[lld] f8cb78e - [ELF] Don't define __rela_iplt_start for -pie/-shared

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-07-15T11:31:11-07:00
New Revision: f8cb78e99aae9aa3f89f7bfe667db2c5b767f21f

URL: https://github.com/llvm/llvm-project/commit/f8cb78e99aae9aa3f89f7bfe667db2c5b767f21f
DIFF: https://github.com/llvm/llvm-project/commit/f8cb78e99aae9aa3f89f7bfe667db2c5b767f21f.diff

LOG: [ELF] Don't define __rela_iplt_start for -pie/-shared

`clang -fuse-ld=lld -static-pie -fpie` produced executable
currently crashes and this patch makes it work.

See https://sourceware.org/bugzilla/show_bug.cgi?id=27164
and https://sourceware.org/pipermail/libc-alpha/2021-July/128810.html

While it seems unreasonable to keep csu/libc-start.c ARCH_APPLY_IREL unclear in
static-pie mode and have an unneeded diff -u =(ld.bfd --verbose) =(ld.bfd -pie
--verbose) difference, glibc folks don't want to fix their code.
I feel sad about that but this patch can remove an iffy condition for lld/ELF
as well: `needsInterpSection()`.

Added: 
    

Modified: 
    lld/ELF/Writer.cpp
    lld/test/ELF/gnu-ifunc-nonpreemptible.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index e22568f53488b..f455d8575e2db 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -1088,7 +1088,7 @@ void PhdrEntry::add(OutputSection *sec) {
 // need these symbols, since IRELATIVE relocs are resolved through GOT
 // and PLT. For details, see http://www.airs.com/blog/archives/403.
 template <class ELFT> void Writer<ELFT>::addRelIpltSymbols() {
-  if (config->relocatable || needsInterpSection())
+  if (config->relocatable || config->isPic)
     return;
 
   // By default, __rela_iplt_{start,end} belong to a dummy section 0

diff  --git a/lld/test/ELF/gnu-ifunc-nonpreemptible.s b/lld/test/ELF/gnu-ifunc-nonpreemptible.s
index 35400e74d802b..dcc4f5d8c7903 100644
--- a/lld/test/ELF/gnu-ifunc-nonpreemptible.s
+++ b/lld/test/ELF/gnu-ifunc-nonpreemptible.s
@@ -20,8 +20,8 @@
 # RUN: ld.lld -shared %t.o -o %t2
 # RUN: llvm-readelf -s %t2 | FileCheck %s --check-prefix=PIC
 
-# PIC:        0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_start
-# PIC-NEXT:   0 NOTYPE  LOCAL  HIDDEN     [[#]] __rela_iplt_end
+# PIC:        0 NOTYPE  WEAK   DEFAULT    UND __rela_iplt_start
+# PIC-NEXT:   0 NOTYPE  WEAK   DEFAULT    UND __rela_iplt_end
 
 # DISASM: Disassembly of section .text:
 # DISASM-EMPTY: