[yaml2obj][ELF] Add support for setting alignment in program headers

Sometimes program headers have larger alignments than any of the
sections they contain. Currently yaml2obj can't produce such files. A
bug recently appeared in llvm-objcopy that failed in such a case. I'd
like to be able to add tests to llvm-objcopy for such cases.

This change adds an optional alignment parameter to program headers that
will be used instead of calculating the alignment.

Differential Revision: https://reviews.llvm.org/D39130

llvm-svn: 317139

include/llvm/ObjectYAML/ELFYAML.h

@@ -83,6 +83,7 @@ struct ProgramHeader {
   ELF_PF Flags;
   llvm::yaml::Hex64 VAddr;
   llvm::yaml::Hex64 PAddr;
+  Optional<llvm::yaml::Hex64> Align;
   std::vector<SectionName> Sections;
 };
 

lib/ObjectYAML/ELFYAML.cpp

@@ -719,6 +719,7 @@ void MappingTraits<ELFYAML::ProgramHeader>::mapping(
   IO.mapOptional("Sections", Phdr.Sections);
   IO.mapOptional("VAddr", Phdr.VAddr, Hex64(0));
   IO.mapOptional("PAddr", Phdr.PAddr, Hex64(0));
+  IO.mapOptional("Align", Phdr.Align);
 }
 
 namespace {

test/tools/yaml2obj/program-header-align.yaml

@@ -0,0 +1,63 @@
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-readobj -program-headers %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 ]
+    AddressAlign:    0x0000000000000008
+    Content:         "00000000"
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         "00000000"
+    AddressAlign:    0x0000000000000010
+ProgramHeaders:
+  - Type: PT_LOAD
+    Flags: [ PF_X, PF_R ]
+    VAddr: 0xAAAA1030
+    PAddr: 0xFFFF1030
+    Align: 0x1000
+    Sections:
+      - Section: .text
+  - Type: PT_LOAD
+    Flags: [ PF_R ]
+    VAddr: 0xAAAA2040
+    PAddr: 0xFFFF2040
+    Align: 0x1000
+    Sections:
+      - Section: .data
+
+#CHECK:     ProgramHeaders [
+#CHECK-NEXT:   ProgramHeader {
+#CHECK-NEXT:    Type: PT_LOAD
+#CHECK-NEXT:    Offset: 0x230
+#CHECK-NEXT:    VirtualAddress: 0xAAAA1030
+#CHECK-NEXT:    PhysicalAddress: 0xFFFF1030
+#CHECK-NEXT:    FileSize: 4
+#CHECK-NEXT:    MemSize: 4
+#CHECK-NEXT:    Flags [
+#CHECK-NEXT:      PF_R
+#CHECK-NEXT:      PF_X
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Alignment: 4096
+#CHECK-NEXT:  }
+#CHECK-NEXT:  ProgramHeader {
+#CHECK-NEXT:    Type: PT_LOAD
+#CHECK-NEXT:    Offset: 0x240
+#CHECK-NEXT:    VirtualAddress: 0xAAAA2040
+#CHECK-NEXT:    PhysicalAddress: 0xFFFF2040
+#CHECK-NEXT:    FileSize: 4
+#CHECK-NEXT:    MemSize: 4
+#CHECK-NEXT:    Flags [
+#CHECK-NEXT:      PF_R
+#CHECK-NEXT:    ]
+#CHECK-NEXT:    Alignment: 4096
+#CHECK-NEXT:  }
+#CHECK-NEXT:]

tools/yaml2obj/yaml2elf.cpp

@@ -378,15 +378,19 @@ void ELFState<ELFT>::setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
     }
 
     // Set the alignment of the segment to be the same as the maximum alignment
-    // of the the sections with the same offset so that by default the segment
+    // of the sections with the same offset so that by default the segment
     // has a valid and sensible alignment.
-    PHeader.p_align = 1;
-    for (auto SecName : YamlPhdr.Sections) {
-      uint32_t Index = 0;
-      SN2I.lookup(SecName.Section, Index);
-      const auto &SHeader = SHeaders[Index];
-      if (SHeader.sh_offset == PHeader.p_offset)
-        PHeader.p_align = std::max(PHeader.p_align, SHeader.sh_addralign);
+    if (YamlPhdr.Align) {
+      PHeader.p_align = *YamlPhdr.Align;
+    } else {
+      PHeader.p_align = 1;
+      for (auto SecName : YamlPhdr.Sections) {
+        uint32_t Index = 0;
+        SN2I.lookup(SecName.Section, Index);
+        const auto &SHeader = SHeaders[Index];
+        if (SHeader.sh_offset == PHeader.p_offset)
+          PHeader.p_align = std::max(PHeader.p_align, SHeader.sh_addralign);
+      }
     }
   }
 }