d3589edafc
`Data` now references the first byte of the fixup offset within the current fragment. MCAssembler::layout asserts that the fixup offset is within either the fixed-size content or the optional variable-size tail, as this is the most the generic code can validate without knowing the target-specific fixup size. Many backends applyFixup assert ``` assert(Offset + Size <= F.getSize() && "Invalid fixup offset!"); ``` This refactoring allows a subsequent change to move the fixed-size content outside of MCSection::ContentStorage, fixing the -fsanitize=pointer-overflow issue of #150846 Pull Request: https://github.com/llvm/llvm-project/pull/151724
117 lines
3.9 KiB
C++
117 lines
3.9 KiB
C++
//===-- WebAssemblyAsmBackend.cpp - WebAssembly Assembler Backend ---------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// This file implements the WebAssemblyAsmBackend class.
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///
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/WebAssemblyFixupKinds.h"
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#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSubtargetInfo.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/MC/MCWasmObjectWriter.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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namespace {
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class WebAssemblyAsmBackend final : public MCAsmBackend {
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bool Is64Bit;
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bool IsEmscripten;
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public:
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explicit WebAssemblyAsmBackend(bool Is64Bit, bool IsEmscripten)
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: MCAsmBackend(llvm::endianness::little), Is64Bit(Is64Bit),
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IsEmscripten(IsEmscripten) {}
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MCFixupKindInfo getFixupKindInfo(MCFixupKind Kind) const override;
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void applyFixup(const MCFragment &, const MCFixup &, const MCValue &Target,
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uint8_t *Data, uint64_t Value, bool) override;
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std::unique_ptr<MCObjectTargetWriter>
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createObjectTargetWriter() const override;
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bool writeNopData(raw_ostream &OS, uint64_t Count,
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const MCSubtargetInfo *STI) const override;
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};
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MCFixupKindInfo
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WebAssemblyAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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const static MCFixupKindInfo Infos[WebAssembly::NumTargetFixupKinds] = {
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// This table *must* be in the order that the fixup_* kinds are defined in
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// WebAssemblyFixupKinds.h.
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//
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// Name Offset (bits) Size (bits) Flags
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{"fixup_sleb128_i32", 0, 5 * 8, 0},
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{"fixup_sleb128_i64", 0, 10 * 8, 0},
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{"fixup_uleb128_i32", 0, 5 * 8, 0},
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{"fixup_uleb128_i64", 0, 10 * 8, 0},
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};
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if (Kind < FirstTargetFixupKind)
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return MCAsmBackend::getFixupKindInfo(Kind);
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assert(unsigned(Kind - FirstTargetFixupKind) <
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WebAssembly::NumTargetFixupKinds &&
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"Invalid kind!");
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return Infos[Kind - FirstTargetFixupKind];
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}
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bool WebAssemblyAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
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const MCSubtargetInfo *STI) const {
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for (uint64_t I = 0; I < Count; ++I)
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OS << char(WebAssembly::Nop);
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return true;
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}
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void WebAssemblyAsmBackend::applyFixup(const MCFragment &F,
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const MCFixup &Fixup,
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const MCValue &Target, uint8_t *Data,
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uint64_t Value, bool IsResolved) {
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if (!IsResolved)
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Asm->getWriter().recordRelocation(F, Fixup, Target, Value);
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MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
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assert(Info.Flags == 0 && "WebAssembly does not use MCFixupKindInfo flags");
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unsigned NumBytes = alignTo(Info.TargetSize, 8) / 8;
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if (Value == 0)
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return; // Doesn't change encoding.
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// Shift the value into position.
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Value <<= Info.TargetOffset;
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assert(Fixup.getOffset() + NumBytes <= F.getSize() &&
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"Invalid fixup offset!");
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// For each byte of the fragment that the fixup touches, mask in the
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// bits from the fixup value.
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for (unsigned I = 0; I != NumBytes; ++I)
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Data[I] |= uint8_t((Value >> (I * 8)) & 0xff);
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}
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std::unique_ptr<MCObjectTargetWriter>
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WebAssemblyAsmBackend::createObjectTargetWriter() const {
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return createWebAssemblyWasmObjectWriter(Is64Bit, IsEmscripten);
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}
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} // end anonymous namespace
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MCAsmBackend *llvm::createWebAssemblyAsmBackend(const Triple &TT) {
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return new WebAssemblyAsmBackend(TT.isArch64Bit(), TT.isOSEmscripten());
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}
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