[yaml2obj][ELF] Make symbols optional for relocations

Some kinds of relocations do not have symbols, like R_X86_64_RELATIVE
for instance. I would like to test this case in D36554 but currently
can't because symbols are required by yaml2obj. The other option is
using the empty symbol but that doesn't seem quite right to me.

This change makes the Symbol field of Relocation optional and in the
case where the user does not specify a symbol name the Symbol index is 0.

Patch by Jake Ehrlich

Differential Revision: https://reviews.llvm.org/D37276

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312192 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ObjectYAML/ELFYAML.h b/include/llvm/ObjectYAML/ELFYAML.h
index c4a1fe2ce39bfc28849fac385540a768feebeb2a..317e982c26fc80e4f2ecef58a11194e31b5bd75c 100644 (file)
--- a/include/llvm/ObjectYAML/ELFYAML.h
+++ b/include/llvm/ObjectYAML/ELFYAML.h
@@ -161,7 +161,7 @@ struct Relocation {
   llvm::yaml::Hex64 Offset;
   int64_t Addend;
   ELF_REL Type;
-  StringRef Symbol;
+  Optional<StringRef> Symbol;
 };
 
 struct RelocationSection : Section {

diff --git a/lib/ObjectYAML/ELFYAML.cpp b/lib/ObjectYAML/ELFYAML.cpp
index fd0aa49445f9227ace5e1398bc2283317f090b19..cf0a943a880e2d721b96dd6ead5ba72d3120ad9b 100644 (file)
--- a/lib/ObjectYAML/ELFYAML.cpp
+++ b/lib/ObjectYAML/ELFYAML.cpp
@@ -853,7 +853,7 @@ void MappingTraits<ELFYAML::Relocation>::mapping(IO &IO,
   assert(Object && "The IO context is not initialized");
 
   IO.mapRequired("Offset", Rel.Offset);
-  IO.mapRequired("Symbol", Rel.Symbol);
+  IO.mapOptional("Symbol", Rel.Symbol);
 
   if (Object->Header.Machine == ELFYAML::ELF_EM(ELF::EM_MIPS) &&
       Object->Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64)) {

diff --git a/test/tools/yaml2obj/invalid-symboless-relocation.yaml b/test/tools/yaml2obj/invalid-symboless-relocation.yaml
new file mode 100644 (file)
index 0000000..538f64c
--- /dev/null
+++ b/test/tools/yaml2obj/invalid-symboless-relocation.yaml
@@ -0,0 +1,29 @@
+# This test succeeds but produces an invalid relocation. This test
+# documents this behavoir.
+# RUN: yaml2obj %s > %t
+# RUN: llvm-readobj -relocations %t | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         "00000000"
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    Info:            .text
+    Relocations:
+      - Offset: 0x1000
+        Type:   R_X86_64_PC32
+
+#CHECK:     Relocations [
+#CHECK-NEXT:  Section (2) .rel.text {
+#CHECK-NEXT:    0x1000 R_X86_64_PC32 - 0x0
+#CHECK-NEXT:  }
+#CHECK-NEXT:]

diff --git a/test/tools/yaml2obj/symboless-relocation.yaml b/test/tools/yaml2obj/symboless-relocation.yaml
new file mode 100644 (file)
index 0000000..99f7af6
--- /dev/null
+++ b/test/tools/yaml2obj/symboless-relocation.yaml
@@ -0,0 +1,21 @@
+# Just make sure this isn't an error even though it has no Symbol
+# RUN: yaml2obj %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         "00000000"
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    Info:            .text
+    Relocations:
+      - Offset: 0x1000
+        Type:   R_X86_64_RELATIVE

diff --git a/tools/yaml2obj/yaml2elf.cpp b/tools/yaml2obj/yaml2elf.cpp
index 1d28a1abffcf3a605f39dc4061add8ca59a94595..e1f73f7f9918a586b670954e2da18146f0949f70 100644 (file)
--- a/tools/yaml2obj/yaml2elf.cpp
+++ b/tools/yaml2obj/yaml2elf.cpp
@@ -459,7 +459,8 @@ ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
     // Some special relocation, R_ARM_v4BX for instance, does not have
     // an external reference.  So it ignores the return value of lookup()
     // here.
-    SymN2I.lookup(Rel.Symbol, SymIdx);
+    if (Rel.Symbol)
+      SymN2I.lookup(*Rel.Symbol, SymIdx);
 
     if (IsRela) {
       Elf_Rela REntry;