[lld] [LLD][COFF] Sort base relocations (PR #121699)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-platform-windows

Author: Jacek Caban (cjacek)

<details>
<summary>Changes</summary>

This change ensures that base relocations are sorted in the output, aligning with MSVC linker behavior. While input files typically provide sorted relocations, this update guarantees correct sorting even if the input relocations are unordered.

---
Full diff: https://github.com/llvm/llvm-project/pull/121699.diff


2 Files Affected:

- (modified) lld/COFF/Writer.cpp (+2) 
- (added) lld/test/COFF/baserel-sort.yaml (+77) 


``````````diff
diff --git a/lld/COFF/Writer.cpp b/lld/COFF/Writer.cpp
index a5b2b6238db1a9..138112f109fd43 100644
--- a/lld/COFF/Writer.cpp
+++ b/lld/COFF/Writer.cpp
@@ -2560,6 +2560,8 @@ void Writer::addBaserelBlocks(std::vector<Baserel> &v) {
   const uint32_t mask = ~uint32_t(pageSize - 1);
   uint32_t page = v[0].rva & mask;
   size_t i = 0, j = 1;
+  llvm::sort(v,
+             [](const Baserel &x, const Baserel &y) { return x.rva < y.rva; });
   for (size_t e = v.size(); j < e; ++j) {
     uint32_t p = v[j].rva & mask;
     if (p == page)
diff --git a/lld/test/COFF/baserel-sort.yaml b/lld/test/COFF/baserel-sort.yaml
new file mode 100644
index 00000000000000..d5affe11b2189b
--- /dev/null
+++ b/lld/test/COFF/baserel-sort.yaml
@@ -0,0 +1,77 @@
+# Verify that lld-link outputs sorted base relocations, even if the input file has unsorted entries.
+
+# RUN: yaml2obj %s -o %t.obj
+# RUN: lld-link -dll -entry:sym -machine:amd64 -out:%t.dll %t.obj
+# RUN: llvm-readobj --coff-basereloc %t.dll | FileCheck %s
+
+# CHECK:      BaseReloc [
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2000
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2008
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Entry {
+# CHECK-NEXT:     Type: DIR64
+# CHECK-NEXT:     Address: 0x2010
+# CHECK-NEXT:   }
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: [  ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     C3
+    SizeOfRawData:   1
+  - Name:            .test
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    SectionData:     '000000000000000000000000000000000000000000000000'
+    SizeOfRawData:   24
+    Relocations:
+      - VirtualAddress:  16
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+      - VirtualAddress:  0
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+      - VirtualAddress:  8
+        SymbolName:      sym
+        Type:            IMAGE_REL_AMD64_ADDR64
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          1
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        40735498
+      Number:          1
+  - Name:            .test
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          24
+      NumberOfRelocations: 3
+      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
+...

``````````

</details>


https://github.com/llvm/llvm-project/pull/121699