[Lldb-commits] [lldb] [lldb][CMake] Extend liblldb interposition fix to lldb-dap and lldb-mcp (PR #207251)

[via lldb-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

<details>
<summary>Changes</summary>

liblldb statically absorbs the lldbHost and lldbUtility archives (and every plugin). A tool that links the shared liblldb while also linking those same archives statically ends up with two copies of that object code. On ELF, if the tool re-exports the archive symbols in its own .dynsym, the dynamic linker can bind liblldb's internal references to the tool's copy instead of liblldb's own, breaking shared-state assumptions such as the HostInfo singletons.

106644f6c835 fixed this for the lldb driver with --exclude-libs,ALL, but lldb-dap and lldb-mcp have the same setup and were left exposed. Factor the logic into a shared lldb_prevent_liblldb_symbol_interposition helper and call it from all three tools.

---
Full diff: https://github.com/llvm/llvm-project/pull/207251.diff


4 Files Affected:

- (modified) lldb/cmake/modules/AddLLDB.cmake (+14) 
- (modified) lldb/tools/driver/CMakeLists.txt (+1-10) 
- (modified) lldb/tools/lldb-dap/tool/CMakeLists.txt (+2) 
- (modified) lldb/tools/lldb-mcp/CMakeLists.txt (+2) 


``````````diff
diff --git a/lldb/cmake/modules/AddLLDB.cmake b/lldb/cmake/modules/AddLLDB.cmake
index 6e56dfd783d1f..5c1a245346f77 100644
--- a/lldb/cmake/modules/AddLLDB.cmake
+++ b/lldb/cmake/modules/AddLLDB.cmake
@@ -469,6 +469,20 @@ function(add_lldb_tool name)
   set_target_properties(${name} PROPERTIES XCODE_GENERATE_SCHEME ON)
 endfunction()
 
+# liblldb statically absorbs lldbHost, lldbUtility, and every plugin. A tool
+# that links the shared liblldb while also linking those archives statically
+# carries a second copy of their object code. On ELF, if the tool re-exports
+# the archive symbols through its own .dynsym, the dynamic linker can bind
+# liblldb's internal references to the tool's copy instead of its own, breaking
+# shared state such as the HostInfo singletons. --exclude-libs,ALL keeps the
+# archive symbols out of the tool's .dynsym. Only ELF is affected: Mach-O uses
+# two-level namespaces and PE/COFF does not export symbols by default.
+function(lldb_prevent_liblldb_symbol_interposition name)
+  if(UNIX AND NOT APPLE)
+    target_link_options(${name} PRIVATE "LINKER:--exclude-libs,ALL")
+  endif()
+endfunction()
+
 # The test suite relies on finding LLDB.framework binary resources in the
 # build-tree. Remove them before installing to avoid collisions with their
 # own install targets.
diff --git a/lldb/tools/driver/CMakeLists.txt b/lldb/tools/driver/CMakeLists.txt
index 38670a14a78b0..19a1cd7bbcea8 100644
--- a/lldb/tools/driver/CMakeLists.txt
+++ b/lldb/tools/driver/CMakeLists.txt
@@ -52,16 +52,7 @@ add_dependencies(lldb
   ${tablegen_deps}
 )
 
-# lldbHost and lldbUtility are also statically linked into liblldb.so, so any
-# state they carry exists in two independent copies. On ELF platforms this
-# creates an interposition hazard: when liblldb.so exports a symbol from those
-# archives (e.g. for dynamic plugin loading), the dynamic linker can resolve
-# it to lldb's copy instead of liblldb.so's, breaking shared-state assumptions.
-# --exclude-libs,ALL keeps archive symbols out of lldb's .dynsym, eliminating
-# the hazard without affecting the executable's own use of those symbols.
-if(UNIX AND NOT APPLE)
-  target_link_options(lldb PRIVATE "LINKER:--exclude-libs,ALL")
-endif()
+lldb_prevent_liblldb_symbol_interposition(lldb)
 
 if(LLDB_BUILD_FRAMEWORK)
   # In the build-tree, we know the exact path to the framework directory.
diff --git a/lldb/tools/lldb-dap/tool/CMakeLists.txt b/lldb/tools/lldb-dap/tool/CMakeLists.txt
index 33263cb5adb6b..3567e9e6e9394 100644
--- a/lldb/tools/lldb-dap/tool/CMakeLists.txt
+++ b/lldb/tools/lldb-dap/tool/CMakeLists.txt
@@ -19,6 +19,8 @@ add_dependencies(lldb-dap
   ${tablegen_deps}
 )
 
+lldb_prevent_liblldb_symbol_interposition(lldb-dap)
+
 if(APPLE)
   configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/lldb-dap-Info.plist.in
diff --git a/lldb/tools/lldb-mcp/CMakeLists.txt b/lldb/tools/lldb-mcp/CMakeLists.txt
index 72b96f2a1f898..ab68f853a0f49 100644
--- a/lldb/tools/lldb-mcp/CMakeLists.txt
+++ b/lldb/tools/lldb-mcp/CMakeLists.txt
@@ -11,6 +11,8 @@ add_lldb_tool(lldb-mcp
     lldbProtocolMCP
   )
 
+lldb_prevent_liblldb_symbol_interposition(lldb-mcp)
+
 if(APPLE)
   configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/lldb-mcp-Info.plist.in

``````````

</details>


https://github.com/llvm/llvm-project/pull/207251