x86emul: correct PUSHF/POPF

Both need to raise #GP(0) when in VM86 mode with IOPL < 3.

Additionally PUSHF is documented to clear VM and RF from the value
placed onto the stack.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: e5c1b8145bccb7fc587ee5b0c95ace6c5e0c7ffd
master date: 2016-12-07 13:55:42 +0100

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index ff952a96f4cd9cbad4e33bfe9b0da4779859e876..9ccfbf0f33e4d646d7a76918d0f4f18f78575ad6 100644 (file)
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -3085,13 +3085,20 @@ x86_emulate(
     }
 
     case 0x9c: /* pushf */
-        src.val = _regs.eflags;
+        generate_exception_if((_regs.eflags & EFLG_VM) &&
+                              MASK_EXTR(_regs.eflags, EFLG_IOPL) != 3,
+                              EXC_GP, 0);
+        src.val = _regs.eflags & ~(EFLG_VM | EFLG_RF);
         goto push;
 
     case 0x9d: /* popf */ {
         uint32_t mask = EFLG_VIP | EFLG_VIF | EFLG_VM;
+
         if ( !mode_ring0() )
         {
+            generate_exception_if((_regs.eflags & EFLG_VM) &&
+                                  MASK_EXTR(_regs.eflags, EFLG_IOPL) != 3,
+                                  EXC_GP, 0);
             mask |= EFLG_IOPL;
             if ( !mode_iopl() )
                 mask |= EFLG_IF;