[CodeGen] Emit necessary .note sections for -fsplit-stack

Summary:
According to https://gcc.gnu.org/wiki/SplitStacks, the linker expects a zero-sized .note.GNU-split-stack section if split-stack is used (and also .note.GNU-no-split-stack section if it also contains non-split-stack functions), so it can handle the cases where a split-stack function calls non-split-stack function.

This change adds the sections if needed.

Fixes PR #34670.

Reviewers: thanm, rnk, luqmana

Reviewed By: rnk

Subscribers: llvm-commits

Patch by Cherry Zhang <cherryyz@google.com>

Differential Revision: https://reviews.llvm.org/D38051

llvm-svn: 314335

diff --git a/llvm/include/llvm/CodeGen/MachineModuleInfo.h b/llvm/include/llvm/CodeGen/MachineModuleInfo.h
index d64941a..7b57a40 100644 (file)
--- a/llvm/include/llvm/CodeGen/MachineModuleInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineModuleInfo.h
@@ -125,6 +125,16 @@ class MachineModuleInfo : public ImmutablePass {
   /// comments in lib/Target/X86/X86FrameLowering.cpp for more details.
   bool UsesMorestackAddr;
 
+  /// True if the module contains split-stack functions. This is used to
+  /// emit .note.GNU-split-stack section as required by the linker for
+  /// special handling split-stack function calling no-split-stack function.
+  bool HasSplitStack;
+
+  /// True if the module contains no-split-stack functions. This is used to
+  /// emit .note.GNU-no-split-stack section when it also contains split-stack
+  /// functions.
+  bool HasNosplitStack;
+
   /// Maps IR Functions to their corresponding MachineFunctions.
   DenseMap<const Function*, std::unique_ptr<MachineFunction>> MachineFunctions;
   /// Next unique number available for a MachineFunction.
@@ -194,6 +204,22 @@ public:
     UsesMorestackAddr = b;
   }
 
+  bool hasSplitStack() const {
+    return HasSplitStack;
+  }
+
+  void setHasSplitStack(bool b) {
+    HasSplitStack = b;
+  }
+
+  bool hasNosplitStack() const {
+    return HasNosplitStack;
+  }
+
+  void setHasNosplitStack(bool b) {
+    HasNosplitStack = b;
+  }
+
   /// Return the symbol to be used for the specified basic block when its
   /// address is taken.  This cannot be its normal LBB label because the block
   /// may be accessed outside its containing function.

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ee5cb35..26ca58a 100644 (file)
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1382,6 +1382,16 @@ bool AsmPrinter::doFinalization(Module &M) {
                                  PtrSize);
   }
 
+  // Emit .note.GNU-split-stack and .note.GNU-no-split-stack sections if
+  // split-stack is used.
+  if (TM.getTargetTriple().isOSBinFormatELF() && MMI->hasSplitStack()) {
+    OutStreamer->SwitchSection(
+        OutContext.getELFSection(".note.GNU-split-stack", ELF::SHT_PROGBITS, 0));
+    if (MMI->hasNosplitStack())
+      OutStreamer->SwitchSection(
+          OutContext.getELFSection(".note.GNU-no-split-stack", ELF::SHT_PROGBITS, 0));
+  }
+
   // If we don't have any trampolines, then we don't require stack memory
   // to be executable. Some targets have a directive to declare this.
   Function *InitTrampolineIntrinsic = M.getFunction("llvm.init.trampoline");

diff --git a/llvm/lib/CodeGen/MachineModuleInfo.cpp b/llvm/lib/CodeGen/MachineModuleInfo.cpp
index f0dd77e..4cedcd0 100644 (file)
--- a/llvm/lib/CodeGen/MachineModuleInfo.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfo.cpp
@@ -208,6 +208,7 @@ bool MachineModuleInfo::doInitialization(Module &M) {
   ObjFileMMI = nullptr;
   CurCallSite = 0;
   DbgInfoAvailable = UsesVAFloatArgument = UsesMorestackAddr = false;
+  HasSplitStack = HasNosplitStack = false;
   AddrLabelSymbols = nullptr;
   TheModule = &M;
   return false;

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 6e44206..032abb4 100644 (file)
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -994,7 +994,11 @@ void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
   if (Fn.shouldSplitStack()) {
     for (MachineBasicBlock *SaveBlock : SaveBlocks)
       TFI.adjustForSegmentedStacks(Fn, *SaveBlock);
-  }
+    // Record that there are split-stack functions, so we will emit a
+    // special section to tell the linker.
+    Fn.getMMI().setHasSplitStack(true);
+  } else
+    Fn.getMMI().setHasNosplitStack(true);
 
   // Emit additional code that is required to explicitly handle the stack in
   // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The

diff --git a/llvm/test/CodeGen/X86/segmented-stacks.ll b/llvm/test/CodeGen/X86/segmented-stacks.ll
index a0cd182..a4861ef 100644 (file)
--- a/llvm/test/CodeGen/X86/segmented-stacks.ll
+++ b/llvm/test/CodeGen/X86/segmented-stacks.ll
@@ -636,8 +636,27 @@ define void @test_nostack() #0 {
 ; X64-DFlyBSD-NOT:   callq __morestack
 }
 
+define void @test_nosplitstck() {
+       ret void
+}
+
 attributes #0 = { "split-stack" }
 
 ; X64-Linux-Large: .rodata
 ; X64-Linux-Large-NEXT: __morestack_addr:
 ; X64-Linux-Large-NEXT: .quad  __morestack
+
+; X32-Linux: .section ".note.GNU-split-stack","",@progbits
+; X32-Linux: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-Linux: .section ".note.GNU-split-stack","",@progbits
+; X64-Linux: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-FreeBSD: .section ".note.GNU-split-stack","",@progbits
+; X64-FreeBSD: .section ".note.GNU-no-split-stack","",@progbits
+
+; X32-DFlyBSD: .section ".note.GNU-split-stack","",@progbits
+; X32-DFlyBSD: .section ".note.GNU-no-split-stack","",@progbits
+
+; X64-DFlyBSD: .section ".note.GNU-split-stack","",@progbits
+; X64-DFlyBSD: .section ".note.GNU-no-split-stack","",@progbits