[PATCH] D118749: [mte] work around lifetime issue with setjmp.

[Florian Mayer via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG8680d6db1e45: [mte] work around lifetime issue with setjmp. (authored by fmayer).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118749/new/

https://reviews.llvm.org/D118749

Files:
  llvm/lib/Target/AArch64/AArch64StackTagging.cpp
  llvm/test/CodeGen/AArch64/stack-tagging-setjmp.ll


Index: llvm/test/CodeGen/AArch64/stack-tagging-setjmp.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/stack-tagging-setjmp.ll
@@ -0,0 +1,44 @@
+; RUN: opt -S -aarch64-stack-tagging %s -o - | FileCheck %s
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-linux-android29"
+
+ at stackbuf = dso_local local_unnamed_addr global i8* null, align 8
+ at jbuf = dso_local global [32 x i64] zeroinitializer, align 8
+
+declare void @may_jump()
+
+define dso_local noundef i1 @_Z6targetv() sanitize_memtag {
+entry:
+  %buf = alloca [4096 x i8], align 1
+  %call = call i32 @setjmp(i64* noundef getelementptr inbounds ([32 x i64], [32 x i64]* @jbuf, i64 0, i64 0))
+  switch i32 %call, label %while.body [
+    i32 1, label %return
+    i32 2, label %sw.bb1
+  ]
+
+sw.bb1:                                           ; preds = %entry
+  br label %return
+
+while.body:                                       ; preds = %entry
+  %0 = getelementptr inbounds [4096 x i8], [4096 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 4096, i8* nonnull %0) #10
+  store i8* %0, i8** @stackbuf, align 8
+  ; may_jump may call longjmp, going back to the switch (and then the return),
+  ; bypassing the lifetime.end. This is why we need to untag on the return,
+  ; rather than the lifetime.end.
+  call void @may_jump()
+  call void @llvm.lifetime.end.p0i8(i64 4096, i8* nonnull %0) #10
+  br label %return
+
+; CHECK-LABEL: return:
+; CHECK: call void @llvm.aarch64.settag
+return:                                           ; preds = %entry, %while.body, %sw.bb1
+  %retval.0 = phi i1 [ true, %while.body ], [ true, %sw.bb1 ], [ false, %entry ]
+  ret i1 %retval.0
+}
+
+declare i32 @setjmp(i64* noundef) returns_twice
+
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture)
+
Index: llvm/lib/Target/AArch64/AArch64StackTagging.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64StackTagging.cpp
+++ llvm/lib/Target/AArch64/AArch64StackTagging.cpp
@@ -536,8 +536,14 @@
   SmallVector<Instruction *, 8> RetVec;
   SmallVector<Instruction *, 4> UnrecognizedLifetimes;
 
+  bool CallsReturnTwice = false;
   for (auto &BB : *F) {
     for (Instruction &I : BB) {
+      if (CallInst *CI = dyn_cast<CallInst>(&I)) {
+        if (CI->canReturnTwice()) {
+          CallsReturnTwice = true;
+        }
+      }
       if (auto *AI = dyn_cast<AllocaInst>(&I)) {
         Allocas[AI].AI = AI;
         Allocas[AI].OldAI = AI;
@@ -639,8 +645,12 @@
     Info.AI->replaceAllUsesWith(TagPCall);
     TagPCall->setOperand(0, Info.AI);
 
+    // Calls to functions that may return twice (e.g. setjmp) confuse the
+    // postdominator analysis, and will leave us to keep memory tagged after
+    // function return. Work around this by always untagging at every return
+    // statement if return_twice functions are called.
     if (UnrecognizedLifetimes.empty() && Info.LifetimeStart.size() == 1 &&
-        Info.LifetimeEnd.size() == 1) {
+        Info.LifetimeEnd.size() == 1 && !CallsReturnTwice) {
       IntrinsicInst *Start = Info.LifetimeStart[0];
       IntrinsicInst *End = Info.LifetimeEnd[0];
       uint64_t Size =


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