[yaml2obj] - Allow overriding sh_offset field from the YAML.

Some of our test cases are using objects which
has sections with a broken sh_offset field.

There was no way to set it from YAML until this patch.

Differential revision: https://reviews.llvm.org/D63879

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@364898 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ObjectYAML/ELFYAML.h b/include/llvm/ObjectYAML/ELFYAML.h
index b12c2936692cd4eb3295bb488f9aa0db2a613846..68a0fc36b501928a76694707a15714dc1e2f3173 100644 (file)
--- a/include/llvm/ObjectYAML/ELFYAML.h
+++ b/include/llvm/ObjectYAML/ELFYAML.h
@@ -140,6 +140,10 @@ struct Section {
   llvm::yaml::Hex64 AddressAlign;
   Optional<llvm::yaml::Hex64> EntSize;
 
+  // This can be used to override the sh_offset field. It does not place the
+  // section data at the offset specified. Useful for creating invalid objects.
+  Optional<llvm::yaml::Hex64> ShOffset;
+
   Section(SectionKind Kind) : Kind(Kind) {}
   virtual ~Section();
 };

diff --git a/lib/ObjectYAML/ELFYAML.cpp b/lib/ObjectYAML/ELFYAML.cpp
index 49161623cd7515c4f1469fa7682527f6acbda5d0..46c96f96778aa3c900d2243f203296ddfff2fc68 100644 (file)
--- a/lib/ObjectYAML/ELFYAML.cpp
+++ b/lib/ObjectYAML/ELFYAML.cpp
@@ -911,6 +911,12 @@ static void commonSectionMapping(IO &IO, ELFYAML::Section &Section) {
   IO.mapOptional("Link", Section.Link, StringRef());
   IO.mapOptional("AddressAlign", Section.AddressAlign, Hex64(0));
   IO.mapOptional("EntSize", Section.EntSize);
+
+  // obj2yaml does not dump this field. It is expected to be empty when we are
+  // producing YAML, because yaml2obj sets an appropriate value for sh_offset
+  // automatically when it is not explicitly defined.
+  assert(!IO.outputting() || !Section.ShOffset.hasValue());
+  IO.mapOptional("ShOffset", Section.ShOffset);
 }
 
