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llvm-mirror/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
Oliver Stannard e538054e6d [Assembler] Make fatal assembler errors non-fatal 
Currently, if the assembler encounters an error after parsing (such as an
out-of-range fixup), it reports this as a fatal error, and so stops after the
first error. However, for most of these there is an obvious way to recover
after emitting the error, such as emitting the fixup with a value of zero. This
means that we can report on all of the errors in a file, not just the first
one. MCContext::reportError records the fact that an error was encountered, so
we won't actually emit an object file with the incorrect contents.

Differential Revision: http://reviews.llvm.org/D14717

llvm-svn: 253328
2015-11-17 10:00:43 +00:00

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//===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/AArch64FixupKinds.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCMachObjectWriter.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachO.h"
using namespace llvm;
namespace {
class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
const MCSymbolRefExpr *Sym,
unsigned &Log2Size, const MCAssembler &Asm);
public:
AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype)
: MCMachObjectTargetWriter(true /* is64Bit */, CPUType, CPUSubtype) {}
void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
const MCAsmLayout &Layout, const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) override;
};
}
bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
const MCFixup &Fixup, unsigned &RelocType, const MCSymbolRefExpr *Sym,
unsigned &Log2Size, const MCAssembler &Asm) {
RelocType = unsigned(MachO::ARM64_RELOC_UNSIGNED);
Log2Size = ~0U;
switch ((unsigned)Fixup.getKind()) {
default:
return false;
case FK_Data_1:
Log2Size = llvm::Log2_32(1);
return true;
case FK_Data_2:
Log2Size = llvm::Log2_32(2);
return true;
case FK_Data_4:
Log2Size = llvm::Log2_32(4);
if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
return true;
case FK_Data_8:
Log2Size = llvm::Log2_32(8);
if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
return true;
case AArch64::fixup_aarch64_add_imm12:
case AArch64::fixup_aarch64_ldst_imm12_scale1:
case AArch64::fixup_aarch64_ldst_imm12_scale2:
case AArch64::fixup_aarch64_ldst_imm12_scale4:
case AArch64::fixup_aarch64_ldst_imm12_scale8:
case AArch64::fixup_aarch64_ldst_imm12_scale16:
Log2Size = llvm::Log2_32(4);
switch (Sym->getKind()) {
default:
llvm_unreachable("Unexpected symbol reference variant kind!");
case MCSymbolRefExpr::VK_PAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_PAGEOFF12);
return true;
case MCSymbolRefExpr::VK_GOTPAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12);
return true;
case MCSymbolRefExpr::VK_TLVPPAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12);
return true;
}
case AArch64::fixup_aarch64_pcrel_adrp_imm21:
Log2Size = llvm::Log2_32(4);
// This encompasses the relocation for the whole 21-bit value.
switch (Sym->getKind()) {
default: {
Asm.getContext().reportError(Fixup.getLoc(),
"ADR/ADRP relocations must be GOT relative");
return false;
}
case MCSymbolRefExpr::VK_PAGE:
RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
return true;
case MCSymbolRefExpr::VK_GOTPAGE:
RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGE21);
return true;
case MCSymbolRefExpr::VK_TLVPPAGE:
RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGE21);
return true;
}
return true;
case AArch64::fixup_aarch64_pcrel_branch26:
case AArch64::fixup_aarch64_pcrel_call26:
Log2Size = llvm::Log2_32(4);
RelocType = unsigned(MachO::ARM64_RELOC_BRANCH26);
return true;
}
}
static bool canUseLocalRelocation(const MCSectionMachO &Section,
const MCSymbol &Symbol, unsigned Log2Size) {
// Debug info sections can use local relocations.
if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
return true;
// Otherwise, only pointer sized relocations are supported.
if (Log2Size != 3)
return false;
// But only if they don't point to a few forbidden sections.
if (!Symbol.isInSection())
return true;
const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
return false;
if (RefSec.getSegmentName() == "__DATA" &&
RefSec.getSectionName() == "__objc_classrefs")
return false;
// FIXME: ld64 currently handles internal pointer-sized relocations
// incorrectly (applying the addend twice). We should be able to return true
// unconditionally by this point when that's fixed.
