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llvm-toolchain-9/lld/ELF/Arch/ARM.cpp

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//===- 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 "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "Thunks.h"
#include "lld/Common/ErrorHandler.h"
#include "llvm/Object/ELF.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
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, uint64_t gotPltEntryAddr, uint64_t pltEntryAddr,
int32_t index, unsigned relOff) 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) const override;
uint32_t getThunkSectionSpacing() const override;
bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
void relocateOne(uint8_t *loc, RelType type, uint64_t val) const override;
};
} // namespace
ARM::ARM() {
copyRel = R_ARM_COPY;
relativeRel = R_ARM_RELATIVE;
iRelativeRel = R_ARM_IRELATIVE;
gotRel = R_ARM_GLOB_DAT;
noneRel = R_ARM_NONE;
pltRel = R_ARM_JUMP_SLOT;
symbolicRel = R_ARM_ABS32;
tlsGotRel = R_ARM_TLS_TPOFF32;
tlsModuleIndexRel = R_ARM_TLS_DTPMOD32;
tlsOffsetRel = R_ARM_TLS_DTPOFF32;
gotBaseSymInGotPlt = false;
pltEntrySize = 16;
pltHeaderSize = 32;
trapInstr = {0xd4, 0xd4, 0xd4, 0xd4};
needsThunks = true;
}
uint32_t ARM::calcEFlags() const {
// The ABIFloatType is used by loaders to detect the floating point calling
// convention.
uint32_t abiFloatType = 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;
// 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;
}
RelExpr ARM::getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const {
switch (type) {
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_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_NONE:
return R_NONE;
case R_ARM_TLS_LE32:
return R_TLS;
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_HINT;
default:
return R_ABS;
}
}
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 {
write32le(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.
write32le(buf, s.getVA());
}
// Long form PLT Header that does not have any restrictions on the displacement
// of the .plt from the .plt.got.
static void writePltHeaderLong(uint8_t *buf) {
const uint8_t pltData[] = {
0x04, 0xe0, 0x2d, 0xe5, // str lr, [sp,#-4]!
0x04, 0xe0, 0x9f, 0xe5, // ldr lr, L2
0x0e, 0xe0, 0x8f, 0xe0, // L1: add lr, pc, lr
0x08, 0xf0, 0xbe, 0xe5, // ldr pc, [lr, #8]
0x00, 0x00, 0x00, 0x00, // L2: .word &(.got.plt) - L1 - 8
0xd4, 0xd4, 0xd4, 0xd4, // Pad to 32-byte boundary
0xd4, 0xd4, 0xd4, 0xd4, // Pad to 32-byte boundary
0xd4, 0xd4, 0xd4, 0xd4};
memcpy(buf, pltData, sizeof(pltData));
uint64_t gotPlt = in.gotPlt->getVA();
uint64_t l1 = in.plt->getVA() + 8;
write32le(buf + 16, gotPlt - l1 - 8);
}
// The default PLT header requires the .plt.got 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;
}
write32le(buf + 0, pltData[0]);
write32le(buf + 4, pltData[1] | ((offset >> 20) & 0xff));
write32le(buf + 8, pltData[2] | ((offset >> 12) & 0xff));
write32le(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 .plt.got.
static void writePltLong(uint8_t *buf, uint64_t gotPltEntryAddr,
uint64_t pltEntryAddr, int32_t index,
unsigned relOff) {
const uint8_t pltData[] = {
0x04, 0xc0, 0x9f, 0xe5, // ldr ip, L2
0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
0x00, 0xf0, 0x9c, 0xe5, // ldr pc, [ip]
0x00, 0x00, 0x00, 0x00, // L2: .word Offset(&(.plt.got) - L1 - 8
};
memcpy(buf, pltData, sizeof(pltData));
uint64_t l1 = pltEntryAddr + 4;
write32le(buf + 12, gotPltEntryAddr - l1 - 8);
}
// The default PLT entries require the .plt.got to be within 128 Mb of the
// .plt in the positive direction.
