[elf2] Assign output sections to PHDRs.

This is a minimal implementation to produce legal output. Future patches will combine multiple compatible PT_LOADs. llvm-svn: 247185
2015-09-09 20:48:09 +00:00 · 2015-09-09 20:48:09 +00:00 · 1d299a8a9d
parent 0dde00d239
commit 1d299a8a9d
7 changed files with 96 additions and 62 deletions
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@ -250,8 +250,9 @@ private:
  unsigned getNumSections() const { return OutputSections.size() + 1; }

  uintX_t FileSize;
-  uintX_t SizeOfHeaders;
+  uintX_t ProgramHeaderOff;
  uintX_t SectionHeaderOff;
+  unsigned NumPhdrs;

  StringTableSection<ELFT::Is64Bits> StrTabSec;
  StringTableSection<ELFT::Is64Bits> DynStrSec;
@ -578,17 +579,34 @@ template <class ELFT> void Writer<ELFT>::createSections() {
    OutputSections[I]->setSectionIndex(I + 1);
 }

+template <class ELFT>
+static bool outputSectionHasPHDR(OutputSectionBase<ELFT::Is64Bits> *Sec) {
+  return (Sec->getSize() != 0) && (Sec->getFlags() & SHF_ALLOC);
+}
+
 // Visits all sections to assign incremental, non-overlapping RVAs and
 // file offsets.
 template <class ELFT> void Writer<ELFT>::assignAddresses() {
-  SizeOfHeaders = RoundUpToAlignment(sizeof(Elf_Ehdr), PageSize);
  uintX_t VA = 0x1000; // The first page is kept unmapped.
-  uintX_t FileOff = SizeOfHeaders;
+  uintX_t FileOff = sizeof(Elf_Ehdr);

+  // Reserve space for PHDRs.
+  ProgramHeaderOff = FileOff;
+  FileOff = RoundUpToAlignment(FileOff, PageSize);
+
+  NumPhdrs = 0;
  for (OutputSectionBase<ELFT::Is64Bits> *Sec : OutputSections) {
    StrTabSec.add(Sec->getName());
    Sec->finalize();

+    // Since each output section gets its own PHDR, align each output section to
+    // a page.
+    if (outputSectionHasPHDR<ELFT>(Sec)) {
+      ++NumPhdrs;
+      VA = RoundUpToAlignment(VA, PageSize);
+      FileOff = RoundUpToAlignment(FileOff, PageSize);
+    }
+
    uintX_t Align = Sec->getAlign();
    uintX_t Size = Sec->getSize();
    if (Sec->getFlags() & SHF_ALLOC) {
@ -600,15 +618,19 @@ template <class ELFT> void Writer<ELFT>::assignAddresses() {
      FileOff += RoundUpToAlignment(Size, Align);
  }

+  // Add a PHDR for the dynamic table.
+  if (!SymTable.getSymTable().getSharedFiles().empty())
+    ++NumPhdrs;
+
  FileOff += OffsetToAlignment(FileOff, ELFT::Is64Bits ? 8 : 4);

  // Add space for section headers.
  SectionHeaderOff = FileOff;
  FileOff += getNumSections() * sizeof(Elf_Shdr);
-  FileSize = SizeOfHeaders + RoundUpToAlignment(FileOff - SizeOfHeaders, 8);
+  FileSize = FileOff;
 }

-static uint32_t convertSectionFlagsToSegmentFlags(uint64_t Flags) {
+static uint32_t convertSectionFlagsToPHDRFlags(uint64_t Flags) {
  uint32_t Ret = PF_R;
  if (Flags & SHF_WRITE)
    Ret |= PF_W;
@ -635,42 +657,41 @@ template <class ELFT> void Writer<ELFT>::writeHeader() {

  // FIXME: Generalize the segment construction similar to how we create
  // output sections.
-  unsigned NumSegments = 1;
  const SymbolTable &Symtab = SymTable.getSymTable();
-  const std::vector<std::unique_ptr<SharedFileBase>> &SharedFiles =
-      Symtab.getSharedFiles();
-  bool HasDynamicSegment = !SharedFiles.empty();
-  if (HasDynamicSegment)
-    NumSegments++;
+  bool HasDynamicSegment = !Symtab.getSharedFiles().empty();

