[LLD][COFF] Use EC load config for ARM64X relocations in load config directory

This change ensures the load config in the hybrid image view is handled correctly.
It introduces a new Arm64XRelocVal class to abstract relocation values, allowing
them to be relative to a symbol. This class will also be useful for managing ARM64X
relocation offsets in the future.

Author: cjacek

lld/COFF/Chunks.cpp

@@ -1150,6 +1150,10 @@ uint32_t ImportThunkChunkARM64EC::extendRanges() {
   return sizeof(arm64Thunk) - sizeof(uint32_t);
 }
 
+uint64_t Arm64XRelocVal::get() const {
+  return (sym ? sym->getRVA() : 0) + value;
+}
+
 size_t Arm64XDynamicRelocEntry::getSize() const {
   switch (type) {
   case IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE:
@@ -1169,13 +1173,13 @@ void Arm64XDynamicRelocEntry::writeTo(uint8_t *buf) const {
     *out |= ((bit_width(size) - 1) << 14); // Encode the size.
     switch (size) {
     case 2:
-      out[1] = value;
+      out[1] = value.get();
       break;
     case 4:
-      *reinterpret_cast<ulittle32_t *>(out + 1) = value;
+      *reinterpret_cast<ulittle32_t *>(out + 1) = value.get();
       break;
     case 8:
-      *reinterpret_cast<ulittle64_t *>(out + 1) = value;
+      *reinterpret_cast<ulittle64_t *>(out + 1) = value.get();
       break;
     default:
       llvm_unreachable("invalid size");

lld/COFF/Chunks.h

@@ -835,18 +835,30 @@ class ECExportThunkChunk : public NonSectionCodeChunk {
   Defined *target;
 };
 
+// ARM64X relocation value, potentially relative to a symbol.
+class Arm64XRelocVal {
+public:
+  Arm64XRelocVal(int64_t value = 0) : value(value) {}
+  Arm64XRelocVal(Defined *sym, int32_t offset = 0) : sym(sym), value(offset) {}
+  uint64_t get() const;
+
+private:
+  Defined *sym = nullptr;
+  uint64_t value;
+};
+
 // ARM64X entry for dynamic relocations.
 class Arm64XDynamicRelocEntry {
 public:
   Arm64XDynamicRelocEntry(llvm::COFF::Arm64XFixupType type, uint8_t size,
-                          uint32_t offset, uint64_t value)
+                          uint32_t offset, Arm64XRelocVal value)
       : offset(offset), value(value), type(type), size(size) {}
 
   size_t getSize() const;
   void writeTo(uint8_t *buf) const;
 
   uint32_t offset;
-  uint64_t value;
+  Arm64XRelocVal value;
 
 private:
   llvm::COFF::Arm64XFixupType type;
@@ -862,7 +874,7 @@ class DynamicRelocsChunk : public NonSectionChunk {
   void finalize();
 
   void add(llvm::COFF::Arm64XFixupType type, uint8_t size, uint32_t offset,
-           uint64_t value) {
+           Arm64XRelocVal value) {
     arm64xRelocs.emplace_back(type, size, offset, value);
   }
 

lld/COFF/Writer.cpp

@@ -2582,18 +2582,17 @@ void Writer::createDynamicRelocs() {
                          coffHeaderOffset + offsetof(coff_file_header, Machine),
                          AMD64);
 
-  // Clear the load config directory.
-  // FIXME: Use the hybrid load config value instead.
+  // Set the hybrid load config to the EC load config.
   ctx.dynamicRelocs->add(IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE, sizeof(uint32_t),
                          dataDirOffset64 +
                              LOAD_CONFIG_TABLE * sizeof(data_directory) +
                              offsetof(data_directory, RelativeVirtualAddress),
-                         0);
+                         ctx.hybridSymtab->loadConfigSym);
   ctx.dynamicRelocs->add(IMAGE_DVRT_ARM64X_FIXUP_TYPE_VALUE, sizeof(uint32_t),
                          dataDirOffset64 +
                              LOAD_CONFIG_TABLE * sizeof(data_directory) +
                              offsetof(data_directory, Size),
-                         0);
+                         ctx.hybridSymtab->loadConfigSize);
 }
 
 PartialSection *Writer::createPartialSection(StringRef name,

lld/test/COFF/arm64x-loadconfig.s

@@ -87,20 +87,49 @@
 // LOADCFG-NEXT:       RVA: 0x150
 // LOADCFG-NEXT:       Type: VALUE
 // LOADCFG-NEXT:       Size: 0x4
-// LOADCFG-NEXT:       Value: 0x0
+// LOADCFG-NEXT:       Value: 0x1140
 // LOADCFG-NEXT:     ]
 // LOADCFG-NEXT:     Entry [
 // LOADCFG-NEXT:       RVA: 0x154
 // LOADCFG-NEXT:       Type: VALUE
 // LOADCFG-NEXT:       Size: 0x4
-// LOADCFG-NEXT:       Value: 0x0
+// LOADCFG-NEXT:       Value: 0x140
 // LOADCFG-NEXT:     ]
 // LOADCFG-NEXT:   ]
 // LOADCFG-NEXT: ]
 // LOADCFG-NEXT: HybridObject {
-// LOADCFG-NEXT:   Format: COFF-x86-64
-// LOADCFG-NEXT:   Arch: x86_64
+// LOADCFG-NEXT:   Format: COFF-ARM64EC
+// LOADCFG-NEXT:   Arch: aarch64
 // LOADCFG-NEXT:   AddressSize: 64bit
+// LOADCFG-NEXT:   LoadConfig [
+// LOADCFG-NEXT:     Size:   0x140
+// LOADCFG:        CHPEMetadata [
+// LOADCFG-NEXT:     Version:   0x2
+// LOADCFG:        ]
+// LOADCFG-NEXT:   DynamicRelocations [
+// LOADCFG-NEXT:     Version: 0x1
+// LOADCFG-NEXT:     Arm64X [
+// LOADCFG-NEXT:       Entry [
+// LOADCFG-NEXT:         RVA: 0x7C
+// LOADCFG-NEXT:         Type: VALUE
+// LOADCFG-NEXT:         Size: 0x2
+// LOADCFG-NEXT:         Value: 0x8664
+// LOADCFG-NEXT:       ]
+// LOADCFG-NEXT:       Entry [
+// LOADCFG-NEXT:         RVA: 0x150
+// LOADCFG-NEXT:         Type: VALUE
+// LOADCFG-NEXT:         Size: 0x4
+// LOADCFG-NEXT:         Value: 0x1140
+// LOADCFG-NEXT:       ]
+// LOADCFG-NEXT:       Entry [
+// LOADCFG-NEXT:         RVA: 0x154
+// LOADCFG-NEXT:         Type: VALUE
+// LOADCFG-NEXT:         Size: 0x4
+// LOADCFG-NEXT:         Value: 0x140
+// LOADCFG-NEXT:       ]
+// LOADCFG-NEXT:     ]
+// LOADCFG-NEXT:   ]
+// LOADCFG-NEXT: }
 
 // RUN: llvm-readobj --coff-basereloc out-hyb.dll | FileCheck --check-prefix=BASERELOC %s
 // BASERELOC:      BaseReloc [