[llvm-readelf]Don't lose negative-ness of negative addends for no sym…

…bol 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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355696 91177308-0d34-0410-b5e6-96231b3b80d8

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

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";
 }