//===- AVR.cpp ------------------------------------------------------------===// // // The LLVM Linker // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // AVR is a Harvard-architecture 8-bit micrcontroller designed for small // baremetal programs. All AVR-family processors have 32 8-bit registers. // The tiniest AVR has 32 byte RAM and 1 KiB program memory, and the largest // one supports up to 2^24 data address space and 2^22 code address space. // // Since it is a baremetal programming, there's usually no loader to load // ELF files on AVRs. You are expected to link your program against address // 0 and pull out a .text section from the result using objcopy, so that you // can write the linked code to on-chip flush memory. You can do that with // the following commands: // // ld.lld -Ttext=0 -o foo foo.o // objcopy -O binary --only-section=.text foo output.bin // // Note that the current AVR support is very preliminary so you can't // link any useful program yet, though. // //===----------------------------------------------------------------------===// #include "InputFiles.h" #include "Symbols.h" #include "Target.h" #include "lld/Common/ErrorHandler.h" #include "llvm/Object/ELF.h" #include "llvm/Support/Endian.h" using namespace llvm; using namespace llvm::object; using namespace llvm::support::endian; using namespace llvm::ELF; using namespace lld; using namespace lld::elf; namespace { class AVR final : public TargetInfo { public: AVR(); RelExpr getRelExpr(RelType Type, const Symbol &S, const uint8_t *Loc) const override; void relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const override; }; } // namespace AVR::AVR() { NoneRel = R_AVR_NONE; } RelExpr AVR::getRelExpr(RelType Type, const Symbol &S, const uint8_t *Loc) const { return R_ABS; } void AVR::relocateOne(uint8_t *Loc, RelType Type, uint64_t Val) const { switch (Type) { case R_AVR_CALL: { uint16_t Hi = Val >> 17; uint16_t Lo = Val >> 1; write16le(Loc, read16le(Loc) | ((Hi >> 1) << 4) | (Hi & 1)); write16le(Loc + 2, Lo); break; } default: error(getErrorLocation(Loc) + "unrecognized reloc " + toString(Type)); } } TargetInfo *elf::getAVRTargetInfo() { static AVR Target; return &Target; } |