[Lldb-commits] [PATCH] D21328: [lldb] Fixed incorrect endianness when evaluating certain expressions

Cameron via lldb-commits lldb-commits at lists.llvm.org
Tue Jun 14 09:55:25 PDT 2016

cameron314 created this revision.
cameron314 added reviewers: spyffe, zturner, clayborg.
cameron314 added a subscriber: lldb-commits.

The `EntityVariable` materializer was, under certain conditions, taking the bytes of a `DataExtractor` that were potentially in host order (e.g. little endian) and putting them in the `IRMemoryMap` (which assumes all values are in target order, e.g. big endian). This caused certain values to have the wrong endianness during expression evaluation.

On our platform, this manifested as certain expressions yielding incorrect results when the variables were in registers (e.g. `argc + 1` would give `0x01000001`).



Index: source/Expression/Materializer.cpp
--- source/Expression/Materializer.cpp
+++ source/Expression/Materializer.cpp
@@ -575,7 +575,7 @@
                 Error write_error;
-                map.WriteMemory(m_temporary_allocation, data.GetDataStart(), data.GetByteSize(), write_error);
+                map.WriteMemory(m_temporary_allocation, data.GetDataStart(), data.GetByteSize(), data.GetByteOrder(), write_error);
                 if (!write_error.Success())
Index: source/Expression/IRMemoryMap.cpp
--- source/Expression/IRMemoryMap.cpp
+++ source/Expression/IRMemoryMap.cpp
@@ -564,6 +564,22 @@
+IRMemoryMap::WriteMemory(lldb::addr_t process_address, const uint8_t *bytes, size_t size, lldb::ByteOrder byteOrder, Error &error)
+    std::vector<uint8_t> temp;
+    if (byteOrder != GetByteOrder())
+    {
+        // Need to byte-swap the bytes before putting them in the map, otherwise they'll
+        // be interpreted with the wrong endianness when they're read back out.
+        temp.reserve(size);
+        typedef std::reverse_iterator<const uint8_t *> revit;
+        temp.assign(revit(bytes + size), revit(bytes));
+        bytes = temp.data();
+    }
+    WriteMemory(process_address, bytes, size, error);
 IRMemoryMap::WriteMemory (lldb::addr_t process_address, const uint8_t *bytes, size_t size, Error &error)
Index: include/lldb/Expression/IRMemoryMap.h
--- include/lldb/Expression/IRMemoryMap.h
+++ include/lldb/Expression/IRMemoryMap.h
@@ -60,6 +60,7 @@
     void Free (lldb::addr_t process_address, Error &error);
     void WriteMemory (lldb::addr_t process_address, const uint8_t *bytes, size_t size, Error &error);
+    void WriteMemory (lldb::addr_t process_address, const uint8_t *bytes, size_t size, lldb::ByteOrder order, Error &error);
     void WriteScalarToMemory (lldb::addr_t process_address, Scalar &scalar, size_t size, Error &error);
     void WritePointerToMemory (lldb::addr_t process_address, lldb::addr_t address, Error &error);
     void ReadMemory (uint8_t *bytes, lldb::addr_t process_address, size_t size, Error &error);

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