[llvm] r334313 - [asan] Instrument comdat globals on COFF targets
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Fri Jun 8 11:33:17 PDT 2018
Author: rnk
Date: Fri Jun 8 11:33:16 2018
New Revision: 334313
URL: http://llvm.org/viewvc/llvm-project?rev=334313&view=rev
Log:
[asan] Instrument comdat globals on COFF targets
Summary:
If we can use comdats, then we can make it so that the global metadata
is thrown away if the prevailing definition of the global was
uninstrumented. I have only tested this on COFF targets, but in theory,
there is no reason that we cannot also do this for ELF.
This will allow us to re-enable string merging with ASan on Windows,
reducing the binary size cost of ASan on Windows.
Reviewers: eugenis, vitalybuka
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D47841
Added:
llvm/trunk/test/Instrumentation/AddressSanitizer/win-string-literal.ll
Modified:
llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
Modified: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp?rev=334313&r1=334312&r2=334313&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp Fri Jun 8 11:33:16 2018
@@ -1655,14 +1655,6 @@ bool AddressSanitizerModule::ShouldInstr
if (!Ty->isSized()) return false;
if (!G->hasInitializer()) return false;
if (GlobalWasGeneratedByCompiler(G)) return false; // Our own globals.
- // Touch only those globals that will not be defined in other modules.
- // Don't handle ODR linkage types and COMDATs since other modules may be built
- // without ASan.
- if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
- G->getLinkage() != GlobalVariable::PrivateLinkage &&
- G->getLinkage() != GlobalVariable::InternalLinkage)
- return false;
- if (G->hasComdat()) return false;
// Two problems with thread-locals:
// - The address of the main thread's copy can't be computed at link-time.
// - Need to poison all copies, not just the main thread's one.
@@ -1670,6 +1662,38 @@ bool AddressSanitizerModule::ShouldInstr
// For now, just ignore this Global if the alignment is large.
if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
+ // If we know this global is defined only in this module (external or static),
+ // we can instrument it.
+ if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
+ G->getLinkage() != GlobalVariable::PrivateLinkage &&
+ G->getLinkage() != GlobalVariable::InternalLinkage) {
+ // For targets that support comdats, we can instrument ODR globals in
+ // comdats. We simply add our global metadata to the group and hope that an
+ // instrumented global is selected.
+ // FIXME: This should work on ELF, enable it there too.
+ if (!TargetTriple.isOSBinFormatCOFF())
+ return false;
+ if (G->getLinkage() != GlobalVariable::WeakODRLinkage &&
+ G->getLinkage() != GlobalVariable::LinkOnceODRLinkage)
+ return false;
+ if (!G->hasComdat())
+ return false;
+ }
+
+ // If a comdat is present, it must have a selection kind that implies ODR
+ // semantics: no duplicates, any, or exact match.
+ if (Comdat *C = G->getComdat()) {
+ switch (C->getSelectionKind()) {
+ case Comdat::Any:
+ case Comdat::ExactMatch:
+ case Comdat::NoDuplicates:
+ break;
+ case Comdat::Largest:
+ case Comdat::SameSize:
+ return false;
+ }
+ }
+
if (G->hasSection()) {
StringRef Section = G->getSection();
@@ -2119,6 +2143,7 @@ bool AddressSanitizerModule::InstrumentG
new GlobalVariable(M, NewTy, G->isConstant(), Linkage, NewInitializer,
"", G, G->getThreadLocalMode());
NewGlobal->copyAttributesFrom(G);
+ NewGlobal->setComdat(G->getComdat());
NewGlobal->setAlignment(MinRZ);
// Move null-terminated C strings to "__asan_cstring" section on Darwin.
Added: llvm/trunk/test/Instrumentation/AddressSanitizer/win-string-literal.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/AddressSanitizer/win-string-literal.ll?rev=334313&view=auto
==============================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/win-string-literal.ll (added)
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/win-string-literal.ll Fri Jun 8 11:33:16 2018
@@ -0,0 +1,46 @@
+; RUN: opt < %s -asan -asan-module -S | FileCheck %s
+
+; Generated like so:
+; $ clang -S -emit-llvm -Xclang -disable-llvm-passes -fsanitize=address -O1 t.cpp -o t.ll
+; const char *getstr() { return "asdf"; }
+
+; CHECK: $"??_C at _04JIHMPGLA@asdf?$AA@" = comdat any
+
+; CHECK: @"??_C at _04JIHMPGLA@asdf?$AA@" =
+; CHECK-SAME: linkonce_odr dso_local unnamed_addr constant { [5 x i8], [59 x i8] }
+; CHECK-SAME: { [5 x i8] c"asdf\00", [59 x i8] zeroinitializer }, comdat, align 32
+
+; CHECK: @"__asan_global_??_C at _04JIHMPGLA@asdf?$AA@" =
+; CHECK-SAME: private global { i64, i64, i64, i64, i64, i64, i64, i64 }
+; CHECK-SAME: { i64 ptrtoint ({ [5 x i8], [59 x i8] }* @"??_C at _04JIHMPGLA@asdf?$AA@" to i64),
+; CHECK-SAME: i64 5, i64 64, i64 ptrtoint ([17 x i8]* @__asan_gen_.1 to i64),
+; CHECK-SAME: i64 ptrtoint ([8 x i8]* @__asan_gen_ to i64), i64 0,
+; CHECK-SAME: i64 ptrtoint ({ [6 x i8]*, i32, i32 }* @__asan_gen_.3 to i64), i64 0 },
+; CHECK-SAME: section ".ASAN$GL", comdat($"??_C at _04JIHMPGLA@asdf?$AA@"), align 64
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.13.26131"
+
+$"??_C at _04JIHMPGLA@asdf?$AA@" = comdat any
+
+@"??_C at _04JIHMPGLA@asdf?$AA@" = linkonce_odr dso_local unnamed_addr constant [5 x i8] c"asdf\00", comdat, align 1
+
+; Function Attrs: nounwind sanitize_address uwtable
+define dso_local i8* @"?getstr@@YAPEBDXZ"() #0 {
+entry:
+ ret i8* getelementptr inbounds ([5 x i8], [5 x i8]* @"??_C at _04JIHMPGLA@asdf?$AA@", i32 0, i32 0)
+}
+
+attributes #0 = { nounwind sanitize_address uwtable }
+
+!llvm.asan.globals = !{!0}
+!llvm.module.flags = !{!2, !3}
+!llvm.ident = !{!4}
+
+!0 = !{[5 x i8]* @"??_C at _04JIHMPGLA@asdf?$AA@", !1, !"<string literal>", i1 false, i1 false}
+!1 = !{!"t.cpp", i32 1, i32 31}
+!2 = !{i32 1, !"wchar_size", i32 2}
+!3 = !{i32 7, !"PIC Level", i32 2}
+!4 = !{!"clang version 7.0.0 "}
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