return false;
}
void AArch64MachObjectWriter::recordRelocation(
MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
// See <reloc.h>.
uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
unsigned Log2Size = 0;
int64_t Value = 0;
unsigned Index = 0;
unsigned Type = 0;
unsigned Kind = Fixup.getKind();
const MCSymbol *RelSymbol = nullptr;
FixupOffset += Fixup.getOffset();
// AArch64 pcrel relocation addends do not include the section offset.
if (IsPCRel)
FixedValue += FixupOffset;
// ADRP fixups use relocations for the whole symbol value and only
// put the addend in the instruction itself. Clear out any value the
// generic code figured out from the sybmol definition.
if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
FixedValue = 0;
// imm19 relocations are for conditional branches, which require
// assembler local symbols. If we got here, that's not what we have,
// so complain loudly.
if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
Asm.getContext().reportError(Fixup.getLoc(),
"conditional branch requires assembler-local"
" label. '" +
Target.getSymA()->getSymbol().getName() +
"' is external.");
return;
}
// 14-bit branch relocations should only target internal labels, and so
// should never get here.
if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
Asm.getContext().reportError(Fixup.getLoc(),
"Invalid relocation on conditional branch!");
return;
}
if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
Asm)) {
Asm.getContext().reportError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
return;
}
Value = Target.getConstant();
if (Target.isAbsolute()) { // constant
// FIXME: Should this always be extern?
// SymbolNum of 0 indicates the absolute section.
Type = MachO::ARM64_RELOC_UNSIGNED;
if (IsPCRel) {
Asm.getContext().reportError(Fixup.getLoc(),
"PC relative absolute relocation!");
return;
// FIXME: x86_64 sets the type to a branch reloc here. Should we do
// something similar?
}
} else if (Target.getSymB()) { // A - B + constant
const MCSymbol *A = &Target.getSymA()->getSymbol();
const MCSymbol *A_Base = Asm.getAtom(*A);
const MCSymbol *B = &Target.getSymB()->getSymbol();
const MCSymbol *B_Base = Asm.getAtom(*B);
// Check for "_foo@got - .", which comes through here as:
// Ltmp0:
// ... _foo@got - Ltmp0
if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
Layout.getSymbolOffset(*B) ==
Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
// SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
IsPCRel = 1;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
return;
} else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) {
// Otherwise, neither symbol can be modified.
Asm.getContext().reportError(Fixup.getLoc(),
"unsupported relocation of modified symbol");
return;
}
// We don't support PCrel relocations of differences.
if (IsPCRel) {
Asm.getContext().reportError(Fixup.getLoc(),
"unsupported pc-relative relocation of "
"difference");
return;
}
// AArch64 always uses external relocations. If there is no symbol to use as
// a base address (a local symbol with no preceding non-local symbol),
// error out.
//
// FIXME: We should probably just synthesize an external symbol and use
// that.
if (!A_Base) {
Asm.getContext().reportError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + A->getName() +
"'. Must have non-local symbol earlier in section.");
return;
}
if (!B_Base) {
Asm.getContext().reportError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + B->getName() +
"'. Must have non-local symbol earlier in section.");
return;
}
if (A_Base == B_Base && A_Base) {
Asm.getContext().reportError(
Fixup.getLoc(), "unsupported relocation with identical base");
return;
}
Value += (!A->getFragment() ? 0 : Writer->getSymbolAddress(*A, Layout)) -
(!A_Base || !A_Base->getFragment() ? 0 : Writer->getSymbolAddress(
*A_Base, Layout));
Value -= (!B->getFragment() ? 0 : Writer->getSymbolAddress(*B, Layout)) -
(!B_Base || !B_Base->getFragment() ? 0 : Writer->getSymbolAddress(
*B_Base, Layout));
Type = MachO::ARM64_RELOC_UNSIGNED;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
RelSymbol = B_Base;
Type = MachO::ARM64_RELOC_SUBTRACTOR;
} else { // A + constant
const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
const MCSectionMachO &Section =
static_cast<const MCSectionMachO &>(*Fragment->getParent());
bool CanUseLocalRelocation =
canUseLocalRelocation(Section, *Symbol, Log2Size);
if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
const MCSection &Sec = Symbol->getSection();
if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
Symbol->setUsedInReloc();
}
const MCSymbol *Base = Asm.getAtom(*Symbol);
// If the symbol is a variable and we weren't able to get a Base for it
// (i.e., it's not in the symbol table associated with a section) resolve
// the relocation based its expansion instead.
