[PATCH] D55857: [asan] Prevent folding of globals with redzones

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka created this revision.
vitalybuka added reviewers: eugenis, pcc.
Herald added a subscriber: hiraditya.

ICF prevented by removing unnamed_addr and local_unnamed_addr for all sanitized
globals.

ICF on globals causes:

1. false ODR reports when we register global on the same address more than once
2. globals buffer overflow if we fold variables of smaller type inside of large

type. Then the smaller one will poison redzone which overlaps with the larger one.

Both can be avoided with private aliases and ODR-indicators, however they
increase size more than just disabling ICF on sanitized globals.


Repository:
  rL LLVM

https://reviews.llvm.org/D55857

Files:
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
  llvm/test/Instrumentation/AddressSanitizer/global_cstring_darwin.ll
  llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
  llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
  llvm/test/Instrumentation/AddressSanitizer/global_metadata_windows.ll
  llvm/test/Instrumentation/AddressSanitizer/win-string-literal.ll


Index: llvm/test/Instrumentation/AddressSanitizer/win-string-literal.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/win-string-literal.ll
+++ llvm/test/Instrumentation/AddressSanitizer/win-string-literal.ll
@@ -7,7 +7,7 @@
 ; 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: linkonce_odr dso_local 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@" =
Index: llvm/test/Instrumentation/AddressSanitizer/global_metadata_windows.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/global_metadata_windows.ll
+++ llvm/test/Instrumentation/AddressSanitizer/global_metadata_windows.ll
@@ -14,8 +14,8 @@
 ; CHECK: $dead_global = comdat noduplicates
 ; CHECK: $private_str = comdat noduplicates
 
-; CHECK: @dead_global = local_unnamed_addr global { i32, [60 x i8] } { i32 42, [60 x i8] zeroinitializer }, comdat, align 32
-; CHECK: @private_str = internal unnamed_addr constant { [8 x i8], [56 x i8] } { [8 x i8] c"private\00", [56 x i8] zeroinitializer }, comdat, align 32
+; CHECK: @dead_global = global { i32, [60 x i8] } { i32 42, [60 x i8] zeroinitializer }, comdat, align 32
+; CHECK: @private_str = internal constant { [8 x i8], [56 x i8] } { [8 x i8] c"private\00", [56 x i8] zeroinitializer }, comdat, align 32
 
 ; CHECK: @__asan_global_dead_global = private global { {{.*}} }, section ".ASAN$GL", comdat($dead_global), align 64
 ; CHECK: @__asan_global_private_str = private global { {{.*}} }, section ".ASAN$GL", comdat($private_str), align 64
Index: llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
+++ llvm/test/Instrumentation/AddressSanitizer/global_metadata_array.ll
@@ -15,7 +15,7 @@
 
 ; Check that globals were instrumented:
 ; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, align 32
-; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }{{.*}}, align 32
+; CHECK: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }{{.*}}, align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
Index: llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
+++ llvm/test/Instrumentation/AddressSanitizer/global_metadata.ll
@@ -15,7 +15,7 @@
 ; Check that globals were instrumented:
 
 ; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, comdat, align 32
-; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, comdat($".str${{[01-9a-f]+}}"), align 32
+; CHECK: @.str = internal constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, comdat($".str${{[01-9a-f]+}}"), align 32
 
 ; Check emitted location descriptions:
 ; CHECK: [[VARNAME:@___asan_gen_.[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
Index: llvm/test/Instrumentation/AddressSanitizer/global_cstring_darwin.ll
===================================================================
--- llvm/test/Instrumentation/AddressSanitizer/global_cstring_darwin.ll
+++ llvm/test/Instrumentation/AddressSanitizer/global_cstring_darwin.ll
@@ -8,14 +8,14 @@
 @.str.1 = private unnamed_addr constant [13 x i8] c"Hello world.\00", align 1
 @.str.2 = private unnamed_addr constant [4 x i8] c"%s\0A\00", align 1
 
-; CHECK: @.str.1 = internal unnamed_addr constant { [13 x i8], [51 x i8] } { [13 x i8] c"Hello world.\00", [51 x i8] zeroinitializer }, section "__TEXT,__asan_cstring,regular", align 32
-; CHECK: @.str.2 = internal unnamed_addr constant { [4 x i8], [60 x i8] } { [4 x i8] c"%s\0A\00", [60 x i8] zeroinitializer }, section "__TEXT,__asan_cstring,regular", align 32
+; CHECK: @.str.1 = internal constant { [13 x i8], [51 x i8] } { [13 x i8] c"Hello world.\00", [51 x i8] zeroinitializer }, section "__TEXT,__asan_cstring,regular", align 32
+; CHECK: @.str.2 = internal constant { [4 x i8], [60 x i8] } { [4 x i8] c"%s\0A\00", [60 x i8] zeroinitializer }, section "__TEXT,__asan_cstring,regular", align 32
 
 ; Shouldn't be put into special section:
 @.str.3 = private unnamed_addr constant [4 x i8] c"\00\01\02\03", align 1
 @.str.4 = private unnamed_addr global [7 x i8] c"Hello.\00", align 1
 @.str.5 = private unnamed_addr constant [8 x i8] c"Hello.\00\00", align 1
 
-; CHECK: @.str.3 = internal unnamed_addr constant { [4 x i8], [60 x i8] } { [4 x i8] c"\00\01\02\03", [60 x i8] zeroinitializer }, align 32
-; CHECK: @.str.4 = private unnamed_addr global { [7 x i8], [57 x i8] } { [7 x i8] c"Hello.\00", [57 x i8] zeroinitializer }, align 32
-; CHECK: @.str.5 = internal unnamed_addr constant { [8 x i8], [56 x i8] } { [8 x i8] c"Hello.\00\00", [56 x i8] zeroinitializer }, align 32
+; CHECK: @.str.3 = internal constant { [4 x i8], [60 x i8] } { [4 x i8] c"\00\01\02\03", [60 x i8] zeroinitializer }, align 32
+; CHECK: @.str.4 = private global { [7 x i8], [57 x i8] } { [7 x i8] c"Hello.\00", [57 x i8] zeroinitializer }, align 32
+; CHECK: @.str.5 = internal constant { [8 x i8], [56 x i8] } { [8 x i8] c"Hello.\00\00", [56 x i8] zeroinitializer }, align 32
Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -2147,6 +2147,9 @@
     NewGlobal->copyAttributesFrom(G);
     NewGlobal->setComdat(G->getComdat());
     NewGlobal->setAlignment(MinRZ);
+    // Don't fold globals with redzones. This will cause false ODR-violation and
+    // global-buffer-overflow reports.
+    NewGlobal->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
 
     // Move null-terminated C strings to "__asan_cstring" section on Darwin.
     if (TargetTriple.isOSBinFormatMachO() && !G->hasSection() &&


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