[lld] r312711 - [ELF] - Store pointer to PT_LOAD instead of pointer to first section in OutputSection

[George Rimar via llvm-commits]

Author: grimar
Date: Thu Sep  7 03:53:07 2017
New Revision: 312711

URL: http://llvm.org/viewvc/llvm-project?rev=312711&view=rev
Log:
[ELF] - Store pointer to PT_LOAD instead of pointer to first section in OutputSection

It is a bit more convinent and helps to simplify logic 
of program headers allocation a little.

Differential revision: https://reviews.llvm.org/D34956

Modified:
    lld/trunk/ELF/InputSection.cpp
    lld/trunk/ELF/LinkerScript.cpp
    lld/trunk/ELF/OutputSections.h
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=312711&r1=312710&r2=312711&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Thu Sep  7 03:53:07 2017
@@ -485,9 +485,9 @@ static uint64_t getAArch64UndefinedRelat
 // of the RW segment.
 static uint64_t getARMStaticBase(const SymbolBody &Body) {
   OutputSection *OS = Body.getOutputSection();
-  if (!OS || !OS->FirstInPtLoad)
+  if (!OS || !OS->PtLoad || !OS->PtLoad->First)
     fatal("SBREL relocation to " + Body.getName() + " without static base");
-  return OS->FirstInPtLoad->Addr;
+  return OS->PtLoad->First->Addr;
 }
 
 static uint64_t getRelocTargetVA(uint32_t Type, int64_t A, uint64_t P,

Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=312711&r1=312710&r2=312711&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Thu Sep  7 03:53:07 2017
@@ -726,6 +726,13 @@ void LinkerScript::adjustSectionsAfterSo
   removeEmptyCommands();
 }
 
+static OutputSection *findFirstSection(PhdrEntry *Load) {
+  for (OutputSection *Sec : OutputSections)
+    if (Sec->PtLoad == Load)
+      return Sec;
+  return nullptr;
+}
+
 // Try to find an address for the file and program headers output sections,
 // which were unconditionally added to the first PT_LOAD segment earlier.
 //
@@ -761,21 +768,9 @@ void LinkerScript::allocateHeaders(std::
     return;
   }
 
-  OutputSection *ActualFirst = nullptr;
-  for (OutputSection *Sec : OutputSections) {
-    if (Sec->FirstInPtLoad == Out::ElfHeader) {
-      ActualFirst = Sec;
-      break;
-    }
-  }
-  if (ActualFirst) {
-    for (OutputSection *Sec : OutputSections)
-      if (Sec->FirstInPtLoad == Out::ElfHeader)
-        Sec->FirstInPtLoad = ActualFirst;
-    FirstPTLoad->First = ActualFirst;
-  } else {
-    Phdrs.erase(It);
-  }
+  Out::ElfHeader->PtLoad = nullptr;
+  Out::ProgramHeaders->PtLoad = nullptr;
+  FirstPTLoad->First = findFirstSection(FirstPTLoad);
 
   llvm::erase_if(Phdrs,
                  [](const PhdrEntry *E) { return E->p_type == PT_PHDR; });

Modified: lld/trunk/ELF/OutputSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=312711&r1=312710&r2=312711&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.h (original)
+++ lld/trunk/ELF/OutputSections.h Thu Sep  7 03:53:07 2017
@@ -61,13 +61,14 @@ public:
       Alignment = Val;
   }
 
-  // Pointer to the first section in PT_LOAD segment, which this section
-  // also resides in. This field is used to correctly compute file offset
-  // of a section. When two sections share the same load segment, difference
-  // between their file offsets should be equal to difference between their
-  // virtual addresses. To compute some section offset we use the following
-  // formula: Off = Off_first + VA - VA_first.
-  OutputSection *FirstInPtLoad = nullptr;
+  // Pointer to the PT_LOAD segment, which this section resides in. This field
+  // is used to correctly compute file offset of a section. When two sections
+  // share the same load segment, difference between their file offsets should
+  // be equal to difference between their virtual addresses. To compute some
+  // section offset we use the following formula: Off = Off_first + VA -
+  // VA_first, where Off_first and VA_first is file offset and VA of first
+  // section in PT_LOAD.
+  PhdrEntry *PtLoad = nullptr;
 
   // Pointer to a relocation section for this section. Usually nullptr because
   // we consume relocations, but if --emit-relocs is specified (which is rare),

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=312711&r1=312710&r2=312711&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Thu Sep  7 03:53:07 2017
@@ -746,7 +746,7 @@ void PhdrEntry::add(OutputSection *Sec)
     First = Sec;
   p_align = std::max(p_align, Sec->Alignment);
   if (p_type == PT_LOAD)
-    Sec->FirstInPtLoad = First;
+    Sec->PtLoad = this;
 }
 
 template <class ELFT>
@@ -1660,11 +1660,11 @@ template <class ELFT> void Writer<ELFT>:
 // virtual address (modulo the page size) so that the loader can load
 // executables without any address adjustment.
 static uint64_t getFileAlignment(uint64_t Off, OutputSection *Cmd) {
-  OutputSection *First = Cmd->FirstInPtLoad;
   // If the section is not in a PT_LOAD, we just have to align it.
-  if (!First)
+  if (!Cmd->PtLoad)
     return alignTo(Off, Cmd->Alignment);
 
+  OutputSection *First = Cmd->PtLoad->First;
   // The first section in a PT_LOAD has to have congruent offset and address
   // module the page size.
   if (Cmd == First)