[llvm] r317622 - Allow yaml2obj to order implicit sections for ELF
Rafael Avila de Espindola via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 7 14:40:57 PST 2017
This is crashing in a lld test. I have attached it.
It crashes with
yaml2obj invalid-relocations.test -o t
Cheers,
Rafael
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Dave Lee via llvm-commits <llvm-commits at lists.llvm.org> writes:
> Author: kastiglione
> Date: Tue Nov 7 14:05:24 2017
> New Revision: 317622
>
> URL: http://llvm.org/viewvc/llvm-project?rev=317622&view=rev
> Log:
> Allow yaml2obj to order implicit sections for ELF
>
> Summary:
> This change allows yaml input to control the order of implicitly added sections
> (`.symtab`, `.strtab`, `.shstrtab`). The order is controlled by adding a
> placeholder section of the given name to the Sections field.
>
> This change is to support changes in D39582, where it is desirable to control
> the location of the `.dynsym` section.
>
> Reviewers: compnerd, jakehehrlich
>
> Reviewed By: jakehehrlich
>
> Subscribers: llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D39749
>
> Added:
> llvm/trunk/test/tools/yaml2obj/section-ordering.yaml
> Modified:
> llvm/trunk/lib/ObjectYAML/ELFYAML.cpp
> llvm/trunk/tools/yaml2obj/yaml2elf.cpp
>
> Modified: llvm/trunk/lib/ObjectYAML/ELFYAML.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ObjectYAML/ELFYAML.cpp?rev=317622&r1=317621&r2=317622&view=diff
> ==============================================================================
> --- llvm/trunk/lib/ObjectYAML/ELFYAML.cpp (original)
> +++ llvm/trunk/lib/ObjectYAML/ELFYAML.cpp Tue Nov 7 14:05:24 2017
> @@ -388,7 +388,7 @@ void ScalarEnumerationTraits<ELFYAML::EL
> #define ECase(X) IO.enumCase(Value, #X, ELF::X)
> ECase(SHT_NULL);
> ECase(SHT_PROGBITS);
> - // No SHT_SYMTAB. Use the top-level `Symbols` key instead.
> + ECase(SHT_SYMTAB);
> // FIXME: Issue a diagnostic with this information.
> ECase(SHT_STRTAB);
> ECase(SHT_RELA);
>
> Added: llvm/trunk/test/tools/yaml2obj/section-ordering.yaml
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/tools/yaml2obj/section-ordering.yaml?rev=317622&view=auto
> ==============================================================================
> --- llvm/trunk/test/tools/yaml2obj/section-ordering.yaml (added)
> +++ llvm/trunk/test/tools/yaml2obj/section-ordering.yaml Tue Nov 7 14:05:24 2017
> @@ -0,0 +1,29 @@
> +# Ensures that implicitly added sections can be ordered within Sections.
> +# RUN: yaml2obj %s -o %t
> +# RUN: llvm-readobj -sections %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 ]
> + - Name: .symtab
> + Type: SHT_SYMTAB
> + - Name: .data
> + Type: SHT_PROGBITS
> + Flags: [ SHF_ALLOC, SHF_WRITE ]
> + - Name: .shstrtab
> + Type: SHT_STRTAB
> + - Name: .strtab
> + Type: SHT_STRTAB
> +
> +# CHECK: Name: .text
> +# CHECK: Name: .symtab
> +# CHECK: Name: .data
> +# CHECK: Name: .shstrtab
> +# CHECK: Name: .strtab
>
> Modified: llvm/trunk/tools/yaml2obj/yaml2elf.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/tools/yaml2obj/yaml2elf.cpp?rev=317622&r1=317621&r2=317622&view=diff
> ==============================================================================
> --- llvm/trunk/tools/yaml2obj/yaml2elf.cpp (original)
> +++ llvm/trunk/tools/yaml2obj/yaml2elf.cpp Tue Nov 7 14:05:24 2017
> @@ -74,6 +74,13 @@ public:
> Idx = I->getValue();
> return false;
> }
> + /// asserts if name is not present in the map
> + unsigned get(StringRef Name) const {
> + unsigned Idx;
> + assert(!lookup(Name, Idx) && "Expected section not found in index");
> + return Idx;
> + }
> + unsigned size() const { return Map.size(); }
> };
> } // end anonymous namespace
>
> @@ -144,19 +151,21 @@ class ELFState {
> ContiguousBlobAccumulator &CBA);
>
> // - SHT_NULL entry (placed first, i.e. 0'th entry)
> - // - symbol table (.symtab) (placed third to last)
> - // - string table (.strtab) (placed second to last)
> - // - section header string table (.shstrtab) (placed last)
> - unsigned getDotSymTabSecNo() const { return Doc.Sections.size() + 1; }
