[ELF] Fix creation of segments.

Linker was creating a separate output segment in some cases if input sections had huge alignments. This patch fixes the issue. llvm-svn: 222974
2014-11-30 04:01:14 +00:00 · 2014-11-30 04:01:14 +00:00 · 25c33d60c2
parent aa00539aa5
commit 25c33d60c2
4 changed files with 206 additions and 5 deletions
--- a/lld/lib/ReaderWriter/ELF/SegmentChunks.h
+++ b/lld/lib/ReaderWriter/ELF/SegmentChunks.h
@ -406,6 +406,8 @@ void Segment<ELFT>::assignFileOffsets(uint64_t startOffset) {
  for (auto &slice : slices()) {
    bool isFirstSection = true;
    for (auto section : slice->sections()) {
+      // Align fileoffset to the alignment of the section.
+      fileOffset = llvm::RoundUpToAlignment(fileOffset, section->align2());
      // If the linker outputmagic is set to OutputMagic::NMAGIC, align the Data
      // to a page boundary
      if (isFirstSection &&
@ -430,8 +432,7 @@ void Segment<ELFT>::assignFileOffsets(uint64_t startOffset) {
        fileOffset =
            llvm::RoundUpToAlignment(fileOffset, this->_context.getPageSize());
        isDataPageAlignedForNMagic = true;
-      } else
-        fileOffset = llvm::RoundUpToAlignment(fileOffset, section->align2());
+      }
      if (isFirstSection) {
        slice->setFileOffset(fileOffset);
        isFirstSection = false;
@ -467,6 +468,7 @@ template <class ELFT> void Segment<ELFT>::assignVirtualAddress(uint64_t addr) {
  SegmentSlice<ELFT> *slice = nullptr;
  uint64_t tlsStartAddr = 0;
  bool alignSegments = this->_context.alignSegments();
+  StringRef prevOutputSectionName;

  for (auto si = _sections.begin(); si != _sections.end(); ++si) {
    // If this is first section in the segment, page align the section start
@ -522,9 +524,18 @@ template <class ELFT> void Segment<ELFT>::assignVirtualAddress(uint64_t addr) {
        isDataPageAlignedForNMagic = true;
      }
      uint64_t newAddr = llvm::RoundUpToAlignment(curAddr, (*si)->align2());
+      Section<ELFT> *sec = dyn_cast<Section<ELFT>>(*si);
+      StringRef curOutputSectionName =
+          sec ? sec->outputSectionName() : (*si)->name();
+      bool autoCreateSlice = true;
+      if (curOutputSectionName == prevOutputSectionName)
+        autoCreateSlice = false;
      // If the newAddress computed is more than a page away, let's create
      // a separate segment, so that memory is not used up while running.
-      if (((newAddr - curAddr) > this->_context.getPageSize()) &&
+      // Dont create a slice, if the new section falls in the same output
+      // section as the previous section.
+      if (autoCreateSlice &&
+          ((newAddr - curAddr) > this->_context.getPageSize()) &&
          (_outputMagic != ELFLinkingContext::OutputMagic::NMAGIC &&
           _outputMagic != ELFLinkingContext::OutputMagic::OMAGIC)) {
        auto sliceIter =
@ -577,6 +588,7 @@ template <class ELFT> void Segment<ELFT>::assignVirtualAddress(uint64_t addr) {
        else
          curSliceSize = newAddr - curSliceAddress;
      }
+      prevOutputSectionName = curOutputSectionName;
    }
    currSection++;
  }
--- a/lld/test/elf/X86_64/alignoffset.test
+++ b/lld/test/elf/X86_64/alignoffset.test
@ -7,7 +7,7 @@
 # RUN: --no-align-segments --rosegment --noinhibit-exec
 # RUN: llvm-readobj -program-headers %t.exe | FileCheck %s
 #
-#CHECK:    Offset: 0x115C
+#CHECK:    Offset: 0x15C
 #CHECK:    VirtualAddress: 0x40015C
 #CHECK:    PhysicalAddress: 0x40015C
 #
--- a/lld/test/elf/X86_64/outputsegments.test
+++ b/lld/test/elf/X86_64/outputsegments.test
@ -0,0 +1,189 @@
+# Tests that lld doesnot create separate segment if the input sections are part
+# of the same output section
+
+# Build executable
+# RUN: yaml2obj -format=elf -docnum 1 %s -o %t.o
+# RUN: lld -flavor gnu -target x86_64 %t.o -o %t1.exe -static \
+# RUN: --no-align-segments --noinhibit-exec
+# RUN: lld -flavor gnu -target x86_64 %t.o -o %t2.exe -static \
+# RUN: --noinhibit-exec
+# RUN: llvm-readobj -program-headers %t1.exe | FileCheck %s -check-prefix=SEGMENTS
+# RUN: llvm-readobj -program-headers %t2.exe | FileCheck %s -check-prefix=SEGMENTS
+#
+#SEGMENTS:    VirtualAddress: 0x400000
+#SEGMENTS:    PhysicalAddress: 0x400000
+#SEGMENTS:    FileSize: 288
+#SEGMENTS:    MemSize: 288
+#SEGMENTS:    VirtualAddress: 0x404000
+#SEGMENTS:    PhysicalAddress: 0x404000
+#SEGMENTS:    FileSize: 16608
+#SEGMENTS:    MemSize: 16608
+#SEGMENTS:    Alignment: 16384
+#
+# object
+---
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  OSABI:           ELFOSABI_GNU
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+  - Name:            .bss
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+  - Name:            .text.foo
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000002000
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+  - Name:            .rela.text.foo
+    Type:            SHT_RELA
+    Link:            .symtab
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+        Type:            R_X86_64_64
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+        Symbol:          printf
+        Type:            R_X86_64_PC32
+        Addend:          -4
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+    AddressAlign:    0x0000000000004000
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+...
--- a/lld/test/elf/phdr.test
+++ b/lld/test/elf/phdr.test
@ -59,7 +59,7 @@ I386-NEXT:     Alignment: 4096
 I386-NEXT:   }
 I386-NEXT:   ProgramHeader {
 I386-NEXT:     Type: PT_LOAD (0x1)
-I386-NEXT:     Offset: 0x2000
+I386-NEXT:     Offset: 0x4000
 I386-NEXT:     VirtualAddress: 0x4000
 I386-NEXT:     PhysicalAddress: 0x4000
 I386-NEXT:     FileSize: 4