[lldb][NFCI] Simplify ProcessElfCore::GetAuxvData()

[igorkudrin]

There is no need to clone the content and set extraction properties because m_auxv is already in the required form.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Igor Kudrin (igorkudrin)

Changes

There is no need to clone the content and set extraction properties because m_auxv is already in the required form.

---

Full diff: https://github.com/llvm/llvm-project/pull/102263.diff

1 Files Affected:

• (modified) lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp (+4-4)

diff --git a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
index 30af9345999c41..e73e31ca78d19f 100644
--- a/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
+++ b/lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
@@ -1077,10 +1077,10 @@ ArchSpec ProcessElfCore::GetArchitecture() {
 }
 
 DataExtractor ProcessElfCore::GetAuxvData() {
-  const uint8_t *start = m_auxv.GetDataStart();
-  size_t len = m_auxv.GetByteSize();
-  lldb::DataBufferSP buffer(new lldb_private::DataBufferHeap(start, len));
-  return DataExtractor(buffer, GetByteOrder(), GetAddressByteSize());
+  assert(m_auxv.GetByteSize() == 0 ||
+         (m_auxv.GetByteOrder() == GetByteOrder() &&
+          m_auxv.GetAddressByteSize() == GetAddressByteSize()));
+  return DataExtractor(m_auxv);
 }
 
 bool ProcessElfCore::GetProcessInfo(ProcessInstanceInfo &info) {

[clayborg]

Do we need this assert? Can't we just change this to:

const DataExtractor &ProcessElfCore::GetAuxvData() { return m_auxv; }

[igorkudrin]

I added the assert to be on the safe side. It shows that the change is eligible, and if I overlooked some exotic execution path, it will trigger and point directly to the problem. If you believe it's excessive, I'll remove it.

The copy constructor for DataExtractor should be called explicitly, see the comment. And GetAuxvData() cannot be changed to return a reference to a data member because in some classes it returns a temporary object.

[clayborg]

There is no need to copy the data extractor. It contains no modifiable state as the position curser is passed in as variables when acessing the data within. I would highly suggest changing to:

const DataExtractor &ProcessElfCore::GetAuxvData() { 
  // Feel free to add asserts here if you want them as long as the code functions correctly
  // even if the asserts get triggered.
  return m_auxv; 
}

[igorkudrin]

I'd also prefer to return a constant reference, but there are other implementations of this virtual function that can't do that, for example, ProcessGDBRemote::GetAuxvData().

[clayborg]

Sorry, I didn't realize this was a virtual function from Process.h...