[llvm] 1724188 - [ObjectYAML][ELF] Take alignment into account when generating notes (#118157)
via llvm-commits
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Mon Dec 2 17:58:51 PST 2024
Author: Igor Kudrin
Date: 2024-12-02T17:58:48-08:00
New Revision: 1724188c19f363c877fcf1bca86d92af3864b338
URL: https://github.com/llvm/llvm-project/commit/1724188c19f363c877fcf1bca86d92af3864b338
DIFF: https://github.com/llvm/llvm-project/commit/1724188c19f363c877fcf1bca86d92af3864b338.diff
LOG: [ObjectYAML][ELF] Take alignment into account when generating notes (#118157)
The [System V ABI](https://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section)
states that the note entries and their descriptor fields must be aligned
to 4 or 8 bytes for 32-bit or 64-bit objects respectively. In practice,
64-bit systems can use both alignments, with the actual format being
determined by the alignment of the segment. For example, the
[Linux gABI extension](https://github.com/hjl-tools/linux-abi/wiki/linux-abi-draft.pdf)
contains a special note on this, see 2.1.7 "Alignment of Note Sections".
This patch adjusts the format of the generated notes to the specified
section alignment. Since `llvm-readobj` was fixed in a similar way in
[D150022](https://reviews.llvm.org/D150022), "[Object] Fix handling of
Elf_Nhdr with sh_addralign=8", the generated notes can now be parsed
successfully by the tool.
Added:
Modified:
llvm/lib/ObjectYAML/ELFEmitter.cpp
llvm/test/tools/yaml2obj/ELF/note-section.yaml
Removed:
################################################################################
diff --git a/llvm/lib/ObjectYAML/ELFEmitter.cpp b/llvm/lib/ObjectYAML/ELFEmitter.cpp
index 476334024151a9..001e701bd0b80d 100644
--- a/llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ b/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.
@@ -1820,14 +1834,15 @@ 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);
}
// Write description and padding.
if (NE.Desc.binary_size() != 0) {
+ CBA.padToAlignment(Align);
CBA.writeAsBinary(NE.Desc);
- CBA.padToAlignment(4);
}
+
+ CBA.padToAlignment(Align);
}
SHeader.sh_size = CBA.tell() - Offset;
diff --git a/llvm/test/tools/yaml2obj/ELF/note-section.yaml b/llvm/test/tools/yaml2obj/ELF/note-section.yaml
index 80359c4ec01833..26b95e1c2379b2 100644
--- a/llvm/test/tools/yaml2obj/ELF/note-section.yaml
+++ b/llvm/test/tools/yaml2obj/ELF/note-section.yaml
@@ -333,3 +333,132 @@ 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 --notes - | \
+# 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 00000000 03000000 |................|
+# TEST17-NEXT: 0020: 02000000 03040500 04000000 00000000 |................|
+# TEST17-NEXT: 0030: 03000000 474E5500 |....GNU.|
+# 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: 00000000 03000000 02000000 00000000 |................|
+# TEST17-NEXT: 0030: 03040500 00000000 04000000 00000000 |................|
+# TEST17-NEXT: 0040: 03000000 474E5500 |....GNU.|
+# TEST17-NEXT: )
+# TEST17: NoteSections [
+# TEST17-NEXT: NoteSection {
+# TEST17-NEXT: Name: .note.foo4
+# TEST17-NEXT: Offset:
+# TEST17-NEXT: Size:
+# TEST17-NEXT: Notes [
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner: ABCD
+# TEST17-NEXT: Data size: 0x2
+# TEST17-NEXT: Type: NT_VERSION (version)
+# TEST17-NEXT: Description data (
+# TEST17-NEXT: 0000: 0102 |..|
+# TEST17-NEXT: )
+# TEST17-NEXT: }
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner:
+# TEST17-NEXT: Data size: 0x3
+# TEST17-NEXT: Type: NT_ARCH (architecture)
+# TEST17-NEXT: Description data (
+# TEST17-NEXT: 0000: 030405 |...|
+# TEST17-NEXT: )
+# TEST17-NEXT: }
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner: GNU
+# TEST17-NEXT: Data size: 0x0
+# TEST17-NEXT: Type: NT_GNU_BUILD_ID (unique build ID bitstring)
+# TEST17-NEXT: Build ID:
+# TEST17-NEXT: }
+# TEST17-NEXT: ]
+# TEST17-NEXT: }
+# TEST17-NEXT: NoteSection {
+# TEST17-NEXT: Name: .note.foo8
+# TEST17-NEXT: Offset:
+# TEST17-NEXT: Size:
+# TEST17-NEXT: Notes [
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner: ABCD
+# TEST17-NEXT: Data size: 0x2
+# TEST17-NEXT: Type: NT_VERSION (version)
+# TEST17-NEXT: Description data (
+# TEST17-NEXT: 0000: 0102 |..|
+# TEST17-NEXT: )
+# TEST17-NEXT: }
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner:
+# TEST17-NEXT: Data size: 0x3
+# TEST17-NEXT: Type: NT_ARCH (architecture)
+# TEST17-NEXT: Description data (
+# TEST17-NEXT: 0000: 030405 |...|
+# TEST17-NEXT: )
+# TEST17-NEXT: }
+# TEST17-NEXT: {
+# TEST17-NEXT: Owner: GNU
+# TEST17-NEXT: Data size: 0x0
+# TEST17-NEXT: Type: NT_GNU_BUILD_ID (unique build ID bitstring)
+# TEST17-NEXT: Build ID:
+# TEST17-NEXT: }
+# TEST17-NEXT: ]
+# TEST17-NEXT: }
+# TEST17-NEXT: ]
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_EXEC
+Sections:
+ - Name: .note.foo4
+ Type: SHT_NOTE
+ AddressAlign: 4
+ Notes:
+ - Name: ABCD
+ Type: NT_VERSION
+ Desc: 0102
+ - Type: NT_ARCH
+ Desc: 030405
+ - Name: GNU
+ Type: NT_GNU_BUILD_ID
+ - Name: .note.foo8
+ Type: SHT_NOTE
+ AddressAlign: 8
+ Notes:
+ - Name: ABCD
+ Type: NT_VERSION
+ Desc: 0102
+ - Type: NT_ARCH
+ Desc: 030405
+ - Name: GNU
+ Type: NT_GNU_BUILD_ID
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