[ARM] Add needed symbols during dynamic executable linking

These include _GLOBAL_OFFSET_TABLE_ and _DYNAMIC.

llvm-svn: 237791

2 files changed, 74 insertions, 0 deletions

diff --git a/lld/lib/ReaderWriter/ELF/ARM/ARMExecutableWriter.h b/lld/lib/ReaderWriter/ELF/ARM/ARMExecutableWriter.h
index bed4e9e78d2..50d4754885d 100644
--- a/lld/lib/ReaderWriter/ELF/ARM/ARMExecutableWriter.h
+++ b/lld/lib/ReaderWriter/ELF/ARM/ARMExecutableWriter.h
@@ -17,6 +17,7 @@
 
 namespace {
 const char *gotSymbol = "_GLOBAL_OFFSET_TABLE_";
+const char *dynamicSymbol = "_DYNAMIC";
 }
 
 namespace lld {
@@ -53,6 +54,13 @@ ARMExecutableWriter::ARMExecutableWriter(ARMLinkingContext &ctx,
 void ARMExecutableWriter::createImplicitFiles(
     std::vector<std::unique_ptr<File>> &result) {
   ExecutableWriter::createImplicitFiles(result);
+  // Add default atoms for ARM.
+  if (_ctx.isDynamic()) {
+    auto file = llvm::make_unique<RuntimeFile<ELF32LE>>(_ctx, "ARM exec file");
+    file->addAbsoluteAtom(gotSymbol);
+    file->addAbsoluteAtom(dynamicSymbol);
+    result.push_back(std::move(file));
+  }
 }
 
 void ARMExecutableWriter::finalizeDefaultAtomValues() {
@@ -68,6 +76,13 @@ void ARMExecutableWriter::finalizeDefaultAtomValues() {
       gotAtom->_virtualAddr = 0;
   }
 
+  if (auto *dynamicAtom = _armLayout.findAbsoluteAtom(dynamicSymbol)) {
+    if (auto dynamicSection = _armLayout.findOutputSection(".dynamic"))
+      dynamicAtom->_virtualAddr = dynamicSection->virtualAddr();
+    else
+      dynamicAtom->_virtualAddr = 0;
+  }
+
   // Set required by gcc libc __ehdr_start symbol with pointer to ELF header
   if (auto ehdr = _armLayout.findAbsoluteAtom("__ehdr_start"))
     ehdr->_virtualAddr = _elfHeader->virtualAddr();
diff --git a/lld/test/elf/ARM/dynamic-symbols.test b/lld/test/elf/ARM/dynamic-symbols.test
new file mode 100644
index 00000000000..82039c274ac
--- /dev/null
+++ b/lld/test/elf/ARM/dynamic-symbols.test
@@ -0,0 +1,59 @@
+# Check that proper dynamic symbols are present in the generated executable
+
+# RUN: yaml2obj -format=elf %s > %t-o.o
+# RUN: lld -flavor gnu -target arm-linux-gnu \
+# RUN: -Bstatic --noinhibit-exec %t-o.o -o %t
+# RUN: llvm-readobj -symbols %t | FileCheck -check-prefix=STATIC %s
+
+# STATIC-NOT:   Name: _GLOBAL_OFFSET_TABLE_
+# STATIC-NOT:   Name: _DYNAMIC
+
+# RUN: yaml2obj -format=elf %s > %t-o.o
+# RUN: lld -flavor gnu -target arm-linux-gnu \
+# RUN: --noinhibit-exec %t-o.o -o %t
+# RUN: llvm-readobj -symbols %t | FileCheck -check-prefix=EXEC-DYN %s
+
+# EXEC-DYN:   Name: _GLOBAL_OFFSET_TABLE_
+# EXEC-DYN-NEXT:   Value: {{[0-9]+}}
+# EXEC-DYN-NEXT:   Size: 0
+# EXEC-DYN-NEXT:   Binding: Global (0x1)
+# EXEC-DYN-NEXT:   Type: Object (0x1)
+# EXEC-DYN-NEXT:   Other: 0
+# EXEC-DYN-NEXT:   Section: Absolute (0xFFF1)
+# EXEC-DYN:   Name: _DYNAMIC
+# EXEC-DYN-NEXT:   Value: {{[0-9]+}}
+# EXEC-DYN-NEXT:   Size: 0
+# EXEC-DYN-NEXT:   Binding: Global (0x1)
+# EXEC-DYN-NEXT:   Type: Object (0x1)
+# EXEC-DYN-NEXT:   Other: 0
+# EXEC-DYN-NEXT:   Section: Absolute (0xFFF1)
+
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_ARM
+  Flags:           [ EF_ARM_EABI_VER5 ]
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000004
+    Content:         04B02DE500B08DE20030A0E30300A0E100D04BE204B09DE41EFF2FE1
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000001
+    Content:         ''
+  - Name:            .bss
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000001
+    Content:         ''
+Symbols:
+  Global:
+    - Name:            main
+      Type:            STT_FUNC
+      Section:         .text
+...