| //===- ARM.cpp ------------------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "InputFiles.h" |
| #include "OutputSections.h" |
| #include "SymbolTable.h" |
| #include "Symbols.h" |
| #include "SyntheticSections.h" |
| #include "Target.h" |
| #include "lld/Common/ErrorHandler.h" |
| #include "lld/Common/Filesystem.h" |
| #include "llvm/BinaryFormat/ELF.h" |
| #include "llvm/Support/Endian.h" |
| |
| using namespace llvm; |
| using namespace llvm::support::endian; |
| using namespace llvm::support; |
| using namespace llvm::ELF; |
| using namespace lld; |
| using namespace lld::elf; |
| using namespace llvm::object; |
| |
| namespace { |
| class ARM final : public TargetInfo { |
| public: |
| ARM(); |
| uint32_t calcEFlags() const override; |
| RelExpr getRelExpr(RelType type, const Symbol &s, |
| const uint8_t *loc) const override; |
| RelType getDynRel(RelType type) const override; |
| int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override; |
| void writeGotPlt(uint8_t *buf, const Symbol &s) const override; |
| void writeIgotPlt(uint8_t *buf, const Symbol &s) const override; |
| void writePltHeader(uint8_t *buf) const override; |
| void writePlt(uint8_t *buf, const Symbol &sym, |
| uint64_t pltEntryAddr) const override; |
| void addPltSymbols(InputSection &isec, uint64_t off) const override; |
| void addPltHeaderSymbols(InputSection &isd) const override; |
| bool needsThunk(RelExpr expr, RelType type, const InputFile *file, |
| uint64_t branchAddr, const Symbol &s, |
| int64_t a) const override; |
| uint32_t getThunkSectionSpacing() const override; |
| bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override; |
| void relocate(uint8_t *loc, const Relocation &rel, |
| uint64_t val) const override; |
| }; |
| enum class CodeState { Data = 0, Thumb = 2, Arm = 4 }; |
| } // namespace |
| |
| static DenseMap<InputSection *, SmallVector<const Defined *, 0>> sectionMap{}; |
| |
| ARM::ARM() { |
| copyRel = R_ARM_COPY; |
| relativeRel = R_ARM_RELATIVE; |
| iRelativeRel = R_ARM_IRELATIVE; |
| gotRel = R_ARM_GLOB_DAT; |
| pltRel = R_ARM_JUMP_SLOT; |
| symbolicRel = R_ARM_ABS32; |
| tlsGotRel = R_ARM_TLS_TPOFF32; |
| tlsModuleIndexRel = R_ARM_TLS_DTPMOD32; |
| tlsOffsetRel = R_ARM_TLS_DTPOFF32; |
| pltHeaderSize = 32; |
| pltEntrySize = 16; |
| ipltEntrySize = 16; |
| trapInstr = {0xd4, 0xd4, 0xd4, 0xd4}; |
| needsThunks = true; |
| defaultMaxPageSize = 65536; |
| } |
| |
| uint32_t ARM::calcEFlags() const { |
| // The ABIFloatType is used by loaders to detect the floating point calling |
| // convention. |
| uint32_t abiFloatType = 0; |
| |
| // Set the EF_ARM_BE8 flag in the ELF header, if ELF file is big-endian |
| // with BE-8 code. |
| uint32_t armBE8 = 0; |
| |
| if (config->armVFPArgs == ARMVFPArgKind::Base || |
| config->armVFPArgs == ARMVFPArgKind::Default) |
| abiFloatType = EF_ARM_ABI_FLOAT_SOFT; |
| else if (config->armVFPArgs == ARMVFPArgKind::VFP) |
| abiFloatType = EF_ARM_ABI_FLOAT_HARD; |
| |
| if (!config->isLE && config->armBe8) |
| armBE8 = EF_ARM_BE8; |
| |
| // We don't currently use any features incompatible with EF_ARM_EABI_VER5, |
| // but we don't have any firm guarantees of conformance. Linux AArch64 |
| // kernels (as of 2016) require an EABI version to be set. |
| return EF_ARM_EABI_VER5 | abiFloatType | armBE8; |
| } |
| |
| RelExpr ARM::getRelExpr(RelType type, const Symbol &s, |
| const uint8_t *loc) const { |
| switch (type) { |
| case R_ARM_ABS32: |
| case R_ARM_MOVW_ABS_NC: |
| case R_ARM_MOVT_ABS: |
| case R_ARM_THM_MOVW_ABS_NC: |
| case R_ARM_THM_MOVT_ABS: |
| case R_ARM_THM_ALU_ABS_G0_NC: |
| case R_ARM_THM_ALU_ABS_G1_NC: |
| case R_ARM_THM_ALU_ABS_G2_NC: |
| case R_ARM_THM_ALU_ABS_G3: |
| return R_ABS; |
| case R_ARM_THM_JUMP8: |
| case R_ARM_THM_JUMP11: |
| return R_PC; |
| case R_ARM_CALL: |
| case R_ARM_JUMP24: |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| case R_ARM_PREL31: |
| case R_ARM_THM_JUMP19: |
| case R_ARM_THM_JUMP24: |
| case R_ARM_THM_CALL: |
| return R_PLT_PC; |
| case R_ARM_GOTOFF32: |
| // (S + A) - GOT_ORG |
| return R_GOTREL; |
| case R_ARM_GOT_BREL: |
| // GOT(S) + A - GOT_ORG |
| return R_GOT_OFF; |
| case R_ARM_GOT_PREL: |
| case R_ARM_TLS_IE32: |
| // GOT(S) + A - P |
| return R_GOT_PC; |
| case R_ARM_SBREL32: |
| return R_ARM_SBREL; |
| case R_ARM_TARGET1: |
| return config->target1Rel ? R_PC : R_ABS; |
| case R_ARM_TARGET2: |
| if (config->target2 == Target2Policy::Rel) |
| return R_PC; |
| if (config->target2 == Target2Policy::Abs) |
| return R_ABS; |
| return R_GOT_PC; |
| case R_ARM_TLS_GD32: |
| return R_TLSGD_PC; |
| case R_ARM_TLS_LDM32: |
| return R_TLSLD_PC; |
| case R_ARM_TLS_LDO32: |
| return R_DTPREL; |
| case R_ARM_BASE_PREL: |
| // B(S) + A - P |
| // FIXME: currently B(S) assumed to be .got, this may not hold for all |
| // platforms. |
| return R_GOTONLY_PC; |
| case R_ARM_MOVW_PREL_NC: |
| case R_ARM_MOVT_PREL: |
| case R_ARM_REL32: |
| case R_ARM_THM_MOVW_PREL_NC: |
| case R_ARM_THM_MOVT_PREL: |
| return R_PC; |
| case R_ARM_ALU_PC_G0: |
| case R_ARM_ALU_PC_G0_NC: |
| case R_ARM_ALU_PC_G1: |
| case R_ARM_ALU_PC_G1_NC: |
| case R_ARM_ALU_PC_G2: |
| case R_ARM_LDR_PC_G0: |
| case R_ARM_LDR_PC_G1: |
| case R_ARM_LDR_PC_G2: |
| case R_ARM_LDRS_PC_G0: |
| case R_ARM_LDRS_PC_G1: |
| case R_ARM_LDRS_PC_G2: |
| case R_ARM_THM_ALU_PREL_11_0: |
| case R_ARM_THM_PC8: |
| case R_ARM_THM_PC12: |
| return R_ARM_PCA; |
| case R_ARM_MOVW_BREL_NC: |
| case R_ARM_MOVW_BREL: |
| case R_ARM_MOVT_BREL: |
| case R_ARM_THM_MOVW_BREL_NC: |
| case R_ARM_THM_MOVW_BREL: |
| case R_ARM_THM_MOVT_BREL: |
| return R_ARM_SBREL; |
| case R_ARM_NONE: |
| return R_NONE; |
| case R_ARM_TLS_LE32: |
| return R_TPREL; |
| case R_ARM_V4BX: |
| // V4BX is just a marker to indicate there's a "bx rN" instruction at the |
| // given address. It can be used to implement a special linker mode which |
| // rewrites ARMv4T inputs to ARMv4. Since we support only ARMv4 input and |
| // not ARMv4 output, we can just ignore it. |
| return R_NONE; |
| default: |
| error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) + |
| ") against symbol " + toString(s)); |
| return R_NONE; |
| } |
| } |
| |
| RelType ARM::getDynRel(RelType type) const { |
| if ((type == R_ARM_ABS32) || (type == R_ARM_TARGET1 && !config->target1Rel)) |
| return R_ARM_ABS32; |
| return R_ARM_NONE; |
| } |
| |
| void ARM::writeGotPlt(uint8_t *buf, const Symbol &) const { |
| write32(buf, in.plt->getVA()); |
| } |
| |
| void ARM::writeIgotPlt(uint8_t *buf, const Symbol &s) const { |
| // An ARM entry is the address of the ifunc resolver function. |
| write32(buf, s.getVA()); |
| } |
| |
| // Long form PLT Header that does not have any restrictions on the displacement |
| // of the .plt from the .got.plt. |
| static void writePltHeaderLong(uint8_t *buf) { |
| write32(buf + 0, 0xe52de004); // str lr, [sp,#-4]! |