void ARM::writePlt(uint8_t *buf, uint64_t gotPltEntryAddr,
uint64_t pltEntryAddr, int32_t index,
unsigned relOff) 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(&(.plt.got) - L1 - 8
0xe28cca00, // add ip, ip, #0x000NN000 Offset(&(.plt.got) - L1 - 8
0xe5bcf000, // ldr pc, [ip, #0x00000NNN] Offset(&(.plt.got) - L1 - 8
};
uint64_t offset = gotPltEntryAddr - pltEntryAddr - 8;
if (!llvm::isUInt<27>(offset)) {
// We cannot encode the Offset, use the long form.
writePltLong(buf, gotPltEntryAddr, pltEntryAddr, index, relOff);
return;
}
write32le(buf + 0, pltData[0] | ((offset >> 20) & 0xff));
write32le(buf + 4, pltData[1] | ((offset >> 12) & 0xff));
write32le(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) 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 (s.isUndefWeak() && !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 Symbol has bit 0 set (Thumb).
if (expr == R_PC && ((s.getVA() & 1) == 1))
return true;
LLVM_FALLTHROUGH;
case R_ARM_CALL: {
uint64_t dst = (expr == R_PLT_PC) ? s.getPltVA() : s.getVA();
return !inBranchRange(type, branchAddr, dst);
}
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 Symbol has bit 0 clear (ARM).
if (expr == R_PLT_PC || ((s.getVA() & 1) == 0))
return true;
LLVM_FALLTHROUGH;
case R_ARM_THM_CALL: {
uint64_t dst = (expr == R_PLT_PC) ? s.getPltVA() : s.getVA();
return !inBranchRange(type, branchAddr, dst);
}
}
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 {
uint64_t range;
uint64_t instrSize;
switch (type) {
case R_ARM_PC24:
case R_ARM_PLT32:
case R_ARM_JUMP24:
case R_ARM_CALL:
range = 0x2000000;
instrSize = 4;
break;
case R_ARM_THM_JUMP19:
range = 0x100000;
instrSize = 2;
break;
case R_ARM_THM_JUMP24:
case R_ARM_THM_CALL:
range = config->armJ1J2BranchEncoding ? 0x1000000 : 0x400000;
instrSize = 2;
break;
default:
return true;
}
// PC at Src is 2 instructions ahead, immediate of branch is signed
if (src > dst)
range -= 2 * instrSize;
else
range += instrSize;
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;
uint64_t distance = (src > dst) ? src - dst : dst - src;
return distance <= range;
}
void ARM::relocateOne(uint8_t *loc, RelType type, uint64_t val) const {
switch (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:
write32le(loc, val);
break;
case R_ARM_PREL31:
checkInt(loc, val, 31, type);
write32le(loc, (read32le(loc) & 0x80000000) | (val & ~0x80000000));
break;
case R_ARM_CALL:
// R_ARM_CALL is used for BL and BLX instructions, depending on the
// value of bit 0 of Val, we must select a BL or BLX instruction
if (val & 1) {
// If bit 0 of Val is 1 the target is Thumb, we must select a BLX.
// The BLX encoding is 0xfa:H:imm24 where Val = imm24:H:'1'
checkInt(loc, val, 26, type);
write32le(loc, 0xfa000000 | // opcode
((val & 2) << 23) | // H
((val >> 2) & 0x00ffffff)); // imm24
break;
}
if ((read32le(loc) & 0xfe000000) == 0xfa000000)
// BLX (always unconditional) instruction to an ARM Target, select an
// unconditional BL.
