From 4a89ed373cdaf2033a8c164d27c4dfe28b3680bd Mon Sep 17 00:00:00 2001
From: Jinsong Ji <jji@us.ibm.com>
Date: Thu, 10 Jun 2021 02:39:57 +0000
Subject: [PATCH] [AIX] Add traceback ssp canary bit support

We will need to set the ssp canary bit in traceback table to communicate
with unwinder about the canary.

Reviewed By: #powerpc, shchenz

Differential Revision: https://reviews.llvm.org/D103202
---
 .../llvm/CodeGen/TargetLoweringObjectFileImpl.h    |  1 +
 llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp  | 11 +++++++
 llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp          |  7 ++++
 .../CodeGen/PowerPC/aix-emit-tracebacktable-ssp.ll | 37 ++++++++++++++++++++++
 4 files changed, 56 insertions(+)
 create mode 100644 llvm/test/CodeGen/PowerPC/aix-emit-tracebacktable-ssp.ll

diff --git a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
index 52c8527..690a3f2 100644
--- a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
+++ b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
@@ -229,6 +229,7 @@ public:
   ~TargetLoweringObjectFileXCOFF() override = default;
 
   static bool ShouldEmitEHBlock(const MachineFunction *MF);
+  static bool ShouldSetSSPCanaryBitInTB(const MachineFunction *MF);
 
   static MCSymbol *getEHInfoTableSymbol(const MachineFunction *MF);
 
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 00a8fca..c7fa1d6 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -2188,6 +2188,17 @@ bool TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(
   return true;
 }
 
+bool TargetLoweringObjectFileXCOFF::ShouldSetSSPCanaryBitInTB(
+    const MachineFunction *MF) {
+  const Function &F = MF->getFunction();
+  if (!F.hasStackProtectorFnAttr())
+    return false;
+  // FIXME: check presence of canary word
+  // There are cases that the stack protectors are not really inserted even if
+  // the attributes are on.
+  return true;
+}
+
 MCSymbol *
 TargetLoweringObjectFileXCOFF::getEHInfoTableSymbol(const MachineFunction *MF) {
   return MF->getMMI().getContext().getOrCreateSymbol(
diff --git a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
index e6326ac..9c32f18 100644
--- a/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -78,6 +78,10 @@ using namespace llvm::XCOFF;
 
 #define DEBUG_TYPE "asmprinter"
 
+static cl::opt<bool> EnableSSPCanaryBitInTB(
+    "aix-ssp-tb-bit", cl::init(false),
+    cl::desc("Enable Passing SSP Canary info in Trackback on AIX"), cl::Hidden);
+
 // Specialize DenseMapInfo to allow
 // std::pair<const MCSymbol *, MCSymbolRefExpr::VariantKind> in DenseMap.
 // This specialization is needed here because that type is used as keys in the
@@ -2120,6 +2124,9 @@ void PPCAIXAsmPrinter::emitTracebackTable() {
   if (SecondHalfOfMandatoryField & TracebackTable::HasExtensionTableMask) {
     if (ShouldEmitEHBlock)
       ExtensionTableFlag |= ExtendedTBTableFlag::TB_EH_INFO;
+    if (EnableSSPCanaryBitInTB &&
+        TargetLoweringObjectFileXCOFF::ShouldSetSSPCanaryBitInTB(MF))
+      ExtensionTableFlag |= ExtendedTBTableFlag::TB_SSP_CANARY;
 
     CommentOS << "ExtensionTableFlag = "
               << getExtendedTBTableFlagString(ExtensionTableFlag);
diff --git a/llvm/test/CodeGen/PowerPC/aix-emit-tracebacktable-ssp.ll b/llvm/test/CodeGen/PowerPC/aix-emit-tracebacktable-ssp.ll
new file mode 100644
index 0000000..ad57d30
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/aix-emit-tracebacktable-ssp.ll
@@ -0,0 +1,37 @@
+; RUN: llc -aix-ssp-tb-bit -mtriple=powerpc64-ibm-aix-xcoff -O0 < %s | FileCheck %s
+
+; CHECK-LABEL: f:
+; CHECK: __ssp_canary_word
+; CHECK: TB_SSP_CANARY
+define i32 @f() #0 personality i8* bitcast (i32 (...)* @__xlcxx_personality_v1 to i8*) {
+  invoke i32 undef(i8* undef)
+    to label %invoke unwind label %lpad
+
+  invoke:
+    %var = alloca i32, align 4
+    store i32 0, i32* %var, align 4
+    %gep = getelementptr inbounds i32, i32* %var, i32 1
+    %ret = load i32, i32* %gep, align 4
+    ret i32 %ret
+  lpad:
+    landingpad { i8*, i32 }
+  catch i8* null
+    unreachable
+
+}
+
+; CHECK-LABEL: f2:
+; CHECK: __ssp_canary_word
+; Not emitting traceback bit when no unwinding needed.
+; CHECK-NOT: TB_SSP_CANARY
+define i32 @f2() #0 {
+  %var = alloca i32, align 4
+  store i32 0, i32* %var, align 4
+  %gep = getelementptr inbounds i32, i32* %var, i32 1
+  %ret = load i32, i32* %gep, align 4
+  ret i32 %ret
+}
+
+declare i32 @__xlcxx_personality_v1(...)
+attributes #0 = { sspstrong }
+
-- 
2.7.4