| write32(buf + 4, 0xe59fe004); // ldr lr, L2 |
| write32(buf + 8, 0xe08fe00e); // L1: add lr, pc, lr |
| write32(buf + 12, 0xe5bef008); // ldr pc, [lr, #8] |
| write32(buf + 16, 0x00000000); // L2: .word &(.got.plt) - L1 - 8 |
| write32(buf + 20, 0xd4d4d4d4); // Pad to 32-byte boundary |
| write32(buf + 24, 0xd4d4d4d4); // Pad to 32-byte boundary |
| write32(buf + 28, 0xd4d4d4d4); |
| uint64_t gotPlt = in.gotPlt->getVA(); |
| uint64_t l1 = in.plt->getVA() + 8; |
| write32(buf + 16, gotPlt - l1 - 8); |
| } |
| |
| // The default PLT header requires the .got.plt to be within 128 Mb of the |
| // .plt in the positive direction. |
| void ARM::writePltHeader(uint8_t *buf) const { |
| // Use a similar sequence to that in writePlt(), the difference is the calling |
| // conventions mean we use lr instead of ip. The PLT entry is responsible for |
| // saving lr on the stack, the dynamic loader is responsible for reloading |
| // it. |
| const uint32_t pltData[] = { |
| 0xe52de004, // L1: str lr, [sp,#-4]! |
| 0xe28fe600, // add lr, pc, #0x0NN00000 &(.got.plt - L1 - 4) |
| 0xe28eea00, // add lr, lr, #0x000NN000 &(.got.plt - L1 - 4) |
| 0xe5bef000, // ldr pc, [lr, #0x00000NNN] &(.got.plt -L1 - 4) |
| }; |
| |
| uint64_t offset = in.gotPlt->getVA() - in.plt->getVA() - 4; |
| if (!llvm::isUInt<27>(offset)) { |
| // We cannot encode the Offset, use the long form. |
| writePltHeaderLong(buf); |
| return; |
| } |
| write32(buf + 0, pltData[0]); |
| write32(buf + 4, pltData[1] | ((offset >> 20) & 0xff)); |
| write32(buf + 8, pltData[2] | ((offset >> 12) & 0xff)); |
| write32(buf + 12, pltData[3] | (offset & 0xfff)); |
| memcpy(buf + 16, trapInstr.data(), 4); // Pad to 32-byte boundary |
| memcpy(buf + 20, trapInstr.data(), 4); |
| memcpy(buf + 24, trapInstr.data(), 4); |
| memcpy(buf + 28, trapInstr.data(), 4); |
| } |
| |
| void ARM::addPltHeaderSymbols(InputSection &isec) const { |
| addSyntheticLocal("$a", STT_NOTYPE, 0, 0, isec); |
| addSyntheticLocal("$d", STT_NOTYPE, 16, 0, isec); |
| } |
| |
| // Long form PLT entries that do not have any restrictions on the displacement |
| // of the .plt from the .got.plt. |
| static void writePltLong(uint8_t *buf, uint64_t gotPltEntryAddr, |
| uint64_t pltEntryAddr) { |
| write32(buf + 0, 0xe59fc004); // ldr ip, L2 |
| write32(buf + 4, 0xe08cc00f); // L1: add ip, ip, pc |
| write32(buf + 8, 0xe59cf000); // ldr pc, [ip] |
| write32(buf + 12, 0x00000000); // L2: .word Offset(&(.got.plt) - L1 - 8 |
| uint64_t l1 = pltEntryAddr + 4; |
| write32(buf + 12, gotPltEntryAddr - l1 - 8); |
| } |
| |
| // The default PLT entries require the .got.plt to be within 128 Mb of the |
| // .plt in the positive direction. |
| void ARM::writePlt(uint8_t *buf, const Symbol &sym, |
| uint64_t pltEntryAddr) const { |
| // The PLT entry is similar to the example given in Appendix A of ELF for |
| // the Arm Architecture. Instead of using the Group Relocations to find the |
| // optimal rotation for the 8-bit immediate used in the add instructions we |
| // hard code the most compact rotations for simplicity. This saves a load |
| // instruction over the long plt sequences. |
| const uint32_t pltData[] = { |
| 0xe28fc600, // L1: add ip, pc, #0x0NN00000 Offset(&(.got.plt) - L1 - 8 |
| 0xe28cca00, // add ip, ip, #0x000NN000 Offset(&(.got.plt) - L1 - 8 |
| 0xe5bcf000, // ldr pc, [ip, #0x00000NNN] Offset(&(.got.plt) - L1 - 8 |
| }; |
| |
| uint64_t offset = sym.getGotPltVA() - pltEntryAddr - 8; |
| if (!llvm::isUInt<27>(offset)) { |
| // We cannot encode the Offset, use the long form. |
| writePltLong(buf, sym.getGotPltVA(), pltEntryAddr); |
| return; |
| } |
| write32(buf + 0, pltData[0] | ((offset >> 20) & 0xff)); |
| write32(buf + 4, pltData[1] | ((offset >> 12) & 0xff)); |
| write32(buf + 8, pltData[2] | (offset & 0xfff)); |
| memcpy(buf + 12, trapInstr.data(), 4); // Pad to 16-byte boundary |
| } |
| |
| void ARM::addPltSymbols(InputSection &isec, uint64_t off) const { |
| addSyntheticLocal("$a", STT_NOTYPE, off, 0, isec); |
| addSyntheticLocal("$d", STT_NOTYPE, off + 12, 0, isec); |
| } |
| |
| bool ARM::needsThunk(RelExpr expr, RelType type, const InputFile *file, |
| uint64_t branchAddr, const Symbol &s, |
| int64_t a) const { |
| // If s is an undefined weak symbol and does not have a PLT entry then it will |
| // be resolved as a branch to the next instruction. If it is hidden, its |
| // binding has been converted to local, so we just check isUndefined() here. A |
| // undefined non-weak symbol will have been errored. |
| if (s.isUndefined() && !s.isInPlt()) |
| return false; |
| // A state change from ARM to Thumb and vice versa must go through an |
| // interworking thunk if the relocation type is not R_ARM_CALL or |
| // R_ARM_THM_CALL. |
| switch (type) { |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| case R_ARM_JUMP24: |
| // Source is ARM, all PLT entries are ARM so no interworking required. |
| // Otherwise we need to interwork if STT_FUNC Symbol has bit 0 set (Thumb). |
| if (s.isFunc() && expr == R_PC && (s.getVA() & 1)) |
| return true; |
| [[fallthrough]]; |
| case R_ARM_CALL: { |
| uint64_t dst = (expr == R_PLT_PC) ? s.getPltVA() : s.getVA(); |
| return !inBranchRange(type, branchAddr, dst + a) || |
| (!config->armHasBlx && (s.getVA() & 1)); |
| } |
| case R_ARM_THM_JUMP19: |
| case R_ARM_THM_JUMP24: |
| // Source is Thumb, all PLT entries are ARM so interworking is required. |
| // Otherwise we need to interwork if STT_FUNC Symbol has bit 0 clear (ARM). |
| if (expr == R_PLT_PC || (s.isFunc() && (s.getVA() & 1) == 0)) |
| return true; |
| [[fallthrough]]; |
| case R_ARM_THM_CALL: { |
| uint64_t dst = (expr == R_PLT_PC) ? s.getPltVA() : s.getVA(); |
| return !inBranchRange(type, branchAddr, dst + a) || |
| (!config->armHasBlx && (s.getVA() & 1) == 0);; |
| } |
| } |
| return false; |
| } |
| |
| uint32_t ARM::getThunkSectionSpacing() const { |
| // The placing of pre-created ThunkSections is controlled by the value |
| // thunkSectionSpacing returned by getThunkSectionSpacing(). The aim is to |
| // place the ThunkSection such that all branches from the InputSections |
| // prior to the ThunkSection can reach a Thunk placed at the end of the |
| // ThunkSection. Graphically: |
| // | up to thunkSectionSpacing .text input sections | |
| // | ThunkSection | |
| // | up to thunkSectionSpacing .text input sections | |
| // | ThunkSection | |
| |
| // Pre-created ThunkSections are spaced roughly 16MiB apart on ARMv7. This |
| // is to match the most common expected case of a Thumb 2 encoded BL, BLX or |
| // B.W: |
| // ARM B, BL, BLX range +/- 32MiB |
| // Thumb B.W, BL, BLX range +/- 16MiB |
| // Thumb B<cc>.W range +/- 1MiB |
| // If a branch cannot reach a pre-created ThunkSection a new one will be |
| // created so we can handle the rare cases of a Thumb 2 conditional branch. |
| // We intentionally use a lower size for thunkSectionSpacing than the maximum |