write32le(loc, 0xeb000000 | (read32le(loc) & 0x00ffffff));
// fall through as BL encoding is shared with B
LLVM_FALLTHROUGH;
case R_ARM_JUMP24:
case R_ARM_PC24:
case R_ARM_PLT32:
checkInt(loc, val, 26, type);
write32le(loc, (read32le(loc) & ~0x00ffffff) | ((val >> 2) & 0x00ffffff));
break;
case R_ARM_THM_JUMP11:
checkInt(loc, val, 12, type);
write16le(loc, (read32le(loc) & 0xf800) | ((val >> 1) & 0x07ff));
break;
case R_ARM_THM_JUMP19:
// Encoding T3: Val = S:J2:J1:imm6:imm11:0
checkInt(loc, val, 21, type);
write16le(loc,
(read16le(loc) & 0xfbc0) | // opcode cond
((val >> 10) & 0x0400) | // S
((val >> 12) & 0x003f)); // imm6
write16le(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, depending on the
// value of bit 0 of Val, we must select a BL or BLX instruction
if ((val & 1) == 0) {
// Ensure BLX destination is 4-byte aligned. As BLX instruction may
// only be two byte aligned. This must be done before overflow check
val = alignTo(val, 4);
}
// Bit 12 is 0 for BLX, 1 for BL
write16le(loc + 2, (read16le(loc + 2) & ~0x1000) | (val & 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, type);
write16le(loc,
0xf000 | // opcode
((val >> 12) & 0x07ff)); // imm11
write16le(loc + 2,
(read16le(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
LLVM_FALLTHROUGH;
case R_ARM_THM_JUMP24:
// Encoding B T4, BL T1, BLX T2: Val = S:I1:I2:imm10:imm11:0
checkInt(loc, val, 25, type);
write16le(loc,
0xf000 | // opcode
((val >> 14) & 0x0400) | // S
((val >> 12) & 0x03ff)); // imm10
write16le(loc + 2,
(read16le(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:
write32le(loc, (read32le(loc) & ~0x000f0fff) | ((val & 0xf000) << 4) |
(val & 0x0fff));
break;
case R_ARM_MOVT_ABS:
case R_ARM_MOVT_PREL:
write32le(loc, (read32le(loc) & ~0x000f0fff) |
(((val >> 16) & 0xf000) << 4) | ((val >> 16) & 0xfff));
break;
case R_ARM_THM_MOVT_ABS:
case R_ARM_THM_MOVT_PREL:
// Encoding T1: A = imm4:i:imm3:imm8
write16le(loc,
0xf2c0 | // opcode
((val >> 17) & 0x0400) | // i
((val >> 28) & 0x000f)); // imm4
write16le(loc + 2,
(read16le(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:
// Encoding T3: A = imm4:i:imm3:imm8
write16le(loc,
0xf240 | // opcode
((val >> 1) & 0x0400) | // i
((val >> 12) & 0x000f)); // imm4
write16le(loc + 2,
(read16le(loc + 2) & 0x8f00) | // opcode
((val << 4) & 0x7000) | // imm3
(val & 0x00ff)); // imm8
break;
default:
error(getErrorLocation(loc) + "unrecognized relocation " + toString(type));
}
}
int64_t ARM::getImplicitAddend(const uint8_t *buf, RelType type) const {
switch (type) {
default:
return 0;
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_TARGET1:
case R_ARM_TARGET2:
case R_ARM_TLS_GD32:
case R_ARM_TLS_LDM32:
case R_ARM_TLS_LDO32:
case R_ARM_TLS_IE32:
case R_ARM_TLS_LE32:
return SignExtend64<32>(read32le(buf));
case R_ARM_PREL31:
return SignExtend64<31>(read32le(buf));
case R_ARM_CALL:
case R_ARM_JUMP24:
case R_ARM_PC24:
case R_ARM_PLT32:
return SignExtend64<26>(read32le(buf) << 2);
case R_ARM_THM_JUMP11:
return SignExtend64<12>(read16le(buf) << 1);
case R_ARM_THM_JUMP19: {
// Encoding T3: A = S:J2:J1:imm10:imm6:0
uint16_t hi = read16le(buf);
uint16_t lo = read16le(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 = read16le(buf);
uint16_t lo = read16le(buf + 2);
return SignExtend64<22>(((hi & 0x7ff) << 12) | // imm11
((lo & 0x7ff) << 1)); // imm11:0
break;
}
LLVM_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 = read16le(buf);
uint16_t lo = read16le(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: {
uint64_t val = read32le(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: {
// Encoding T3: A = imm4:i:imm3:imm8
uint16_t hi = read16le(buf);
uint16_t lo = read16le(buf + 2);
return SignExtend64<16>(((hi & 0x000f) << 12) | // imm4
((hi & 0x0400) << 1) | // i
((lo & 0x7000) >> 4) | // imm3
(lo & 0x00ff)); // imm8
}
}
}
TargetInfo *elf::getARMTargetInfo() {
static ARM target;
return &target;
}
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