[lld] r345899 - [ELF] Change sh_link of .rel{, a}.plt to make GNU strip happy

[Fangrui Song via llvm-commits]

Author: maskray
Date: Thu Nov  1 15:28:58 2018
New Revision: 345899

URL: http://llvm.org/viewvc/llvm-project?rev=345899&view=rev
Log:
[ELF] Change sh_link of .rel{,a}.plt to make GNU strip happy

Summary:
D52830 sets sh_link to .symtab in static link, which breaks executable stripped by GNU strip.
It may also be odd that .rela.plt (SHF_ALLOC) points to .symtab (non-SHF_ALLOC).

Change the logic on pcc's suggestion.

Before:

% clang -fuse-ld=lld -static -xc =(printf 'int main(){}') # or gcc
% strip a.out; ./a.out
unexpected reloc type in static binary[1]    61634 segmentation fault  ./a.out

Reviewers: ruiu, grimar, emaste, espindola

Reviewed By: ruiu

Subscribers: pcc, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D53993

Modified:
    lld/trunk/ELF/SyntheticSections.cpp
    lld/trunk/test/ELF/aarch64-gnu-ifunc.s
    lld/trunk/test/ELF/gnu-ifunc-i386.s
    lld/trunk/test/ELF/gnu-ifunc.s

Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=345899&r1=345898&r2=345899&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Thu Nov  1 15:28:58 2018
@@ -1491,15 +1491,11 @@ void RelocationBaseSection::addReloc(con
 }
 
 void RelocationBaseSection::finalizeContents() {
-  // If all relocations are R_*_{,I}RELATIVE they don't refer to any dynamic
-  // symbol and we don't need a dynamic symbol table. If that is the case, use
-  // the index of the regular symbol table section (if exists) or 0.
-  if (In.DynSymTab)
-    getParent()->Link = In.DynSymTab->getParent()->SectionIndex;
-  else if (In.SymTab)
-    getParent()->Link = In.SymTab->getParent()->SectionIndex;
-  else
-    getParent()->Link = 0;
+  // When linking glibc statically, .rel{,a}.plt contains R_*_IRELATIVE
+  // relocations due to IFUNC (e.g. strcpy). sh_link will be set to 0 in that
+  // case.
+  InputSection *SymTab = Config->Relocatable ? In.SymTab : In.DynSymTab;
+  getParent()->Link = SymTab ? SymTab->getParent()->SectionIndex : 0;
 
   if (In.RelaIplt == this || In.RelaPlt == this)
     getParent()->Info = In.GotPlt->getParent()->SectionIndex;

Modified: lld/trunk/test/ELF/aarch64-gnu-ifunc.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/aarch64-gnu-ifunc.s?rev=345899&r1=345898&r2=345899&view=diff
==============================================================================
--- lld/trunk/test/ELF/aarch64-gnu-ifunc.s (original)
+++ lld/trunk/test/ELF/aarch64-gnu-ifunc.s Thu Nov  1 15:28:58 2018
@@ -15,7 +15,7 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0x158
 // CHECK-NEXT:  Size: 48
-// CHECK-NEXT:  Link: 6
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: 4
 // CHECK-NEXT:  AddressAlignment: 8
 // CHECK-NEXT:  EntrySize: 24

Modified: lld/trunk/test/ELF/gnu-ifunc-i386.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gnu-ifunc-i386.s?rev=345899&r1=345898&r2=345899&view=diff
==============================================================================
--- lld/trunk/test/ELF/gnu-ifunc-i386.s (original)
+++ lld/trunk/test/ELF/gnu-ifunc-i386.s Thu Nov  1 15:28:58 2018
@@ -15,7 +15,7 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0xD4
 // CHECK-NEXT:  Size: 16
-// CHECK-NEXT:  Link: 6
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: 4
 // CHECK-NEXT:  AddressAlignment: 4
 // CHECK-NEXT:  EntrySize: 8

Modified: lld/trunk/test/ELF/gnu-ifunc.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/gnu-ifunc.s?rev=345899&r1=345898&r2=345899&view=diff
==============================================================================
--- lld/trunk/test/ELF/gnu-ifunc.s (original)
+++ lld/trunk/test/ELF/gnu-ifunc.s Thu Nov  1 15:28:58 2018
@@ -15,16 +15,13 @@
 // CHECK-NEXT:  Address: [[RELA:.*]]
 // CHECK-NEXT:  Offset: 0x158
 // CHECK-NEXT:  Size: 48
-// CHECK-NEXT:  Link: [[SYMTAB:.*]]
+// CHECK-NEXT:  Link: 0
 // CHECK-NEXT:  Info: [[GOTPLT:.*]]
 // CHECK-NEXT:  AddressAlignment: 8
 // CHECK-NEXT:  EntrySize: 24
 // CHECK-NEXT: }
 // CHECK:      Index: [[GOTPLT]]
 // CHECK-NEXT: Name: .got.plt
-// CHECK:      Index: [[SYMTAB]]
-// CHECK-NEXT: Name: .symtab
-// CHECK-NEXT: Type: SHT_SYMTAB
 // CHECK:      Relocations [
 // CHECK-NEXT:   Section ({{.*}}) .rela.plt {
 // CHECK-NEXT:     0x202000 R_X86_64_IRELATIVE