| // branch range so the end of the ThunkSection is more likely to be within |
| // range of the branch instruction that is furthest away. The value we shorten |
| // thunkSectionSpacing by is set conservatively to allow us to create 16,384 |
| // 12 byte Thunks at any offset in a ThunkSection without risk of a branch to |
| // one of the Thunks going out of range. |
| |
| // On Arm the thunkSectionSpacing depends on the range of the Thumb Branch |
| // range. On earlier Architectures such as ARMv4, ARMv5 and ARMv6 (except |
| // ARMv6T2) the range is +/- 4MiB. |
| |
| return (config->armJ1J2BranchEncoding) ? 0x1000000 - 0x30000 |
| : 0x400000 - 0x7500; |
| } |
| |
| bool ARM::inBranchRange(RelType type, uint64_t src, uint64_t dst) const { |
| if ((dst & 0x1) == 0) |
| // Destination is ARM, if ARM caller then Src is already 4-byte aligned. |
| // If Thumb Caller (BLX) the Src address has bottom 2 bits cleared to ensure |
| // destination will be 4 byte aligned. |
| src &= ~0x3; |
| else |
| // Bit 0 == 1 denotes Thumb state, it is not part of the range. |
| dst &= ~0x1; |
| |
| int64_t offset = dst - src; |
| switch (type) { |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| case R_ARM_JUMP24: |
| case R_ARM_CALL: |
| return llvm::isInt<26>(offset); |
| case R_ARM_THM_JUMP19: |
| return llvm::isInt<21>(offset); |
| case R_ARM_THM_JUMP24: |
| case R_ARM_THM_CALL: |
| return config->armJ1J2BranchEncoding ? llvm::isInt<25>(offset) |
| : llvm::isInt<23>(offset); |
| default: |
| return true; |
| } |
| } |
| |
| // Helper to produce message text when LLD detects that a CALL relocation to |
| // a non STT_FUNC symbol that may result in incorrect interworking between ARM |
| // or Thumb. |
| static void stateChangeWarning(uint8_t *loc, RelType relt, const Symbol &s) { |
| assert(!s.isFunc()); |
| const ErrorPlace place = getErrorPlace(loc); |
| std::string hint; |
| if (!place.srcLoc.empty()) |
| hint = "; " + place.srcLoc; |
| if (s.isSection()) { |
| // Section symbols must be defined and in a section. Users cannot change |
| // the type. Use the section name as getName() returns an empty string. |
| warn(place.loc + "branch and link relocation: " + toString(relt) + |
| " to STT_SECTION symbol " + cast<Defined>(s).section->name + |
| " ; interworking not performed" + hint); |
| } else { |
| // Warn with hint on how to alter the symbol type. |
| warn(getErrorLocation(loc) + "branch and link relocation: " + |
| toString(relt) + " to non STT_FUNC symbol: " + s.getName() + |
| " interworking not performed; consider using directive '.type " + |
| s.getName() + |
| ", %function' to give symbol type STT_FUNC if interworking between " |
| "ARM and Thumb is required" + |
| hint); |
| } |
| } |
| |
| // Rotate a 32-bit unsigned value right by a specified amt of bits. |
| static uint32_t rotr32(uint32_t val, uint32_t amt) { |
| assert(amt < 32 && "Invalid rotate amount"); |
| return (val >> amt) | (val << ((32 - amt) & 31)); |
| } |
| |
| static std::pair<uint32_t, uint32_t> getRemAndLZForGroup(unsigned group, |
| uint32_t val) { |
| uint32_t rem, lz; |
| do { |
| lz = llvm::countl_zero(val) & ~1; |
| rem = val; |
| if (lz == 32) // implies rem == 0 |
| break; |
| val &= 0xffffff >> lz; |
| } while (group--); |
| return {rem, lz}; |
| } |
| |
| static void encodeAluGroup(uint8_t *loc, const Relocation &rel, uint64_t val, |
| int group, bool check) { |
| // ADD/SUB (immediate) add = bit23, sub = bit22 |
| // immediate field carries is a 12-bit modified immediate, made up of a 4-bit |
| // even rotate right and an 8-bit immediate. |
| uint32_t opcode = 0x00800000; |
| if (val >> 63) { |
| opcode = 0x00400000; |
| val = -val; |
| } |
| uint32_t imm, lz; |
| std::tie(imm, lz) = getRemAndLZForGroup(group, val); |
| uint32_t rot = 0; |
| if (lz < 24) { |
| imm = rotr32(imm, 24 - lz); |
| rot = (lz + 8) << 7; |
| } |
| if (check && imm > 0xff) |
| error(getErrorLocation(loc) + "unencodeable immediate " + Twine(val).str() + |
| " for relocation " + toString(rel.type)); |
| write32(loc, (read32(loc) & 0xff3ff000) | opcode | rot | (imm & 0xff)); |
| } |
| |
| static void encodeLdrGroup(uint8_t *loc, const Relocation &rel, uint64_t val, |
| int group) { |
| // R_ARM_LDR_PC_Gn is S + A - P, we have ((S + A) | T) - P, if S is a |
| // function then addr is 0 (modulo 2) and Pa is 0 (modulo 4) so we can clear |
| // bottom bit to recover S + A - P. |
| if (rel.sym->isFunc()) |
| val &= ~0x1; |
| // LDR (literal) u = bit23 |
| uint32_t opcode = 0x00800000; |
| if (val >> 63) { |
| opcode = 0x0; |
| val = -val; |
| } |
| uint32_t imm = getRemAndLZForGroup(group, val).first; |
| checkUInt(loc, imm, 12, rel); |
| write32(loc, (read32(loc) & 0xff7ff000) | opcode | imm); |
| } |
| |
| static void encodeLdrsGroup(uint8_t *loc, const Relocation &rel, uint64_t val, |
| int group) { |
| // R_ARM_LDRS_PC_Gn is S + A - P, we have ((S + A) | T) - P, if S is a |
| // function then addr is 0 (modulo 2) and Pa is 0 (modulo 4) so we can clear |
| // bottom bit to recover S + A - P. |
| if (rel.sym->isFunc()) |
| val &= ~0x1; |
| // LDRD/LDRH/LDRSB/LDRSH (literal) u = bit23 |
| uint32_t opcode = 0x00800000; |
| if (val >> 63) { |
| opcode = 0x0; |
| val = -val; |
| } |
| uint32_t imm = getRemAndLZForGroup(group, val).first; |
| checkUInt(loc, imm, 8, rel); |
| write32(loc, (read32(loc) & 0xff7ff0f0) | opcode | ((imm & 0xf0) << 4) | |
| (imm & 0xf)); |
| } |
| |
| void ARM::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const { |
| switch (rel.type) { |
| case R_ARM_ABS32: |
| case R_ARM_BASE_PREL: |
| case R_ARM_GOTOFF32: |
| case R_ARM_GOT_BREL: |
| case R_ARM_GOT_PREL: |
| case R_ARM_REL32: |
| case R_ARM_RELATIVE: |
| case R_ARM_SBREL32: |
| case R_ARM_TARGET1: |
| case R_ARM_TARGET2: |
| case R_ARM_TLS_GD32: |
| case R_ARM_TLS_IE32: |
| case R_ARM_TLS_LDM32: |
| case R_ARM_TLS_LDO32: |
| case R_ARM_TLS_LE32: |
| case R_ARM_TLS_TPOFF32: |
| case R_ARM_TLS_DTPOFF32: |
| write32(loc, val); |
| break; |
| case R_ARM_PREL31: |
| checkInt(loc, val, 31, rel); |
| write32(loc, (read32(loc) & 0x80000000) | (val & ~0x80000000)); |
| break; |
| case R_ARM_CALL: { |
| // R_ARM_CALL is used for BL and BLX instructions, for symbols of type |
| // STT_FUNC we choose whether to write a BL or BLX depending on the |
| // value of bit 0 of Val. With bit 0 == 1 denoting Thumb. If the symbol is |
| // not of type STT_FUNC then we must preserve the original instruction. |
| // PLT entries are always ARM state so we know we don't need to interwork. |
| assert(rel.sym); // R_ARM_CALL is always reached via relocate(). |
| bool bit0Thumb = val & 1; |
| bool isBlx = (read32(loc) & 0xfe000000) == 0xfa000000; |
| // lld 10.0 and before always used bit0Thumb when deciding to write a BLX |
| // even when type not STT_FUNC. |
| if (!rel.sym->isFunc() && isBlx != bit0Thumb) |
