[llvm] [Object][COFF] Introduce the .llvm.arm64x section (PR #205156)
Jacek Caban via llvm-commits
llvm-commits at lists.llvm.org
Mon Jun 29 13:53:24 PDT 2026
https://github.com/cjacek updated https://github.com/llvm/llvm-project/pull/205156
>From 7566157f38e908eb6185895e4850485a382bfb28 Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Fri, 22 May 2026 22:39:11 +0200
Subject: [PATCH] [Object][COFF] Introduce the .obj.arm64ec section
Introduce a new extension section allowing the embedding of ARM64EC
object files inside native ARM64 object files. Its content consists
of an entire, valid ARM64EC COFF object file.
---
llvm/include/llvm/Object/COFF.h | 3 +
llvm/lib/Object/COFFObjectFile.cpp | 20 ++++
.../llvm-readobj/COFF/arm64x-hybridobj.yaml | 102 ++++++++++++++++++
llvm/tools/llvm-readobj/llvm-readobj.cpp | 11 +-
4 files changed, 133 insertions(+), 3 deletions(-)
create mode 100644 llvm/test/tools/llvm-readobj/COFF/arm64x-hybridobj.yaml
diff --git a/llvm/include/llvm/Object/COFF.h b/llvm/include/llvm/Object/COFF.h
index ed2addbc69487..dea922553ca3d 100644
--- a/llvm/include/llvm/Object/COFF.h
+++ b/llvm/include/llvm/Object/COFF.h
@@ -877,6 +877,8 @@ struct coff_dynamic_relocation64_v2 {
support::ulittle32_t Flags;
};
+static constexpr StringLiteral kArm64ECSectionName = ".obj.arm64ec";
+
class LLVM_ABI COFFObjectFile : public ObjectFile {
private:
COFFObjectFile(MemoryBufferRef Object);
@@ -1100,6 +1102,7 @@ class LLVM_ABI COFFObjectFile : public ObjectFile {
return SubtargetFeatures();
}
std::unique_ptr<MemoryBuffer> getHybridObjectView() const;
+ std::optional<MemoryBufferRef> findHybridObjectSection() const;
import_directory_iterator import_directory_begin() const;
import_directory_iterator import_directory_end() const;
diff --git a/llvm/lib/Object/COFFObjectFile.cpp b/llvm/lib/Object/COFFObjectFile.cpp
index 14a2343811a38..5cf10b6e95ab7 100644
--- a/llvm/lib/Object/COFFObjectFile.cpp
+++ b/llvm/lib/Object/COFFObjectFile.cpp
@@ -1560,6 +1560,26 @@ std::unique_ptr<MemoryBuffer> COFFObjectFile::getHybridObjectView() const {
return HybridView;
}
+std::optional<MemoryBufferRef> COFFObjectFile::findHybridObjectSection() const {
+ if (getDOSHeader() || getMachine() != COFF::IMAGE_FILE_MACHINE_ARM64)
+ return std::nullopt;
+
+ // Search for the .obj.arm64ec section, which may be used to embed a full
+ // ARM64EC object file into an ARM64 object file.
+ for (SectionRef S : sections()) {
+ Expected<StringRef> Name = S.getName();
+ if (errorToBool(Name.takeError()) || *Name != kArm64ECSectionName)
+ continue;
+
+ Expected<StringRef> ContentsOrErr = S.getContents();
+ if (errorToBool(ContentsOrErr.takeError()) || ContentsOrErr->empty())
+ continue;
+ return MemoryBufferRef(*ContentsOrErr, getFileName());
+ }
+
+ return std::nullopt;
+}
+
bool ImportDirectoryEntryRef::
operator==(const ImportDirectoryEntryRef &Other) const {
return ImportTable == Other.ImportTable && Index == Other.Index;
diff --git a/llvm/test/tools/llvm-readobj/COFF/arm64x-hybridobj.yaml b/llvm/test/tools/llvm-readobj/COFF/arm64x-hybridobj.yaml
new file mode 100644
index 0000000000000..a63b56e679b82
--- /dev/null
+++ b/llvm/test/tools/llvm-readobj/COFF/arm64x-hybridobj.yaml
@@ -0,0 +1,102 @@
+# RUN: yaml2obj -DMACHINE=IMAGE_FILE_MACHINE_ARM64 %s -o %t-aarch64.o
+# RUN: yaml2obj -DMACHINE=IMAGE_FILE_MACHINE_ARM64EC %s -o %t-arm64ec.o
+# RUN: llvm-objcopy --add-section=.obj.arm64ec=%t-arm64ec.o --set-section-flags=.obj.arm64ec=debug %t-aarch64.o %t.o
+# RUN: llvm-readobj --sections %t.o | FileCheck %s
+
+# CHECK: Format: COFF-ARM64
+# CHECK-NEXT: Arch: aarch64
