[PATCH] D28500: [asan] Make ASan compatible with linker dead stripping on Linux, compiler-rt part

[Evgeniy Stepanov via Phabricator via llvm-commits]

eugenis created this revision.
eugenis added reviewers: pcc, rnk.
eugenis added a subscriber: llvm-commits.
eugenis set the repository for this revision to rL LLVM.
Herald added subscribers: dberris, kubabrecka.

This is the compiler-rt part of https://reviews.llvm.org/D28498


Repository:
  rL LLVM

https://reviews.llvm.org/D28500

Files:
  lib/asan/asan_globals.cc
  lib/asan/asan_interface_internal.h
  test/asan/TestCases/Linux/globals-gc-sections-lld.cc
  test/asan/TestCases/Linux/globals-gc-sections.cc


Index: test/asan/TestCases/Linux/globals-gc-sections.cc
===================================================================
--- test/asan/TestCases/Linux/globals-gc-sections.cc
+++ test/asan/TestCases/Linux/globals-gc-sections.cc
@@ -1,11 +1,15 @@
-// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -ffunction-sections -mllvm -asan-globals=0
-// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -ffunction-sections -mllvm -asan-globals=1
+// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -fuse-ld=bfd -ffunction-sections -fdata-sections -mllvm -asan-globals=0
+// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -fuse-ld=bfd -ffunction-sections -fdata-sections -mllvm -asan-globals=1
 
 // https://code.google.com/p/address-sanitizer/issues/detail?id=260
-// XFAIL: *
 
 int undefined();
 
+// bug in ld.bfd: with multiple "asan_globals" sections, __start_asan_globals is
+// treated as a strong GC reference to the first such section. As a result, the
+// first (for some definition of the word) global is never gc-ed.
+int first_unused = 42;
+
 int (*unused)() = undefined;
 
 int main() {
Index: test/asan/TestCases/Linux/globals-gc-sections-lld.cc
===================================================================
--- /dev/null
+++ test/asan/TestCases/Linux/globals-gc-sections-lld.cc
@@ -0,0 +1,14 @@
+// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -fuse-ld=lld -ffunction-sections -fdata-sections -mllvm -asan-globals=0
+// RUN: %clangxx_asan %s -o %t -Wl,--gc-sections -fuse-ld=lld -ffunction-sections -fdata-sections -mllvm -asan-globals=1
+
+// https://code.google.com/p/address-sanitizer/issues/detail?id=260
+
+// REQUIRES: lld
+
+int undefined();
+
+int (*unused)() = undefined;
+
+int main() {
+        return 0;
+}
Index: lib/asan/asan_interface_internal.h
===================================================================
--- lib/asan/asan_interface_internal.h
+++ lib/asan/asan_interface_internal.h
@@ -67,6 +67,11 @@
   SANITIZER_INTERFACE_ATTRIBUTE
   void __asan_unregister_image_globals(uptr *flag);
 
+  SANITIZER_INTERFACE_ATTRIBUTE
+  void __asan_register_elf_globals(uptr *flag, void *start, void *stop);
+  SANITIZER_INTERFACE_ATTRIBUTE
+  void __asan_unregister_elf_globals(uptr *flag, void *start, void *stop);
+
   // These two functions should be called by the instrumented code.
   // 'globals' is an array of structures describing 'n' globals.
   SANITIZER_INTERFACE_ATTRIBUTE
Index: lib/asan/asan_globals.cc
===================================================================
--- lib/asan/asan_globals.cc
+++ lib/asan/asan_globals.cc
@@ -332,6 +332,26 @@
   *flag = 0;
 }
 
+void __asan_register_elf_globals(uptr *flag, void *start, void *stop) {
+  if (*flag) return;
+  if (!start) return;
+  CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
+  __asan_global *globals_start = (__asan_global*)start;
+  __asan_global *globals_stop = (__asan_global*)stop;
+  __asan_register_globals(globals_start, globals_stop - globals_start);
+  *flag = 1;
+}
+
+void __asan_unregister_elf_globals(uptr *flag, void *start, void *stop) {
+  if (!*flag) return;
+  if (!start) return;
+  CHECK_EQ(0, ((uptr)stop - (uptr)start) % sizeof(__asan_global));
+  __asan_global *globals_start = (__asan_global*)start;
+  __asan_global *globals_stop = (__asan_global*)stop;
+  __asan_unregister_globals(globals_start, globals_stop - globals_start);
+  *flag = 0;
+}
+
 // Register an array of globals.
 void __asan_register_globals(__asan_global *globals, uptr n) {
   if (!flags()->report_globals) return;


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