From e09ae042a38e47491e5182c05036988679100f42 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Mon, 17 Aug 2015 15:09:22 +0200
Subject: [PATCH] Setup SSE because rust needs it

---
 src/arch/x86_64/long_mode_init.asm | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/arch/x86_64/long_mode_init.asm b/src/arch/x86_64/long_mode_init.asm
index 4640c0b1..6e4c281e 100644
--- a/src/arch/x86_64/long_mode_init.asm
+++ b/src/arch/x86_64/long_mode_init.asm
@@ -18,6 +18,7 @@ extern main
 section .text
 bits 64
 long_mode_start:
+    call setup_SSE
 
     ; call rust main
     call main
@@ -26,6 +27,28 @@ long_mode_start:
     mov qword [0xb8000], rax
     hlt
 
+; Check for SSE and enable it. If it's not supported throw error "a".
+setup_SSE:
+    ; check for SSE
+    mov rax, 0x1
+    cpuid
+    test edx, 1<<25
+    jz .no_SSE
+
+    ; enable SSE
+    mov rax, cr0
+    and ax, 0xFFFB      ; clear coprocessor emulation CR0.EM
+    or ax, 0x2          ; set coprocessor monitoring  CR0.MP
+    mov cr0, rax
+    mov rax, cr4
+    or ax, 3 << 9       ; set CR4.OSFXSR and CR4.OSXMMEXCPT at the same time
+    mov cr4, rax
+
+    ret
+.no_SSE:
+    mov al, "a"
+    jmp error
+
 ; Prints `ERROR: ` and the given error code to screen and hangs.
 ; parameter: error code (in ascii) in al
 error:
@@ -35,3 +58,4 @@ error:
     mov [0xb8008], rbx
     mov byte [0xb800e], al
     hlt
+    jmp error