From cd789d8cfe12aa374e66eafc748f4fc06e149ca7 Mon Sep 17 00:00:00 2001
From: Sylvestre Ledru <sylvestre@debian.org>
Date: Mon, 17 Apr 2017 20:51:50 +0000
Subject: [PATCH] Add a linker script to version LLVM symbols
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Summary:
This patch adds a very simple linker script to version the lib's symbols
and thus trying to avoid crashes if an application loads two different
LLVM versions (as long as they do not share data between them).

Note that we deliberately *don't* make LLVM_5.0 depend on LLVM_4.0:
they're incompatible and the whole point of this patch is
to tell the linker that.


Avoid unexpected crashes when two LLVM versions are used in the same process.

Author: Rebecca N. Palmer <rebecca_palmer@zoho.com>
Author: Lisandro Damían Nicanor Pérez Meyer <lisandro@debian.org>
Author: Sylvestre Ledru <sylvestre@debian.org>
Bug-Debian:  https://bugs.debian.org/848368


Reviewers: beanz, rnk

Reviewed By: rnk

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D31524

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300496 91177308-0d34-0410-b5e6-96231b3b80d8
---
 cmake/modules/AddLLVM.cmake                   | 3 ++-
 tools/llvm-shlib/CMakeLists.txt               | 6 +++++-
 tools/llvm-shlib/simple_version_script.map.in | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)
 create mode 100644 tools/llvm-shlib/simple_version_script.map.in

diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index 7f7608cff33..e011bb40275 100644
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -81,8 +81,9 @@ function(add_llvm_symbol_exports target_name export_file)
     # Gold and BFD ld require a version script rather than a plain list.
     set(native_export_file "${target_name}.exports")
     # FIXME: Don't write the "local:" line on OpenBSD.
+    # in the export file, also add a linker script to version LLVM symbols (form: LLVM_N.M)
     add_custom_command(OUTPUT ${native_export_file}
-      COMMAND echo "{" > ${native_export_file}
+      COMMAND echo "LLVM_${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR} {" > ${native_export_file}
       COMMAND grep -q "[[:alnum:]]" ${export_file} && echo "  global:" >> ${native_export_file} || :
       COMMAND sed -e "s/$/;/" -e "s/^/    /" < ${export_file} >> ${native_export_file}
       COMMAND echo "  local: *;" >> ${native_export_file}
diff --git a/tools/llvm-shlib/CMakeLists.txt b/tools/llvm-shlib/CMakeLists.txt
index c68a2b0e60e..27815868629 100644
--- a/tools/llvm-shlib/CMakeLists.txt
+++ b/tools/llvm-shlib/CMakeLists.txt
@@ -38,8 +38,12 @@ add_llvm_library(LLVM SHARED DISABLE_LLVM_LINK_LLVM_DYLIB SONAME ${SOURCES})
 
 list(REMOVE_DUPLICATES LIB_NAMES)
 if(("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux") OR (MINGW) OR ("${CMAKE_SYSTEM_NAME}" STREQUAL "FreeBSD") OR ("${CMAKE_SYSTEM_NAME}" STREQUAL "DragonFly")) # FIXME: It should be "GNU ld for elf"
+  configure_file(
+  ${CMAKE_CURRENT_SOURCE_DIR}/simple_version_script.map.in
+  ${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map)
+
   # GNU ld doesn't resolve symbols in the version script.
-  set(LIB_NAMES -Wl,--whole-archive ${LIB_NAMES} -Wl,--no-whole-archive)
+  set(LIB_NAMES -Wl,--version-script,${LLVM_LIBRARY_DIR}/tools/llvm-shlib/simple_version_script.map -Wl,--whole-archive ${LIB_NAMES} -Wl,--no-whole-archive)
 elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
   set(LIB_NAMES -Wl,-all_load ${LIB_NAMES})
 endif()
diff --git a/tools/llvm-shlib/simple_version_script.map.in b/tools/llvm-shlib/simple_version_script.map.in
new file mode 100644
index 00000000000..e9515fe7862
--- /dev/null
+++ b/tools/llvm-shlib/simple_version_script.map.in
@@ -0,0 +1 @@
+LLVM_@LLVM_VERSION_MAJOR@.@LLVM_VERSION_MINOR@ { global: *; };