[llvm] cd40bd0 - hwasan: Move .note.hwasan.globals note to hwasan.module_ctor comdat.

[Peter Collingbourne via llvm-commits]

Author: Peter Collingbourne
Date: 2020-01-17T13:40:52-08:00
New Revision: cd40bd0a32e29fb62c89b120adbc89a847443da3

URL: https://github.com/llvm/llvm-project/commit/cd40bd0a32e29fb62c89b120adbc89a847443da3
DIFF: https://github.com/llvm/llvm-project/commit/cd40bd0a32e29fb62c89b120adbc89a847443da3.diff

LOG: hwasan: Move .note.hwasan.globals note to hwasan.module_ctor comdat.

As of D70146 lld GCs comdats as a group and no longer considers notes in
comdats to be GC roots, so we need to move the note to a comdat with a GC root
section (.init_array) in order to prevent lld from discarding the note.

Differential Revision: https://reviews.llvm.org/D72936

Added: 
    

Modified: 
    llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
    llvm/test/Instrumentation/HWAddressSanitizer/globals.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 7e8f8e27a97b..4f69234a58b9 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -1325,8 +1325,9 @@ void HWAddressSanitizer::instrumentGlobals() {
   // cases where two libraries mutually depend on each other.
   //
   // We only need one note per binary, so put everything for the note in a
-  // comdat.
-  Comdat *NoteComdat = M.getOrInsertComdat(kHwasanNoteName);
+  // comdat. This need to be a comdat with an .init_array section to prevent
+  // newer versions of lld from discarding the note.
+  Comdat *NoteComdat = M.getOrInsertComdat(kHwasanModuleCtorName);
 
   Type *Int8Arr0Ty = ArrayType::get(Int8Ty, 0);
   auto Start =

diff  --git a/llvm/test/Instrumentation/HWAddressSanitizer/globals.ll b/llvm/test/Instrumentation/HWAddressSanitizer/globals.ll
index d5516bfae92d..e85a70365ace 100644
--- a/llvm/test/Instrumentation/HWAddressSanitizer/globals.ll
+++ b/llvm/test/Instrumentation/HWAddressSanitizer/globals.ll
@@ -7,9 +7,9 @@
 ; CHECK30: @__start_hwasan_globals = external hidden constant [0 x i8]
 ; CHECK30: @__stop_hwasan_globals = external hidden constant [0 x i8]
 
-; CHECK30: @hwasan.note = private constant { i32, i32, i32, [8 x i8], i32, i32 } { i32 8, i32 8, i32 3, [8 x i8] c"LLVM\00\00\00\00", i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__start_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__stop_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32) }, section ".note.hwasan.globals", comdat, align 4
+; CHECK30: @hwasan.note = private constant { i32, i32, i32, [8 x i8], i32, i32 } { i32 8, i32 8, i32 3, [8 x i8] c"LLVM\00\00\00\00", i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__start_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint ([0 x i8]* @__stop_hwasan_globals to i64), i64 ptrtoint ({ i32, i32, i32, [8 x i8], i32, i32 }* @hwasan.note to i64)) to i32) }, section ".note.hwasan.globals", comdat($hwasan.module_ctor), align 4
 
-; CHECK30: @hwasan.dummy.global = private constant [0 x i8] zeroinitializer, section "hwasan_globals", comdat($hwasan.note), !associated [[NOTE:![0-9]+]]
+; CHECK30: @hwasan.dummy.global = private constant [0 x i8] zeroinitializer, section "hwasan_globals", comdat($hwasan.module_ctor), !associated [[NOTE:![0-9]+]]
 
 ; CHECK30: @four.hwasan = private global { i32, [12 x i8] } { i32 1, [12 x i8] c"\00\00\00\00\00\00\00\00\00\00\00\AC" }, align 16
 ; CHECK30: @four.hwasan.descriptor = private constant { i32, i32 } { i32 trunc (i64 sub (i64 ptrtoint ({ i32, [12 x i8] }* @four.hwasan to i64), i64 ptrtoint ({ i32, i32 }* @four.hwasan.descriptor to i64)) to i32), i32 -1409286140 }, section "hwasan_globals", !associated [[FOUR:![0-9]+]]