[llvm] 6bdad85 - [MC] Fix llvm_unreachable when a STB_GNU_UNIQUE symbol needs a relocation

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2022-03-28T13:40:48-07:00
New Revision: 6bdad85b26fbfd064772f2b382b27fbbf0b0afce

URL: https://github.com/llvm/llvm-project/commit/6bdad85b26fbfd064772f2b382b27fbbf0b0afce
DIFF: https://github.com/llvm/llvm-project/commit/6bdad85b26fbfd064772f2b382b27fbbf0b0afce.diff

LOG: [MC] Fix llvm_unreachable when a STB_GNU_UNIQUE symbol needs a relocation

STB_GNU_UNIQUE should be treated in a way similar to STB_GLOBAL.
This fixes an "Invalid Binding" failure in an LLVM_ENABLE_ASSERTIONS=on build
for source files like glibc elf/tst-unique1mod1.c .

This bug has been benign so far because (a) Clang does not produce
%gnu_unique_object by itself (b) a non-assertion build likely picks the
STB_GLOBAL code path anyway.

Added: 
    

Modified: 
    llvm/lib/MC/ELFObjectWriter.cpp
    llvm/test/MC/ELF/gnu-unique.s

Removed: 
    


################################################################################
diff  --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index 00d18cd35ab40..fe11768ca9943 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1325,6 +1325,7 @@ bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
     // can update it.
     return true;
   case ELF::STB_GLOBAL:
+  case ELF::STB_GNU_UNIQUE:
     // Global ELF symbols can be preempted by the dynamic linker. The relocation
     // has to point to the symbol for a reason analogous to the STB_WEAK case.
     return true;

diff  --git a/llvm/test/MC/ELF/gnu-unique.s b/llvm/test/MC/ELF/gnu-unique.s
index 8948b33b9afbd..21609365d5277 100644
--- a/llvm/test/MC/ELF/gnu-unique.s
+++ b/llvm/test/MC/ELF/gnu-unique.s
@@ -1,5 +1,7 @@
 # RUN: llvm-mc -triple=x86_64 %s | FileCheck %s --check-prefix=ASM
-# RUN: llvm-mc -filetype=obj -triple=x86_64 %s | llvm-readelf -h -s - | FileCheck %s --check-prefix=OBJ
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t
+# RUN: llvm-readelf -h -s %t | FileCheck %s --check-prefix=OBJ
+# RUN: llvm-objdump -d -r --no-show-raw-insn %t | FileCheck %s --check-prefix=DISASM
 
 # ASM: .type unique, at gnu_unique_object
 
@@ -7,6 +9,13 @@
 # OBJ: Type   Bind   Vis     Ndx Name
 # OBJ: OBJECT UNIQUE DEFAULT [[#]] unique
 
+# DISASM-LABEL: <.text>:
+# DISASM-NEXT:    movl $1, 0
+## unique has a non-local binding. Reference unique instead of .data
+# DISASM-NEXT:      R_X86_64_32S unique
+
+  movl $1, unique
+
 .data
 .globl unique
 .type unique, @gnu_unique_object