From 97866d74db72157c3e3cc22d6805f22e204c01b7 Mon Sep 17 00:00:00 2001
From: Jason Molenda <jmolenda@apple.com>
Date: Wed, 13 Mar 2019 23:34:20 +0000
Subject: [PATCH] Reorder the operations in
 DynamicLoaderDarwinKernel::KextImageInfo::LoadImageUsingMemoryModule a bit so
 that we only read the binaries out of memory once we've determined that we
 can find a real binary on the local system.

Previously, lldb would read all of the kext binaries out of memory
and then determine if it had the local copy.  The kext table gives
us most the information we need (address, name, uuid) so lldb only
needs the actual in-memory load commands when it comes time to set
the section load addresses.  Delay reading until that point for all
the kexts.

NFC; doing the operations in a different order.


<rdar://problem/41181173>

llvm-svn: 356108
---
 .../DynamicLoaderDarwinKernel.cpp             | 41 +++++++++----------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
index 2d927ffc2988..d88ce1c9fb7c 100644
--- a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
+++ b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
@@ -766,24 +766,24 @@ bool DynamicLoaderDarwinKernel::KextImageInfo::LoadImageUsingMemoryModule(
 
   Target &target = process->GetTarget();
 
-  // If we don't have / can't create a memory module for this kext, don't try
-  // to load it - we won't have the correct segment load addresses.
-  if (!ReadMemoryModule(process)) {
-    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
-    if (log)
-      log->Printf("Unable to read '%s' from memory at address 0x%" PRIx64
-                  " to get the segment load addresses.",
-                  m_name.c_str(), m_load_address);
-    return false;
+  // kexts will have a uuid from the table.
+  // for the kernel, we'll need to read the load commands out of memory to get it.
+  if (m_uuid.IsValid() == false) {
+    if (ReadMemoryModule(process) == false) {
+      Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
+      if (log)
+        log->Printf("Unable to read '%s' from memory at address 0x%" PRIx64
+                    " to get the segment load addresses.",
+                    m_name.c_str(), m_load_address);
+      return false;
+    }
   }
 
-  bool uuid_is_valid = m_uuid.IsValid();
-
-  if (IsKernel() && uuid_is_valid && m_memory_module_sp.get()) {
+  if (IsKernel() && m_uuid.IsValid()) {
     Stream *s = target.GetDebugger().GetOutputFile().get();
     if (s) {
       s->Printf("Kernel UUID: %s\n",
-                m_memory_module_sp->GetUUID().GetAsString().c_str());
+                m_uuid.GetAsString().c_str());
       s->Printf("Load Address: 0x%" PRIx64 "\n", m_load_address);
     }
   }
@@ -795,7 +795,7 @@ bool DynamicLoaderDarwinKernel::KextImageInfo::LoadImageUsingMemoryModule(
     m_module_sp = target_images.FindModule(m_uuid);
 
     // Search for the kext on the local filesystem via the UUID
-    if (!m_module_sp && uuid_is_valid) {
+    if (!m_module_sp && m_uuid.IsValid()) {
       ModuleSpec module_spec;
       module_spec.GetUUID() = m_uuid;
       module_spec.GetArchitecture() = target.GetArchitecture();
@@ -857,13 +857,7 @@ bool DynamicLoaderDarwinKernel::KextImageInfo::LoadImageUsingMemoryModule(
     // images. If we also have a memory module, require that they have matching
     // UUIDs
     if (m_module_sp) {
-      bool uuid_match_ok = true;
-      if (m_memory_module_sp) {
-        if (m_module_sp->GetUUID() != m_memory_module_sp->GetUUID()) {
-          uuid_match_ok = false;
-        }
-      }
-      if (uuid_match_ok) {
+      if (m_uuid.IsValid() && m_module_sp->GetUUID() == m_uuid) {
         target.GetImages().AppendIfNeeded(m_module_sp);
         if (IsKernel() &&
             target.GetExecutableModulePointer() != m_module_sp.get()) {
@@ -873,6 +867,11 @@ bool DynamicLoaderDarwinKernel::KextImageInfo::LoadImageUsingMemoryModule(
     }
   }
 
+  // If we've found a binary, read the load commands out of memory so we
+  // can set the segment load addresses.
+  if (m_module_sp)
+    ReadMemoryModule (process);
+
   static ConstString g_section_name_LINKEDIT("__LINKEDIT");
 
   if (m_memory_module_sp && m_module_sp) {