| stateChangeWarning(loc, rel.type, *rel.sym); |
| if (rel.sym->isFunc() ? bit0Thumb : isBlx) { |
| // The BLX encoding is 0xfa:H:imm24 where Val = imm24:H:'1' |
| checkInt(loc, val, 26, rel); |
| write32(loc, 0xfa000000 | // opcode |
| ((val & 2) << 23) | // H |
| ((val >> 2) & 0x00ffffff)); // imm24 |
| break; |
| } |
| // BLX (always unconditional) instruction to an ARM Target, select an |
| // unconditional BL. |
| write32(loc, 0xeb000000 | (read32(loc) & 0x00ffffff)); |
| // fall through as BL encoding is shared with B |
| } |
| [[fallthrough]]; |
| case R_ARM_JUMP24: |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| checkInt(loc, val, 26, rel); |
| write32(loc, (read32(loc) & ~0x00ffffff) | ((val >> 2) & 0x00ffffff)); |
| break; |
| case R_ARM_THM_JUMP8: |
| // We do a 9 bit check because val is right-shifted by 1 bit. |
| checkInt(loc, val, 9, rel); |
| write16(loc, (read32(loc) & 0xff00) | ((val >> 1) & 0x00ff)); |
| break; |
| case R_ARM_THM_JUMP11: |
| // We do a 12 bit check because val is right-shifted by 1 bit. |
| checkInt(loc, val, 12, rel); |
| write16(loc, (read32(loc) & 0xf800) | ((val >> 1) & 0x07ff)); |
| break; |
| case R_ARM_THM_JUMP19: |
| // Encoding T3: Val = S:J2:J1:imm6:imm11:0 |
| checkInt(loc, val, 21, rel); |
| write16(loc, |
| (read16(loc) & 0xfbc0) | // opcode cond |
| ((val >> 10) & 0x0400) | // S |
| ((val >> 12) & 0x003f)); // imm6 |
| write16(loc + 2, |
| 0x8000 | // opcode |
| ((val >> 8) & 0x0800) | // J2 |
| ((val >> 5) & 0x2000) | // J1 |
| ((val >> 1) & 0x07ff)); // imm11 |
| break; |
| case R_ARM_THM_CALL: { |
| // R_ARM_THM_CALL is used for BL and BLX instructions, for symbols of type |
| // STT_FUNC we choose whether to write a BL or BLX depending on the |
| // value of bit 0 of Val. With bit 0 == 0 denoting ARM, if the symbol is |
| // not of type STT_FUNC then we must preserve the original instruction. |
| // PLT entries are always ARM state so we know we need to interwork. |
| assert(rel.sym); // R_ARM_THM_CALL is always reached via relocate(). |
| bool bit0Thumb = val & 1; |
| bool isBlx = (read16(loc + 2) & 0x1000) == 0; |
| // lld 10.0 and before always used bit0Thumb when deciding to write a BLX |
| // even when type not STT_FUNC. PLT entries generated by LLD are always ARM. |
| if (!rel.sym->isFunc() && !rel.sym->isInPlt() && isBlx == bit0Thumb) |
| stateChangeWarning(loc, rel.type, *rel.sym); |
| if (rel.sym->isFunc() || rel.sym->isInPlt() ? !bit0Thumb : isBlx) { |
| // We are writing a BLX. Ensure BLX destination is 4-byte aligned. As |
| // the BLX instruction may only be two byte aligned. This must be done |
| // before overflow check. |
| val = alignTo(val, 4); |
| write16(loc + 2, read16(loc + 2) & ~0x1000); |
| } else { |
| write16(loc + 2, (read16(loc + 2) & ~0x1000) | 1 << 12); |
| } |
| if (!config->armJ1J2BranchEncoding) { |
| // Older Arm architectures do not support R_ARM_THM_JUMP24 and have |
| // different encoding rules and range due to J1 and J2 always being 1. |
| checkInt(loc, val, 23, rel); |
| write16(loc, |
| 0xf000 | // opcode |
| ((val >> 12) & 0x07ff)); // imm11 |
| write16(loc + 2, |
| (read16(loc + 2) & 0xd000) | // opcode |
| 0x2800 | // J1 == J2 == 1 |
| ((val >> 1) & 0x07ff)); // imm11 |
| break; |
| } |
| } |
| // Fall through as rest of encoding is the same as B.W |
| [[fallthrough]]; |
| case R_ARM_THM_JUMP24: |
| // Encoding B T4, BL T1, BLX T2: Val = S:I1:I2:imm10:imm11:0 |
| checkInt(loc, val, 25, rel); |
| write16(loc, |
| 0xf000 | // opcode |
| ((val >> 14) & 0x0400) | // S |
| ((val >> 12) & 0x03ff)); // imm10 |
| write16(loc + 2, |
| (read16(loc + 2) & 0xd000) | // opcode |
| (((~(val >> 10)) ^ (val >> 11)) & 0x2000) | // J1 |
| (((~(val >> 11)) ^ (val >> 13)) & 0x0800) | // J2 |
| ((val >> 1) & 0x07ff)); // imm11 |
| break; |
| case R_ARM_MOVW_ABS_NC: |
| case R_ARM_MOVW_PREL_NC: |
| case R_ARM_MOVW_BREL_NC: |
| write32(loc, (read32(loc) & ~0x000f0fff) | ((val & 0xf000) << 4) | |
| (val & 0x0fff)); |
| break; |
| case R_ARM_MOVT_ABS: |
| case R_ARM_MOVT_PREL: |
| case R_ARM_MOVT_BREL: |
| write32(loc, (read32(loc) & ~0x000f0fff) | |
| (((val >> 16) & 0xf000) << 4) | ((val >> 16) & 0xfff)); |
| break; |
| case R_ARM_THM_MOVT_ABS: |
| case R_ARM_THM_MOVT_PREL: |
| case R_ARM_THM_MOVT_BREL: |
| // Encoding T1: A = imm4:i:imm3:imm8 |
| |
| write16(loc, |
| 0xf2c0 | // opcode |
| ((val >> 17) & 0x0400) | // i |
| ((val >> 28) & 0x000f)); // imm4 |
| |
| write16(loc + 2, |
| (read16(loc + 2) & 0x8f00) | // opcode |
| ((val >> 12) & 0x7000) | // imm3 |
| ((val >> 16) & 0x00ff)); // imm8 |
| break; |
| case R_ARM_THM_MOVW_ABS_NC: |
| case R_ARM_THM_MOVW_PREL_NC: |
| case R_ARM_THM_MOVW_BREL_NC: |
| // Encoding T3: A = imm4:i:imm3:imm8 |
| write16(loc, |
| 0xf240 | // opcode |
| ((val >> 1) & 0x0400) | // i |
| ((val >> 12) & 0x000f)); // imm4 |
| write16(loc + 2, |
| (read16(loc + 2) & 0x8f00) | // opcode |
| ((val << 4) & 0x7000) | // imm3 |
| (val & 0x00ff)); // imm8 |
| break; |
| case R_ARM_THM_ALU_ABS_G3: |
| write16(loc, (read16(loc) &~ 0x00ff) | ((val >> 24) & 0x00ff)); |
| break; |
| case R_ARM_THM_ALU_ABS_G2_NC: |
| write16(loc, (read16(loc) &~ 0x00ff) | ((val >> 16) & 0x00ff)); |
| break; |
| case R_ARM_THM_ALU_ABS_G1_NC: |
| write16(loc, (read16(loc) &~ 0x00ff) | ((val >> 8) & 0x00ff)); |
| break; |
| case R_ARM_THM_ALU_ABS_G0_NC: |
| write16(loc, (read16(loc) &~ 0x00ff) | (val & 0x00ff)); |
| break; |
| case R_ARM_ALU_PC_G0: |
| encodeAluGroup(loc, rel, val, 0, true); |
| break; |
| case R_ARM_ALU_PC_G0_NC: |
| encodeAluGroup(loc, rel, val, 0, false); |
| break; |
| case R_ARM_ALU_PC_G1: |
| encodeAluGroup(loc, rel, val, 1, true); |
| break; |
| case R_ARM_ALU_PC_G1_NC: |
| encodeAluGroup(loc, rel, val, 1, false); |
| break; |
| case R_ARM_ALU_PC_G2: |
| encodeAluGroup(loc, rel, val, 2, true); |
| break; |
| case R_ARM_LDR_PC_G0: |
| encodeLdrGroup(loc, rel, val, 0); |
| break; |
| case R_ARM_LDR_PC_G1: |
| encodeLdrGroup(loc, rel, val, 1); |
| break; |
| case R_ARM_LDR_PC_G2: |
| encodeLdrGroup(loc, rel, val, 2); |
| break; |
| case R_ARM_LDRS_PC_G0: |
| encodeLdrsGroup(loc, rel, val, 0); |
| break; |
| case R_ARM_LDRS_PC_G1: |
| encodeLdrsGroup(loc, rel, val, 1); |
| break; |
| case R_ARM_LDRS_PC_G2: |
| encodeLdrsGroup(loc, rel, val, 2); |
| break; |
| case R_ARM_THM_ALU_PREL_11_0: { |
| // ADR encoding T2 (sub), T3 (add) i:imm3:imm8 |
| int64_t imm = val; |
| uint16_t sub = 0; |
| if (imm < 0) { |
| imm = -imm; |
| sub = 0x00a0; |
| } |
| checkUInt(loc, imm, 12, rel); |
| write16(loc, (read16(loc) & 0xfb0f) | sub | (imm & 0x800) >> 1); |
| write16(loc + 2, |
| (read16(loc + 2) & 0x8f00) | (imm & 0x700) << 4 | (imm & 0xff)); |
| break; |
| } |
| case R_ARM_THM_PC8: |
| // ADR and LDR literal encoding T1 positive offset only imm8:00 |
| // R_ARM_THM_PC8 is S + A - Pa, we have ((S + A) | T) - Pa, if S is a |
