Add support to read aux vector values

Summary:
This is the second patch to improve module loading in a series that started here (where I explain the motivation and solution): https://reviews.llvm.org/D62499

I need to read the aux vector to know where the r_debug map with the loaded libraries are.
The AuxVector class was made generic so it could be reused between the POSIX-DYLD plugin and NativeProcess*. The class itself ended up in the ProcessUtility plugin.

Reviewers: clayborg, xiaobai, labath, JDevlieghere

Reviewed By: clayborg, labath, JDevlieghere

Subscribers: emaste, JDevlieghere, mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D62500

llvm-svn: 363098

Author: aadsm

lldb/include/lldb/Host/common/NativeProcessProtocol.h

@@ -133,6 +133,10 @@ class NativeProcessProtocol {
     return GetArchitecture().GetByteOrder();
   }
 
+  uint32_t GetAddressByteSize() const {
+    return GetArchitecture().GetAddressByteSize();
+  }
+
   virtual llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
   GetAuxvData() const = 0;
 

lldb/include/lldb/Target/Process.h

@@ -670,8 +670,8 @@ class Process : public std::enable_shared_from_this<Process>,
   // The default action is to return an empty data buffer.
   //
   // \return
-  //    A data buffer containing the contents of the AUXV data.
-  virtual const lldb::DataBufferSP GetAuxvData();
+  //    A data extractor containing the contents of the AUXV data.
+  virtual DataExtractor GetAuxvData();
 
   /// Sometimes processes know how to retrieve and load shared libraries. This
   /// is normally done by DynamicLoader plug-ins, but sometimes the connection

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/AuxVector.h

@@ -1,5 +1,4 @@
 add_lldb_library(lldbPluginDynamicLoaderPosixDYLD PLUGIN
-  AuxVector.cpp
   DYLDRendezvous.cpp
   DynamicLoaderPOSIXDYLD.cpp
 
@@ -10,6 +9,7 @@ add_lldb_library(lldbPluginDynamicLoaderPosixDYLD PLUGIN
     lldbSymbol
     lldbTarget
     lldbPluginProcessElfCore
+    lldbPluginProcessUtility
   LINK_COMPONENTS
     Support
   )

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/CMakeLists.txt

@@ -9,8 +9,6 @@
 // Main header include
 #include "DynamicLoaderPOSIXDYLD.h"
 
-#include "AuxVector.h"
-
 #include "lldb/Breakpoint/BreakpointLocation.h"
 #include "lldb/Core/Module.h"
 #include "lldb/Core/ModuleSpec.h"
@@ -90,8 +88,8 @@ void DynamicLoaderPOSIXDYLD::DidAttach() {
   if (log)
     log->Printf("DynamicLoaderPOSIXDYLD::%s() pid %" PRIu64, __FUNCTION__,
                 m_process ? m_process->GetID() : LLDB_INVALID_PROCESS_ID);
+  m_auxv = llvm::make_unique<AuxVector>(m_process->GetAuxvData());
 
-  m_auxv.reset(new AuxVector(m_process));
   if (log)
     log->Printf("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " reloaded auxv data",
                 __FUNCTION__,
@@ -182,7 +180,7 @@ void DynamicLoaderPOSIXDYLD::DidLaunch() {
   ModuleSP executable;
   addr_t load_offset;
 
-  m_auxv.reset(new AuxVector(m_process));
+  m_auxv = llvm::make_unique<AuxVector>(m_process->GetAuxvData());
 
   executable = GetTargetExecutable();
   load_offset = ComputeLoadOffset();
@@ -628,13 +626,13 @@ addr_t DynamicLoaderPOSIXDYLD::ComputeLoadOffset() {
 }
 
 void DynamicLoaderPOSIXDYLD::EvalSpecialModulesStatus() {
-  auto I = m_auxv->FindEntry(AuxVector::AUXV_AT_SYSINFO_EHDR);
-  if (I != m_auxv->end() && I->value != 0)
-    m_vdso_base = I->value;
+  if (llvm::Optional<uint64_t> vdso_base =
+          m_auxv->GetAuxValue(AuxVector::AUXV_AT_SYSINFO_EHDR))
+    m_vdso_base = *vdso_base;
 
