[lld] r361125 - [ELF] -z combreloc: sort dynamic relocations by (symbol_index, r_offset)

Fangrui Song via llvm-commits llvm-commits at lists.llvm.org
Mon May 20 00:22:55 PDT 2019


Author: maskray
Date: Mon May 20 00:22:55 2019
New Revision: 361125

URL: http://llvm.org/viewvc/llvm-project?rev=361125&view=rev
Log:
[ELF] -z combreloc: sort dynamic relocations by (symbol_index,r_offset)

Fixes PR41692.

We currently sort dynamic relocations by (!is_relative,symbol_index).
Change it to (symbol_index,r_offset). We still place relative
relocations first because R_*_RELATIVE are the only dynamic relocations
with 0 symbol index (except on MIPS, which doesn't use DT_REL[A]COUNT
anyway).

This makes `readelf -r` debugging easier (relocations to the same symbol
are ordered by r_offset).

Refactor the test combreloc.s (renamed from combrelocs.s) to check
R_X86_64_RELATIVE, and delete --expand-relocs.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D61477

Added:
    lld/trunk/test/ELF/combreloc.s
Removed:
    lld/trunk/test/ELF/combrelocs.s
Modified:
    lld/trunk/ELF/SyntheticSections.cpp
    lld/trunk/test/ELF/i386-got-and-copy.s
    lld/trunk/test/ELF/mips-mgot.s

Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=361125&r1=361124&r2=361125&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Mon May 20 00:22:55 2019
@@ -1488,17 +1488,15 @@ RelocationSection<ELFT>::RelocationSecti
   this->Entsize = Config->IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
 }
 
-static bool compRelocations(const DynamicReloc &A, const DynamicReloc &B) {
-  bool AIsRel = A.Type == Target->RelativeRel;
-  bool BIsRel = B.Type == Target->RelativeRel;
-  if (AIsRel != BIsRel)
-    return AIsRel;
-  return A.getSymIndex() < B.getSymIndex();
-}
-
 template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
+  // Sort symbol index then by r_offset. Because we only emit R_*_RELATIVE as
+  // dynamic relocations with symbol index 0, this essentially places
+  // R_*_RELATIVE first (required by DT_REL[A]COUNT).
   if (Sort)
-    llvm::stable_sort(Relocs, compRelocations);
+    llvm::stable_sort(Relocs, [](const DynamicReloc &A, const DynamicReloc &B) {
+      return std::make_tuple(A.getSymIndex(), A.getOffset()) <
+             std::make_tuple(B.getSymIndex(), B.getOffset());
+    });
 
   for (const DynamicReloc &Rel : Relocs) {
     encodeDynamicReloc<ELFT>(reinterpret_cast<Elf_Rela *>(Buf), Rel);

Added: lld/trunk/test/ELF/combreloc.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/combreloc.s?rev=361125&view=auto
==============================================================================
--- lld/trunk/test/ELF/combreloc.s (added)
+++ lld/trunk/test/ELF/combreloc.s Mon May 20 00:22:55 2019
@@ -0,0 +1,48 @@
+# REQUIRES: x86
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: echo 'mov aaa at gotpcrel(%rip), %rax' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+
+# RUN: ld.lld -shared %t.o %t1.o -o %t.so
+# RUN: llvm-readobj -r --dynamic-table %t.so | FileCheck %s
+# RUN: ld.lld -shared %t.o %t1.o -o %t.so -z combreloc
+# RUN: llvm-readobj -r --dynamic-table %t.so | FileCheck %s
+
+# -z combreloc is the default: sort relocations by (SymIndex, r_offset), and
+# emit DT_RELACOUNT (except on MIPS) to indicate the number of relative
+# relocations.
+
+# CHECK:      Relocations [
+# CHECK-NEXT:   Section ({{.*}}) .rela.dyn {
+# CHECK-NEXT:     0x3020 R_X86_64_RELATIVE - 0x3028
+# CHECK-NEXT:     0x20B0 R_X86_64_GLOB_DAT aaa 0x0
+# CHECK-NEXT:     0x3000 R_X86_64_64 aaa 0x0
+# CHECK-NEXT:     0x3018 R_X86_64_64 aaa 0x0
+# CHECK-NEXT:     0x3010 R_X86_64_64 bbb 0x0
+# CHECK-NEXT:     0x3008 R_X86_64_64 ccc 0x0
+# CHECK-NEXT:   }
+# CHECK:      DynamicSection [
+# CHECK:        RELACOUNT 1
+
+# RUN: ld.lld -z nocombreloc -shared %t.o %t1.o -o %t.so
+# RUN: llvm-readobj -r --dynamic-table %t.so | FileCheck --check-prefix=NOCOMB %s
+
+# NOCOMB:      Relocations [
+# NOCOMB-NEXT:   Section ({{.*}}) .rela.dyn {
+# NOCOMB-NEXT:     0x3000 R_X86_64_64 aaa 0x0
+# NOCOMB-NEXT:     0x3008 R_X86_64_64 ccc 0x0
+# NOCOMB-NEXT:     0x3010 R_X86_64_64 bbb 0x0
+# NOCOMB-NEXT:     0x3018 R_X86_64_64 aaa 0x0
+# NOCOMB-NEXT:     0x3020 R_X86_64_RELATIVE - 0x3028
+# NOCOMB-NEXT:     0x20A0 R_X86_64_GLOB_DAT aaa 0x0
+# NOCOMB-NEXT:   }
+# NOCOMB:      DynamicSection [
+# NOCOMB-NOT:    RELACOUNT
+
+.data
+ .quad aaa
+ .quad ccc
+ .quad bbb
+ .quad aaa
+ .quad relative
+relative:

