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      1 //===-- X86ELFRelocationInfo.cpp ----------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "MCTargetDesc/X86MCTargetDesc.h"
     11 #include "llvm/MC/MCContext.h"
     12 #include "llvm/MC/MCExpr.h"
     13 #include "llvm/MC/MCInst.h"
     14 #include "llvm/MC/MCSymbol.h"
     15 #include "llvm/MC/MCRelocationInfo.h"
     16 #include "llvm/Object/ELF.h"
     17 #include "llvm/Support/ELF.h"
     18 
     19 using namespace llvm;
     20 using namespace object;
     21 using namespace ELF;
     22 
     23 namespace {
     24 class X86_64ELFRelocationInfo : public MCRelocationInfo {
     25 public:
     26   X86_64ELFRelocationInfo(MCContext &Ctx) : MCRelocationInfo(Ctx) {}
     27 
     28   const MCExpr *createExprForRelocation(RelocationRef Rel) {
     29     uint64_t RelType; Rel.getType(RelType);
     30     symbol_iterator SymI = Rel.getSymbol();
     31 
     32     StringRef SymName; SymI->getName(SymName);
     33     uint64_t  SymAddr; SymI->getAddress(SymAddr);
     34     uint64_t  SymSize; SymI->getSize(SymSize);
     35     int64_t  Addend;  getELFRelocationAddend(Rel, Addend);
     36 
     37     MCSymbol *Sym = Ctx.GetOrCreateSymbol(SymName);
     38     // FIXME: check that the value is actually the same.
     39     if (Sym->isVariable() == false)
     40       Sym->setVariableValue(MCConstantExpr::Create(SymAddr, Ctx));
     41 
     42     const MCExpr *Expr = 0;
     43     // If hasAddend is true, then we need to add Addend (r_addend) to Expr.
     44     bool hasAddend = false;
     45 
     46     // The AMD64 SysV ABI says:
     47     // A: the addend used to compute the value of the relocatable field.
     48     // B: the base address at which a shared object has been loaded into memory
     49     //    during execution. Generally, a shared object is built with a 0 base
     50     //    virtual address, but the execution address will be different.
     51     // G: the offset into the global offset table at which the relocation
     52     //    entry's symbol will reside during execution.
     53     // GOT: the address of the global offset table.
     54     // L: the place (section offset or address) of the Procedure Linkage Table
     55     //    entry for a symbol.
     56     // P: the place (section offset or address) of the storage unit being
     57     //    relocated (computed using r_offset).
     58     // S: the value of the symbol whose index resides in the relocation entry.
     59     // Z: the size of the symbol whose index resides in the relocation entry.
     60 
     61     switch(RelType) {
     62     case R_X86_64_NONE:
     63     case R_X86_64_COPY:
     64       // none
     65       break;
     66     case R_X86_64_64:
     67     case R_X86_64_16:
     68     case R_X86_64_8:
     69       // S + A
     70     case R_X86_64_32:
     71     case R_X86_64_32S:
     72       // S + A (We don't care about the result not fitting in 32 bits.)
     73     case R_X86_64_PC32:
     74     case R_X86_64_PC16:
     75     case R_X86_64_PC8:
     76     case R_X86_64_PC64:
     77       // S + A - P (P/pcrel is implicit)
     78       hasAddend = true;
     79       Expr = MCSymbolRefExpr::Create(Sym, Ctx);
     80       break;
     81     case R_X86_64_GOT32:
     82     case R_X86_64_GOT64:
     83     case R_X86_64_GOTPC32:
     84     case R_X86_64_GOTPC64:
     85     case R_X86_64_GOTPLT64:
     86       // G + A
     87       hasAddend = true;
     88       Expr = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOT, Ctx);
     89       break;
     90     case R_X86_64_PLT32:
     91       // L + A - P -> S@PLT + A
     92       hasAddend = true;
     93       Expr = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_PLT, Ctx);
     94       break;
     95     case R_X86_64_GLOB_DAT:
     96     case R_X86_64_JUMP_SLOT:
     97       // S
     98       Expr = MCSymbolRefExpr::Create(Sym, Ctx);
     99       break;
    100     case R_X86_64_GOTPCREL:
    101     case R_X86_64_GOTPCREL64:
    102       // G + GOT + A - P -> S@GOTPCREL + A
    103       hasAddend = true;
    104       Expr = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, Ctx);
    105       break;
    106     case R_X86_64_GOTOFF64:
    107       // S + A - GOT
    108       Expr = MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTOFF, Ctx);
    109       break;
    110     case R_X86_64_PLTOFF64:
    111       // L + A - GOT
    112       break;
    113     case R_X86_64_SIZE32:
    114     case R_X86_64_SIZE64:
    115       // Z + A
    116       Expr = MCConstantExpr::Create(SymSize, Ctx);
    117       break;
    118     default:
    119       Expr = MCSymbolRefExpr::Create(Sym, Ctx);
    120       break;
    121     }
    122     if (Expr && hasAddend && Addend != 0)
    123       Expr = MCBinaryExpr::CreateAdd(Expr,
    124                                      MCConstantExpr::Create(Addend, Ctx),
    125                                      Ctx);
    126     return Expr;
    127   }
    128 };
    129 } // End unnamed namespace
    130 
    131 /// createX86ELFRelocationInfo - Construct an X86 Mach-O RelocationInfo.
    132 MCRelocationInfo *llvm::createX86_64ELFRelocationInfo(MCContext &Ctx) {
    133   // We only handle x86-64 for now.
    134   return new X86_64ELFRelocationInfo(Ctx);
    135 }
    136