[ELF] Fix error reporting for eh_frame and other synthetic sections

[evgeny777]

Summary

Such sections don't belong to any specific file, so getLocation<ELFT>() will crash for them. One of possible cases is
out of range relocation in .eh_frame section

[grimar]

Looks testcase can be simplified a bit.

test/ELF/linkerscript/eh-frame-reloc-out-of-range.s

6

Do you need PHDRS for this testcase ?

8

Do you need to place .eh_frame_hdr explicitly ?

[ruiu]

LGTM

[evgeny777]

test/ELF/linkerscript/eh-frame-reloc-out-of-range.s

6

By default "A" (eh_frame and eh_frame_hdr) and "AX" (text) sections go to the same segment. If you remove PHDRS you'll get very large (> 60GB) output file.

ELF/InputSection.cpp

InputSectionBase *InputSectionBase::getLinkOrderDep() const {
   if ((Flags & SHF_LINK_ORDER) && Link != 0)
     return getFile<ELFT>()->getSections()[Link];
   return nullptr;
 }
 
 // Returns a source location string. Used to construct an error message.
 template <class ELFT>
 std::string InputSectionBase::getLocation(uint64_t Offset) {
+  // We don't have file for synthetic sections.
+  if (getFile<ELFT>() == nullptr)
+    return (Config->OutputFile + ":(" + Name + "+0x" + utohexstr(Offset) + ")")
+        .str();
+
   // First check if we can get desired values from debugging information.
   std::string LineInfo = getFile<ELFT>()->getLineInfo(this, Offset);
   if (!LineInfo.empty())
     return LineInfo;
 
   // File->SourceFile contains STT_FILE symbol that contains a
   // source file name. If it's missing, we use an object file name.
   std::string SrcFile = getFile<ELFT>()->SourceFile;

test/ELF/linkerscript/eh-frame-reloc-out-of-range.s

+## Check that error is correctly reported when .eh_frame reloc
+## is out of range
+
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "PHDRS { eh PT_LOAD; text PT_LOAD; }  \
+# RUN:       SECTIONS { . = 0x10000; \
+# RUN:         .eh_frame_hdr : { *(.eh_frame_hdr*) } : eh \
+# RUN:         .eh_frame : { *(.eh_frame) } : eh \
+# RUN:         . = 0xF00000000; \
+# RUN:         .text : { *(.text*) } : text \
+# RUN:       }" > %t.script
+# RUN: not ld.lld %t.o -T %t.script -o %t 2>&1 | FileCheck %s
+
+# CHECK: error: {{.*}}:(.eh_frame+0x20): relocation R_X86_64_PC32 out of range
+
+  .text
+  .globl _start
+_start:
+  .cfi_startproc
+  .cfi_lsda 0, _ex
+  nop
+  .cfi_endproc
+
+  .data
+_ex:
+  .word 0