From a5d79d79579126e815ff3547e9f06fdd622d7973 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Thu, 8 Sep 2016 15:45:26 -0600
Subject: [PATCH] Nographic mode, fix userspace transition by setting kernel
 TLS back on syscall

---
 Makefile                               |  2 +-
 arch/x86_64/src/interrupt/exception.rs |  4 +++-
 arch/x86_64/src/interrupt/mod.rs       | 20 ++++++++++++++------
 arch/x86_64/src/interrupt/syscall.rs   | 13 ++++++++++++-
 arch/x86_64/src/lib.rs                 | 21 ++++++++++++++++-----
 arch/x86_64/src/paging/mod.rs          |  4 ++--
 6 files changed, 48 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index 0bf1ea1..d879ba5 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,8 @@ ifeq ($(ARCH),arm)
 else
 	LD=ld
 	QEMUFLAGS+=-enable-kvm -cpu host -machine q35 -smp 4
+	QEMUFLAGS+=-nographic -vga none
 	#,int,pcall
-	#-nographic
 	#-device intel-iommu
 
 	UNAME := $(shell uname)
diff --git a/arch/x86_64/src/interrupt/exception.rs b/arch/x86_64/src/interrupt/exception.rs
index 40f54d5..369f448 100644
--- a/arch/x86_64/src/interrupt/exception.rs
+++ b/arch/x86_64/src/interrupt/exception.rs
@@ -71,7 +71,9 @@ interrupt_error!(protection, {
 });
 
 interrupt_error!(page, {
-    print!("Page fault\n");
+    let cr2: usize;
+    asm!("mov rax, cr2" : "={rax}"(cr2) : : : "intel", "volatile");
+    println!("Page fault: {:>016X}", cr2);
     stack_trace();
     loop { halt(); }
 });
diff --git a/arch/x86_64/src/interrupt/mod.rs b/arch/x86_64/src/interrupt/mod.rs
index d7c6ddc..ad93b1a 100644
--- a/arch/x86_64/src/interrupt/mod.rs
+++ b/arch/x86_64/src/interrupt/mod.rs
@@ -52,13 +52,21 @@ pub unsafe fn stack_trace() {
     //Maximum 64 frames
     let active_table = ActivePageTable::new();
     for _frame in 0..64 {
-        if active_table.translate(VirtualAddress::new(rbp)).is_some() && active_table.translate(VirtualAddress::new(rbp + mem::size_of::<usize>())).is_some() {
-            let rip = *(rbp as *const usize).offset(1);
-            println!("  {:>016X}: {:>016X}", rbp, rip);
-            rbp = *(rbp as *const usize);
+        if let Some(rip_rbp) = rbp.checked_add(mem::size_of::<usize>()) {
+            if active_table.translate(VirtualAddress::new(rbp)).is_some() && active_table.translate(VirtualAddress::new(rip_rbp)).is_some() {
+                let rip = *(rip_rbp as *const usize);
+                if rip == 0 {
+                    println!(" {:>016X}: EMPTY RETURN", rbp);
+                    break;
+                }
+                println!("  {:>016X}: {:>016X}", rbp, rip);
+                rbp = *(rbp as *const usize);
+            } else {
+                println!("  {:>016X}: GUARD PAGE", rbp);
+                break;
+            }
         } else {
-            println!("  {:>016X}: GUARD PAGE", rbp);
-            break;
+            println!("  {:>016X}: RBP OVERFLOW", rbp);
         }
     }
 }
diff --git a/arch/x86_64/src/interrupt/syscall.rs b/arch/x86_64/src/interrupt/syscall.rs
index feac040..7dfaf38 100644
--- a/arch/x86_64/src/interrupt/syscall.rs
+++ b/arch/x86_64/src/interrupt/syscall.rs
@@ -22,8 +22,19 @@ pub unsafe extern fn syscall() {
         asm!("xchg bx, bx" : : "{rax}"(a) : : "intel", "volatile");
     }
 
+    asm!("xchg bx, bx
+        push fs
+        push rax
+        mov rax, 0x18
+        mov fs, ax
+        pop rax"
+        : : : : "intel", "volatile");
+
     inner();
 
     // Interrupt return
-    asm!("iretq" : : : : "intel", "volatile");
+    asm!("xchg bx, bx
+        pop fs
+        iretq"
+        : : : : "intel", "volatile");
 }
diff --git a/arch/x86_64/src/lib.rs b/arch/x86_64/src/lib.rs
index 02a5ff3..fdcea65 100644
--- a/arch/x86_64/src/lib.rs
+++ b/arch/x86_64/src/lib.rs
@@ -48,7 +48,8 @@ macro_rules! interrupt {
             }
 
             // Push scratch registers
-            asm!("push rax
+            asm!("xchg bx, bx
+                push rax
                 push rcx
                 push rdx
                 push rdi
@@ -56,14 +57,19 @@ macro_rules! interrupt {
                 push r8
                 push r9
                 push r10
-                push r11"
+                push r11
+                push fs
+                mov rax, 0x18
+                mov fs, ax"
                 : : : : "intel", "volatile");
 
             // Call inner rust function
             inner();
 
             // Pop scratch registers and return
-            asm!("pop r11
+            asm!("xchg bx, bx
+                pop fs
+                pop r11
                 pop r10
                 pop r9
                 pop r8
@@ -98,14 +104,19 @@ macro_rules! interrupt_error {
                 push r8
                 push r9
                 push r10
-                push r11"
+                push r11
+                push fs
+                mov rax, 0x18
+                mov fs, ax"
                 : : : : "intel", "volatile");
 
             // Call inner rust function
             inner();
 
             // Pop scratch registers, error code, and return
-            asm!("pop r11
+            asm!("xchg bx, bx
+                pop fs
+                pop r11
                 pop r10
                 pop r9
                 pop r8
diff --git a/arch/x86_64/src/paging/mod.rs b/arch/x86_64/src/paging/mod.rs
index f55e015..0c48f7a 100644
--- a/arch/x86_64/src/paging/mod.rs
+++ b/arch/x86_64/src/paging/mod.rs
@@ -303,8 +303,8 @@ impl Page {
     }
 
     pub fn containing_address(address: VirtualAddress) -> Page {
-        assert!(address.get() < 0x0000_8000_0000_0000 || address.get() >= 0xffff_8000_0000_0000,
-            "invalid address: 0x{:x}", address.get());
+        //TODO assert!(address.get() < 0x0000_8000_0000_0000 || address.get() >= 0xffff_8000_0000_0000,
+        //    "invalid address: 0x{:x}", address.get());
         Page { number: address.get() / PAGE_SIZE }
     }