[COFF] Emit @feat.00 on 64-bit and set the CFG bit when emitting guardcf tables
The 0x800 bit in @feat.00 needs to be set in order to make LLD pick up
the .gfid$y table. I believe this is fine to set even if we don't emit
the instrumentation.
We haven't emitted @feat.00 on 64-bit before. I see that MSVC does emit
it, but I'm not entirely sure what the default value should be. I went
with zero since that seems as safe as not emitting the symbol in the
first place.
Differential Revision: https://reviews.llvm.org/D52235
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342532 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index c6026f8..74dbdcd 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -587,21 +587,28 @@
if (TT.isOSBinFormatCOFF()) {
// Emit an absolute @feat.00 symbol. This appears to be some kind of
// compiler features bitfield read by link.exe.
+ MCSymbol *S = MMI->getContext().getOrCreateSymbol(StringRef("@feat.00"));
+ OutStreamer->BeginCOFFSymbolDef(S);
+ OutStreamer->EmitCOFFSymbolStorageClass(COFF::IMAGE_SYM_CLASS_STATIC);
+ OutStreamer->EmitCOFFSymbolType(COFF::IMAGE_SYM_DTYPE_NULL);
+ OutStreamer->EndCOFFSymbolDef();
+ int64_t Feat00Flags = 0;
+
if (TT.getArch() == Triple::x86) {
- MCSymbol *S = MMI->getContext().getOrCreateSymbol(StringRef("@feat.00"));
- OutStreamer->BeginCOFFSymbolDef(S);
- OutStreamer->EmitCOFFSymbolStorageClass(COFF::IMAGE_SYM_CLASS_STATIC);
- OutStreamer->EmitCOFFSymbolType(COFF::IMAGE_SYM_DTYPE_NULL);
- OutStreamer->EndCOFFSymbolDef();
// According to the PE-COFF spec, the LSB of this value marks the object
// for "registered SEH". This means that all SEH handler entry points
// must be registered in .sxdata. Use of any unregistered handlers will
// cause the process to terminate immediately. LLVM does not know how to
// register any SEH handlers, so its object files should be safe.
- OutStreamer->EmitSymbolAttribute(S, MCSA_Global);
- OutStreamer->EmitAssignment(
- S, MCConstantExpr::create(int64_t(1), MMI->getContext()));
+ Feat00Flags |= 1;
}
+
+ if (M.getModuleFlag("cfguardtable"))
+ Feat00Flags |= 0x800; // Object is CFG-aware.
+
+ OutStreamer->EmitSymbolAttribute(S, MCSA_Global);
+ OutStreamer->EmitAssignment(
+ S, MCConstantExpr::create(Feat00Flags, MMI->getContext()));
}
OutStreamer->EmitSyntaxDirective();
diff --git a/test/CodeGen/WinCFGuard/cfguard.ll b/test/CodeGen/WinCFGuard/cfguard.ll
index b0a7193..2ddd346 100644
--- a/test/CodeGen/WinCFGuard/cfguard.ll
+++ b/test/CodeGen/WinCFGuard/cfguard.ll
@@ -1,5 +1,7 @@
; RUN: llc < %s | FileCheck %s
+; CHECK: .set @feat.00, 2048
+
; CHECK: .section .gfids$y
; CHECK: .symidx "?address_taken@@YAXXZ"
; CHECK: .symidx "?virt_method@Derived@@UEBAHXZ"
