- Small patch to fix (delayed) loading of floating point state. Enables the special...

[reactos.git] / reactos / ntoskrnl / ke / i386 / ctxswitch.S

diff --git a/reactos/ntoskrnl/ke/i386/ctxswitch.S b/reactos/ntoskrnl/ke/i386/ctxswitch.S
index 3491fcb..3a35a3a 100644 (file)
--- a/reactos/ntoskrnl/ke/i386/ctxswitch.S
+++ b/reactos/ntoskrnl/ke/i386/ctxswitch.S
@@ -159,4 +159,28 @@ PUBLIC @Ki386BiosCallReturnAddress@4
     popad
     ret 4
 
+PUBLIC _FrRestore
+PUBLIC @Ke386LoadFpuState@4
+@Ke386LoadFpuState@4:
+
+    /* Check if we have FXSR and choose which operand to use */
+    test byte ptr [_KeI386FxsrPresent], 1
+    jz _FrRestore
+
+    /* Restore all the FPU, MMX, XMM and MXCSR registers */
+    fxrstor [ecx]
+    ret
+
+    /*
+     * Just restore the basic FPU registers.
+     * This may raise an exception depending
+     * on the status word, which KiNpxHandler will
+     * need to check for and handle during delayed load
+     * to avoid raising an unhandled exception
+     * and crashing the system.
+     */
+_FrRestore:
+    frstor [ecx]
+    ret
+
 END