-  I = m_auxv->FindEntry(AuxVector::AUXV_AT_BASE);
-  if (I != m_auxv->end() && I->value != 0)
-    m_interpreter_base = I->value;
+  if (llvm::Optional<uint64_t> interpreter_base =
+          m_auxv->GetAuxValue(AuxVector::AUXV_AT_BASE))
+    m_interpreter_base = *interpreter_base;
 }
 
 addr_t DynamicLoaderPOSIXDYLD::GetEntryPoint() {
@@ -644,12 +642,12 @@ addr_t DynamicLoaderPOSIXDYLD::GetEntryPoint() {
   if (m_auxv == nullptr)
     return LLDB_INVALID_ADDRESS;
 
-  AuxVector::iterator I = m_auxv->FindEntry(AuxVector::AUXV_AT_ENTRY);
-
-  if (I == m_auxv->end())
+  llvm::Optional<uint64_t> entry_point =
+      m_auxv->GetAuxValue(AuxVector::AUXV_AT_ENTRY);
+  if (!entry_point)
     return LLDB_INVALID_ADDRESS;
 
-  m_entry_point = static_cast<addr_t>(I->value);
+  m_entry_point = static_cast<addr_t>(*entry_point);
 
   const ArchSpec &arch = m_process->GetTarget().GetArchitecture();
 

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp

@@ -13,6 +13,7 @@
 #include <memory>
 
 #include "DYLDRendezvous.h"
+#include "Plugins/Process/Utility/AuxVector.h"
 #include "lldb/Breakpoint/StoppointCallbackContext.h"
 #include "lldb/Core/ModuleList.h"
 #include "lldb/Target/DynamicLoader.h"

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.h

@@ -876,7 +876,7 @@ bool ProcessFreeBSD::IsAThreadRunning() {
   return is_running;
 }
 
-const DataBufferSP ProcessFreeBSD::GetAuxvData() {
+lldb_private::DataExtractor ProcessFreeBSD::GetAuxvData() {
   // If we're the local platform, we can ask the host for auxv data.
   PlatformSP platform_sp = GetTarget().GetPlatform();
   assert(platform_sp && platform_sp->IsHost());
@@ -890,7 +890,7 @@ const DataBufferSP ProcessFreeBSD::GetAuxvData() {
     buf_sp.reset();
   }
 
-  return buf_sp;
+  return DataExtractor(buf_sp, GetByteOrder(), GetAddressByteSize());
 }
 
 struct EmulatorBaton {

lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp

@@ -127,7 +127,7 @@ class ProcessFreeBSD : public lldb_private::Process {
   size_t PutSTDIN(const char *buf, size_t len,
                   lldb_private::Status &error) override;
 
-  const lldb::DataBufferSP GetAuxvData() override;
+  const lldb_private::DataExtractor GetAuxvData() override;
 
   // ProcessFreeBSD internal API.
 

lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.h

@@ -2082,3 +2082,18 @@ Status NativeProcessLinux::StopProcessorTracingOnThread(lldb::user_id_t traceid,
 
   return error;
 }
+
+llvm::Optional<uint64_t>
+NativeProcessLinux::GetAuxValue(enum AuxVector::EntryType type) {
+  if (m_aux_vector == nullptr) {
+    auto buffer_or_error = GetAuxvData();
+    if (!buffer_or_error)
+      return llvm::None;
+    DataExtractor auxv_data(buffer_or_error.get()->getBufferStart(),
+                            buffer_or_error.get()->getBufferSize(),
+                            GetByteOrder(), GetAddressByteSize());
+    m_aux_vector = llvm::make_unique<AuxVector>(auxv_data);
+  }
+
+  return m_aux_vector->GetAuxValue(type);
+}

lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp

@@ -12,6 +12,7 @@
 #include <csignal>
 #include <unordered_set>
 
+#include "Plugins/Process/Utility/AuxVector.h"
 #include "lldb/Host/Debug.h"
 #include "lldb/Host/HostThread.h"
 #include "lldb/Host/linux/Support.h"
@@ -102,6 +103,8 @@ class NativeProcessLinux : public NativeProcessProtocol {
     return getProcFile(GetID(), "auxv");
   }
 
+  llvm::Optional<uint64_t> GetAuxValue(enum AuxVector::EntryType type);
+
   lldb::user_id_t StartTrace(const TraceOptions &config,
                              Status &error) override;
 
@@ -132,6 +135,7 @@ class NativeProcessLinux : public NativeProcessProtocol {
 private:
   MainLoop::SignalHandleUP m_sigchld_handle;
   ArchSpec m_arch;
+  std::unique_ptr<AuxVector> m_aux_vector;
 
   LazyBool m_supports_mem_region = eLazyBoolCalculate;
   std::vector<std::pair<MemoryRegionInfo, FileSpec>> m_mem_region_cache;