From 858a659a4fe242cc1aabfa9c7648bb2818224620 Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Fri, 17 Feb 2017 19:46:47 +0000
Subject: [PATCH] [ELF] - Added support of linkerscript's "/DISCARD/" for
 --emit-relocs

Previously LLD crashed on on provided testcases because "/DISCARD/" was
not supported. Patch implements that.

After this I think there is no known issues with --emit-relocs implementation
required for linux kernel linking.

Differential revision: https://reviews.llvm.org/D29273

llvm-svn: 295488
---
 lld/ELF/InputFiles.cpp                             |  8 ++++++--
 lld/test/ELF/linkerscript/emit-relocs-discard.s    | 14 ++++++++++++++
 .../ELF/linkerscript/emit-relocs-ehframe-discard.s | 11 +++++++++++
 3 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 lld/test/ELF/linkerscript/emit-relocs-discard.s
 create mode 100644 lld/test/ELF/linkerscript/emit-relocs-ehframe-discard.s

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index c9e775d92c2b..8564b25f59da 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -406,8 +406,12 @@ elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
     // from the output, so returning `nullptr` for the normal case.
     // However, if -emit-relocs is given, we need to leave them in the output.
     // (Some post link analysis tools need this information.)
-    if (Config->EmitRelocs)
-      return make<InputSection<ELFT>>(this, &Sec, Name);
+    if (Config->EmitRelocs) {
+      InputSection<ELFT> *RelocSec = make<InputSection<ELFT>>(this, &Sec, Name);
+      // We will not emit relocation section if target was discarded.
+      Target->DependentSections.push_back(RelocSec);
+      return RelocSec;
+    }
     return nullptr;
   }
   }
diff --git a/lld/test/ELF/linkerscript/emit-relocs-discard.s b/lld/test/ELF/linkerscript/emit-relocs-discard.s
new file mode 100644
index 000000000000..2f1f6c6b4b0a
--- /dev/null
+++ b/lld/test/ELF/linkerscript/emit-relocs-discard.s
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS { /DISCARD/ : { *(.bbb) } }" > %t.script
+# RUN: ld.lld --emit-relocs --script %t.script %t.o -o %t1
+# RUN: llvm-readobj -r %t1 | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT: ]
+
+.section .aaa,"",@progbits
+.Lfoo:
+
+.section .bbb,"",@progbits
+.long .Lfoo
diff --git a/lld/test/ELF/linkerscript/emit-relocs-ehframe-discard.s b/lld/test/ELF/linkerscript/emit-relocs-ehframe-discard.s
new file mode 100644
index 000000000000..9df0e8ce9dcb
--- /dev/null
+++ b/lld/test/ELF/linkerscript/emit-relocs-ehframe-discard.s
@@ -0,0 +1,11 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
+# RUN: echo "SECTIONS { /DISCARD/ : { *(.eh_frame) } }" > %t.script
+# RUN: ld.lld --emit-relocs --script %t.script %t1.o -o %t
+# RUN: llvm-objdump -section-headers %t | FileCheck %s
+
+# CHECK-NOT: .rela.eh_frame
+
+.section .foo,"ax",@progbits
+.cfi_startproc
+.cfi_endproc