| // function then addr is 0 (modulo 2) and Pa is 0 (modulo 4) so we can clear |
| // bottom bit to recover S + A - Pa. |
| if (rel.sym->isFunc()) |
| val &= ~0x1; |
| checkUInt(loc, val, 10, rel); |
| checkAlignment(loc, val, 4, rel); |
| write16(loc, (read16(loc) & 0xff00) | (val & 0x3fc) >> 2); |
| break; |
| case R_ARM_THM_PC12: { |
| // LDR (literal) encoding T2, add = (U == '1') imm12 |
| // imm12 is unsigned |
| // R_ARM_THM_PC12 is S + A - Pa, we have ((S + A) | T) - Pa, if S is a |
| // function then addr is 0 (modulo 2) and Pa is 0 (modulo 4) so we can clear |
| // bottom bit to recover S + A - Pa. |
| if (rel.sym->isFunc()) |
| val &= ~0x1; |
| int64_t imm12 = val; |
| uint16_t u = 0x0080; |
| if (imm12 < 0) { |
| imm12 = -imm12; |
| u = 0; |
| } |
| checkUInt(loc, imm12, 12, rel); |
| write16(loc, read16(loc) | u); |
| write16(loc + 2, (read16(loc + 2) & 0xf000) | imm12); |
| break; |
| } |
| default: |
| llvm_unreachable("unknown relocation"); |
| } |
| } |
| |
| int64_t ARM::getImplicitAddend(const uint8_t *buf, RelType type) const { |
| switch (type) { |
| default: |
| internalLinkerError(getErrorLocation(buf), |
| "cannot read addend for relocation " + toString(type)); |
| return 0; |
| case R_ARM_ABS32: |
| case R_ARM_BASE_PREL: |
| case R_ARM_GLOB_DAT: |
| case R_ARM_GOTOFF32: |
| case R_ARM_GOT_BREL: |
| case R_ARM_GOT_PREL: |
| case R_ARM_IRELATIVE: |
| case R_ARM_REL32: |
| case R_ARM_RELATIVE: |
| case R_ARM_SBREL32: |
| case R_ARM_TARGET1: |
| case R_ARM_TARGET2: |
| case R_ARM_TLS_DTPMOD32: |
| case R_ARM_TLS_DTPOFF32: |
| case R_ARM_TLS_GD32: |
| case R_ARM_TLS_IE32: |
| case R_ARM_TLS_LDM32: |
| case R_ARM_TLS_LE32: |
| case R_ARM_TLS_LDO32: |
| case R_ARM_TLS_TPOFF32: |
| return SignExtend64<32>(read32(buf)); |
| case R_ARM_PREL31: |
| return SignExtend64<31>(read32(buf)); |
| case R_ARM_CALL: |
| case R_ARM_JUMP24: |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| return SignExtend64<26>(read32(buf) << 2); |
| case R_ARM_THM_JUMP8: |
| return SignExtend64<9>(read16(buf) << 1); |
| case R_ARM_THM_JUMP11: |
| return SignExtend64<12>(read16(buf) << 1); |
| case R_ARM_THM_JUMP19: { |
| // Encoding T3: A = S:J2:J1:imm10:imm6:0 |
| uint16_t hi = read16(buf); |
| uint16_t lo = read16(buf + 2); |
| return SignExtend64<20>(((hi & 0x0400) << 10) | // S |
| ((lo & 0x0800) << 8) | // J2 |
| ((lo & 0x2000) << 5) | // J1 |
| ((hi & 0x003f) << 12) | // imm6 |
| ((lo & 0x07ff) << 1)); // imm11:0 |
| } |
| case R_ARM_THM_CALL: |
| if (!config->armJ1J2BranchEncoding) { |
| // Older Arm architectures do not support R_ARM_THM_JUMP24 and have |
| // different encoding rules and range due to J1 and J2 always being 1. |
| uint16_t hi = read16(buf); |
| uint16_t lo = read16(buf + 2); |
| return SignExtend64<22>(((hi & 0x7ff) << 12) | // imm11 |
| ((lo & 0x7ff) << 1)); // imm11:0 |
| break; |
| } |
| [[fallthrough]]; |
| case R_ARM_THM_JUMP24: { |
| // Encoding B T4, BL T1, BLX T2: A = S:I1:I2:imm10:imm11:0 |
| // I1 = NOT(J1 EOR S), I2 = NOT(J2 EOR S) |
| uint16_t hi = read16(buf); |
| uint16_t lo = read16(buf + 2); |
| return SignExtend64<24>(((hi & 0x0400) << 14) | // S |
| (~((lo ^ (hi << 3)) << 10) & 0x00800000) | // I1 |
| (~((lo ^ (hi << 1)) << 11) & 0x00400000) | // I2 |
| ((hi & 0x003ff) << 12) | // imm0 |
| ((lo & 0x007ff) << 1)); // imm11:0 |
| } |
| // ELF for the ARM Architecture 4.6.1.1 the implicit addend for MOVW and |
| // MOVT is in the range -32768 <= A < 32768 |
| case R_ARM_MOVW_ABS_NC: |
| case R_ARM_MOVT_ABS: |
| case R_ARM_MOVW_PREL_NC: |
| case R_ARM_MOVT_PREL: |
| case R_ARM_MOVW_BREL_NC: |
| case R_ARM_MOVT_BREL: { |
| uint64_t val = read32(buf) & 0x000f0fff; |
| return SignExtend64<16>(((val & 0x000f0000) >> 4) | (val & 0x00fff)); |
| } |
| case R_ARM_THM_MOVW_ABS_NC: |
| case R_ARM_THM_MOVT_ABS: |
| case R_ARM_THM_MOVW_PREL_NC: |
| case R_ARM_THM_MOVT_PREL: |
| case R_ARM_THM_MOVW_BREL_NC: |
| case R_ARM_THM_MOVT_BREL: { |
| // Encoding T3: A = imm4:i:imm3:imm8 |
| uint16_t hi = read16(buf); |
| uint16_t lo = read16(buf + 2); |
| return SignExtend64<16>(((hi & 0x000f) << 12) | // imm4 |
| ((hi & 0x0400) << 1) | // i |
| ((lo & 0x7000) >> 4) | // imm3 |
| (lo & 0x00ff)); // imm8 |
| } |
| case R_ARM_THM_ALU_ABS_G0_NC: |
| case R_ARM_THM_ALU_ABS_G1_NC: |
| case R_ARM_THM_ALU_ABS_G2_NC: |
| case R_ARM_THM_ALU_ABS_G3: |
| return read16(buf) & 0xff; |
| case R_ARM_ALU_PC_G0: |
| case R_ARM_ALU_PC_G0_NC: |
| case R_ARM_ALU_PC_G1: |
| case R_ARM_ALU_PC_G1_NC: |
| case R_ARM_ALU_PC_G2: { |
| // 12-bit immediate is a modified immediate made up of a 4-bit even |
| // right rotation and 8-bit constant. After the rotation the value |
| // is zero-extended. When bit 23 is set the instruction is an add, when |
| // bit 22 is set it is a sub. |
| uint32_t instr = read32(buf); |
| uint32_t val = rotr32(instr & 0xff, ((instr & 0xf00) >> 8) * 2); |
| return (instr & 0x00400000) ? -val : val; |
| } |
| case R_ARM_LDR_PC_G0: |
| case R_ARM_LDR_PC_G1: |
| case R_ARM_LDR_PC_G2: { |
| // ADR (literal) add = bit23, sub = bit22 |
| // LDR (literal) u = bit23 unsigned imm12 |
| bool u = read32(buf) & 0x00800000; |
| uint32_t imm12 = read32(buf) & 0xfff; |
| return u ? imm12 : -imm12; |
| } |
| case R_ARM_LDRS_PC_G0: |
| case R_ARM_LDRS_PC_G1: |
| case R_ARM_LDRS_PC_G2: { |
| // LDRD/LDRH/LDRSB/LDRSH (literal) u = bit23 unsigned imm8 |
| uint32_t opcode = read32(buf); |
| bool u = opcode & 0x00800000; |
| uint32_t imm4l = opcode & 0xf; |
| uint32_t imm4h = (opcode & 0xf00) >> 4; |
| return u ? (imm4h | imm4l) : -(imm4h | imm4l); |
| } |
| case R_ARM_THM_ALU_PREL_11_0: { |
| // Thumb2 ADR, which is an alias for a sub or add instruction with an |
| // unsigned immediate. |
| // ADR encoding T2 (sub), T3 (add) i:imm3:imm8 |
| uint16_t hi = read16(buf); |
| uint16_t lo = read16(buf + 2); |
| uint64_t imm = (hi & 0x0400) << 1 | // i |
| (lo & 0x7000) >> 4 | // imm3 |
| (lo & 0x00ff); // imm8 |
| // For sub, addend is negative, add is positive. |
| return (hi & 0x00f0) ? -imm : imm; |
| } |
| case R_ARM_THM_PC8: |
| // ADR and LDR (literal) encoding T1 |
| // From ELF for the ARM Architecture the initial signed addend is formed |
| // from an unsigned field using expression (((imm8:00 + 4) & 0x3ff) ā 4) |
| // this trick permits the PC bias of -4 to be encoded using imm8 = 0xff |
| return ((((read16(buf) & 0xff) << 2) + 4) & 0x3ff) - 4; |
| case R_ARM_THM_PC12: { |
| // LDR (literal) encoding T2, add = (U == '1') imm12 |
| bool u = read16(buf) & 0x0080; |
| uint64_t imm12 = read16(buf + 2) & 0x0fff; |
| return u ? imm12 : -imm12; |
| } |
| case R_ARM_NONE: |
| case R_ARM_V4BX: |
| case R_ARM_JUMP_SLOT: |
| // These relocations are defined as not having an implicit addend. |
| return 0; |
| } |
| } |
| |
| static bool isArmMapSymbol(const Symbol *b) { |
| return b->getName() == "$a" || b->getName().startswith("$a."); |
| } |
| |
| static bool isThumbMapSymbol(const Symbol *s) { |
