[yaml2obj] - Allow setting cutom Flags for implicit sections.

With this patch we get ability to set any flags we want
for implicit sections defined in YAML.

Differential revision: https://reviews.llvm.org/D63136

llvm-svn: 363367

include/llvm/ObjectYAML/ELFYAML.h

@@ -129,7 +129,7 @@ struct Section {
   SectionKind Kind;
   StringRef Name;
   ELF_SHT Type;
-  ELF_SHF Flags;
+  Optional<ELF_SHF> Flags;
   llvm::yaml::Hex64 Address;
   StringRef Link;
   llvm::yaml::Hex64 AddressAlign;

lib/ObjectYAML/ELFYAML.cpp

@@ -900,7 +900,7 @@ StringRef MappingTraits<ELFYAML::Symbol>::validate(IO &IO,
 static void commonSectionMapping(IO &IO, ELFYAML::Section &Section) {
   IO.mapOptional("Name", Section.Name, StringRef());
   IO.mapRequired("Type", Section.Type);
-  IO.mapOptional("Flags", Section.Flags, ELFYAML::ELF_SHF(0));
+  IO.mapOptional("Flags", Section.Flags);
   IO.mapOptional("Address", Section.Address, Hex64(0));
   IO.mapOptional("Link", Section.Link, StringRef());
   IO.mapOptional("AddressAlign", Section.AddressAlign, Hex64(0));

test/tools/yaml2obj/strtab-implicit-sections-flags.yaml

@@ -0,0 +1,79 @@
+## For implicit string table sections, the `Flags` field can also
+## be specified in YAML. Here we test the behavior in different cases.
+
+## When flags are not explicitly specified, yaml2obj assigns no flags
+## for .strtab and the SHF_ALLOC flag for .dynstr by default.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-readobj %t1 -S | FileCheck %s --check-prefix=CASE1
+
+# CASE1:      Name: .strtab
+# CASE1-NEXT: Type: SHT_STRTAB
+# CASE1-NEXT: Flags [
+# CASE1-NEXT: ]
+# CASE1:      Name: .dynstr
+# CASE1-NEXT: Type: SHT_STRTAB
+# CASE1-NEXT: Flags [
+# CASE1-NEXT:   SHF_ALLOC
+# CASE1-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name:    .strtab
+    Type:    SHT_STRTAB
+  - Name:    .dynstr
+    Type:    SHT_STRTAB
+
+## Check we can set arbitrary flags for .strtab/.dynstr.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2
+# RUN: llvm-readobj %t2 -S | FileCheck %s --check-prefix=CASE2
+
+# CASE2:      Name: .strtab
+# CASE2-NEXT: Type: SHT_STRTAB
+# CASE2-NEXT: Flags [
+# CASE2-NEXT:   SHF_ALLOC
+# CASE2-NEXT:   SHF_STRINGS
+# CASE2-NEXT: ]
+# CASE2:      Name: .dynstr
+# CASE2-NEXT: Type: SHT_STRTAB
+# CASE2-NEXT: Flags [
+# CASE2-NEXT:   SHF_STRINGS
+# CASE2-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name:  .strtab
+    Type:  SHT_STRTAB
+    Flags: [ SHF_ALLOC, SHF_STRINGS ]
+  - Name:  .dynstr
+    Type:  SHT_STRTAB
+    Flags: [ SHF_STRINGS ]
+
+## Check no flags are set by default for .strtab when it is not
+## described in the YAML.
+
+# RUN: yaml2obj --docnum=3 %s -o %t3
+# RUN: llvm-readobj %t3 -S | FileCheck %s --check-prefix=CASE3
+
+# CASE3:      Name: .strtab
+# CASE3-NEXT: Type: SHT_STRTAB
+# CASE3-NEXT: Flags [
+# CASE3-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64

