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 //
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.
41 const MCExpr *AArch64TargetStreamer::addConstantPoolEntry(const MCExpr *Expr,
42                                                           unsigned Size,
43                                                           SMLoc Loc) {
44   return ConstantPools->addEntry(Streamer, Expr, Size, Loc);
45 }
46 
47 void AArch64TargetStreamer::emitCurrentConstantPool() {
48   ConstantPools->emitForCurrentSection(Streamer);
49 }
50 
51 void AArch64TargetStreamer::emitConstantPools() {
52   ConstantPools->emitAll(Streamer);
53 }
54 
55 // finish() - write out any non-empty assembler constant pools and
56 //   write out note.gnu.properties if need.
57 void AArch64TargetStreamer::finish() {
58   if (MarkBTIProperty)
59     emitNoteSection(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
60 }
61 
62 void AArch64TargetStreamer::emitNoteSection(unsigned Flags) {
63   if (Flags == 0)
64     return;
65 
66   MCStreamer &OutStreamer = getStreamer();
67   MCContext &Context = OutStreamer.getContext();
68   // Emit a .note.gnu.property section with the flags.
69   MCSectionELF *Nt = Context.getELFSection(".note.gnu.property", ELF::SHT_NOTE,
70                                            ELF::SHF_ALLOC);
71   if (Nt->isRegistered()) {
72     SMLoc Loc;
73     Context.reportWarning(
74         Loc,
75         "The .note.gnu.property is not emitted because it is already present.");
76     return;
77   }
78   MCSection *Cur = OutStreamer.getCurrentSectionOnly();
79   OutStreamer.switchSection(Nt);
80 
81   // Emit the note header.
82   OutStreamer.emitValueToAlignment(Align(8));
83   OutStreamer.emitIntValue(4, 4);     // data size for "GNU\0"
84   OutStreamer.emitIntValue(4 * 4, 4); // Elf_Prop size
85   OutStreamer.emitIntValue(ELF::NT_GNU_PROPERTY_TYPE_0, 4);
86   OutStreamer.emitBytes(StringRef("GNU", 4)); // note name
87 
88   // Emit the PAC/BTI properties.
89   OutStreamer.emitIntValue(ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND, 4);
90   OutStreamer.emitIntValue(4, 4);     // data size
91   OutStreamer.emitIntValue(Flags, 4); // data
92   OutStreamer.emitIntValue(0, 4);     // pad
93 
94   OutStreamer.endSection(Nt);
95   OutStreamer.switchSection(Cur);
96 }
97 
98 void AArch64TargetStreamer::emitInst(uint32_t Inst) {
99   char Buffer[4];
100 
101   // We can't just use EmitIntValue here, as that will swap the
102   // endianness on big-endian systems (instructions are always
103   // little-endian).
104   for (char &C : Buffer) {
105     C = uint8_t(Inst);
106     Inst >>= 8;
107   }
108 
109   getStreamer().emitBytes(StringRef(Buffer, 4));
110 }
111 
112 MCTargetStreamer *
113 llvm::createAArch64ObjectTargetStreamer(MCStreamer &S,
114                                         const MCSubtargetInfo &STI) {
115   const Triple &TT = STI.getTargetTriple();
116   if (TT.isOSBinFormatELF())
117     return new AArch64TargetELFStreamer(S);
118   if (TT.isOSBinFormatCOFF())
119     return new AArch64TargetWinCOFFStreamer(S);
120   return nullptr;
121 }
122 
123 MCTargetStreamer *llvm::createAArch64NullTargetStreamer(MCStreamer &S) {
124   return new AArch64TargetStreamer(S);
125 }
126