchg bx, bx
         mov ds, ax
         mov es, ax
-        mov fs, ax
+        mov fs, bx
         mov gs, ax
-        wrfsbase rbx
         push rax
         push rcx
         push rdx
@@ -174,7 +173,7 @@ pub unsafe fn usermode(ip: usize, sp: usize, fs: usize) -> ! {
         iretq"
         : // No output because it never returns
         :   "{rax}"(gdt::GDT_USER_DATA << 3 | 3), // Data segment
-            "{rbx}"(fs), // TLS segment
+            "{rbx}"(gdt::GDT_USER_TLS << 3 | 3), // TLS segment
             "{rcx}"(sp), // Stack pointer
             "{rdx}"(3 << 12 | 1 << 9), // Flags - Set IOPL and interrupt enable flag
             "{rsi}"(gdt::GDT_USER_CODE << 3 | 3), // Code segment