  EHdr->e_type = ET_EXEC;
  auto &FirstObj = cast<ObjectFile<ELFT>>(*Symtab.getFirstELF());
  EHdr->e_machine = FirstObj.getEMachine();
  EHdr->e_version = EV_CURRENT;
  EHdr->e_entry = getSymVA(cast<DefinedRegular<ELFT>>(Symtab.getEntrySym()));
-  EHdr->e_phoff = sizeof(Elf_Ehdr);
+  EHdr->e_phoff = ProgramHeaderOff;
  EHdr->e_shoff = SectionHeaderOff;
  EHdr->e_ehsize = sizeof(Elf_Ehdr);
  EHdr->e_phentsize = sizeof(Elf_Phdr);
-  EHdr->e_phnum = NumSegments;
+  EHdr->e_phnum = NumPhdrs;
  EHdr->e_shentsize = sizeof(Elf_Shdr);
  EHdr->e_shnum = getNumSections();
  EHdr->e_shstrndx = StrTabSec.getSectionIndex();

  auto PHdrs = reinterpret_cast<Elf_Phdr *>(Buf + EHdr->e_phoff);
-  PHdrs->p_type = PT_LOAD;
-  PHdrs->p_flags = PF_R | PF_X;
-  PHdrs->p_offset = 0x1000;
-  PHdrs->p_vaddr = 0x1000;
-  PHdrs->p_paddr = PHdrs->p_vaddr;
-  PHdrs->p_filesz = FileSize;
-  PHdrs->p_memsz = FileSize;
-  PHdrs->p_align = 0x4000;
+  for (OutputSectionBase<ELFT::Is64Bits> *Sec : OutputSections) {
+    if (!outputSectionHasPHDR<ELFT>(Sec))
+      continue;
+    PHdrs->p_type = PT_LOAD;
+    PHdrs->p_flags = convertSectionFlagsToPHDRFlags(Sec->getFlags());
+    PHdrs->p_offset = Sec->getFileOff();
+    PHdrs->p_vaddr = Sec->getVA();
+    PHdrs->p_paddr = PHdrs->p_vaddr;
+    PHdrs->p_filesz = Sec->getType() == SHT_NOBITS ? 0 : Sec->getSize();
+    PHdrs->p_memsz = Sec->getSize();
+    PHdrs->p_align = PageSize;
+    ++PHdrs;
+  }

  if (HasDynamicSegment) {
-    PHdrs++;
    PHdrs->p_type = PT_DYNAMIC;
-    PHdrs->p_flags = convertSectionFlagsToSegmentFlags(DynamicSec.getFlags());
+    PHdrs->p_flags = convertSectionFlagsToPHDRFlags(DynamicSec.getFlags());
    PHdrs->p_offset = DynamicSec.getFileOff();
    PHdrs->p_vaddr = DynamicSec.getVA();
    PHdrs->p_paddr = PHdrs->p_vaddr;
--- a/lld/test/elf2/basic.s
+++ b/lld/test/elf2/basic.s
@ -154,13 +154,13 @@ _start:
 # CHECK-NEXT:     Offset: 0x1000
 # CHECK-NEXT:     VirtualAddress: 0x1000
 # CHECK-NEXT:     PhysicalAddress: 0x1000
-# CHECK-NEXT:     FileSize: 4592
-# CHECK-NEXT:     MemSize: 4592
+# CHECK-NEXT:     FileSize: 16
+# CHECK-NEXT:     MemSize: 16
 # CHECK-NEXT:     Flags [ (0x5)
 # CHECK-NEXT:       PF_R (0x4)
 # CHECK-NEXT:       PF_X (0x1)
 # CHECK-NEXT:     ]
-# CHECK-NEXT:     Alignment: 16384
+# CHECK-NEXT:     Alignment: 4096
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]

