fix fxsave/fxrstor

apparently the fxsaved memory needs to be zeroed out before...

src/arch/x86/task.c

@@ -175,13 +175,15 @@ struct Task *new_ktask(void(*fn), char *name) {
     new->frame.ip = (uint64_t) fn;
     new->frame.cs = GDTSEL(gdt_code);
     new->frame.ss = GDTSEL(gdt_data);
-    __builtin_ia32_fxsave64((void *) (((uintptr_t) (new->frame.ssestate) + 32) & 0xFFFFFFFFFFFFFFF0));
+    for (int i = 0; i < 512; i++) new->frame.ssestate[i] = 0;
     new->frame.flags = flags();
     new->frame.guard = IDT_GUARD;
     new->addressSpace = KERN_AddressSpace;
     new->state = TS_RUNNING;
     new->mode = TASKMODE_KERN;
 
+    sanity_check_frame(&new->frame);
+
     m_lock(&NewTasks_lock);
     append_task(&NewTasks, new);
     m_unlock(&NewTasks_lock);

src/arch/x86/task.inc.asm

@@ -25,13 +25,16 @@
 
     ; Ensure 16-byte alignment
     ; This works as last bunch of bits in fxsave state aren't used
-    sub rsp, 512
+    ; Fxsaved memory needs to be zeroed before!
+    mov rsi, 0x0000000000000000
+    times 64 push rsi
+
     mov rsi, rsp
     add rsi, 32
     mov rdi, 0xFFFFFFFFFFFFFFF0
     and rsi, rdi
-; TODO: Fix!!
-;    fxsave [rsi]
+
+    fxsave64 [rsi]
 
 %endmacro
 %macro popaq 0
@@ -43,7 +46,7 @@
     mov rdi, 0xFFFFFFFFFFFFFFF0
     and rsi, rdi
 
-;    fxrstor [rsi]
+    fxrstor64 [rsi]
     add rsp, 512
 
     pop r15