Removed: lld/trunk/test/ELF/combrelocs.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/combrelocs.s?rev=361124&view=auto
==============================================================================
--- lld/trunk/test/ELF/combrelocs.s (original)
+++ lld/trunk/test/ELF/combrelocs.s (removed)
@@ -1,95 +0,0 @@
-# REQUIRES: x86
-
-# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
-# RUN: ld.lld -shared %t.o -o %t.out
-# RUN: llvm-readobj -r --expand-relocs --dynamic-table %t.out | FileCheck %s
-
-# RUN: ld.lld -shared %t.o -o %t.out -z combreloc
-# RUN: llvm-readobj -r --expand-relocs --dynamic-table %t.out | FileCheck %s
-
-# CHECK:      Relocations [
-# CHECK-NEXT:   Section ({{.*}}) .rela.dyn {
-# CHECK-NEXT:     Relocation {
-# CHECK-NEXT:       Offset: 0x2000
-# CHECK-NEXT:       Type: R_X86_64_64
-# CHECK-NEXT:       Symbol: aaa (1)
-# CHECK-NEXT:       Addend: 0x0
-# CHECK-NEXT:     }
-# CHECK-NEXT:     Relocation {
-# CHECK-NEXT:       Offset: 0x2018
-# CHECK-NEXT:       Type: R_X86_64_64
-# CHECK-NEXT:       Symbol: aaa (1)
-# CHECK-NEXT:       Addend: 0x0
-# CHECK-NEXT:     }
-# CHECK-NEXT:     Relocation {
-# CHECK-NEXT:       Offset: 0x2010
-# CHECK-NEXT:       Type: R_X86_64_64
-# CHECK-NEXT:       Symbol: bbb (2)
-# CHECK-NEXT:       Addend: 0x0
-# CHECK-NEXT:     }
-# CHECK-NEXT:     Relocation {
-# CHECK-NEXT:       Offset: 0x2008
-# CHECK-NEXT:       Type: R_X86_64_64
-# CHECK-NEXT:       Symbol: ccc (3)
-# CHECK-NEXT:       Addend: 0x0
-# CHECK-NEXT:     }
-# CHECK-NEXT:     Relocation {
-# CHECK-NEXT:       Offset: 0x2020
-# CHECK-NEXT:       Type: R_X86_64_64
-# CHECK-NEXT:       Symbol: ddd (4)
-# CHECK-NEXT:       Addend: 0x0
-# CHECK-NEXT:     }
-# CHECK-NEXT:   }
-# CHECK-NEXT: ]
-# CHECK:      DynamicSection [
-# CHECK-NEXT:   Tag
-# CHECK-NOT:    RELACOUNT
-
-# RUN: ld.lld -z nocombreloc -shared %t.o -o %t.out
-# RUN: llvm-readobj -r --expand-relocs --dynamic-table %t.out | \
-# RUN:    FileCheck --check-prefix=NOCOMB %s
-
-# NOCOMB:      Relocations [
-# NOCOMB-NEXT:    Section ({{.*}}) .rela.dyn {
-# NOCOMB-NEXT:     Relocation {
-# NOCOMB-NEXT:       Offset: 0x2000
-# NOCOMB-NEXT:       Type: R_X86_64_64
-# NOCOMB-NEXT:       Symbol: aaa (1)
-# NOCOMB-NEXT:       Addend: 0x0
-# NOCOMB-NEXT:     }
-# NOCOMB-NEXT:     Relocation {
-# NOCOMB-NEXT:       Offset: 0x2008
-# NOCOMB-NEXT:       Type: R_X86_64_64
-# NOCOMB-NEXT:       Symbol: ccc (3)
-# NOCOMB-NEXT:       Addend: 0x0
-# NOCOMB-NEXT:     }
-# NOCOMB-NEXT:     Relocation {
-# NOCOMB-NEXT:       Offset: 0x2010
-# NOCOMB-NEXT:       Type: R_X86_64_64
-# NOCOMB-NEXT:       Symbol: bbb (2)
-# NOCOMB-NEXT:       Addend: 0x0
-# NOCOMB-NEXT:     }
-# NOCOMB-NEXT:     Relocation {
-# NOCOMB-NEXT:       Offset: 0x2018
-# NOCOMB-NEXT:       Type: R_X86_64_64
-# NOCOMB-NEXT:       Symbol: aaa (1)
-# NOCOMB-NEXT:       Addend: 0x0
-# NOCOMB-NEXT:     }
-# NOCOMB-NEXT:     Relocation {
-# NOCOMB-NEXT:       Offset: 0x2020
-# NOCOMB-NEXT:       Type: R_X86_64_64
-# NOCOMB-NEXT:       Symbol: ddd (4)
-# NOCOMB-NEXT:       Addend: 0x0
-# NOCOMB-NEXT:     }
-# NOCOMB-NEXT:   }
-# NOCOMB-NEXT:  ]
-# NOCOMB:      DynamicSection [
-# NOCOMB-NEXT:   Tag
-# NOCOMB-NOT:    RELACOUNT
-
-.data
- .quad aaa
- .quad ccc
- .quad bbb
- .quad aaa
- .quad ddd

