[lld] [LLD][COFF] Emit base relocation for native CHPE metadata pointer on ARM64X (PR #121500)

[Jacek Caban via llvm-commits]

https://github.com/cjacek created https://github.com/llvm/llvm-project/pull/121500

None

>From 8a369899dea44ed68b6c675644177d12f264b73a Mon Sep 17 00:00:00 2001
From: Jacek Caban <jacek at codeweavers.com>
Date: Mon, 9 Dec 2024 15:19:43 +0100
Subject: [PATCH] [LLD][COFF] Emit base relocation for native CHPE metadata
 pointer on ARM64X

---
 lld/COFF/Writer.cpp               | 32 +++++++++++++++++++++++++++++++
 lld/test/COFF/arm64x-loadconfig.s |  6 +++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index b3dd5f6cf49265..a0ab80f0bf2d16 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -2594,6 +2594,38 @@ void Writer::createDynamicRelocs() {
                              LOAD_CONFIG_TABLE * sizeof(data_directory) +
                              offsetof(data_directory, Size),
                          0);
+
+  // Insert a 64-bit relocation for CHPEMetadataPointer. Its value will be set
+  // later in prepareLoadConfig to match the value in the EC load config.
+  // However, a base relocation must be allocated in advance, so we handle it
+  // here.
+  if (ctx.symtab.loadConfigSym && ctx.hybridSymtab->loadConfigSym &&
+      ctx.symtab.loadConfigSize >=
+          offsetof(coff_load_configuration64, CHPEMetadataPointer) +
+              sizeof(coff_load_configuration64::CHPEMetadataPointer)) {
+    DefinedRegular *sym = ctx.symtab.loadConfigSym;
+    SectionChunk *chunk = sym->getChunk();
+    ArrayRef<coff_relocation> curRelocs = chunk->getRelocs();
+    MutableArrayRef<coff_relocation> newRelocs(
+        bAlloc().Allocate<coff_relocation>(curRelocs.size() + 1),
+        curRelocs.size() + 1);
+    size_t chpeOffset = sym->getValue() + offsetof(coff_load_configuration64,
+                                                   CHPEMetadataPointer);
+    size_t i;
+    for (i = 0;
+         i < curRelocs.size() && curRelocs[i].VirtualAddress < chpeOffset; ++i)
+      newRelocs[i] = curRelocs[i];
+    newRelocs[i].VirtualAddress = chpeOffset;
+    // The specific symbol used here is irrelevant as long as it's valid, since
+    // it will be overridden by prepareLoadConfig. Use the load config symbol
+    // itself.
+    newRelocs[i].SymbolTableIndex =
+        chunk->file->getCOFFObj()->getSymbolIndex(sym->getCOFFSymbol());
+    newRelocs[i].Type = IMAGE_REL_ARM64_ADDR64;
+    for (; i < curRelocs.size(); ++i)
+      newRelocs[i + 1] = curRelocs[i];
+    chunk->setRelocs(newRelocs);
+  }
 }
 
 PartialSection *Writer::createPartialSection(StringRef name,
diff --git a/lld/test/COFF/arm64x-loadconfig.s b/lld/test/COFF/arm64x-loadconfig.s
index d21f4bfe95b843..3b53d32a9b5492 100644
--- a/lld/test/COFF/arm64x-loadconfig.s
+++ b/lld/test/COFF/arm64x-loadconfig.s
@@ -118,10 +118,14 @@
 // BASERELOC:      BaseReloc [
 // BASERELOC-NEXT:   Entry {
 // BASERELOC-NEXT:     Type: DIR64
+// BASERELOC-NEXT:     Address: 0x10C8
+// BASERELOC-NEXT:   }
+// BASERELOC-NEXT:   Entry {
+// BASERELOC-NEXT:     Type: DIR64
 // BASERELOC-NEXT:     Address: 0x1208
 // BASERELOC-NEXT:   }
 // BASERELOC-NEXT:   Entry {
-// BASERELOC:          Type: DIR64
+// BASERELOC-NEXT:     Type: DIR64
 // BASERELOC-NEXT:     Address: 0x2074
 // BASERELOC-NEXT:   }