From ae73091f30245852817c5c0af050a5a731dee50a Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Tue, 27 Oct 2020 09:30:10 -0700
Subject: [PATCH] [ELF] -r: don't crash when a non-SHF_LINK_ORDER orphan is
 added before a SHF_LINK_ORDER orphan

Fixes https://github.com/ClangBuiltLinux/linux/issues/1186

If a non-SHF_LINK_ORDER orphan is added first, `firstIsec->flags & SHF_LINK_ORDER`
will be zero and we currently assert when calling `getLinkOrderDep`.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D90200
---
 lld/ELF/LinkerScript.cpp        |  7 +++++--
 lld/test/ELF/linkorder-mixed2.s | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 lld/test/ELF/linkorder-mixed2.s

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index ba51a8b..9d612ae 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -690,8 +690,11 @@ addInputSec(StringMap<TinyPtrVector<OutputSection *>> &map,
       auto *firstIsec = cast<InputSectionBase>(
           cast<InputSectionDescription>(sec->sectionCommands[0])
               ->sectionBases[0]);
-      if (firstIsec->getLinkOrderDep()->getOutputSection() !=
-          isec->getLinkOrderDep()->getOutputSection())
+      OutputSection *firstIsecOut =
+          firstIsec->flags & SHF_LINK_ORDER
+              ? firstIsec->getLinkOrderDep()->getOutputSection()
+              : nullptr;
+      if (firstIsecOut != isec->getLinkOrderDep()->getOutputSection())
         continue;
     }
 
diff --git a/lld/test/ELF/linkorder-mixed2.s b/lld/test/ELF/linkorder-mixed2.s
new file mode 100644
index 0000000..26ab970
--- /dev/null
+++ b/lld/test/ELF/linkorder-mixed2.s
@@ -0,0 +1,22 @@
+# REQUIRES: x86
+## In a relocatable link, don't combine SHF_LINK_ORDER and non-SHF_LINK_ORDER
+## like we don't combine SHF_LINK_ORDER with different linked-to sections
+## (see linkerscript/linkorder-linked-to.s).
+## Test we support adding a non-SHF_LINK_ORDER section as an orphan first.
+
+# RUN: llvm-mc -filetype=obj --triple=x86_64 %s -o %t.o
+
+# RUN: ld.lld -r %t.o -o %t.ro
+# RUN: llvm-readelf -x foo %t.ro | FileCheck %s
+
+# CHECK:      Hex dump of section 'foo':
+# CHECK-NEXT: 0x00000000 0100
+
+.section foo,"a"
+.byte 0
+
+.section .text,"ax",@progbits
+ret
+
+.section foo,"ao",@progbits,.text
+.byte 1
-- 
2.7.4