[elf2] Correctly handle sections with an alignment of 0. Spec says to treat it as an alignment of 1.

llvm-svn: 246901

lld/ELF/Chunks.h

@@ -42,7 +42,11 @@ public:
 
   // The writer sets and uses the addresses.
   uintX_t getOutputSectionOff() const { return OutputSectionOff; }
-  uintX_t getAlign() { return Header->sh_addralign; }
+  uintX_t getAlign() {
+    // The ELF spec states that a value of 0 means the section has no alignment
+    // constraits.
+    return std::max<uintX_t>(Header->sh_addralign, 1);
+  }
   void setOutputSectionOff(uint64_t V) { OutputSectionOff = V; }
 
   void setOutputSection(OutputSection<ELFT> *O) { Out = O; }

lld/ELF/Writer.cpp

@@ -63,7 +63,11 @@ public:
   void setSize(uintX_t Val) { Header.sh_size = Val; }
   uintX_t getFlags() { return Header.sh_flags; }
   uintX_t getFileOff() { return Header.sh_offset; }
-  uintX_t getAlign() { return Header.sh_addralign; }
+  uintX_t getAlign() {
+    // The ELF spec states that a value of 0 means the section has no alignment
+    // constraits.
+    return std::max<uintX_t>(Header.sh_addralign, 1);
+  }
   uint32_t getType() { return Header.sh_type; }
 
   virtual void finalize() {}

lld/test/elf2/section-align-0.test

@@ -0,0 +1,19 @@
+# RUN: yaml2obj -format elf %s -o %t
+# RUN: lld -flavor gnu2 %t -o %tout
+
+# Verify that lld can handle sections with an alignment of zero.
+
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    AddressAlign:    0
+
+Symbols:
+  Global:
+    - Name:            _start
+      Section:         .text