From c75ef85e84a9437695f7b8a5778a8e3fc6ca746e Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Wed, 21 Sep 2016 03:22:18 +0000
Subject: [PATCH] Accept sh_entsize = 0.

This surfaced again with Rust. As per bug 30435, rustc creates a
mergeable section with a sh_entsize zero. It bit us before, too.
I think we should relax the input check rather than being too picky.

Differential Revision: https://reviews.llvm.org/D24789

llvm-svn: 282049
---
 lld/ELF/InputFiles.cpp            | 16 ++++++++++++----
 lld/test/ELF/invalid-elf.test     |  4 ----
 lld/test/ELF/merge-invalid-size.s |  7 +++++--
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 4857d5768e76..7d6a36815cdd 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -184,15 +184,23 @@ bool elf::ObjectFile<ELFT>::shouldMerge(const Elf_Shdr &Sec) {
   if (Sec.sh_size == 0)
     return false;
 
+  // Check for sh_entsize. The ELF spec is not clear about the zero
+  // sh_entsize. It says that "the member [sh_entsize] contains 0 if
+  // the section does not hold a table of fixed-size entries". We know
+  // that Rust 1.13 produces a string mergeable section with a zero
+  // sh_entsize. Here we just accept it rather than being picky about it.
+  uintX_t EntSize = Sec.sh_entsize;
+  if (EntSize == 0)
+    return false;
+  if (Sec.sh_size % EntSize)
+    fatal(getFilename(this) +
+          ": SHF_MERGE section size must be a multiple of sh_entsize");
+
   uintX_t Flags = Sec.sh_flags;
   if (!(Flags & SHF_MERGE))
     return false;
   if (Flags & SHF_WRITE)
     fatal(getFilename(this) + ": writable SHF_MERGE section is not supported");
-  uintX_t EntSize = Sec.sh_entsize;
-  if (!EntSize || Sec.sh_size % EntSize)
-    fatal(getFilename(this) +
-          ": SHF_MERGE section size must be a multiple of sh_entsize");
 
   // Don't try to merge if the alignment is larger than the sh_entsize and this
   // is not SHF_STRINGS.
diff --git a/lld/test/ELF/invalid-elf.test b/lld/test/ELF/invalid-elf.test
index c3a97d37ffa9..73516a41a8c1 100644
--- a/lld/test/ELF/invalid-elf.test
+++ b/lld/test/ELF/invalid-elf.test
@@ -24,10 +24,6 @@
 # RUN:   FileCheck --check-prefix=INVALID-SECTION-INDEX %s
 # INVALID-SECTION-INDEX: Invalid section index
 
-# RUN: not ld.lld %p/Inputs/invalid-shentsize-zero.elf -o %t2 2>&1 | \
-# RUN:   FileCheck --check-prefix=INVALID-SHENTSIZE-ZERO %s
-# INVALID-SHENTSIZE-ZERO: SHF_MERGE section size must be a multiple of sh_entsize
-
 # RUN: not ld.lld %p/Inputs/invalid-multiple-eh-relocs.elf -o %t2 2>&1 | \
 # RUN:   FileCheck --check-prefix=INVALID-EH-RELOCS %s
 # INVALID-EH-RELOCS: multiple relocation sections to .eh_frame are not supported
diff --git a/lld/test/ELF/merge-invalid-size.s b/lld/test/ELF/merge-invalid-size.s
index 2a99e14ad836..c27b21b7caaa 100644
--- a/lld/test/ELF/merge-invalid-size.s
+++ b/lld/test/ELF/merge-invalid-size.s
@@ -3,5 +3,8 @@
 // RUN: not ld.lld %t.o -o %t.so 2>&1 | FileCheck %s
 // CHECK: SHF_MERGE section size must be a multiple of sh_entsize
 
-        .section	.foo,"aM",@progbits,4
-        .short 42
+// Test that we accept a zero sh_entsize.
+// RUN: ld.lld %p/Inputs/invalid-shentsize-zero.elf -o %t2
+
+.section .foo,"aM",@progbits,4
+.short 42