[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

3 files changed, 16 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index ee5cb35fa9d..26ca58a76e4 100644
--- 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 f0dd77ef0da..4cedcd03a2d 100644
--- 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 6e442065ef7..032abb441dd 100644
--- 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