From 994140183fc622631d305a216b3fbfa776137b8e Mon Sep 17 00:00:00 2001
From: Jeff Fan <jeff.fan@intel.com>
Date: Mon, 27 Apr 2015 05:23:43 +0000
Subject: SourceLevelDebugPkg/DebugAgent: Clear/Restore EFLAGS.IF

Clear EFLAGS.IF before executing Stepping command and save original
value in DEBUG_AGENT_FLAG. It could avoid pending interrupt issued
during executing Stepping command. Restore EFLAGS.IF after Stepping
command execution finished.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17204 6f19259b-4bc3-4df7-8a09-765794883524
---
 .../DebugAgent/DebugAgentCommon/DebugAgent.c       | 49 ++++++++++++++++++----
 1 file changed, 41 insertions(+), 8 deletions(-)

diff --git a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
index f51ad4b456..7f597352f1 100644
--- a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
+++ b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgent.c
@@ -785,7 +785,7 @@ CommandGo (
 }
 
 /**
-  Exectue Stepping command.
+  Execute Stepping command.
 
   @param[in] CpuContext        Pointer to saved CPU context.
 
@@ -800,6 +800,39 @@ CommandStepping (
   Eflags = (IA32_EFLAGS32 *) &CpuContext->Eflags;
   Eflags->Bits.TF = 1;
   Eflags->Bits.RF = 1;
+  //
+  // Save and clear EFLAGS.IF to avoid interrupt happen when executing Stepping
+  //
+  SetDebugFlag (DEBUG_AGENT_FLAG_INTERRUPT_FLAG, Eflags->Bits.IF);
+  Eflags->Bits.IF = 0;
+  //
+  // Set Stepping Flag
+  //
+  SetDebugFlag (DEBUG_AGENT_FLAG_STEPPING, 1);
+}
+
+/**
+  Do some cleanup after Stepping command done.
+
+  @param[in] CpuContext        Pointer to saved CPU context.
+
+**/
+VOID
+CommandSteppingCleanup (
+  IN DEBUG_CPU_CONTEXT          *CpuContext
+  )
+{
+  IA32_EFLAGS32                *Eflags;
+
+  Eflags = (IA32_EFLAGS32 *) &CpuContext->Eflags;
+  //
+  // Restore EFLAGS.IF
+  //
+  Eflags->Bits.IF = GetDebugFlag (DEBUG_AGENT_FLAG_INTERRUPT_FLAG);
+  //
+  // Clear Stepping flag
+  //
+  SetDebugFlag (DEBUG_AGENT_FLAG_STEPPING, 0);
 }
 
 /**
@@ -2066,10 +2099,6 @@ CommandCommunication (
       }
 
       mDebugMpContext.BreakAtCpuIndex = (UINT32) (-1);
-      //
-      // Set Stepping Flag
-      //
-      SetDebugFlag (DEBUG_AGENT_FLAG_STEPPING, 1);
       ReleaseMpSpinLock (&mDebugMpContext.DebugPortSpinLock);
       //
       // Executing stepping command directly without sending ACK packet,
@@ -2405,11 +2434,11 @@ InterruptProcess (
       if (MultiProcessorDebugSupport()) {
         mDebugMpContext.BreakAtCpuIndex = ProcessorIndex;
       }
-      SendAckPacket (DEBUG_COMMAND_OK);
       //
-      // Clear Stepping Flag
+      // Clear Stepping Flag and restore EFLAGS.IF
       //
-      SetDebugFlag (DEBUG_AGENT_FLAG_STEPPING, 0);
+      CommandSteppingCleanup (CpuContext);
+      SendAckPacket (DEBUG_COMMAND_OK);
       CommandCommunication (Vector, CpuContext, BreakReceived);
       break;
 
@@ -2582,6 +2611,10 @@ InterruptProcess (
         if (MultiProcessorDebugSupport()) {
           mDebugMpContext.BreakAtCpuIndex = ProcessorIndex;
         }
+        //
+        // Clear Stepping flag and restore EFLAGS.IF
+        //
+        CommandSteppingCleanup (CpuContext);
         SendAckPacket (DEBUG_COMMAND_OK);
       } else {
         //
-- 
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