--- a/lld/test/elf2/basic32.s
+++ b/lld/test/elf2/basic32.s
@ -133,12 +133,12 @@ _start:
 # CHECK-NEXT:     Offset: 0x1000
 # CHECK-NEXT:     VirtualAddress: 0x1000
 # CHECK-NEXT:     PhysicalAddress: 0x1000
-# CHECK-NEXT:     FileSize: 4424
-# CHECK-NEXT:     MemSize: 4424
+# CHECK-NEXT:     FileSize: 12
+# CHECK-NEXT:     MemSize: 12
 # CHECK-NEXT:     Flags [ (0x5)
 # CHECK-NEXT:       PF_R (0x4)
 # CHECK-NEXT:       PF_X (0x1)
 # CHECK-NEXT:     ]
-# CHECK-NEXT:     Alignment: 16384
+# CHECK-NEXT:     Alignment: 4096
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
--- a/lld/test/elf2/basic32be.s
+++ b/lld/test/elf2/basic32be.s
@ -133,12 +133,12 @@ _start:
 # CHECK-NEXT:     Offset: 0x1000
 # CHECK-NEXT:     VirtualAddress: 0x1000
 # CHECK-NEXT:     PhysicalAddress: 0x1000
-# CHECK-NEXT:     FileSize: 4424
-# CHECK-NEXT:     MemSize: 4424
+# CHECK-NEXT:     FileSize: 12
+# CHECK-NEXT:     MemSize: 12
 # CHECK-NEXT:     Flags [ (0x5)
 # CHECK-NEXT:       PF_R (0x4)
 # CHECK-NEXT:       PF_X (0x1)
 # CHECK-NEXT:     ]
-# CHECK-NEXT:     Alignment: 16384
+# CHECK-NEXT:     Alignment: 4096
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
--- a/lld/test/elf2/basic64be.s
+++ b/lld/test/elf2/basic64be.s
@ -28,14 +28,14 @@ _start:
 # CHECK-NEXT:   Type: Executable (0x2)
 # CHECK-NEXT:   Machine: EM_PPC64 (0x15)
 # CHECK-NEXT:   Version: 1
-# CHECK-NEXT:   Entry: 0x100C
+# CHECK-NEXT:   Entry: 0x2000
 # CHECK-NEXT:   ProgramHeaderOffset: 0x40
-# CHECK-NEXT:   SectionHeaderOffset: 0x1088
+# CHECK-NEXT:   SectionHeaderOffset: 0x2078
 # CHECK-NEXT:   Flags [ (0x0)
 # CHECK-NEXT:   ]
 # CHECK-NEXT:   HeaderSize: 64
 # CHECK-NEXT:   ProgramHeaderEntrySize: 56
-# CHECK-NEXT:   ProgramHeaderCount: 1
+# CHECK-NEXT:   ProgramHeaderCount: 2
 # CHECK-NEXT:   SectionHeaderEntrySize: 64
 # CHECK-NEXT:   SectionHeaderCount: 7
 # CHECK-NEXT:    StringTableSectionIndex: 6
@ -111,8 +111,8 @@ _start:
 # CHECK-NEXT:       SHF_ALLOC (0x2)
 # CHECK-NEXT:       SHF_WRITE (0x1)
 # CHECK-NEXT:     ]
-# CHECK-NEXT:     Address: 0x100C
-# CHECK-NEXT:     Offset: 0x100C
+# CHECK-NEXT:     Address: 0x2000
+# CHECK-NEXT:     Offset: 0x2000
 # CHECK-NEXT:     Size: 24
 # CHECK-NEXT:     Link: 0
 # CHECK-NEXT:     Info: 0
@ -126,7 +126,7 @@ _start:
 # CHECK-NEXT:     Flags [
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Address: 0x0
-# CHECK-NEXT:     Offset: 0x1024
+# CHECK-NEXT:     Offset: 0x2018
 # CHECK-NEXT:     Size: 48
 # CHECK-NEXT:     Link: 6
 # CHECK-NEXT:     Info: 1
@ -140,7 +140,7 @@ _start:
 # CHECK-NEXT:     Flags [ (0x0)
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Address: 0x0
-# CHECK-NEXT:     Offset: 0x1054
+# CHECK-NEXT:     Offset: 0x2048
 # CHECK-NEXT:     Size: 46
 # CHECK-NEXT:     Link: 0
 # CHECK-NEXT:     Info: 0
@ -149,17 +149,30 @@ _start:
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
 # CHECK-NEXT: ProgramHeaders [
-# CHECK-NEXT:   ProgramHeader {
-# CHECK-NEXT:     Type: PT_LOAD (0x1)
-# CHECK-NEXT:     Offset: 0x1000
-# CHECK-NEXT:     VirtualAddress: 0x1000
-# CHECK-NEXT:     PhysicalAddress: 0x1000
-# CHECK-NEXT:     FileSize: 4680
-# CHECK-NEXT:     MemSize: 4680
-# CHECK-NEXT:     Flags [ (0x5)
-# CHECK-NEXT:       PF_R (0x4)
-# CHECK-NEXT:       PF_X (0x1)
-# CHECK-NEXT:     ]
-# CHECK-NEXT:     Alignment: 16384
-# CHECK-NEXT:   }
-# CHECK-NEXT: ]
+# CHECK-NEXT:  ProgramHeader {
+# CHECK-NEXT:    Type: PT_LOAD (0x1)
+# CHECK-NEXT:    Offset: 0x1000
+# CHECK-NEXT:    VirtualAddress: 0x1000
+# CHECK-NEXT:    PhysicalAddress: 0x1000
+# CHECK-NEXT:    FileSize: 12
+# CHECK-NEXT:    MemSize: 12
+# CHECK-NEXT:    Flags [ (0x5)
+# CHECK-NEXT:      PF_R (0x4)
+# CHECK-NEXT:      PF_X (0x1)
+# CHECK-NEXT:    ]
+# CHECK-NEXT:    Alignment: 4096
+# CHECK-NEXT:  }
+# CHECK-NEXT:  ProgramHeader {
+# CHECK-NEXT:    Type: PT_LOAD (0x1)
+# CHECK-NEXT:    Offset: 0x2000
+# CHECK-NEXT:    VirtualAddress: 0x2000
+# CHECK-NEXT:    PhysicalAddress: 0x2000
+# CHECK-NEXT:    FileSize: 24
+# CHECK-NEXT:    MemSize: 24
+# CHECK-NEXT:    Flags [ (0x6)
+# CHECK-NEXT:      PF_R (0x4)
+# CHECK-NEXT:      PF_W (0x2)
+# CHECK-NEXT:    ]
+# CHECK-NEXT:    Alignment: 4096
+# CHECK-NEXT:  }
+# CHECK-NEXT:]
--- a/lld/test/elf2/relocation.s
+++ b/lld/test/elf2/relocation.s
@ -26,4 +26,4 @@ bar:
 // CHECK: e8 04 00 00 00  callq   4

