Index: llvm/trunk/test/tools/llvm-objcopy/ELF/no-build-id.test
===================================================================
--- llvm/trunk/test/tools/llvm-objcopy/ELF/no-build-id.test
+++ llvm/trunk/test/tools/llvm-objcopy/ELF/no-build-id.test
@@ -18,4 +18,4 @@
   - Type: PT_NOTE
     Flags: [ PF_R ]
     Sections:
-      - Section: .note.gnu.foo
+      - Section: .note.foo
Index: llvm/trunk/test/tools/yaml2obj/program-header.yaml
===================================================================
--- llvm/trunk/test/tools/yaml2obj/program-header.yaml
+++ llvm/trunk/test/tools/yaml2obj/program-header.yaml
@@ -1,7 +1,7 @@
-# RUN: yaml2obj %s -o %t
+# RUN: yaml2obj --docnum=1 %s -o %t
 # RUN: llvm-readobj -l %t | FileCheck %s
 
-!ELF
+--- !ELF
 FileHeader:
   Class:           ELFCLASS64
   Data:            ELFDATA2LSB
@@ -65,3 +65,18 @@
 #CHECK-NEXT:    Alignment: 4096
 #CHECK-NEXT:  }
 #CHECK-NEXT:]
+
+## Check we do not allow referencing sections that do not exist.
+# RUN: not yaml2obj --docnum=2 %s -o %t 2>&1 | FileCheck %s --check-prefix=ERR
+# ERR: error: Unknown section referenced: '.foo' by program header.
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+ProgramHeaders:
+  - Type: PT_LOAD
+    Sections:
+      - Section: .foo
Index: llvm/trunk/tools/yaml2obj/yaml2elf.cpp
===================================================================
--- llvm/trunk/tools/yaml2obj/yaml2elf.cpp
+++ llvm/trunk/tools/yaml2obj/yaml2elf.cpp
@@ -390,7 +390,18 @@
                                             std::vector<Elf_Shdr> &SHeaders) {
   uint32_t PhdrIdx = 0;
   for (auto &YamlPhdr : Doc.ProgramHeaders) {
-    auto &PHeader = PHeaders[PhdrIdx++];
+    Elf_Phdr &PHeader = PHeaders[PhdrIdx++];
+
+    std::vector<Elf_Shdr *> Sections;
+    for (const ELFYAML::SectionName &SecName : YamlPhdr.Sections) {
+      unsigned Index;
+      if (SN2I.lookup(SecName.Section, Index)) {
+        WithColor::error() << "Unknown section referenced: '" << SecName.Section
+                           << "' by program header.\n";
+        exit(1);
+      }
+      Sections.push_back(&SHeaders[Index]);
+    }
 
     if (YamlPhdr.Offset) {
       PHeader.p_offset = *YamlPhdr.Offset;
@@ -401,12 +412,8 @@
         PHeader.p_offset = 0;
 
       // Find the minimum offset for the program header.
-      for (auto SecName : YamlPhdr.Sections) {
-        uint32_t Index = 0;
-        SN2I.lookup(SecName.Section, Index);
-        const auto &SHeader = SHeaders[Index];
-        PHeader.p_offset = std::min(PHeader.p_offset, SHeader.sh_offset);
-      }
+      for (Elf_Shdr *SHeader : Sections)
+        PHeader.p_offset = std::min(PHeader.p_offset, SHeader->sh_offset);
     }
 
     // Find the maximum offset of the end of a section in order to set p_filesz,
@@ -415,15 +422,12 @@
       PHeader.p_filesz = *YamlPhdr.FileSize;
     } else {
       PHeader.p_filesz = 0;
-      for (auto SecName : YamlPhdr.Sections) {
-        uint32_t Index = 0;
-        SN2I.lookup(SecName.Section, Index);
-        const auto &SHeader = SHeaders[Index];
+      for (Elf_Shdr *SHeader : Sections) {
         uint64_t EndOfSection;
-        if (SHeader.sh_type == llvm::ELF::SHT_NOBITS)
-          EndOfSection = SHeader.sh_offset;
+        if (SHeader->sh_type == llvm::ELF::SHT_NOBITS)
+          EndOfSection = SHeader->sh_offset;
         else
-          EndOfSection = SHeader.sh_offset + SHeader.sh_size;
+          EndOfSection = SHeader->sh_offset + SHeader->sh_size;
         uint64_t EndOfSegment = PHeader.p_offset + PHeader.p_filesz;
         EndOfSegment = std::max(EndOfSegment, EndOfSection);
         PHeader.p_filesz = EndOfSegment - PHeader.p_offset;
@@ -437,13 +441,9 @@
       PHeader.p_memsz = *YamlPhdr.MemSize;
     } else {
       PHeader.p_memsz = PHeader.p_filesz;
-      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_filesz)
-          PHeader.p_memsz += SHeader.sh_size;
-      }
+      for (Elf_Shdr *SHeader : Sections)
+        if (SHeader->sh_offset == PHeader.p_offset + PHeader.p_filesz)
+          PHeader.p_memsz += SHeader->sh_size;
     }
 
     // Set the alignment of the segment to be the same as the maximum alignment
@@ -453,13 +453,9 @@
       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);
-      }
+      for (Elf_Shdr *SHeader : Sections)
+        if (SHeader->sh_offset == PHeader.p_offset)
+          PHeader.p_align = std::max(PHeader.p_align, SHeader->sh_addralign);
     }
   }
 }