test/tools/yaml2obj/symtab-implicit-sections-flags.yaml

@@ -0,0 +1,79 @@
+## For implicit symbol table sections, the `Flags` field can also
+## be specified in YAML. Here we test the behavior in different cases.
+
+## When flags are not explicitly specified, yaml2obj assigns no flags
+## for .symtab and the SHF_ALLOC flag for .dynsym by default.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-readobj %t1 -S | FileCheck %s --check-prefix=CASE1
+
+# CASE1:      Name: .symtab
+# CASE1-NEXT: Type: SHT_SYMTAB
+# CASE1-NEXT: Flags [
+# CASE1-NEXT: ]
+# CASE1:      Name: .dynsym
+# CASE1-NEXT: Type: SHT_DYNSYM
+# CASE1-NEXT: Flags [
+# CASE1-NEXT:   SHF_ALLOC
+# CASE1-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .symtab
+    Type: SHT_SYMTAB
+  - Name: .dynsym
+    Type: SHT_SYMTAB
+
+## Check we can set arbitrary flags for .symtab/.dynsym.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2
+# RUN: llvm-readobj %t2 -S | FileCheck %s --check-prefix=CASE2
+
+# CASE2:      Name: .symtab
+# CASE2-NEXT: Type: SHT_SYMTAB
+# CASE2-NEXT: Flags [
+# CASE2-NEXT:   SHF_ALLOC
+# CASE2-NEXT:   SHF_STRINGS
+# CASE2-NEXT: ]
+# CASE2:      Name: .dynsym
+# CASE2-NEXT: Type: SHT_DYNSYM
+# CASE2-NEXT: Flags [
+# CASE2-NEXT:   SHF_STRINGS
+# CASE2-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name:  .symtab
+    Type:  SHT_SYMTAB
+    Flags: [ SHF_ALLOC, SHF_STRINGS ]
+  - Name:  .dynsym
+    Type:  SHT_SYMTAB
+    Flags: [ SHF_STRINGS ]
+
+## Check no flags are set by default for .symtab when it is not
+## described in the YAML.
+
+# RUN: yaml2obj --docnum=3 %s -o %t3
+# RUN: llvm-readobj %t3 -S | FileCheck %s --check-prefix=CASE3
+
+# CASE3:      Name: .symtab
+# CASE3-NEXT: Type: SHT_SYMTAB
+# CASE3-NEXT: Flags [
+# CASE3-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64

tools/obj2yaml/elf2yaml.cpp

@@ -329,7 +329,8 @@ template <class ELFT>
 std::error_code ELFDumper<ELFT>::dumpCommonSection(const Elf_Shdr *Shdr,
                                                    ELFYAML::Section &S) {
   S.Type = Shdr->sh_type;
-  S.Flags = Shdr->sh_flags;
+  if (Shdr->sh_flags)
+    S.Flags = static_cast<ELFYAML::ELF_SHF>(Shdr->sh_flags);
   S.Address = Shdr->sh_addr;
   S.AddressAlign = Shdr->sh_addralign;
   if (Shdr->sh_entsize)

tools/yaml2obj/yaml2elf.cpp

@@ -303,7 +303,8 @@ bool ELFState<ELFT>::initSectionHeaders(ELFState<ELFT> &State,
 
     SHeader.sh_name = DotShStrtab.getOffset(SecName);
     SHeader.sh_type = Sec->Type;
-    SHeader.sh_flags = Sec->Flags;
+    if (Sec->Flags)
+      SHeader.sh_flags = *Sec->Flags;
     SHeader.sh_addr = Sec->Address;
     SHeader.sh_addralign = Sec->AddressAlign;
 
@@ -424,8 +425,10 @@ void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
     SHeader.sh_link = Link;
   }
 
-  if (!IsStatic)
-    SHeader.sh_flags |= ELF::SHF_ALLOC;
+  if (YAMLSec && YAMLSec->Flags)
+    SHeader.sh_flags = *YAMLSec->Flags;
+  else if (!IsStatic)
+    SHeader.sh_flags = ELF::SHF_ALLOC;
 
   // If the symbol table section is explicitly described in the YAML
   // then we should set the fields requested.
@@ -481,14 +484,16 @@ void ELFState<ELFT>::initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
   if (YAMLSec && YAMLSec->EntSize)
     SHeader.sh_entsize = *YAMLSec->EntSize;
 
+  if (YAMLSec && YAMLSec->Flags)
+    SHeader.sh_flags = *YAMLSec->Flags;
+  else if (Name == ".dynstr")
+    SHeader.sh_flags = ELF::SHF_ALLOC;
+
   // If .dynstr section is explicitly described in the YAML
   // then we want to use its section address.
-  if (Name == ".dynstr") {
-    if (YAMLSec)
-      SHeader.sh_addr = YAMLSec->Address;
-    // We assume that .dynstr is always allocatable.
-    SHeader.sh_flags |= ELF::SHF_ALLOC;
-  }
+  // TODO: Allow this for any explicitly described section.
+  if (YAMLSec && Name == ".dynstr")
+    SHeader.sh_addr = YAMLSec->Address;
 }
 
 template <class ELFT>