[libc++] Add build and CI support for pointer field protection

libcxx/CMakeLists.txt

@@ -66,6 +66,14 @@ if (NOT "${LIBCXX_HARDENING_MODE}" IN_LIST LIBCXX_SUPPORTED_HARDENING_MODES)
   message(FATAL_ERROR
     "Unsupported hardening mode: '${LIBCXX_HARDENING_MODE}'. Supported values are ${LIBCXX_SUPPORTED_HARDENING_MODES}.")
 endif()
+set(LIBCXX_SUPPORTED_PFP none untagged tagged)
+set(LIBCXX_PFP none CACHE STRING
+  "Specify whether to build with pointer field protection.
+   Supported values are ${LIBCXX_SUPPORTED_PFP}.")
+if (NOT "${LIBCXX_PFP}" IN_LIST LIBCXX_SUPPORTED_PFP)
+  message(FATAL_ERROR
+    "Unsupported PFP mode: '${LIBCXX_PFP}'. Supported values are ${LIBCXX_SUPPORTED_PFP}.")
+endif()
 set(LIBCXX_ASSERTION_HANDLER_FILE
   "vendor/llvm/default_assertion_handler.in"
   CACHE STRING
@@ -567,6 +575,17 @@ function(cxx_add_rtti_flags target)
   endif()
 endfunction()
 
+function(cxx_add_pfp_flags target)
+  if (LIBCXX_PFP STREQUAL untagged)
+    target_add_compile_flags_if_supported(${target} PUBLIC
+      -fexperimental-pointer-field-protection)
+  elseif (LIBCXX_PFP STREQUAL tagged)
+    target_add_compile_flags_if_supported(${target} PUBLIC
+      -fexperimental-pointer-field-protection
+      -fexperimental-pointer-field-protection-tagged)
+  endif()
+endfunction()
+
 # Modules flags ===============================================================
 # FIXME The libc++ sources are fundamentally non-modular. They need special
 # versions of the headers in order to provide C++03 and legacy ABI definitions.
@@ -823,6 +842,7 @@ function(cxx_add_common_build_flags target)
   cxx_add_windows_flags(${target})
   cxx_add_exception_flags(${target})
   cxx_add_rtti_flags(${target})
+  cxx_add_pfp_flags(${target})
   cxx_add_module_flags(${target})
   cxx_link_system_libraries(${target})
   target_link_libraries(${target} PRIVATE cxx-sanitizer-flags)

libcxx/cmake/caches/Generic-pfp.cmake

@@ -0,0 +1,7 @@
+set(LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
+set(LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
+set(LIBCXX_PFP "tagged" CACHE STRING "")
+set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
+set(LIBCXX_INCLUDE_BENCHMARKS OFF CACHE BOOL "")
+set(LIBCXX_TEST_CONFIG "llvm-libc++-static.cfg.in" CACHE STRING "")
+set(LIBUNWIND_ENABLE_SHARED OFF CACHE BOOL "")

libcxx/test/CMakeLists.txt

@@ -79,6 +79,7 @@ if (NOT LIBCXX_ENABLE_RTTI)
 endif()
 
 serialize_lit_string_param(SERIALIZED_LIT_PARAMS hardening_mode "${LIBCXX_HARDENING_MODE}")
+serialize_lit_string_param(SERIALIZED_LIT_PARAMS pfp "${LIBCXX_PFP}")
 
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_string_param(SERIALIZED_LIT_PARAMS target_triple "${CMAKE_CXX_COMPILER_TARGET}")

libcxx/test/libcxx/gdb/gdb_pretty_printer_test.sh.cpp

@@ -24,6 +24,9 @@
 // This test doesn't work as such on Windows.
 // UNSUPPORTED: windows
 
+// GDB doesn't know how to read PFP fields correctly yet.
+// UNSUPPORTED: pfp
+
 // RUN: %{cxx} %{flags} %s -o %t.exe %{compile_flags} -g %{link_flags}
 // Ensure locale-independence for unicode tests.
 // RUN: env LANG=en_US.UTF-8 %{gdb} -nx -batch -iex "set autoload off" -ex "source %S/../../../utils/gdb/libcxx/printers.py" -ex "python register_libcxx_printer_loader()" -ex "source %S/gdb_pretty_printer_test.py" %t.exe

libcxx/test/libcxx/type_traits/is_trivially_relocatable.compile.pass.cpp

@@ -6,6 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+// With PFP we return different values for __libcpp_is_trivially_relocatable.
+// UNSUPPORTED: pfp
+
 #include <__type_traits/is_trivially_relocatable.h>
 #include <array>
 #include <deque>

libcxx/utils/ci/run-buildbot

@@ -376,6 +376,11 @@ generic-ubsan)
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-ubsan.cmake"
     check-runtimes
 ;;
+generic-pfp)
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-pfp.cmake"
+    check-runtimes
+;;
 #
 # Various build configurations
 #

libcxx/utils/libcxx/test/params.py

@@ -343,6 +343,24 @@ def getSuitableClangTidy(cfg):
             ]
         )
     ),
+    Parameter(
+        name="pfp",
+        choices=["none", "untagged", "tagged"],
+        type=str,
+        default="none",
+        help="Whether to build with pointer field protection.",
+        actions=lambda pfp: [] if pfp == "none" else [
+            AddCompileFlag("-fexperimental-pointer-field-protection"),
+            AddCompileFlag("-fexperimental-pointer-field-protection-tagged") if pfp == "tagged" else None,
+            # Requires support for new relocations which are only implemented in lld for now.
+            AddLinkFlag("-fuse-ld=lld"),
+            # Requires emulated PAC support in compiler-rt.
+            AddCompileFlag("--rtlib=compiler-rt"),
+            AddLinkFlag("--rtlib=compiler-rt"),
+            AddLinkFlag("--unwindlib=libunwind"),
+            AddFeature("pfp"),
+        ],
+    ),
     Parameter(
         name="enable_experimental",
         choices=[True, False],

libcxxabi/test/CMakeLists.txt

@@ -80,6 +80,10 @@ if (LLVM_USE_SANITIZER)
   serialize_lit_string_param(SERIALIZED_LIT_PARAMS use_sanitizer "${LLVM_USE_SANITIZER}")
 endif()
 
+if (DEFINED LIBCXX_PFP)
+  serialize_lit_string_param(SERIALIZED_LIT_PARAMS pfp "${LIBCXX_PFP}")
+endif()
+
 if (CMAKE_CXX_COMPILER_TARGET)
   serialize_lit_string_param(SERIALIZED_LIT_PARAMS target_triple "${CMAKE_CXX_COMPILER_TARGET}")
 else()