1 //===- AArch64TargetStreamer.cpp - AArch64TargetStreamer class ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the AArch64TargetStreamer class.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "AArch64TargetStreamer.h"
14 #include "AArch64MCAsmInfo.h"
15 #include "AArch64Subtarget.h"
16 #include "llvm/BinaryFormat/ELF.h"
17 #include "llvm/MC/ConstantPools.h"
18 #include "llvm/MC/MCContext.h"
19 #include "llvm/MC/MCSection.h"
20 #include "llvm/MC/MCSectionELF.h"
21 #include "llvm/MC/MCSubtargetInfo.h"
22 #include "llvm/Support/CommandLine.h"
23
24 using namespace llvm;
25
26 static cl::opt<bool> MarkBTIProperty(
27 "aarch64-mark-bti-property", cl::Hidden,
28 cl::desc("Add .note.gnu.property with BTI to assembly files"),
29 cl::init(false));
30
31 //
32 // AArch64TargetStreamer Implemenation
33 //
AArch64TargetStreamer(MCStreamer & S)34 AArch64TargetStreamer::AArch64TargetStreamer(MCStreamer &S)
35 : MCTargetStreamer(S), ConstantPools(new AssemblerConstantPools()) {}
36
37 AArch64TargetStreamer::~AArch64TargetStreamer() = default;
38
39 // The constant pool handling is shared by all AArch64TargetStreamer
40 // implementations.
addConstantPoolEntry(const MCExpr * Expr,unsigned Size,SMLoc Loc)41 const MCExpr *AArch64TargetStreamer::addConstantPoolEntry(const MCExpr *Expr,
42 unsigned Size,
43 SMLoc Loc) {
44 return ConstantPools->addEntry(Streamer, Expr, Size, Loc);
45 }
46
emitCurrentConstantPool()47 void AArch64TargetStreamer::emitCurrentConstantPool() {
48 ConstantPools->emitForCurrentSection(Streamer);
49 }
50
51 // finish() - write out any non-empty assembler constant pools and
52 // write out note.gnu.properties if need.
finish()53 void AArch64TargetStreamer::finish() {
54 ConstantPools->emitAll(Streamer);
55
56 if (MarkBTIProperty)
57 emitNoteSection(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
58 }
59
emitNoteSection(unsigned Flags)60 void AArch64TargetStreamer::emitNoteSection(unsigned Flags) {
61 if (Flags == 0)
62 return;
63
64 MCStreamer &OutStreamer = getStreamer();
65 MCContext &Context = OutStreamer.getContext();
66 // Emit a .note.gnu.property section with the flags.
67 MCSectionELF *Nt = Context.getELFSection(".note.gnu.property", ELF::SHT_NOTE,
68 ELF::SHF_ALLOC);
69 if (Nt->isRegistered()) {
70 SMLoc Loc;
71 Context.reportWarning(
72 Loc,
73 "The .note.gnu.property is not emitted because it is already present.");
74 return;
75 }
76 MCSection *Cur = OutStreamer.getCurrentSectionOnly();
77 OutStreamer.SwitchSection(Nt);
78
79 // Emit the note header.
80 OutStreamer.emitValueToAlignment(Align(8).value());
81 OutStreamer.emitIntValue(4, 4); // data size for "GNU\0"
82 OutStreamer.emitIntValue(4 * 4, 4); // Elf_Prop size
83 OutStreamer.emitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4);
84 OutStreamer.emitBytes(StringRef("GNU", 4)); // note name
85
86 // Emit the PAC/BTI properties.
87 OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
88 OutStreamer.emitIntValue(4, 4); // data size
89 OutStreamer.emitIntValue(Flags, 4); // data
90 OutStreamer.emitIntValue(0, 4); // pad
91
92 OutStreamer.endSection(Nt);
93 OutStreamer.SwitchSection(Cur);
94 }
95
emitInst(uint32_t Inst)96 void AArch64TargetStreamer::emitInst(uint32_t Inst) {
97 char Buffer[4];
98
99 // We can't just use EmitIntValue here, as that will swap the
100 // endianness on big-endian systems (instructions are always
101 // little-endian).
102 for (unsigned I = 0; I < 4; ++I) {
103 Buffer[I] = uint8_t(Inst);
104 Inst >>= 8;
105 }
106
107 getStreamer().emitBytes(StringRef(Buffer, 4));
108 }
109
110 namespace llvm {
111
112 MCTargetStreamer *
createAArch64ObjectTargetStreamer(MCStreamer & S,const MCSubtargetInfo & STI)113 createAArch64ObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
114 const Triple &TT = STI.getTargetTriple();
115 if (TT.isOSBinFormatELF())
116 return new AArch64TargetELFStreamer(S);
117 if (TT.isOSBinFormatCOFF())
118 return new AArch64TargetWinCOFFStreamer(S);
119 return nullptr;
120 }
121
122 } // end namespace llvm
123