[Lldb-commits] [lldb] 425fe33 - [lldb] Fix unaligned writes in ObjectFileELF (#165759)

[via lldb-commits]

Author: Alex Langford
Date: 2025-11-03T10:20:08-08:00
New Revision: 425fe3362d49ff1b2958f8ec9cae49e587b57e7e

URL: https://github.com/llvm/llvm-project/commit/425fe3362d49ff1b2958f8ec9cae49e587b57e7e
DIFF: https://github.com/llvm/llvm-project/commit/425fe3362d49ff1b2958f8ec9cae49e587b57e7e.diff

LOG: [lldb] Fix unaligned writes in ObjectFileELF (#165759)

The code to apply relocations was sometimes creating unaligned
destination pointers. Instead of giving them an explicit type (i.e.
`uint64_t *`) and forcing the compiler to generate unaligned stores,
mark the pointer as `void *`. The compiler will figure out the correct
series of store instructions.

Added: 
    

Modified: 
    lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

Removed: 
    


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diff  --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index 49841e7307443..e06e69fb08305 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -2735,9 +2735,8 @@ static void ApplyELF64ABS64Relocation(Symtab *symtab, ELFRelocation &rel,
     // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
     WritableDataBuffer *data_buffer =
         llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
-    uint64_t *dst = reinterpret_cast<uint64_t *>(
-        data_buffer->GetBytes() + rel_section->GetFileOffset() +
-        ELFRelocation::RelocOffset64(rel));
+    void *const dst = data_buffer->GetBytes() + rel_section->GetFileOffset() +
+                      ELFRelocation::RelocOffset64(rel);
     uint64_t val_offset = value + ELFRelocation::RelocAddend64(rel);
     memcpy(dst, &val_offset, sizeof(uint64_t));
   }
@@ -2762,9 +2761,8 @@ static void ApplyELF64ABS32Relocation(Symtab *symtab, ELFRelocation &rel,
     // ObjectFileELF creates a WritableDataBuffer in CreateInstance.
     WritableDataBuffer *data_buffer =
         llvm::cast<WritableDataBuffer>(data_buffer_sp.get());
-    uint32_t *dst = reinterpret_cast<uint32_t *>(
-        data_buffer->GetBytes() + rel_section->GetFileOffset() +
-        ELFRelocation::RelocOffset32(rel));
+    void *const dst = data_buffer->GetBytes() + rel_section->GetFileOffset() +
+                      ELFRelocation::RelocOffset32(rel);
     memcpy(dst, &truncated_addr, sizeof(uint32_t));
   }
 }