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 "llvm/BinaryFormat/ELF.h"
16 #include "llvm/MC/ConstantPools.h"
17 #include "llvm/MC/MCContext.h"
18 #include "llvm/MC/MCSection.h"
19 #include "llvm/MC/MCSectionELF.h"
20 #include "llvm/MC/MCSubtargetInfo.h"
21 #include "llvm/Support/CommandLine.h"
22
23 using namespace llvm;
24
25 static cl::opt<bool> MarkBTIProperty(
26 "aarch64-mark-bti-property", cl::Hidden,
27 cl::desc("Add .note.gnu.property with BTI to assembly files"),
28 cl::init(false));
29
30 //
31 // AArch64TargetStreamer Implemenation
32 //
AArch64TargetStreamer(MCStreamer & S)33 AArch64TargetStreamer::AArch64TargetStreamer(MCStreamer &S)
34 : MCTargetStreamer(S), ConstantPools(new AssemblerConstantPools()) {}
35
36 AArch64TargetStreamer::~AArch64TargetStreamer() = default;
37
38 // The constant pool handling is shared by all AArch64TargetStreamer
39 // implementations.
addConstantPoolEntry(const MCExpr * Expr,unsigned Size,SMLoc Loc)40 const MCExpr *AArch64TargetStreamer::addConstantPoolEntry(const MCExpr *Expr,
41 unsigned Size,
42 SMLoc Loc) {
43 return ConstantPools->addEntry(Streamer, Expr, Size, Loc);
44 }
45
emitCurrentConstantPool()46 void AArch64TargetStreamer::emitCurrentConstantPool() {
47 ConstantPools->emitForCurrentSection(Streamer);
48 }
49
emitConstantPools()50 void AArch64TargetStreamer::emitConstantPools() {
51 ConstantPools->emitAll(Streamer);
52 }
53
54 // finish() - write out any non-empty assembler constant pools and
55 // write out note.gnu.properties if need.
finish()56 void AArch64TargetStreamer::finish() {
57 if (MarkBTIProperty)
58 emitNoteSection(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
59 }
60
emitNoteSection(unsigned Flags,uint64_t PAuthABIPlatform,uint64_t PAuthABIVersion)61 void AArch64TargetStreamer::emitNoteSection(unsigned Flags,
62 uint64_t PAuthABIPlatform,
63 uint64_t PAuthABIVersion) {
64 assert((PAuthABIPlatform == uint64_t(-1)) ==
65 (PAuthABIVersion == uint64_t(-1)));
66 uint64_t DescSz = 0;
67 if (Flags != 0)
68 DescSz += 4 * 4;
69 if (PAuthABIPlatform != uint64_t(-1))
70 DescSz += 4 + 4 + 8 * 2;
71 if (DescSz == 0)
72 return;
73
74 MCStreamer &OutStreamer = getStreamer();
75 MCContext &Context = OutStreamer.getContext();
76 // Emit a .note.gnu.property section with the flags.
77 MCSectionELF *Nt = Context.getELFSection(".note.gnu.property", ELF::SHT_NOTE,
78 ELF::SHF_ALLOC);
79 if (Nt->isRegistered()) {
80 SMLoc Loc;
81 Context.reportWarning(
82 Loc,
83 "The .note.gnu.property is not emitted because it is already present.");
84 return;
85 }
86 MCSection *Cur = OutStreamer.getCurrentSectionOnly();
87 OutStreamer.switchSection(Nt);
88
89 // Emit the note header.
90 OutStreamer.emitValueToAlignment(Align(8));
91 OutStreamer.emitIntValue(4, 4); // data size for "GNU\0"
92 OutStreamer.emitIntValue(DescSz, 4); // Elf_Prop array size
93 OutStreamer.emitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4);
94 OutStreamer.emitBytes(StringRef("GNU", 4)); // note name
95
96 // Emit the PAC/BTI properties.
97 if (Flags != 0) {
98 OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
99 OutStreamer.emitIntValue(4, 4); // data size
100 OutStreamer.emitIntValue(Flags, 4); // data
101 OutStreamer.emitIntValue(0, 4); // pad
102 }
103
104 // Emit the PAuth ABI compatibility info
105 if (PAuthABIPlatform != uint64_t(-1)) {
106 OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_PAUTH, 4);
107 OutStreamer.emitIntValue(8 * 2, 4); // data size
108 OutStreamer.emitIntValue(PAuthABIPlatform, 8);
109 OutStreamer.emitIntValue(PAuthABIVersion, 8);
110 }
111
112 OutStreamer.endSection(Nt);
113 OutStreamer.switchSection(Cur);
114 }
115
emitInst(uint32_t Inst)116 void AArch64TargetStreamer::emitInst(uint32_t Inst) {
117 char Buffer[4];
118
119 // We can't just use EmitIntValue here, as that will swap the
120 // endianness on big-endian systems (instructions are always
121 // little-endian).
122 for (char &C : Buffer) {
123 C = uint8_t(Inst);
124 Inst >>= 8;
125 }
126
127 getStreamer().emitBytes(StringRef(Buffer, 4));
128 }
129
130 MCTargetStreamer *
createAArch64ObjectTargetStreamer(MCStreamer & S,const MCSubtargetInfo & STI)131 llvm::createAArch64ObjectTargetStreamer(MCStreamer &S,
132 const MCSubtargetInfo &STI) {
133 const Triple &TT = STI.getTargetTriple();
134 if (TT.isOSBinFormatELF())
135 return new AArch64TargetELFStreamer(S);
136 if (TT.isOSBinFormatCOFF())
137 return new AArch64TargetWinCOFFStreamer(S);
138 return nullptr;
139 }
140
createAArch64NullTargetStreamer(MCStreamer & S)141 MCTargetStreamer *llvm::createAArch64NullTargetStreamer(MCStreamer &S) {
142 return new AArch64TargetStreamer(S);
143 }
144