| return s->getName() == "$t" || s->getName().startswith("$t."); |
| } |
| |
| static bool isDataMapSymbol(const Symbol *b) { |
| return b->getName() == "$d" || b->getName().startswith("$d."); |
| } |
| |
| void elf::sortArmMappingSymbols() { |
| // For each input section make sure the mapping symbols are sorted in |
| // ascending order. |
| for (auto &kv : sectionMap) { |
| SmallVector<const Defined *, 0> &mapSyms = kv.second; |
| llvm::stable_sort(mapSyms, [](const Defined *a, const Defined *b) { |
| return a->value < b->value; |
| }); |
| } |
| } |
| |
| void elf::addArmInputSectionMappingSymbols() { |
| // Collect mapping symbols for every executable input sections. |
| // The linker generated mapping symbols for all the synthetic |
| // sections are adding into the sectionmap through the function |
| // addArmSyntheitcSectionMappingSymbol. |
| for (ELFFileBase *file : ctx.objectFiles) { |
| for (Symbol *sym : file->getLocalSymbols()) { |
| auto *def = dyn_cast<Defined>(sym); |
| if (!def) |
| continue; |
| if (!isArmMapSymbol(def) && !isDataMapSymbol(def) && |
| !isThumbMapSymbol(def)) |
| continue; |
| if (auto *sec = cast_if_present<InputSection>(def->section)) |
| if (sec->flags & SHF_EXECINSTR) |
| sectionMap[sec].push_back(def); |
| } |
| } |
| } |
| |
| // Synthetic sections are not backed by an ELF file where we can access the |
| // symbol table, instead mapping symbols added to synthetic sections are stored |
| // in the synthetic symbol table. Due to the presence of strip (--strip-all), |
| // we can not rely on the synthetic symbol table retaining the mapping symbols. |
| // Instead we record the mapping symbols locally. |
| void elf::addArmSyntheticSectionMappingSymbol(Defined *sym) { |
| if (!isArmMapSymbol(sym) && !isDataMapSymbol(sym) && !isThumbMapSymbol(sym)) |
| return; |
| if (auto *sec = cast_if_present<InputSection>(sym->section)) |
| if (sec->flags & SHF_EXECINSTR) |
| sectionMap[sec].push_back(sym); |
| } |
| |
| static void toLittleEndianInstructions(uint8_t *buf, uint64_t start, |
| uint64_t end, uint64_t width) { |
| CodeState curState = static_cast<CodeState>(width); |
| if (curState == CodeState::Arm) |
| for (uint64_t i = start; i < end; i += width) |
| write32le(buf + i, read32(buf + i)); |
| |
| if (curState == CodeState::Thumb) |
| for (uint64_t i = start; i < end; i += width) |
| write16le(buf + i, read16(buf + i)); |
| } |
| |
| // Arm BE8 big endian format requires instructions to be little endian, with |
| // the initial contents big-endian. Convert the big-endian instructions to |
| // little endian leaving literal data untouched. We use mapping symbols to |
| // identify half open intervals of Arm code [$a, non $a) and Thumb code |
| // [$t, non $t) and convert these to little endian a word or half word at a |
| // time respectively. |
| void elf::convertArmInstructionstoBE8(InputSection *sec, uint8_t *buf) { |
| if (!sectionMap.contains(sec)) |
| return; |
| |
| SmallVector<const Defined *, 0> &mapSyms = sectionMap[sec]; |
| |
| if (mapSyms.empty()) |
| return; |
| |
| CodeState curState = CodeState::Data; |
| uint64_t start = 0, width = 0, size = sec->getSize(); |
| for (auto &msym : mapSyms) { |
| CodeState newState = CodeState::Data; |
| if (isThumbMapSymbol(msym)) |
| newState = CodeState::Thumb; |
| else if (isArmMapSymbol(msym)) |
| newState = CodeState::Arm; |
| |
| if (newState == curState) |
| continue; |
| |
| if (curState != CodeState::Data) { |
| width = static_cast<uint64_t>(curState); |
| toLittleEndianInstructions(buf, start, msym->value, width); |
| } |
| start = msym->value; |
| curState = newState; |
| } |
| |
| // Passed last mapping symbol, may need to reverse |
| // up to end of section. |
| if (curState != CodeState::Data) { |
| width = static_cast<uint64_t>(curState); |
| toLittleEndianInstructions(buf, start, size, width); |
| } |
| } |
| |
| // The Arm Cortex-M Security Extensions (CMSE) splits a system into two parts; |
| // the non-secure and secure states with the secure state inaccessible from the |
| // non-secure state, apart from an area of memory in secure state called the |
| // secure gateway which is accessible from non-secure state. The secure gateway |
| // contains one or more entry points which must start with a landing pad |
| // instruction SG. Arm recommends that the secure gateway consists only of |
| // secure gateway veneers, which are made up of a SG instruction followed by a |
| // branch to the destination in secure state. Full details can be found in Arm |
| // v8-M Security Extensions Requirements on Development Tools. |
| // |
| // The CMSE model of software development requires the non-secure and secure |
| // states to be developed as two separate programs. The non-secure developer is |
| // provided with an import library defining symbols describing the entry points |
| // in the secure gateway. No additional linker support is required for the |
| // non-secure state. |
| // |
| // Development of the secure state requires linker support to manage the secure |
| // gateway veneers. The management consists of: |
| // - Creation of new secure gateway veneers based on symbol conventions. |
| // - Checking the address of existing secure gateway veneers. |
| // - Warning when existing secure gateway veneers removed. |
| // |
| // The secure gateway veneers are created in an import library, which is just an |
| // ELF object with a symbol table. The import library is controlled by two |
| // command line options: |
| // --in-implib (specify an input import library from a previous revision of the |
| // program). |
| // --out-implib (specify an output import library to be created by the linker). |
| // |
| // The input import library is used to manage consistency of the secure entry |
| // points. The output import library is for new and updated secure entry points. |
| // |
| // The symbol convention that identifies secure entry functions is the prefix |
| // __acle_se_ for a symbol called name the linker is expected to create a secure |
| // gateway veneer if symbols __acle_se_name and name have the same address. |
| // After creating a secure gateway veneer the symbol name labels the secure |
| // gateway veneer and the __acle_se_name labels the function definition. |
| // |
| // The LLD implementation: |
| // - Reads an existing import library with importCmseSymbols(). |
| // - Determines which new secure gateway veneers to create and redirects calls |
| // within the secure state to the __acle_se_ prefixed symbol with |
| // processArmCmseSymbols(). |
| // - Models the SG veneers as a synthetic section. |
| |
| // Initialize symbols. symbols is a parallel array to the corresponding ELF |
| // symbol table. |
| template <class ELFT> void ObjFile<ELFT>::importCmseSymbols() { |
| ArrayRef<Elf_Sym> eSyms = getELFSyms<ELFT>(); |
