[PATCH] D34344: [LLD][ELF] Extract allocateHeaders() from assignAddresses()

[Peter Smith via Phabricator via llvm-commits]

peter.smith created this revision.
Herald added a subscriber: emaste.

The allocateHeaders() function is called at the end of assignAddresses(), it decides whether the ELF header and program header table can be allocated to
a PT_LOAD program header. As the function alters state, it prevents assignAddresses() from being called multiple times. This change splits out the call to allocateHeaders() from assignAddresses() this will permit assignAddresses() to be called while processing range extension thunks without trying to allocateHeaders().

This change on its own is insufficient to allow assignAddresses() to be called multiple times in all cases, I'll send a follow up patch that resets the state accumulated during the assignAddresses().


https://reviews.llvm.org/D34344

Files:
  ELF/LinkerScript.cpp
  ELF/LinkerScript.h
  ELF/Writer.cpp


Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -216,7 +216,8 @@
       OutputSectionCommands.begin(), OutputSectionCommands.end(),
       [](OutputSectionCommand *Cmd) { Cmd->maybeCompress<ELFT>(); });
 
-  Script->assignAddresses(Phdrs);
+  Script->assignAddresses();
+  Script->allocateHeaders(Phdrs);
 
   // Remove empty PT_LOAD to avoid causing the dynamic linker to try to mmap a
   // 0 sized region. This has to be done late since only after assignAddresses
Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -281,8 +281,8 @@
   void assignOffsets(OutputSectionCommand *Cmd);
   void createOrphanCommands();
   void processNonSectionCommands();
-  void assignAddresses(std::vector<PhdrEntry> &Phdrs);
-
+  void assignAddresses();
+  void allocateHeaders(std::vector<PhdrEntry> &Phdrs);
   void addSymbol(SymbolAssignment *Cmd);
   void processCommands(OutputSectionFactory &Factory);
 
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -784,22 +784,26 @@
   }
 }
 
-static bool
-allocateHeaders(std::vector<PhdrEntry> &Phdrs,
-                ArrayRef<OutputSectionCommand *> OutputSectionCommands,
-                uint64_t Min) {
+void LinkerScript::allocateHeaders(std::vector<PhdrEntry> &Phdrs) {
+  uint64_t Min = std::numeric_limits<uint64_t>::max();
+  for (OutputSectionCommand *Cmd : OutputSectionCommands) {
+    OutputSection *Sec = Cmd->Sec;
+    if (Sec->Flags & SHF_ALLOC)
+      Min = std::min<uint64_t>(Min, Sec->Addr);
+  }
+
   auto FirstPTLoad =
       std::find_if(Phdrs.begin(), Phdrs.end(),
                    [](const PhdrEntry &E) { return E.p_type == PT_LOAD; });
   if (FirstPTLoad == Phdrs.end())
-    return false;
+    return;
 
   uint64_t HeaderSize = getHeaderSize();
   if (HeaderSize <= Min || Script->hasPhdrsCommands()) {
     Min = alignDown(Min - HeaderSize, Config->MaxPageSize);
     Out::ElfHeader->Addr = Min;
     Out::ProgramHeaders->Addr = Min + Out::ElfHeader->Size;
-    return true;
+    return;
   }
 
   assert(FirstPTLoad->First == Out::ElfHeader);
@@ -827,10 +831,10 @@
   });
   if (PhdrI != Phdrs.end())
     Phdrs.erase(PhdrI);
-  return false;
+  return;
 }
 
-void LinkerScript::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
+void LinkerScript::assignAddresses() {
   // Assign addresses as instructed by linker script SECTIONS sub-commands.
   Dot = 0;
   ErrorOnMissingSection = true;
@@ -850,15 +854,6 @@
     auto *Cmd = cast<OutputSectionCommand>(Base);
     assignOffsets(Cmd);
   }
-
-  uint64_t MinVA = std::numeric_limits<uint64_t>::max();
-  for (OutputSectionCommand *Cmd : OutputSectionCommands) {
-    OutputSection *Sec = Cmd->Sec;
-    if (Sec->Flags & SHF_ALLOC)
-      MinVA = std::min<uint64_t>(MinVA, Sec->Addr);
-  }
-
-  allocateHeaders(Phdrs, OutputSectionCommands, MinVA);
 }
 
 // Creates program headers as instructed by PHDRS linker script command.


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