maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/lld/ELF/Arch/ARM.cpp

853 lines
31 KiB
C++
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

//===- 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, 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;
};
} // 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;
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;
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_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_LDR_PC_G0:
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:
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) {
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, 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(&(.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 = sym.getGotPltVA() - pltEntryAddr - 8;
if (!llvm::isUInt<27>(offset)) {
// We cannot encode the Offset, use the long form.
writePltLong(buf, sym.getGotPltVA(), pltEntryAddr);
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,
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 (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 STT_FUNC Symbol has bit 0 set (Thumb).
if (s.isFunc() && expr == R_PC && (s.getVA() & 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 STT_FUNC Symbol has bit 0 clear (ARM).
if (expr == R_PLT_PC || (s.isFunc() && (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;
}
// 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());
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(getErrorLocation(loc) + "branch and link relocation: " +
toString(relt) + " to STT_SECTION symbol " +
cast<Defined>(s).section->name + " ; interworking not performed");
} 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");
}
}
// Utility functions taken from ARMAddressingModes.h, only changes are LLD
// coding style.
// 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));
}
// Rotate a 32-bit unsigned value left by a specified amt of bits.
static uint32_t rotl32(uint32_t val, uint32_t amt) {
assert(amt < 32 && "Invalid rotate amount");
return (val << amt) | (val >> ((32 - amt) & 31));
}
// Try to encode a 32-bit unsigned immediate imm with an immediate shifter
// operand, this form is an 8-bit immediate rotated right by an even number of
// bits. We compute the rotate amount to use. If this immediate value cannot be
// handled with a single shifter-op, determine a good rotate amount that will
// take a maximal chunk of bits out of the immediate.
static uint32_t getSOImmValRotate(uint32_t imm) {
// 8-bit (or less) immediates are trivially shifter_operands with a rotate
// of zero.
if ((imm & ~255U) == 0)
return 0;
// Use CTZ to compute the rotate amount.
unsigned tz = llvm::countTrailingZeros(imm);
// Rotate amount must be even. Something like 0x200 must be rotated 8 bits,
// not 9.
unsigned rotAmt = tz & ~1;
// If we can handle this spread, return it.
if ((rotr32(imm, rotAmt) & ~255U) == 0)
return (32 - rotAmt) & 31; // HW rotates right, not left.
// For values like 0xF000000F, we should ignore the low 6 bits, then
// retry the hunt.
if (imm & 63U) {
unsigned tz2 = countTrailingZeros(imm & ~63U);
unsigned rotAmt2 = tz2 & ~1;
if ((rotr32(imm, rotAmt2) & ~255U) == 0)
return (32 - rotAmt2) & 31; // HW rotates right, not left.
}
// Otherwise, we have no way to cover this span of bits with a single
// shifter_op immediate. Return a chunk of bits that will be useful to
// handle.
return (32 - rotAmt) & 31; // HW rotates right, not left.
}
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:
write32le(loc, val);
break;
case R_ARM_PREL31:
checkInt(loc, val, 31, rel);
write32le(loc, (read32le(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 = (read32le(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);
write32le(loc, 0xfa000000 | // opcode
((val & 2) << 23) | // H
((val >> 2) & 0x00ffffff)); // imm24
break;
}
// 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, rel);
write32le(loc, (read32le(loc) & ~0x00ffffff) | ((val >> 2) & 0x00ffffff));
break;
case R_ARM_THM_JUMP11:
checkInt(loc, val, 12, rel);
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, rel);
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, 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 = (read16le(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);
write16le(loc + 2, read16le(loc + 2) & ~0x1000);
} else {
write16le(loc + 2, (read16le(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);
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, rel);
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:
case R_ARM_MOVW_BREL_NC:
write32le(loc, (read32le(loc) & ~0x000f0fff) | ((val & 0xf000) << 4) |
(val & 0x0fff));
break;
case R_ARM_MOVT_ABS:
case R_ARM_MOVT_PREL:
case R_ARM_MOVT_BREL:
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:
case R_ARM_THM_MOVT_BREL:
// 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:
case R_ARM_THM_MOVW_BREL_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;
case R_ARM_ALU_PC_G0: {
// ADR (literal) add = bit23, sub = bit22
// literal is a 12-bit modified immediate, made up of a 4-bit even rotate
// right and an 8-bit immediate. The code-sequence here is derived from
// ARMAddressingModes.h in llvm/Target/ARM/MCTargetDesc. In our case we
// want to give an error if we cannot encode the constant.
uint32_t opcode = 0x00800000;
if (val >> 63) {
opcode = 0x00400000;
val = ~val + 1;
}
if ((val & ~255U) != 0) {
uint32_t rotAmt = getSOImmValRotate(val);
// Error if we cannot encode this with a single shift
if (rotr32(~255U, rotAmt) & val)
error(getErrorLocation(loc) + "unencodeable immediate " +
Twine(val).str() + " for relocation " + toString(rel.type));
val = rotl32(val, rotAmt) | ((rotAmt >> 1) << 8);
}
write32le(loc, (read32le(loc) & 0xff0ff000) | opcode | val);
break;
}
case R_ARM_LDR_PC_G0: {
// R_ARM_LDR_PC_G0 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
int64_t imm = val;
uint32_t u = 0x00800000;
if (imm < 0) {
imm = -imm;
u = 0;
}
checkUInt(loc, imm, 12, rel);
write32le(loc, (read32le(loc) & 0xff7ff000) | u | imm);
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);
write16le(loc, (read16le(loc) & 0xfb0f) | sub | (imm & 0x800) >> 1);
write16le(loc + 2,
(read16le(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);
write16le(loc, (read16le(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);
write16le(loc, read16le(loc) | u);
write16le(loc + 2, (read16le(loc + 2) & 0xf000) | imm12);
break;
}
default:
error(getErrorLocation(loc) + "unrecognized relocation " +
toString(rel.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:
case R_ARM_MOVW_BREL_NC:
case R_ARM_MOVT_BREL: {
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:
case R_ARM_THM_MOVW_BREL_NC:
case R_ARM_THM_MOVT_BREL: {
// 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
}
case R_ARM_ALU_PC_G0: {
// 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 = read32le(buf);
uint32_t val = rotr32(instr & 0xff, ((instr & 0xf00) >> 8) * 2);
return (instr & 0x00400000) ? -val : val;
}
case R_ARM_LDR_PC_G0: {
// ADR (literal) add = bit23, sub = bit22
// LDR (literal) u = bit23 unsigned imm12
bool u = read32le(buf) & 0x00800000;
uint32_t imm12 = read32le(buf) & 0xfff;
return u ? imm12 : -imm12;
}
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 = read16le(buf);
uint16_t lo = read16le(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) – 4)
// this trick permits the PC bias of -4 to be encoded using imm8 = 0xff
return ((((read16le(buf) & 0xff) << 2) + 4) & 0x3ff) - 4;
case R_ARM_THM_PC12: {
// LDR (literal) encoding T2, add = (U == '1') imm12
bool u = read16le(buf) & 0x0080;
uint64_t imm12 = read16le(buf + 2) & 0x0fff;
return u ? imm12 : -imm12;
}
}
}
TargetInfo *elf::getARMTargetInfo() {
static ARM target;
return &target;
}
Reference in New Issue View Git Blame Copy Permalink