| // Error for local symbols. The symbol at index 0 is LOCAL. So skip it. |
| for (size_t i = 1, end = firstGlobal; i != end; ++i) { |
| errorOrWarn("CMSE symbol '" + CHECK(eSyms[i].getName(stringTable), this) + |
| "' in import library '" + toString(this) + "' is not global"); |
| } |
| |
| for (size_t i = firstGlobal, end = eSyms.size(); i != end; ++i) { |
| const Elf_Sym &eSym = eSyms[i]; |
| Defined *sym = reinterpret_cast<Defined *>(make<SymbolUnion>()); |
| |
| // Initialize symbol fields. |
| memset(sym, 0, sizeof(Symbol)); |
| sym->setName(CHECK(eSyms[i].getName(stringTable), this)); |
| sym->value = eSym.st_value; |
| sym->size = eSym.st_size; |
| sym->type = eSym.getType(); |
| sym->binding = eSym.getBinding(); |
| sym->stOther = eSym.st_other; |
| |
| if (eSym.st_shndx != SHN_ABS) { |
| error("CMSE symbol '" + sym->getName() + "' in import library '" + |
| toString(this) + "' is not absolute"); |
| continue; |
| } |
| |
| if (!(eSym.st_value & 1) || (eSym.getType() != STT_FUNC)) { |
| error("CMSE symbol '" + sym->getName() + "' in import library '" + |
| toString(this) + "' is not a Thumb function definition"); |
| continue; |
| } |
| |
| if (symtab.cmseImportLib.count(sym->getName())) { |
| error("CMSE symbol '" + sym->getName() + |
| "' is multiply defined in import library '" + toString(this) + "'"); |
| continue; |
| } |
| |
| if (eSym.st_size != ACLESESYM_SIZE) { |
| warn("CMSE symbol '" + sym->getName() + "' in import library '" + |
| toString(this) + "' does not have correct size of " + |
| Twine(ACLESESYM_SIZE) + " bytes"); |
| } |
| |
| symtab.cmseImportLib[sym->getName()] = sym; |
| } |
| } |
| |
| // Check symbol attributes of the acleSeSym, sym pair. |
| // Both symbols should be global/weak Thumb code symbol definitions. |
| static std::string checkCmseSymAttributes(Symbol *acleSeSym, Symbol *sym) { |
| auto check = [](Symbol *s, StringRef type) -> std::optional<std::string> { |
| auto d = dyn_cast_or_null<Defined>(s); |
| if (!(d && d->isFunc() && (d->value & 1))) |
| return (Twine(toString(s->file)) + ": cmse " + type + " symbol '" + |
| s->getName() + "' is not a Thumb function definition") |
| .str(); |
| if (!d->section) |
| return (Twine(toString(s->file)) + ": cmse " + type + " symbol '" + |
| s->getName() + "' cannot be an absolute symbol") |
| .str(); |
| return std::nullopt; |
| }; |
| for (auto [sym, type] : |
| {std::make_pair(acleSeSym, "special"), std::make_pair(sym, "entry")}) |
| if (auto err = check(sym, type)) |
| return *err; |
| return ""; |
| } |
| |
| // Look for [__acle_se_<sym>, <sym>] pairs, as specified in the Cortex-M |
| // Security Extensions specification. |
| // 1) <sym> : A standard function name. |
| // 2) __acle_se_<sym> : A special symbol that prefixes the standard function |
| // name with __acle_se_. |
| // Both these symbols are Thumb function symbols with external linkage. |
| // <sym> may be redefined in .gnu.sgstubs. |
| void elf::processArmCmseSymbols() { |
| if (!config->cmseImplib) |
| return; |
| // Only symbols with external linkage end up in symtab, so no need to do |
| // linkage checks. Only check symbol type. |
| for (Symbol *acleSeSym : symtab.getSymbols()) { |
| if (!acleSeSym->getName().startswith(ACLESESYM_PREFIX)) |
| continue; |
| // If input object build attributes do not support CMSE, error and disable |
| // further scanning for <sym>, __acle_se_<sym> pairs. |
| if (!config->armCMSESupport) { |
| error("CMSE is only supported by ARMv8-M architecture or later"); |
| config->cmseImplib = false; |
| break; |
| } |
| |
| // Try to find the associated symbol definition. |
| // Symbol must have external linkage. |
| StringRef name = acleSeSym->getName().substr(std::strlen(ACLESESYM_PREFIX)); |
| Symbol *sym = symtab.find(name); |
| if (!sym) { |
| error(toString(acleSeSym->file) + ": cmse special symbol '" + |
| acleSeSym->getName() + |
| "' detected, but no associated entry function definition '" + name + |
| "' with external linkage found"); |
| continue; |
| } |
| |
| std::string errMsg = checkCmseSymAttributes(acleSeSym, sym); |
| if (!errMsg.empty()) { |
| error(errMsg); |
| continue; |
| } |
| |
| // <sym> may be redefined later in the link in .gnu.sgstubs |
| symtab.cmseSymMap[name] = {acleSeSym, sym}; |
| } |
| |
| // If this is an Arm CMSE secure app, replace references to entry symbol <sym> |
| // with its corresponding special symbol __acle_se_<sym>. |
| parallelForEach(ctx.objectFiles, [&](InputFile *file) { |
| MutableArrayRef<Symbol *> syms = file->getMutableSymbols(); |
| for (size_t i = 0, e = syms.size(); i != e; ++i) { |
| StringRef symName = syms[i]->getName(); |
| if (symtab.cmseSymMap.count(symName)) |
| syms[i] = symtab.cmseSymMap[symName].acleSeSym; |
| } |
| }); |
| } |
| |
| class elf::ArmCmseSGVeneer { |
| public: |
| ArmCmseSGVeneer(Symbol *sym, Symbol *acleSeSym, |
| std::optional<uint64_t> addr = std::nullopt) |
| : sym(sym), acleSeSym(acleSeSym), entAddr{addr} {} |
| static const size_t size{ACLESESYM_SIZE}; |
| const std::optional<uint64_t> getAddr() const { return entAddr; }; |
| |
| Symbol *sym; |
| Symbol *acleSeSym; |
| uint64_t offset = 0; |
| |
| private: |
| const std::optional<uint64_t> entAddr; |
| }; |
| |
| ArmCmseSGSection::ArmCmseSGSection() |
| : SyntheticSection(llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_EXECINSTR, |
| llvm::ELF::SHT_PROGBITS, |
| /*alignment=*/32, ".gnu.sgstubs") { |
| entsize = ACLESESYM_SIZE; |
| // The range of addresses used in the CMSE import library should be fixed. |
| for (auto &[_, sym] : symtab.cmseImportLib) { |
| if (impLibMaxAddr <= sym->value) |
| impLibMaxAddr = sym->value + sym->size; |
| } |
| if (symtab.cmseSymMap.empty()) |
| return; |
| addMappingSymbol(); |
| for (auto &[_, entryFunc] : symtab.cmseSymMap) |
| addSGVeneer(cast<Defined>(entryFunc.acleSeSym), |
| cast<Defined>(entryFunc.sym)); |
| for (auto &[_, sym] : symtab.cmseImportLib) { |
| if (!symtab.inCMSEOutImpLib.count(sym->getName())) |
| warn("entry function '" + sym->getName() + |
| "' from CMSE import library is not present in secure application"); |
| } |
| |
| if (!symtab.cmseImportLib.empty() && config->cmseOutputLib.empty()) { |
| for (auto &[_, entryFunc] : symtab.cmseSymMap) { |
| Symbol *sym = entryFunc.sym; |
| if (!symtab.inCMSEOutImpLib.count(sym->getName())) |
| warn("new entry function '" + sym->getName() + |
| "' introduced but no output import library specified"); |
| } |
| } |
| } |
| |
| void ArmCmseSGSection::addSGVeneer(Symbol *acleSeSym, Symbol *sym) { |
| entries.emplace_back(acleSeSym, sym); |
| if (symtab.cmseImportLib.count(sym->getName())) |
| symtab.inCMSEOutImpLib[sym->getName()] = true; |
| // Symbol addresses different, nothing to do. |
| if (acleSeSym->file != sym->file || |
| cast<Defined>(*acleSeSym).value != cast<Defined>(*sym).value) |
| return; |
| // Only secure symbols with values equal to that of it's non-secure |