Modified: lld/trunk/test/ELF/i386-got-and-copy.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/i386-got-and-copy.s?rev=361125&r1=361124&r2=361125&view=diff
==============================================================================
--- lld/trunk/test/ELF/i386-got-and-copy.s (original)
+++ lld/trunk/test/ELF/i386-got-and-copy.s Mon May 20 00:22:55 2019
@@ -14,8 +14,8 @@
 
 # CHECK:      Relocations [
 # CHECK-NEXT:   Section (4) .rel.dyn {
-# CHECK-NEXT:     0x{{[0-9A-F]+}} R_386_COPY foo
 # CHECK-NEXT:     0x{{[0-9A-F]+}} R_386_GLOB_DAT foo
+# CHECK-NEXT:     0x{{[0-9A-F]+}} R_386_COPY foo
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
 

Modified: lld/trunk/test/ELF/mips-mgot.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/mips-mgot.s?rev=361125&r1=361124&r2=361125&view=diff
==============================================================================
--- lld/trunk/test/ELF/mips-mgot.s (original)
+++ lld/trunk/test/ELF/mips-mgot.s Mon May 20 00:22:55 2019
@@ -34,14 +34,14 @@
 # GOT-NEXT:     0x70024 R_MIPS_REL32 - 0x0
 # GOT-NEXT:     0x70028 R_MIPS_REL32 - 0x0
 # GOT-NEXT:     0x7002C R_MIPS_REL32 - 0x0
-# GOT-NEXT:     0x70030 R_MIPS_REL32 foo0 0x0
-# GOT-NEXT:     0x70034 R_MIPS_REL32 foo2 0x0
 # GOT-NEXT:     0x70044 R_MIPS_TLS_DTPMOD32 - 0x0
 # GOT-NEXT:     0x70010 R_MIPS_TLS_TPREL32 tls0 0x0
 # GOT-NEXT:     0x70038 R_MIPS_TLS_TPREL32 tls0 0x0
 # GOT-NEXT:     0x7003C R_MIPS_TLS_DTPMOD32 tls0 0x0
 # GOT-NEXT:     0x70040 R_MIPS_TLS_DTPREL32 tls0 0x0
 # GOT-NEXT:     0x70014 R_MIPS_TLS_TPREL32 tls1 0x0
+# GOT-NEXT:     0x70030 R_MIPS_REL32 foo0 0x0
+# GOT-NEXT:     0x70034 R_MIPS_REL32 foo2 0x0
 # GOT-NEXT:   }
 # GOT-NEXT: ]
 




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