From b41130bedcd3605b821f51ea70cbf0672066f96a Mon Sep 17 00:00:00 2001
From: James Henderson <jh7370@my.bristol.ac.uk>
Date: Fri, 8 Mar 2019 13:22:05 +0000
Subject: [PATCH] [llvm-readelf]Don't lose negative-ness of negative addends
 for no symbol relocations

llvm-readelf prints relocation addends as:

  <symbol value>[+-]<absolute addend>

where [+-] is determined from whether addend is less than zero or not.
However, it does not print the +/- if there is no symbol, which meant
that negative addends became their positive value with no indication
that this had happened. This patch stops the absolute conversion when
addends are negative and there is no associated symbol.

Reviewed by: Higuoxing, mattd, MaskRay

Differential Revision: https://reviews.llvm.org/D59095

llvm-svn: 355696
---
 .../elf-reloc-negative-addend-no-sym.test          | 74 ++++++++++++++++++++++
 llvm/tools/llvm-readobj/ELFDumper.cpp              | 38 ++++++-----
 2 files changed, 95 insertions(+), 17 deletions(-)
 create mode 100644 llvm/test/tools/llvm-readobj/elf-reloc-negative-addend-no-sym.test

diff --git a/llvm/test/tools/llvm-readobj/elf-reloc-negative-addend-no-sym.test b/llvm/test/tools/llvm-readobj/elf-reloc-negative-addend-no-sym.test
new file mode 100644
index 0000000..13e6a96
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/elf-reloc-negative-addend-no-sym.test
@@ -0,0 +1,74 @@
+# Show that llvm-readelf properly prints the addend for relocations that do not
+# have an associated symbol but have a negative addend.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readelf --relocations %t | FileCheck %s --check-prefix=REL
+# RUN: llvm-readelf --dyn-relocations %t | FileCheck %s --check-prefix=DYN
+
+# REL:      Relocation section '.rela.text' at offset {{.*}} contains 1 entries:
+# REL-NEXT:    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
+# REL-NEXT: 0000000000000000  0000000000000000 R_X86_64_NONE                     ffffffffffffffff
+# REL-EMPTY:
+# REL-NEXT: Relocation section '.rela.dyn' at offset {{.*}} contains 1 entries:
+# REL-NEXT:    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
+# REL-NEXT: 0000000000000008  0000000000000000 R_X86_64_NONE                     ffffffffffffffff
+
+# DYN:      'RELA' relocation section at offset {{.*}} contains 24 bytes:
+# DYN-NEXT:     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
+# DYN-NEXT: 0000000000000008  0000000000000000 R_X86_64_NONE                     ffffffffffffffff
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name: .text
+    Type: SHT_PROGBITS
+    Size: 0x10
+  - Name: .rela.text
+    Type: SHT_RELA
+    Link: .symtab
+    Info: .text
+    Relocations:
+      - Offset: 0
+        Type: R_X86_64_NONE
+        Addend: -1
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    Flags: [SHF_ALLOC]
+    Address: 0x1000
+    AddressAlign: 0x1000
+    Entries:
+      - Tag: DT_RELA
+        Value: 0x1100
+      - Tag: DT_RELASZ
+        Value: 24
+      - Tag: DT_RELAENT
+        Value: 24
+      - Tag: DT_NULL
+        Value: 0
+  - Name: .rela.dyn
+    Type: SHT_RELA
+    Flags: [SHF_ALLOC]
+    Info: .text
+    Address: 0x1100
+    AddressAlign: 0x100
+    Relocations:
+      - Offset: 8
+        Type: R_X86_64_NONE
+        Addend: -1
+DynamicSymbols:
+  Global:
+    - Name: force_dynsym
+ProgramHeaders:
+  - Type: PT_LOAD
+    VAddr: 0x1000
+    Sections:
+      - Section: .rela.dyn
+      - Section: .dynamic
+  - Type: PT_DYNAMIC
+    VAddr: 0x1000
+    Sections:
+      - Section: .dynamic
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index a406d36..793bbf0 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -2730,15 +2730,18 @@ void GNUStyle<ELFT>::printRelocation(const ELFO *Obj, const Elf_Shdr *SymTab,
     printField(F);
 
   std::string Addend;
-  if (Sym && IsRela) {
-    if (R.r_addend < 0)
-      Addend = " - ";
-    else
-      Addend = " + ";
-  }
+  if (IsRela) {
+    int64_t RelAddend = R.r_addend;
+    if (Sym) {
+      if (R.r_addend < 0) {
+        Addend = " - ";
+        RelAddend = std::abs(RelAddend);
+      } else
+        Addend = " + ";
+    }
 
-  if (IsRela)
-    Addend += to_hexString(std::abs(R.r_addend), false);
+    Addend += to_hexString(RelAddend, false);
+  }
   OS << Addend << "\n";
 }
 
@@ -3388,17 +3391,18 @@ void GNUStyle<ELFT>::printDynamicRelocation(const ELFO *Obj, Elf_Rela R,
   for (auto &Field : Fields)
     printField(Field);
 
-  int64_t RelAddend = R.r_addend;
   std::string Addend;
-  if (!SymbolName.empty() && IsRela) {
-    if (R.r_addend < 0)
-      Addend = " - ";
-    else
-      Addend = " + ";
+  if (IsRela) {
+    int64_t RelAddend = R.r_addend;
+    if (!SymbolName.empty()) {
+      if (R.r_addend < 0) {
+        Addend = " - ";
+        RelAddend = std::abs(RelAddend);
+      } else
+        Addend = " + ";
+    }
+    Addend += to_string(format_hex_no_prefix(RelAddend, 1));
   }
-
-  if (IsRela)
-    Addend += to_string(format_hex_no_prefix(std::abs(RelAddend), 1));
   OS << Addend << "\n";
 }
 
-- 
2.7.4