[ObjectYAML][ELF] Take alignment into account when generating notes

llvm/lib/ObjectYAML/ELFEmitter.cpp

@@ -1799,6 +1799,20 @@ void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
   if (!Section.Notes)
     return;
 
+  unsigned Align;
+  switch (SHeader.sh_addralign) {
+  case 0:
+  case 4:
+    Align = 4;
+    break;
+  case 8:
+    Align = 8;
+    break;
+  default:
+    reportError(Section.Name + ": invalid alignment for a note section: 0x" +
+                Twine::utohexstr(SHeader.sh_addralign));
+  }
+
   uint64_t Offset = CBA.tell();
   for (const ELFYAML::NoteEntry &NE : *Section.Notes) {
     // Write name size.
@@ -1820,13 +1834,13 @@ void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
     if (!NE.Name.empty()) {
       CBA.write(NE.Name.data(), NE.Name.size());
       CBA.write('\0');
-      CBA.padToAlignment(4);
+      CBA.padToAlignment(Align);
     }
 
     // Write description and padding.
     if (NE.Desc.binary_size() != 0) {
       CBA.writeAsBinary(NE.Desc);
-      CBA.padToAlignment(4);
+      CBA.padToAlignment(Align);
     }
   }
 

llvm/test/tools/yaml2obj/ELF/note-section.yaml

@@ -333,3 +333,74 @@ Sections:
       - Name: ABC
         Desc: '123456'
         Type: NT_VERSION
+
+## Check that an incorrect alignment is reported
+
+# RUN: not yaml2obj --docnum=16 %s 2>&1 | FileCheck %s --check-prefix=ERR_ALIGN1
+# ERR_ALIGN1: error: .note.foo: invalid alignment for a note section: 0x1
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+Sections:
+  - Name:         .note.foo
+    Type:         SHT_NOTE
+    AddressAlign: 1
+    Notes:
+      - Type: 0x1
+
+## Check that note entries and their `Desc` fields are aligned according to the
+## specified section alignment
+
+# RUN: yaml2obj --docnum=17 %s -o - | \
+# RUN:   llvm-readobj --sections --section-data - | \
+# RUN:   FileCheck %s --check-prefix=TEST17
+
+# TEST17:      Name: .note.foo4
+# TEST17:      SectionData (
+# TEST17-NEXT:   0000: 05000000 02000000 01000000 41424344  |............ABCD|
+# TEST17-NEXT:   0010: 00000000 01020000 03000000 03000000  |................|
+# TEST17-NEXT:   0020: 02000000 41420000 03040500 03000000  |....AB..........|
+# TEST17-NEXT:   0030: 00000000 03000000 41420000           |........AB..|
+# TEST17-NEXT: )
+# TEST17:      Name: .note.foo8
+# TEST17:      SectionData (
+# TEST17-NEXT:   0000: 05000000 02000000 01000000 41424344  |............ABCD|
+# TEST17-NEXT:   0010: 00000000 00000000 01020000 00000000  |................|
+# TEST17-NEXT:   0020: 03000000 03000000 02000000 41420000  |............AB..|
+# TEST17-NEXT:   0030: 03040500 00000000 03000000 00000000  |................|
+# TEST17-NEXT:   0040: 03000000 41420000                    |....AB..|
+# TEST17-NEXT: )
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+Sections:
+  - Name:         .note.foo4
+    Type:         SHT_NOTE
+    AddressAlign: 4
+    Notes:
+      - Name: ABCD
+        Desc: 0102
+        Type: NT_VERSION
+      - Name: AB
+        Desc: 030405
+        Type: NT_ARCH
+      - Name: AB
+        Type: NT_GNU_BUILD_ID
+  - Name:        .note.foo8
+    Type:         SHT_NOTE
+    AddressAlign: 8
+    Notes:
+      - Name: ABCD
+        Desc: 0102
+        Type: NT_VERSION
+      - Name: AB
+        Desc: 030405
+        Type: NT_ARCH
+      - Name: AB
+        Type: NT_GNU_BUILD_ID