if (Symbol->isVariable() && !Base) {
// If the evaluation is an absolute value, just use that directly
// to keep things easy.
int64_t Res;
if (Symbol->getVariableValue()->evaluateAsAbsolute(
Res, Layout, Writer->getSectionAddressMap())) {
FixedValue = Res;
return;
}
// FIXME: Will the Target we already have ever have any data in it
// we need to preserve and merge with the new Target? How about
// the FixedValue?
if (!Symbol->getVariableValue()->evaluateAsRelocatable(Target, &Layout,
&Fixup)) {
Asm.getContext().reportError(Fixup.getLoc(),
"unable to resolve variable '" +
Symbol->getName() + "'");
return;
}
return recordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
FixedValue);
}
// Relocations inside debug sections always use local relocations when
// possible. This seems to be done because the debugger doesn't fully
// understand relocation entries and expects to find values that
// have already been fixed up.
if (Symbol->isInSection()) {
if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
Base = nullptr;
}
// AArch64 uses external relocations as much as possible. For debug
// sections, and for pointer-sized relocations (.quad), we allow section
// relocations. It's code sections that run into trouble.
if (Base) {
RelSymbol = Base;
// Add the local offset, if needed.
if (Base != Symbol)
Value +=
Layout.getSymbolOffset(*Symbol) - Layout.getSymbolOffset(*Base);
} else if (Symbol->isInSection()) {
if (!CanUseLocalRelocation) {
Asm.getContext().reportError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + Symbol->getName() +
"'. Must have non-local symbol earlier in section.");
return;
}
// Adjust the relocation to be section-relative.
// The index is the section ordinal (1-based).
const MCSection &Sec = Symbol->getSection();
Index = Sec.getOrdinal() + 1;
Value += Writer->getSymbolAddress(*Symbol, Layout);
if (IsPCRel)
Value -= Writer->getFragmentAddress(Fragment, Layout) +
Fixup.getOffset() + (1ULL << Log2Size);
} else {
// Resolve constant variables.
if (Symbol->isVariable()) {
int64_t Res;
if (Symbol->getVariableValue()->evaluateAsAbsolute(
Res, Layout, Writer->getSectionAddressMap())) {
FixedValue = Res;
return;
}
}
Asm.getContext().reportError(Fixup.getLoc(),
"unsupported relocation of variable '" +
Symbol->getName() + "'");
return;
}
}
// If the relocation kind is Branch26, Page21, or Pageoff12, any addend
// is represented via an Addend relocation, not encoded directly into
// the instruction.
if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
Type == MachO::ARM64_RELOC_PAGE21 ||
Type == MachO::ARM64_RELOC_PAGEOFF12) &&
Value) {
assert((Value & 0xff000000) == 0 && "Added relocation out of range!");
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 =
(Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
// Now set up the Addend relocation.
Type = MachO::ARM64_RELOC_ADDEND;
Index = Value;
RelSymbol = nullptr;
IsPCRel = 0;
Log2Size = 2;
// Put zero into the instruction itself. The addend is in the relocation.
Value = 0;
}
// If there's any addend left to handle, encode it in the instruction.
FixedValue = Value;
// struct relocation_info (8 bytes)
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 =
(Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
}
MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_pwrite_stream &OS,
uint32_t CPUType,
uint32_t CPUSubtype) {
return createMachObjectWriter(
new AArch64MachObjectWriter(CPUType, CPUSubtype), OS,
/*IsLittleEndian=*/true);
}
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