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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
This commit is contained in:
Peter Collingbourne 2020-01-17 09:49:40 -08:00
parent a8b9c93601
commit cd40bd0a32
2 changed files with 5 additions and 4 deletions
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5
llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
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@ -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 =

4
llvm/test/Instrumentation/HWAddressSanitizer/globals.ll
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@ -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]+]]