[LLD] [COFF] Add initial support for linking ARM64 binaries

[mstorsjo]

Summary

A plain empty entry point function that returns 0 seems to produce a binary that loads and runs fine in wine.

[ruiu]

Can you add a testcase?

This patch seems too simple to submit. Do you think you can improve it so that you can create an executable that does nothing but just exit with 0?

[mstorsjo]

Added a testcase, sorted the ARM64 declaration alphabetically.

The test case checks the pe32+ magic value, which llvm-readobj doesn't output (yet), but I'll send a separate patch for that.

[mstorsjo]

The testcase depends on D34836.

[mstorsjo]

Updated the test case to check for a hex printout.

[ruiu]

Are you able to create an executable that exits 0 using this patch?

[mstorsjo]

In D34833#795864, @ruiu wrote:

Are you able to create an executable that exits 0 using this patch?

Yes; the executable built by the test does that - tested in wine (which is the only arm64 windows environment I've got; prior to this patch it didn't work).

[ruiu]

test/COFF/arm64-magic.test

2

Rename this file arm64-magic.yaml and merge with Inputs/arm64-executable.obj.yaml.

[mstorsjo]

Merged the test files as suggested.

[ruiu]

Does this patch emits other headers correctly? See lld/test/COFF/hello32.test as an example for i386.

[mstorsjo]

In D34833#795887, @ruiu wrote:

Does this patch emits other headers correctly? See lld/test/COFF/hello32.test as an example for i386.

I think it's mostly right enough so far, although I haven't checked everything in detail yet - at least it seemed right enough for wine to run, and after fixing the is64 function, most of the critical flags seem to match the upstream microsoft arm64 exes I've got to compare to.

[ruiu]

But at least you want to make sure that these bits are updated for ARM64, right?

HEADER:      Format: COFF-i386
HEADER-NEXT: Arch: i386
HEADER-NEXT: AddressSize: 32bit
HEADER-NEXT: ImageFileHeader {
HEADER-NEXT:   Machine: IMAGE_FILE_MACHINE_I386 (0x14C)

[mstorsjo]

Added a few more trivial cases where the arm64 machine type is mapped, extended the test to check more flags. I've doublechecked the flags that the test checks with binaries from microsoft.

[mstorsjo]

Rui, is this version ok now?

[ruiu]

Yes, it LGTM. Thank you for doing this!

COFF/Config.h

 class DefinedAbsolute;
 class DefinedRelative;
 class StringChunk;
 struct Symbol;
 class SymbolBody;
 
 // Short aliases.
 static const auto AMD64 = llvm::COFF::IMAGE_FILE_MACHINE_AMD64;
+static const auto ARM64 = llvm::COFF::IMAGE_FILE_MACHINE_ARM64;
 static const auto ARMNT = llvm::COFF::IMAGE_FILE_MACHINE_ARMNT;
 static const auto I386 = llvm::COFF::IMAGE_FILE_MACHINE_I386;
 
 // Represents an /export option.
 struct Export {
   StringRef Name;       // N in /export:N or /export:E=N
   StringRef ExtName;    // E in /export:E=N
   SymbolBody *Sym = nullptr;
enum class DebugType {
   CV    = 0x1,  /// CodeView
   PData = 0x2,  /// Procedure Data
   Fixup = 0x4,  /// Relocation Table
 };
 
 // Global configuration.
 struct Configuration {
   enum ManifestKind { SideBySide, Embed, No };
-  bool is64() { return Machine == AMD64; }
+  bool is64() { return Machine == AMD64 || Machine == ARM64; }
 
   llvm::COFF::MachineTypes Machine = IMAGE_FILE_MACHINE_UNKNOWN;
   bool Verbose = false;
   WindowsSubsystem Subsystem = llvm::COFF::IMAGE_SUBSYSTEM_UNKNOWN;
   SymbolBody *Entry = nullptr;
   bool NoEntry = false;
   std::string OutputFile;
   bool ColorDiagnostics;

test/COFF/Inputs/arm64-executable.obj.yaml

+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_ARM64
+  Characteristics: []
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_PURGEABLE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     'e0031f2ac0035fd6'
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          8
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          1
+  - Name:            mainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...

test/COFF/arm64-magic.test

+# RUN: yaml2obj < %p/Inputs/arm64-executable.obj.yaml > %t.obj
+# RUN: lld-link /out:%t.exe /entry:mainCRTStartup /subsystem:console %t.obj
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck %s
+
+CHECK: Magic: 523