[PATCH] D111344: [HWASan] Use tagged-globals feature on x86.

[Matt Morehouse via Phabricator via cfe-commits]

morehouse created this revision.
morehouse added reviewers: pcc, eugenis, vitalybuka.
morehouse requested review of this revision.
Herald added projects: clang, Sanitizers.
Herald added subscribers: Sanitizers, cfe-commits.

Allows us to use the small code model when we disable relocation
relaxation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111344

Files:
  clang/lib/Driver/SanitizerArgs.cpp
  compiler-rt/test/hwasan/TestCases/global.c
  compiler-rt/test/hwasan/lit.cfg.py


Index: compiler-rt/test/hwasan/lit.cfg.py
===================================================================
--- compiler-rt/test/hwasan/lit.cfg.py
+++ compiler-rt/test/hwasan/lit.cfg.py
@@ -18,10 +18,12 @@
 else:
   config.available_features.add('pointer-tagging')
 if config.target_arch == 'x86_64':
-  # This does basically the same thing as tagged-globals on aarch64. Because
-  # the x86_64 implementation is for testing purposes only there is no
-  # equivalent target feature implemented on x86_64.
-  clang_hwasan_common_cflags += ["-mcmodel=large"]
+  # By default the assembler uses R_X86_64_REX_GOTPCRELX relocations, which can
+  # be relaxed to direct references.  When tagged globals are enabled, these
+  # references fail to link since they have more than a 32-bit offset from RIP.
+  # As a workaround, we disable the relaxation.
+  # TODO: Implement a way to disable for the affected relocations only.
+  clang_hwasan_common_cflags += ["-Wa,-mrelax-relocations=no"]
 
   # The callback instrumentation used on x86_64 has a 1/64 chance of choosing a
   # stack tag of 0.  This causes stack tests to become flaky, so we force tags
Index: compiler-rt/test/hwasan/TestCases/global.c
===================================================================
--- compiler-rt/test/hwasan/TestCases/global.c
+++ compiler-rt/test/hwasan/TestCases/global.c
@@ -5,6 +5,15 @@
 // RUN: not %run %t -1 2>&1 | FileCheck --check-prefixes=CHECK,LSYM %s
 // RUN: not %env_hwasan_opts=symbolize=0 %run %t -1 2>&1 | FileCheck --check-prefixes=CHECK,LNOSYM %s
 
+// Test with and without optimizations, with and without PIC, since different
+// backend passes run depending on these flags.
+// RUN: %clang_hwasan -fno-pic %s -o %t
+// RUN: not %run %t 1 2>&1 | FileCheck --check-prefixes=CHECK,RSYM %s
+// RUN: %clang_hwasan -fno-pic -O2 %s -o %t
+// RUN: not %run %t 1 2>&1 | FileCheck --check-prefixes=CHECK,RSYM %s
+// RUN: %clang_hwasan -O2 %s -o %t
+// RUN: not %run %t 1 2>&1 | FileCheck --check-prefixes=CHECK,RSYM %s
+
 // REQUIRES: pointer-tagging
 
 int x = 1;
Index: clang/lib/Driver/SanitizerArgs.cpp
===================================================================
--- clang/lib/Driver/SanitizerArgs.cpp
+++ clang/lib/Driver/SanitizerArgs.cpp
@@ -1146,7 +1146,7 @@
     CmdArgs.push_back(Args.MakeArgString("hwasan-abi=" + HwasanAbi));
   }
 
-  if (Sanitizers.has(SanitizerKind::HWAddress) && TC.getTriple().isAArch64()) {
+  if (Sanitizers.has(SanitizerKind::HWAddress) && !HwasanUseAliases) {
     CmdArgs.push_back("-target-feature");
     CmdArgs.push_back("+tagged-globals");
   }


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