[ELF] Support for setting the base address

The -image-base option allows for overriding the base address.

Differential Revision: http://reviews.llvm.org/D22116

llvm-svn: 275206

lld/ELF/Config.h

@@ -117,6 +117,7 @@ struct Configuration {
   ELFKind EKind = ELFNoneKind;
   uint16_t EMachine = llvm::ELF::EM_NONE;
   uint64_t EntryAddr = -1;
+  uint64_t VAStart;
   unsigned LtoJobs;
   unsigned LtoO;
   unsigned Optimize;

lld/ELF/Driver.cpp

@@ -532,6 +532,16 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
       Config->EntrySym = Symtab.addUndefined(S);
   }
 
+  if (auto *Arg = Args.getLastArg(OPT_image_base)) {
+    StringRef S = Arg->getValue();
+    if (S.getAsInteger(0, Config->VAStart))
+      error(Arg->getSpelling() + ": number expected, but got " + S);
+    else if ((Config->VAStart % Target->PageSize) != 0)
+      warning(Arg->getSpelling() + ": address isn't multiple of page size");
+  } else {
+    Config->VAStart = Target->getVAStart();
+  }
+
   for (std::unique_ptr<InputFile> &F : Files)
     Symtab.addFile(std::move(F));
   if (HasError)

lld/ELF/Options.td

@@ -79,6 +79,8 @@ def help: F<"help">, HelpText<"Print option help">;
 
 def icf: F<"icf=all">, HelpText<"Enable identical code folding">;
 
+def image_base : J<"image-base=">, HelpText<"Set the base address">;
+
 def gc_sections: F<"gc-sections">,
   HelpText<"Enable garbage collection of unused sections">;
 

lld/ELF/Writer.cpp

@@ -1022,15 +1022,15 @@ template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
 // sections. These are special, we do not include them into output sections
 // list, but have them to simplify the code.
 template <class ELFT> void Writer<ELFT>::fixHeaders() {
-  uintX_t BaseVA = ScriptConfig->DoLayout ? 0 : Target->getVAStart();
+  uintX_t BaseVA = ScriptConfig->DoLayout ? 0 : Config->VAStart;
   Out<ELFT>::ElfHeader->setVA(BaseVA);
   uintX_t Off = Out<ELFT>::ElfHeader->getSize();
   Out<ELFT>::ProgramHeaders->setVA(Off + BaseVA);
 }
 
 // Assign VAs (addresses at run-time) to output sections.
 template <class ELFT> void Writer<ELFT>::assignAddresses() {
-  uintX_t VA = Target->getVAStart() + Out<ELFT>::ElfHeader->getSize() +
+  uintX_t VA = Config->VAStart + Out<ELFT>::ElfHeader->getSize() +
                Out<ELFT>::ProgramHeaders->getSize();
 
   uintX_t ThreadBssOffset = 0;

lld/test/ELF/ttext-segment.s

@@ -0,0 +1,60 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: ld.lld -image-base=0x1000000 %t -o %t1
+# RUN: llvm-readobj -program-headers %t1 | FileCheck %s
+
+.global _start
+_start:
+  nop
+
+# CHECK:      ProgramHeaders [
+# CHECK-NEXT:   ProgramHeader {
+# CHECK-NEXT:     Type: PT_PHDR (0x6)
+# CHECK-NEXT:     Offset: 0x40
+# CHECK-NEXT:     VirtualAddress: 0x1000040
+# CHECK-NEXT:     PhysicalAddress: 0x1000040
+# CHECK-NEXT:     FileSize: 224
+# CHECK-NEXT:     MemSize: 224
+# CHECK-NEXT:     Flags [ (0x4)
+# CHECK-NEXT:       PF_R (0x4)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Alignment: 8
+# CHECK-NEXT:   }
+# CHECK-NEXT:   ProgramHeader {
+# CHECK-NEXT:     Type: PT_LOAD (0x1)
+# CHECK-NEXT:     Offset: 0x0
+# CHECK-NEXT:     VirtualAddress: 0x1000000
+# CHECK-NEXT:     PhysicalAddress: 0x1000000
+# CHECK-NEXT:     FileSize: 288
+# CHECK-NEXT:     MemSize: 288
+# CHECK-NEXT:     Flags [ (0x4)
+# CHECK-NEXT:       PF_R (0x4)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Alignment: 4096
+# CHECK-NEXT:   }
+# CHECK-NEXT:   ProgramHeader {
+# CHECK-NEXT:     Type: PT_LOAD (0x1)
+# CHECK-NEXT:     Offset: 0x1000
+# CHECK-NEXT:     VirtualAddress: 0x1001000
+# CHECK-NEXT:     PhysicalAddress: 0x1001000
+# CHECK-NEXT:     FileSize: 1
+# CHECK-NEXT:     MemSize: 1
+# 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_GNU_STACK (0x6474E551)
+# CHECK-NEXT:     Offset: 0x0
+# CHECK-NEXT:     VirtualAddress: 0x0
+# CHECK-NEXT:     PhysicalAddress: 0x0
+# CHECK-NEXT:     FileSize: 0
+# CHECK-NEXT:     MemSize: 0
+# CHECK-NEXT:     Flags [ (0x6)
+# CHECK-NEXT:       PF_R (0x4)
+# CHECK-NEXT:       PF_W (0x2)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Alignment: 0
+# CHECK-NEXT:   }