> - unsigned getDotStrTabSecNo() const { return Doc.Sections.size() + 2; }
> - unsigned getDotShStrTabSecNo() const { return Doc.Sections.size() + 3; }
> - unsigned getSectionCount() const { return Doc.Sections.size() + 4; }
> + // - symbol table (.symtab) (defaults to third to last)
> + // - string table (.strtab) (defaults to second to last)
> + // - section header string table (.shstrtab) (defaults to last)
> + unsigned getDotSymTabSecNo() const { return SN2I.get(".symtab"); }
> + unsigned getDotStrTabSecNo() const { return SN2I.get(".strtab"); }
> + unsigned getDotShStrTabSecNo() const { return SN2I.get(".shstrtab"); }
> + unsigned getSectionCount() const { return SN2I.size() + 1; }
>
> ELFState(const ELFYAML::Object &D) : Doc(D) {}
>
> public:
> static int writeELF(raw_ostream &OS, const ELFYAML::Object &Doc);
> };
> +
> +static const char * const ImplicitSecNames[] = {".symtab", ".strtab", ".shstrtab"};
> } // end anonymous namespace
>
> template <class ELFT>
> @@ -211,10 +220,6 @@ bool ELFState<ELFT>::initSectionHeaders(
> zero(SHeader);
> SHeaders.push_back(SHeader);
>
> - for (const auto &Sec : Doc.Sections)
> - DotShStrtab.add(Sec->Name);
> - DotShStrtab.finalize();
> -
> for (const auto &Sec : Doc.Sections) {
> zero(SHeader);
> SHeader.sh_name = DotShStrtab.getOffset(Sec->Name);
> @@ -547,10 +552,6 @@ bool ELFState<ELFT>::writeSectionContent
> }
>
> template <class ELFT> bool ELFState<ELFT>::buildSectionIndex() {
> - SN2I.addName(".symtab", getDotSymTabSecNo());
> - SN2I.addName(".strtab", getDotStrTabSecNo());
> - SN2I.addName(".shstrtab", getDotShStrTabSecNo());
> -
> for (unsigned i = 0, e = Doc.Sections.size(); i != e; ++i) {
> StringRef Name = Doc.Sections[i]->Name;
> if (Name.empty())
> @@ -561,7 +562,19 @@ template <class ELFT> bool ELFState<ELFT
> << "' at YAML section number " << i << ".\n";
> return false;
> }
> + DotShStrtab.add(Name);
> }
> +
> + auto SecNo = 1 + Doc.Sections.size();
> + // Add special sections after input sections, if necessary.
> + for (const auto &Name : ImplicitSecNames)
> + if (!SN2I.addName(Name, SecNo)) {
> + // Account for this section, since it wasn't in the Doc
> + ++SecNo;
> + DotShStrtab.add(Name);
> + }
> +
> + DotShStrtab.finalize();
> return true;
> }
>
> @@ -608,32 +621,23 @@ int ELFState<ELFT>::writeELF(raw_ostream
> Header.e_shentsize * Header.e_shnum;
> ContiguousBlobAccumulator CBA(SectionContentBeginOffset);
>
> - // Doc might not contain .symtab, .strtab and .shstrtab sections,
> - // but we will emit them, so make sure to add them to ShStrTabSHeader.
> - State.DotShStrtab.add(".symtab");
> - State.DotShStrtab.add(".strtab");
> - State.DotShStrtab.add(".shstrtab");
> -
> std::vector<Elf_Shdr> SHeaders;
> + SHeaders.reserve(State.SN2I.size());
> if(!State.initSectionHeaders(SHeaders, CBA))
> return 1;
>
> - // .symtab section.
> - Elf_Shdr SymtabSHeader;
> - State.initSymtabSectionHeader(SymtabSHeader, CBA);
> - SHeaders.push_back(SymtabSHeader);
> -
> - // .strtab string table header.
> - Elf_Shdr DotStrTabSHeader;
> - State.initStrtabSectionHeader(DotStrTabSHeader, ".strtab", State.DotStrtab,
> - CBA);
> - SHeaders.push_back(DotStrTabSHeader);
> -
> - // .shstrtab string table header.
> - Elf_Shdr ShStrTabSHeader;
> - State.initStrtabSectionHeader(ShStrTabSHeader, ".shstrtab", State.DotShStrtab,
> - CBA);
> - SHeaders.push_back(ShStrTabSHeader);
> + // Populate SHeaders with implicit sections not present in the Doc
> + for (const auto &Name : ImplicitSecNames)
> + if (State.SN2I.get(Name) >= SHeaders.size())
> + SHeaders.push_back({});
> +
> + // Initialize the implicit sections
> + auto Index = State.SN2I.get(".symtab");
> + State.initSymtabSectionHeader(SHeaders[Index], CBA);
> + Index = State.SN2I.get(".strtab");
> + State.initStrtabSectionHeader(SHeaders[Index], ".strtab", State.DotStrtab, CBA);
> + Index = State.SN2I.get(".shstrtab");
> + State.initStrtabSectionHeader(SHeaders[Index], ".shstrtab", State.DotShStrtab, CBA);
>
> // Now we can decide segment offsets
> State.setProgramHeaderLayout(PHeaders, SHeaders);
>
>
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