[Lldb-commits] [lldb] r260559 - Improve ReadRegister for RegisterContextWindowsx86

[Adrian McCarthy via lldb-commits]

Author: amccarth
Date: Thu Feb 11 12:24:57 2016
New Revision: 260559

URL: http://llvm.org/viewvc/llvm-project?rev=260559&view=rev
Log:
Improve ReadRegister for RegisterContextWindowsx86

In some circumstances (notably, certain minidumps), the thread CONTEXT does not have values for the
control registers (EIP, ESP, EBP, EFLAGS).  There are flags in the CONTEXT which indicate which
portions are valid, but those flags weren't checked.  The old code would not detect this and give a
garbage value for the register.  The new code will log the problem and return an error.

I consolidated the error checking and logging into a helper function, which makes the big switch
statement easier to read and verify.

Ran tests to ensure this doesn't break anything.  Manually verified that a minidump without info on
the control registers now indicates the problem instead of giving bad information.

Differential Review: http://reviews.llvm.org/D17152

Modified:
    lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp
    lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.h

Modified: lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp?rev=260559&r1=260558&r2=260559&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp (original)
+++ lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp Thu Feb 11 12:24:57 2016
@@ -131,48 +131,42 @@ RegisterContextWindows_x86::ReadRegister
     switch (reg)
     {
         case lldb_eax_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EAX", m_context.Eax);
-            reg_value.SetUInt32(m_context.Eax);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "EAX", m_context.Eax, reg_value);
         case lldb_ebx_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EBX", m_context.Ebx);
-            reg_value.SetUInt32(m_context.Ebx);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "EBX", m_context.Ebx, reg_value);
         case lldb_ecx_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from ECX", m_context.Ecx);
-            reg_value.SetUInt32(m_context.Ecx);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "ECX", m_context.Ecx, reg_value);
         case lldb_edx_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EDX", m_context.Edx);
-            reg_value.SetUInt32(m_context.Edx);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "EDX", m_context.Edx, reg_value);
         case lldb_edi_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EDI", m_context.Edi);
-            reg_value.SetUInt32(m_context.Edi);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "EDI", m_context.Edi, reg_value);
         case lldb_esi_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from ESI", m_context.Esi);
-            reg_value.SetUInt32(m_context.Esi);
-            break;
+            return ReadRegisterHelper(CONTEXT_INTEGER, "ESI", m_context.Esi, reg_value);
         case lldb_ebp_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EBP", m_context.Ebp);
-            reg_value.SetUInt32(m_context.Ebp);
-            break;
+            return ReadRegisterHelper(CONTEXT_CONTROL, "EBP", m_context.Ebp, reg_value);
         case lldb_esp_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from ESP", m_context.Esp);
-            reg_value.SetUInt32(m_context.Esp);
-            break;
+            return ReadRegisterHelper(CONTEXT_CONTROL, "ESP", m_context.Esp, reg_value);
         case lldb_eip_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EIP", m_context.Eip);
-            reg_value.SetUInt32(m_context.Eip);
-            break;
+            return ReadRegisterHelper(CONTEXT_CONTROL, "EIP", m_context.Eip, reg_value);
         case lldb_eflags_i386:
-            WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from EFLAGS", m_context.EFlags);
-            reg_value.SetUInt32(m_context.EFlags);
-            break;
+            return ReadRegisterHelper(CONTEXT_CONTROL, "EFLAGS", m_context.EFlags, reg_value);
         default:
             WINWARN_IFALL(WINDOWS_LOG_REGISTERS, "Requested unknown register %u", reg);
             break;
     }
+    return false;
+}
+
+bool
+RegisterContextWindows_x86::ReadRegisterHelper(DWORD flags_required, const char *reg_name, DWORD value,
+                                               RegisterValue &reg_value) const
+{
+    if ((m_context.ContextFlags & flags_required) != flags_required)
+    {
+        WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Thread context doesn't have %s", reg_name);
+        return false;
+    }
+    WINLOG_IFALL(WINDOWS_LOG_REGISTERS, "Read value 0x%x from %s", value, reg_name);
+    reg_value.SetUInt32(value);
     return true;
 }

Modified: lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.h
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.h?rev=260559&r1=260558&r2=260559&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.h (original)
+++ lldb/trunk/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.h Thu Feb 11 12:24:57 2016
@@ -41,6 +41,9 @@ class RegisterContextWindows_x86 : publi
 
     bool ReadRegister(const RegisterInfo *reg_info, RegisterValue &reg_value) override;
 
+private:
+    bool
+    ReadRegisterHelper(DWORD flags_required, const char *reg_name, DWORD value, RegisterValue &reg_value) const;
 };
 
 }