 // Also check that symbols match.
-// CHECK: 0000000000001000         .text           00000000 bar
+// CHECK: 000000000001000         .text           00000000 bar
--- a/lld/test/elf2/symbols.s
+++ b/lld/test/elf2/symbols.s
@ -59,8 +59,8 @@ internal:
 // CHECK-NEXT:   SHF_ALLOC (0x2)
 // CHECK-NEXT:   SHF_WRITE (0x1)
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x1004
-// CHECK-NEXT: Offset: 0x1004
+// CHECK-NEXT: Address: 0x2000
+// CHECK-NEXT: Offset: 0x2000
 // CHECK-NEXT: Size: 4

 // CHECK:      Name: foobar
@ -68,7 +68,7 @@ internal:
 // CHECK-NEXT: Flags [
 // CHECK-NEXT:   SHF_ALLOC
 // CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x1008
+// CHECK-NEXT: Address: 0x3000

 // CHECK:      Symbols [
 // CHECK-NEXT:   Symbol {
@ -118,7 +118,7 @@ internal:
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: common (34)
-// CHECK-NEXT:     Value: 0x1004
+// CHECK-NEXT:     Value: 0x2000
 // CHECK-NEXT:     Size: 4
 // CHECK-NEXT:     Binding: Global (0x1)
 // CHECK-NEXT:     Type: Object (0x1)
@ -127,7 +127,7 @@ internal:
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed
-// CHECK-NEXT:     Value: 0x1008
+// CHECK-NEXT:     Value: 0x3000
 // CHECK-NEXT:     Size: 0
 // CHECK-NEXT:     Binding: Global (0x1)
 // CHECK-NEXT:     Type: None
@ -136,7 +136,7 @@ internal:
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: protected
-// CHECK-NEXT:     Value: 0x1010
+// CHECK-NEXT:     Value: 0x3008
 // CHECK-NEXT:     Size: 0
 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None
@ -145,7 +145,7 @@ internal:
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed3
-// CHECK-NEXT:     Value: 0x1010
+// CHECK-NEXT:     Value: 0x3008
 // CHECK-NEXT:     Size: 4
 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None
@ -154,7 +154,7 @@ internal:
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: zed2
-// CHECK-NEXT:     Value: 0x100C
+// CHECK-NEXT:     Value: 0x3004
 // CHECK-NEXT:     Size: 0
 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None