+# CHECK-NEXT: AddressSize: 64bit
+# CHECK-NEXT: Sections [
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 1
+# CHECK-NEXT: Name: .data (2E 64 61 74 61 00 00 00)
+# CHECK-NEXT: VirtualSize: 0x0
+# CHECK-NEXT: VirtualAddress: 0x0
+# CHECK-NEXT: RawDataSize: 4
+# CHECK-NEXT: PointerToRawData: 0x64
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0xC0300040)
+# CHECK-NEXT: IMAGE_SCN_ALIGN_4BYTES (0x300000)
+# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_WRITE (0x80000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 2
+# CHECK-NEXT: Name: .obj.arm64ec (2F 34 00 00 00 00 00 00)
+# CHECK-NEXT: VirtualSize: 0x7A
+# CHECK-NEXT: VirtualAddress: 0x0
+# CHECK-NEXT: RawDataSize: 122
+# CHECK-NEXT: PointerToRawData: 0x68
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0xC2000040)
+# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
+# CHECK-NEXT: IMAGE_SCN_MEM_DISCARDABLE (0x2000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_WRITE (0x80000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: ]
+# CHECK-NEXT: HybridObject {
+# CHECK: Format: COFF-ARM64EC
+# CHECK-NEXT: Arch: aarch64
+# CHECK-NEXT: AddressSize: 64bit
+# CHECK-NEXT: Sections [
+# CHECK-NEXT: Section {
+# CHECK-NEXT: Number: 1
+# CHECK-NEXT: Name: .data (2E 64 61 74 61 00 00 00)
+# CHECK-NEXT: VirtualSize: 0x0
+# CHECK-NEXT: VirtualAddress: 0x0
+# CHECK-NEXT: RawDataSize: 4
+# CHECK-NEXT: PointerToRawData: 0x3C
+# CHECK-NEXT: PointerToRelocations: 0x0
+# CHECK-NEXT: PointerToLineNumbers: 0x0
+# CHECK-NEXT: RelocationCount: 0
+# CHECK-NEXT: LineNumberCount: 0
+# CHECK-NEXT: Characteristics [ (0xC0300040)
+# CHECK-NEXT: IMAGE_SCN_ALIGN_4BYTES (0x300000)
+# CHECK-NEXT: IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
+# CHECK-NEXT: IMAGE_SCN_MEM_READ (0x40000000)
+# CHECK-NEXT: IMAGE_SCN_MEM_WRITE (0x80000000)
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+# CHECK-NEXT: ]
+# CHECK-NEXT: }
+
+--- !COFF
+header:
+ Machine: [[MACHINE]]
+ Characteristics: [ ]
+sections:
+ - Name: .data
+ Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+ Alignment: 4
+ SectionData: '00000000'
+ SizeOfRawData: 4
+symbols:
+ - Name: .data
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_STATIC
+ SectionDefinition:
+ Length: 4
+ NumberOfRelocations: 0
+ NumberOfLinenumbers: 0
+ CheckSum: 0
+ Number: 2
+ - Name: sym
+ Value: 0
+ SectionNumber: 1
+ SimpleType: IMAGE_SYM_TYPE_NULL
+ ComplexType: IMAGE_SYM_DTYPE_NULL
+ StorageClass: IMAGE_SYM_CLASS_EXTERNAL
+...
diff --git a/llvm/tools/llvm-readobj/llvm-readobj.cpp b/llvm/tools/llvm-readobj/llvm-readobj.cpp
index 9d6522f87f936..146855b78c4fc 100644
--- a/llvm/tools/llvm-readobj/llvm-readobj.cpp
+++ b/llvm/tools/llvm-readobj/llvm-readobj.cpp
@@ -605,11 +605,16 @@ static void dumpCOFFObject(COFFObjectFile *Obj, ScopedPrinter &Writer) {
dumpObject(*Obj, Writer);
// Dump a hybrid object when available.
- std::unique_ptr<MemoryBuffer> HybridView = Obj->getHybridObjectView();
- if (!HybridView)
+ MemoryBufferRef HybridView;
+ std::unique_ptr<MemoryBuffer> HybridViewBuf;
+ if (std::optional<MemoryBufferRef> HybridSec = Obj->findHybridObjectSection())
+ HybridView = *HybridSec;
+ else if ((HybridViewBuf = Obj->getHybridObjectView()))
+ HybridView = HybridViewBuf->getMemBufferRef();
+ else
return;
Expected<std::unique_ptr<COFFObjectFile>> HybridObjOrErr =
- COFFObjectFile::create(*HybridView);
+ COFFObjectFile::create(HybridView);
if (!HybridObjOrErr)
reportError(HybridObjOrErr.takeError(), Obj->getFileName().str());
DictScope D(Writer, "HybridObject");
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