| // counterpart needs to be in the .gnu.sgstubs section. |
| ArmCmseSGVeneer *ss = nullptr; |
| if (symtab.cmseImportLib.count(sym->getName())) { |
| Defined *impSym = symtab.cmseImportLib[sym->getName()]; |
| ss = make<ArmCmseSGVeneer>(sym, acleSeSym, impSym->value); |
| } else { |
| ss = make<ArmCmseSGVeneer>(sym, acleSeSym); |
| ++newEntries; |
| } |
| sgVeneers.emplace_back(ss); |
| } |
| |
| void ArmCmseSGSection::writeTo(uint8_t *buf) { |
| for (ArmCmseSGVeneer *s : sgVeneers) { |
| uint8_t *p = buf + s->offset; |
| write16(p + 0, 0xe97f); // SG |
| write16(p + 2, 0xe97f); |
| write16(p + 4, 0xf000); // B.W S |
| write16(p + 6, 0xb000); |
| target->relocateNoSym(p + 4, R_ARM_THM_JUMP24, |
| s->acleSeSym->getVA() - |
| (getVA() + s->offset + s->size)); |
| } |
| } |
| |
| void ArmCmseSGSection::addMappingSymbol() { |
| addSyntheticLocal("$t", STT_NOTYPE, /*off=*/0, /*size=*/0, *this); |
| } |
| |
| size_t ArmCmseSGSection::getSize() const { |
| if (sgVeneers.empty()) |
| return (impLibMaxAddr ? impLibMaxAddr - getVA() : 0) + newEntries * entsize; |
| |
| return entries.size() * entsize; |
| } |
| |
| void ArmCmseSGSection::finalizeContents() { |
| if (sgVeneers.empty()) |
| return; |
| |
| auto it = |
| std::stable_partition(sgVeneers.begin(), sgVeneers.end(), |
| [](auto *i) { return i->getAddr().has_value(); }); |
| std::sort(sgVeneers.begin(), it, [](auto *a, auto *b) { |
| return a->getAddr().value() < b->getAddr().value(); |
| }); |
| // This is the partition of the veneers with fixed addresses. |
| uint64_t addr = (*sgVeneers.begin())->getAddr().has_value() |
| ? (*sgVeneers.begin())->getAddr().value() |
| : getVA(); |
| // Check if the start address of '.gnu.sgstubs' correspond to the |
| // linker-synthesized veneer with the lowest address. |
| if ((getVA() & ~1) != (addr & ~1)) { |
| error("start address of '.gnu.sgstubs' is different from previous link"); |
| return; |
| } |
| |
| for (size_t i = 0; i < sgVeneers.size(); ++i) { |
| ArmCmseSGVeneer *s = sgVeneers[i]; |
| s->offset = i * s->size; |
| Defined(file, StringRef(), s->sym->binding, s->sym->stOther, s->sym->type, |
| s->offset | 1, s->size, this) |
| .overwrite(*s->sym); |
| } |
| } |
| |
| // Write the CMSE import library to disk. |
| // The CMSE import library is a relocatable object with only a symbol table. |
| // The symbols are copies of the (absolute) symbols of the secure gateways |
| // in the executable output by this link. |
| // See ArmĀ® v8-M Security Extensions: Requirements on Development Tools |
| // https://developer.arm.com/documentation/ecm0359818/latest |
| template <typename ELFT> void elf::writeARMCmseImportLib() { |
| StringTableSection *shstrtab = |
| make<StringTableSection>(".shstrtab", /*dynamic=*/false); |
| StringTableSection *strtab = |
| make<StringTableSection>(".strtab", /*dynamic=*/false); |
| SymbolTableBaseSection *impSymTab = make<SymbolTableSection<ELFT>>(*strtab); |
| |
| SmallVector<std::pair<OutputSection *, SyntheticSection *>, 0> osIsPairs; |
| osIsPairs.emplace_back(make<OutputSection>(strtab->name, 0, 0), strtab); |
| osIsPairs.emplace_back(make<OutputSection>(impSymTab->name, 0, 0), impSymTab); |
| osIsPairs.emplace_back(make<OutputSection>(shstrtab->name, 0, 0), shstrtab); |
| |
| std::sort(symtab.cmseSymMap.begin(), symtab.cmseSymMap.end(), |
| [](const auto &a, const auto &b) -> bool { |
| return a.second.sym->getVA() < b.second.sym->getVA(); |
| }); |
| // Copy the secure gateway entry symbols to the import library symbol table. |
| for (auto &p : symtab.cmseSymMap) { |
| Defined *d = cast<Defined>(p.second.sym); |
| impSymTab->addSymbol(makeDefined(nullptr, d->getName(), d->computeBinding(), |
| /*stOther=*/0, STT_FUNC, d->getVA(), |
| d->getSize(), nullptr)); |
| } |
| |
| size_t idx = 0; |
| uint64_t off = sizeof(typename ELFT::Ehdr); |
| for (auto &[osec, isec] : osIsPairs) { |
| osec->sectionIndex = ++idx; |
| osec->recordSection(isec); |
| osec->finalizeInputSections(); |
| osec->shName = shstrtab->addString(osec->name); |
| osec->size = isec->getSize(); |
| isec->finalizeContents(); |
| osec->offset = alignToPowerOf2(off, osec->addralign); |
| off = osec->offset + osec->size; |
| } |
| |
| const uint64_t sectionHeaderOff = alignToPowerOf2(off, config->wordsize); |
| const auto shnum = osIsPairs.size() + 1; |
| const uint64_t fileSize = |
| sectionHeaderOff + shnum * sizeof(typename ELFT::Shdr); |
| const unsigned flags = |
| config->mmapOutputFile ? 0 : (unsigned)FileOutputBuffer::F_no_mmap; |
| unlinkAsync(config->cmseOutputLib); |
| Expected<std::unique_ptr<FileOutputBuffer>> bufferOrErr = |
| FileOutputBuffer::create(config->cmseOutputLib, fileSize, flags); |
| if (!bufferOrErr) { |
| error("failed to open " + config->cmseOutputLib + ": " + |
| llvm::toString(bufferOrErr.takeError())); |
| return; |
| } |
| |
| // Write the ELF Header |
| std::unique_ptr<FileOutputBuffer> &buffer = *bufferOrErr; |
| uint8_t *const buf = buffer->getBufferStart(); |
| memcpy(buf, "\177ELF", 4); |
| auto *eHdr = reinterpret_cast<typename ELFT::Ehdr *>(buf); |
| eHdr->e_type = ET_REL; |
| eHdr->e_entry = 0; |
| eHdr->e_shoff = sectionHeaderOff; |
| eHdr->e_ident[EI_CLASS] = ELFCLASS32; |
| eHdr->e_ident[EI_DATA] = config->isLE ? ELFDATA2LSB : ELFDATA2MSB; |
| eHdr->e_ident[EI_VERSION] = EV_CURRENT; |
| eHdr->e_ident[EI_OSABI] = config->osabi; |
| eHdr->e_ident[EI_ABIVERSION] = 0; |
| eHdr->e_machine = EM_ARM; |
| eHdr->e_version = EV_CURRENT; |
| eHdr->e_flags = config->eflags; |
| eHdr->e_ehsize = sizeof(typename ELFT::Ehdr); |
| eHdr->e_phnum = 0; |
| eHdr->e_shentsize = sizeof(typename ELFT::Shdr); |
| eHdr->e_phoff = 0; |
| eHdr->e_phentsize = 0; |
| eHdr->e_shnum = shnum; |
| eHdr->e_shstrndx = shstrtab->getParent()->sectionIndex; |
| |
| // Write the section header table. |
| auto *sHdrs = reinterpret_cast<typename ELFT::Shdr *>(buf + eHdr->e_shoff); |
| for (auto &[osec, _] : osIsPairs) |
| osec->template writeHeaderTo<ELFT>(++sHdrs); |
| |
| // Write section contents to a mmap'ed file. |
| { |
| parallel::TaskGroup tg; |
| for (auto &[osec, _] : osIsPairs) |
| osec->template writeTo<ELFT>(buf + osec->offset, tg); |
| } |
| |
| if (auto e = buffer->commit()) |
| fatal("failed to write output '" + buffer->getPath() + |
| "': " + toString(std::move(e))); |
| } |
| |
| TargetInfo *elf::getARMTargetInfo() { |
| static ARM target; |
| return ⌖ |
| } |
| |
| template void elf::writeARMCmseImportLib<ELF32LE>(); |
| template void elf::writeARMCmseImportLib<ELF32BE>(); |
| template void elf::writeARMCmseImportLib<ELF64LE>(); |
| template void elf::writeARMCmseImportLib<ELF64BE>(); |
| |
| template void ObjFile<ELF32LE>::importCmseSymbols(); |
| template void ObjFile<ELF32BE>::importCmseSymbols(); |
| template void ObjFile<ELF64LE>::importCmseSymbols(); |
| template void ObjFile<ELF64BE>::importCmseSymbols(); |