[lld] [LLD] [COFF] Set the right alignment for DelayDirectoryChunk (PR #84697)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-coff

Author: Martin Storsjö (mstorsjo)

<details>
<summary>Changes</summary>

This makes a difference when linking executables with delay loaded libraries for arm32; the delay loader implementation can load data from the registry with instructions that assume alignment.

This issue does not show up when linking in MinGW mode, because a PseudoRelocTableChunk gets injected, which also sets alignment, even if the chunk itself is empty.

---
Full diff: https://github.com/llvm/llvm-project/pull/84697.diff


2 Files Affected:

- (modified) lld/COFF/DLL.cpp (+1-1) 
- (modified) lld/test/COFF/delayimports-armnt.yaml (+19-6) 


``````````diff
diff --git a/lld/COFF/DLL.cpp b/lld/COFF/DLL.cpp
index d0b74ac445499a..5f00eaded76d3a 100644
--- a/lld/COFF/DLL.cpp
+++ b/lld/COFF/DLL.cpp
@@ -172,7 +172,7 @@ binImports(COFFLinkerContext &ctx,
 // A chunk for the delay import descriptor table etnry.
 class DelayDirectoryChunk : public NonSectionChunk {
 public:
-  explicit DelayDirectoryChunk(Chunk *n) : dllName(n) {}
+  explicit DelayDirectoryChunk(Chunk *n) : dllName(n) { setAlignment(4); }
 
   size_t getSize() const override {
     return sizeof(delay_import_directory_table_entry);
diff --git a/lld/test/COFF/delayimports-armnt.yaml b/lld/test/COFF/delayimports-armnt.yaml
index 7d9bc38c5c3606..ea96d864ef53d5 100644
--- a/lld/test/COFF/delayimports-armnt.yaml
+++ b/lld/test/COFF/delayimports-armnt.yaml
@@ -6,6 +6,7 @@
 # RUN: llvm-readobj --coff-imports %t.exe | FileCheck -check-prefix=IMPORT %s
 # RUN: llvm-readobj --coff-basereloc %t.exe | FileCheck -check-prefix=BASEREL %s
 # RUN: llvm-objdump --no-print-imm-hex -d %t.exe | FileCheck --check-prefix=DISASM %s
+# RUN: llvm-readobj --file-headers %t.exe | FileCheck -check-prefix=DIR %s
 
 # IMPORT:      Format: COFF-ARM
 # IMPORT-NEXT: Arch: thumb
@@ -13,9 +14,9 @@
 # IMPORT-NEXT: DelayImport {
 # IMPORT-NEXT:   Name: library.dll
 # IMPORT-NEXT:   Attributes: 0x1
-# IMPORT-NEXT:   ModuleHandle: 0x3000
-# IMPORT-NEXT:   ImportAddressTable: 0x3008
-# IMPORT-NEXT:   ImportNameTable: 0x2040
+# IMPORT-NEXT:   ModuleHandle: 0x3008
+# IMPORT-NEXT:   ImportAddressTable: 0x3010
+# IMPORT-NEXT:   ImportNameTable: 0x2044
 # IMPORT-NEXT:   BoundDelayImportTable: 0x0
 # IMPORT-NEXT:   UnloadDelayImportTable: 0x0
 # IMPORT-NEXT:   Import {
@@ -43,7 +44,7 @@
 # BASEREL-NEXT:   }
 # BASEREL-NEXT:   Entry {
 # BASEREL-NEXT:     Type: HIGHLOW
-# BASEREL-NEXT:     Address: 0x3008
+# BASEREL-NEXT:     Address: 0x3010
 # BASEREL-NEXT:   }
 # BASEREL-NEXT:   Entry {
 # BASEREL-NEXT:     Type: ABSOLUTE
@@ -52,20 +53,24 @@
 # BASEREL-NEXT: ]
 #
 # DISASM:    00401000 <.text>:
-# DISASM:      40100c:       f243 0c08       movw r12, #12296
+# DISASM:      40100c:       f243 0c10       movw r12, #12304
 # DISASM-NEXT:               f2c0 0c40       movt    r12, #64
 # DISASM-NEXT:               f000 b800       b.w     {{.+}} @ imm = #0
 # DISASM-NEXT:               e92d 480f       push.w  {r0, r1, r2, r3, r11, lr}
 # DISASM-NEXT:               f20d 0b10       addw    r11, sp, #16
 # DISASM-NEXT:               ed2d 0b10       vpush   {d0, d1, d2, d3, d4, d5, d6, d7}
 # DISASM-NEXT:               4661            mov     r1, r12
-# DISASM-NEXT:               f242 0000       movw r0, #8192
+# DISASM-NEXT:               f242 0004       movw r0, #8196
 # DISASM-NEXT:               f2c0 0040       movt    r0, #64
 # DISASM-NEXT:               f7ff ffe7       bl      0x401000 <.text>
 # DISASM-NEXT:               4684            mov     r12, r0
 # DISASM-NEXT:               ecbd 0b10       vpop    {d0, d1, d2, d3, d4, d5, d6, d7}
 # DISASM-NEXT:               e8bd 480f       pop.w   {r0, r1, r2, r3, r11, lr}
 # DISASM-NEXT:               4760            bx      r12
+#
+# DIR:         DelayImportDescriptorRVA: 0x2004
+# DIR-NEXT:    DelayImportDescriptorSize: 0x40
+
 
 --- !COFF
 header:
@@ -80,6 +85,14 @@ sections:
       - VirtualAddress:  0
         SymbolName:      __imp_function
         Type:            IMAGE_REL_ARM_MOV32T
+  - Name:            .rdata
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ ]
+    Alignment:       1
+    SectionData:     01
+  - Name:            .data
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE ]
+    Alignment:       1
+    SectionData:     02
 symbols:
   - Name:            .text
     Value:           0

``````````

</details>


https://github.com/llvm/llvm-project/pull/84697