[Xen-changelog] [xen-unstable] x86_emulate: Check single-step status at instruction start rather than end.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1211615699 -3600
# Node ID 30bf34f5a414d5400028ec094688be696234fcdf
# Parent  ef7525e87030281c74768f6310f18bf4ed44ac15
x86_emulate: Check single-step status at instruction start rather than end.

This fixes booting of FreeDOS with HIMEM.SYS enabled.

Signed-off-by: Trolle Selander <trolle.selander@xxxxxxxxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff -r ef7525e87030 -r 30bf34f5a414 xen/arch/x86/x86_emulate/x86_emulate.c
--- a/xen/arch/x86/x86_emulate/x86_emulate.c    Fri May 23 11:58:08 2008 +0100
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c    Sat May 24 08:54:59 2008 +0100
@@ -2105,12 +2105,14 @@ x86_emulate(
         break;
     }
 
+    /* Inject #DB if single-step tracing was enabled at instruction start. */
+    if ( (ctxt->regs->eflags & EFLG_TF) && (rc == X86EMUL_OKAY) &&
+         (ops->inject_hw_exception != NULL) )
+        rc = ops->inject_hw_exception(EXC_DB, -1, ctxt) ? : X86EMUL_EXCEPTION;
+
     /* Commit shadow register state. */
     _regs.eflags &= ~EFLG_RF;
     *ctxt->regs = _regs;
-    if ( (_regs.eflags & EFLG_TF) && (rc == X86EMUL_OKAY) &&
-         (ops->inject_hw_exception != NULL) )
-        rc = ops->inject_hw_exception(EXC_DB, -1, ctxt) ? : X86EMUL_EXCEPTION;
 
  done:
     return rc;

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