From 89481f363a4311d679daa81ca1365460132f8935 Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Wed, 21 Mar 2018 09:19:34 +0000
Subject: [PATCH] [ELF] - Teach LLD to hint about -fdebug-types-section.

Patch teaches LLD to hint user about -fdebug-types-section flag
if relocation overflow happens in debug section.

Differential revision: https://reviews.llvm.org/D40954

llvm-svn: 328081
---
 lld/ELF/Target.cpp                         | 16 ++++++++--------
 lld/ELF/Target.h                           | 24 ++++++++++++++++++++----
 lld/test/ELF/x86-64-reloc-debug-overflow.s |  9 +++++++++
 3 files changed, 37 insertions(+), 12 deletions(-)
 create mode 100644 lld/test/ELF/x86-64-reloc-debug-overflow.s

diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index b528fd5..c19cb5f 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -87,7 +87,7 @@ TargetInfo *elf::getTarget() {
   fatal("unknown target machine");
 }
 
-template <class ELFT> static std::string getErrorLoc(const uint8_t *Loc) {
+template <class ELFT> static ErrorPlace getErrPlace(const uint8_t *Loc) {
   for (InputSectionBase *D : InputSections) {
     auto *IS = dyn_cast<InputSection>(D);
     if (!IS || !IS->getParent())
@@ -95,21 +95,21 @@ template <class ELFT> static std::string getErrorLoc(const uint8_t *Loc) {
 
     uint8_t *ISLoc = IS->getParent()->Loc + IS->OutSecOff;
     if (ISLoc <= Loc && Loc < ISLoc + IS->getSize())
-      return IS->template getLocation<ELFT>(Loc - ISLoc) + ": ";
+      return {IS, IS->template getLocation<ELFT>(Loc - ISLoc) + ": "};
   }
-  return "";
+  return {};
 }
 
-std::string elf::getErrorLocation(const uint8_t *Loc) {
+ErrorPlace elf::getErrorPlace(const uint8_t *Loc) {
   switch (Config->EKind) {
   case ELF32LEKind:
-    return getErrorLoc<ELF32LE>(Loc);
+    return getErrPlace<ELF32LE>(Loc);
   case ELF32BEKind:
-    return getErrorLoc<ELF32BE>(Loc);
+    return getErrPlace<ELF32BE>(Loc);
   case ELF64LEKind:
-    return getErrorLoc<ELF64LE>(Loc);
+    return getErrPlace<ELF64LE>(Loc);
   case ELF64BEKind:
-    return getErrorLoc<ELF64BE>(Loc);
+    return getErrPlace<ELF64BE>(Loc);
   default:
     llvm_unreachable("unknown ELF type");
   }
diff --git a/lld/ELF/Target.h b/lld/ELF/Target.h
index 4e97058..f02b7ac 100644
--- a/lld/ELF/Target.h
+++ b/lld/ELF/Target.h
@@ -143,7 +143,17 @@ TargetInfo *getX86TargetInfo();
 TargetInfo *getX86_64TargetInfo();
 template <class ELFT> TargetInfo *getMipsTargetInfo();
 
-std::string getErrorLocation(const uint8_t *Loc);
+struct ErrorPlace {
+  InputSectionBase *IS;
+  std::string Loc;
+};
+
+// Returns input section and corresponding source string for the given location.
+ErrorPlace getErrorPlace(const uint8_t *Loc);
+
+static inline std::string getErrorLocation(const uint8_t *Loc) {
+  return getErrorPlace(Loc).Loc;
+}
 
 uint64_t getPPC64TocBase();
 uint64_t getAArch64Page(uint64_t Expr);
@@ -155,9 +165,15 @@ template <class ELFT> bool isMipsPIC(const Defined *Sym);
 
 static inline void reportRangeError(uint8_t *Loc, RelType Type, const Twine &V,
                                     int64_t Min, uint64_t Max) {
-  error(getErrorLocation(Loc) + "relocation " + lld::toString(Type) +
-        " out of range: " + V + " is not in [" + Twine(Min) + ", " +
-        Twine(Max) + "]");
+  ErrorPlace ErrPlace = getErrorPlace(Loc);
+  StringRef Hint;
+  if (ErrPlace.IS && ErrPlace.IS->Name.startswith(".debug"))
+    Hint = "; consider recompiling with -fdebug-types-section to reduce size "
+           "of debug sections";
+
+  error(ErrPlace.Loc + "relocation " + lld::toString(Type) +
+        " out of range: " + V.str() + " is not in [" + Twine(Min).str() + ", " +
+        Twine(Max).str() + "]" + Hint);
 }
 
 template <unsigned N>
diff --git a/lld/test/ELF/x86-64-reloc-debug-overflow.s b/lld/test/ELF/x86-64-reloc-debug-overflow.s
new file mode 100644
index 0000000..364c3bf
--- /dev/null
+++ b/lld/test/ELF/x86-64-reloc-debug-overflow.s
@@ -0,0 +1,9 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %S/Inputs/x86-64-reloc-error.s -o %tabs
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t
+# RUN: not ld.lld -shared %tabs %t -o %t2 2>&1 | FileCheck %s
+
+# CHECK: (.debug_info+0x0): relocation R_X86_64_32 out of range: 281474976710656 is not in [0, 4294967295]; consider recompiling with -fdebug-types-section to reduce size of debug sections
+
+.section .debug_info,"",@progbits
+ .long .debug_info + 0x1000000000000
-- 
2.7.4