 static void sectionMapping(IO &IO, ELFYAML::DynamicSection &Section) {

diff --git a/test/tools/yaml2obj/elf-override-shoffset.yaml b/test/tools/yaml2obj/elf-override-shoffset.yaml
new file mode 100644 (file)
index 0000000..66636b4
--- /dev/null
+++ b/test/tools/yaml2obj/elf-override-shoffset.yaml
@@ -0,0 +1,106 @@
+## Check we are able to set custom sh_offset field
+## for different sections.
+
+# RUN: yaml2obj --docnum=1 %s -o %t1
+# RUN: llvm-readelf --sections %t1 | FileCheck %s --check-prefix=CASE1
+
+# CASE1:      Section Headers:
+# CASE1-NEXT:  [Nr] Name           Type     Address Off
+# CASE1-NEXT:  [ 0]                NULL     {{.*}}  000000
+# CASE1-NEXT:  [ 1] .dynsym        DYNSYM   {{.*}}  000001
+# CASE1-NEXT:  [ 2] .symtab        SYMTAB   {{.*}}  000002
+# CASE1-NEXT:  [ 3] .dynamic       DYNAMIC  {{.*}}  000003
+# CASE1-NEXT:  [ 4] .rela          RELA     {{.*}}  000004
+# CASE1-NEXT:  [ 5] .nobits        NOBITS   {{.*}}  000005
+# CASE1-NEXT:  [ 6] .group         GROUP    {{.*}}  000006
+# CASE1-NEXT:  [ 7] .gnu.version   VERSYM   {{.*}}  000007
+# CASE1-NEXT:  [ 8] .gnu.version_r VERNEED  {{.*}}  000008
+# CASE1-NEXT:  [ 9] .gnu.version_d VERDEF   {{.*}}  000009
+# CASE1-NEXT:  [10] .regular       PROGBITS {{.*}}  00000a
+# CASE1-NEXT:  [11] .strtab        STRTAB   {{.*}}  00000b
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .dynsym
+    Type: SHT_DYNSYM
+    ShOffset: 0x000000001
+  - Name: .symtab
+    Type: SHT_SYMTAB
+    ShOffset: 0x000000002
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    ShOffset: 0x000000003
+  - Name: .rela
+    Type: SHT_RELA
+    ShOffset: 0x000000004
+  - Name: .nobits
+    Type: SHT_NOBITS
+    ShOffset: 0x000000005
+  - Name: .group
+    Type: SHT_GROUP
+    Info: 0
+    ShOffset: 0x000000006
+    Members:
+  - Name: .gnu.version
+    Type: SHT_GNU_versym
+    Entries: [ ]
+    ShOffset: 0x000000007
+  - Name: .gnu.version_r
+    Type: SHT_GNU_verneed
+    Info: 0x0000000000000001
+    ShOffset: 0x000000008
+    Dependencies:
+  - Name: .gnu.version_d
+    Type: SHT_GNU_verdef
+    Info: 0x0000000000000001
+    ShOffset: 0x000000009
+    Entries:
+  - Name: .regular
+    Type: SHT_PROGBITS
+    ShOffset: 0x00000000A
+  - Name: .strtab
+    Type: SHT_STRTAB
+    ShOffset: 0x00000000B
+
+## Here we check that defining ShOffset does not actually change
+## the offset at which section data is placed and also does
+## not affect file size.
+
+# RUN: yaml2obj --docnum=2 %s -o %t2
+# RUN: yaml2obj --docnum=3 %s -o %t3
+# RUN: od -t x8 -v %t2 > %t.txt
+# RUN: od -t x8 -v %t3 >> %t.txt
+# RUN: FileCheck %s --input-file=%t.txt --check-prefix=CASE2
+
+# CASE2: [[OFFSET:.*]] 8877665544332211
+# CASE2: [[FILESIZE:.*]]{{$}}
+# CASE2: [[OFFSET]] 8877665544332211
+# CASE2: [[FILESIZE]]{{$}}
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .foo
+    Type: SHT_PROGBITS
+    Content: "1122334455667788"
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+Sections:
+  - Name: .foo
+    Type: SHT_PROGBITS
+    ShOffset: 0xFFFF0000
+    Content: "1122334455667788"

diff --git a/tools/obj2yaml/elf2yaml.cpp b/tools/obj2yaml/elf2yaml.cpp
index 804101f2deee559b4f3e79762abaa6f655d2cdea..7404bae2a08acb97b06867ab56393d271ba60708 100644 (file)
--- a/tools/obj2yaml/elf2yaml.cpp
+++ b/tools/obj2yaml/elf2yaml.cpp
@@ -360,6 +360,8 @@ std::error_code ELFDumper<ELFT>::dumpRelocation(const RelT *Rel,
 template <class ELFT>
 std::error_code ELFDumper<ELFT>::dumpCommonSection(const Elf_Shdr *Shdr,
                                                    ELFYAML::Section &S) {
+  // Dump fields. We do not dump the ShOffset field. When not explicitly
+  // set, the value is set by yaml2obj automatically.
   S.Type = Shdr->sh_type;
   if (Shdr->sh_flags)
     S.Flags = static_cast<ELFYAML::ELF_SHF>(Shdr->sh_flags);

diff --git a/tools/yaml2obj/yaml2elf.cpp b/tools/yaml2obj/yaml2elf.cpp
index e093ed8d72f81647c3df8d6a9f52c9437a3eb550..735057f6e7daa1709784d6108192de738093c553 100644 (file)
--- a/tools/yaml2obj/yaml2elf.cpp
+++ b/tools/yaml2obj/yaml2elf.cpp
@@ -269,6 +269,11 @@ bool ELFState<ELFT>::initImplicitHeader(ELFState<ELFT> &State,
                                   YAMLSec);
   else
     return false;
+
+  // Override the sh_offset field if requested.
+  if (YAMLSec && YAMLSec->ShOffset)
+    Header.sh_offset = *YAMLSec->ShOffset;
+
   return true;
 }
 
@@ -358,6 +363,10 @@ bool ELFState<ELFT>::initSectionHeaders(ELFState<ELFT> &State,
         return false;
     } else
       llvm_unreachable("Unknown section type");
+
+    // Override the sh_offset field if requested.
+    if (Sec && Sec->ShOffset)
+      SHeader.sh_offset = *Sec->ShOffset;
   }
 
   return true;