[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

1 files changed, 10 insertions, 0 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");