1//===- lib/MC/GOFFObjectWriter.cpp - GOFF File Writer ---------------------===//
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 GOFF object file writer information.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/BinaryFormat/GOFF.h"
14#include "llvm/MC/MCAsmLayout.h"
15#include "llvm/MC/MCAssembler.h"
16#include "llvm/MC/MCGOFFObjectWriter.h"
17#include "llvm/MC/MCValue.h"
18#include "llvm/Support/Debug.h"
19#include "llvm/Support/Endian.h"
20#include "llvm/Support/Path.h"
21#include "llvm/Support/raw_ostream.h"
22
23using namespace llvm;
24
25#define DEBUG_TYPE "goff-writer"
26
27namespace {
28
29// The standard System/390 convention is to name the high-order (leftmost) bit
30// in a byte as bit zero. The Flags type helps to set bits in a byte according
31// to this numeration order.
32class Flags {
33 uint8_t Val;
34
35 constexpr static uint8_t bits(uint8_t BitIndex, uint8_t Length, uint8_t Value,
36 uint8_t OldValue) {
37 assert(BitIndex < 8 && "Bit index out of bounds!");
38 assert(Length + BitIndex <= 8 && "Bit length too long!");
39
40 uint8_t Mask = ((1 << Length) - 1) << (8 - BitIndex - Length);
41 Value = Value << (8 - BitIndex - Length);
42 assert((Value & Mask) == Value && "Bits set outside of range!");
43
44 return (OldValue & ~Mask) | Value;
45 }
46
47public:
48 constexpr Flags() : Val(0) {}
49 constexpr Flags(uint8_t BitIndex, uint8_t Length, uint8_t Value)
50 : Val(bits(BitIndex, Length, Value, OldValue: 0)) {}
51
52 void set(uint8_t BitIndex, uint8_t Length, uint8_t Value) {
53 Val = bits(BitIndex, Length, Value, OldValue: Val);
54 }
55
56 constexpr operator uint8_t() const { return Val; }
57};
58
59// Common flag values on records.
60
61// Flag: This record is continued.
62constexpr uint8_t RecContinued = Flags(7, 1, 1);
63
64// Flag: This record is a continuation.
65constexpr uint8_t RecContinuation = Flags(6, 1, 1);
66
67// The GOFFOstream is responsible to write the data into the fixed physical
68// records of the format. A user of this class announces the start of a new
69// logical record and the size of its content. While writing the content, the
70// physical records are created for the data. Possible fill bytes at the end of
71// a physical record are written automatically. In principle, the GOFFOstream
72// is agnostic of the endianness of the content. However, it also supports
73// writing data in big endian byte order.
74class GOFFOstream : public raw_ostream {
75 /// The underlying raw_pwrite_stream.
76 raw_pwrite_stream &OS;
77
78 /// The remaining size of this logical record, including fill bytes.
79 size_t RemainingSize;
80
81#ifndef NDEBUG
82 /// The number of bytes needed to fill up the last physical record.
83 size_t Gap = 0;
84#endif
85
86 /// The number of logical records emitted to far.
87 uint32_t LogicalRecords;
88
89 /// The type of the current (logical) record.
90 GOFF::RecordType CurrentType;
91
92 /// Signals start of new record.
93 bool NewLogicalRecord;
94
95 /// Static allocated buffer for the stream, used by the raw_ostream class. The
96 /// buffer is sized to hold the content of a physical record.
97 char Buffer[GOFF::RecordContentLength];
98
99 // Return the number of bytes left to write until next physical record.
100 // Please note that we maintain the total numbers of byte left, not the
101 // written size.
102 size_t bytesToNextPhysicalRecord() {
103 size_t Bytes = RemainingSize % GOFF::RecordContentLength;
104 return Bytes ? Bytes : GOFF::RecordContentLength;
105 }
106
107 /// Write the record prefix of a physical record, using the given record type.
108 static void writeRecordPrefix(raw_ostream &OS, GOFF::RecordType Type,
109 size_t RemainingSize,
110 uint8_t Flags = RecContinuation);
111
112 /// Fill the last physical record of a logical record with zero bytes.
113 void fillRecord();
114
115 /// See raw_ostream::write_impl.
116 void write_impl(const char *Ptr, size_t Size) override;
117
118 /// Return the current position within the stream, not counting the bytes
119 /// currently in the buffer.
120 uint64_t current_pos() const override { return OS.tell(); }
121
122public:
123 explicit GOFFOstream(raw_pwrite_stream &OS)
124 : OS(OS), RemainingSize(0), LogicalRecords(0), NewLogicalRecord(false) {
125 SetBuffer(BufferStart: Buffer, Size: sizeof(Buffer));
126 }
127
128 ~GOFFOstream() { finalize(); }
129
130 raw_pwrite_stream &getOS() { return OS; }
131
132 void newRecord(GOFF::RecordType Type, size_t Size);
133
134 void finalize() { fillRecord(); }
135
136 uint32_t logicalRecords() { return LogicalRecords; }
137
138 // Support for endian-specific data.
139 template <typename value_type> void writebe(value_type Value) {
140 Value =
141 support::endian::byte_swap<value_type>(Value, llvm::endianness::big);
142 write(Ptr: reinterpret_cast<const char *>(&Value), Size: sizeof(value_type));
143 }
144};
145
146void GOFFOstream::writeRecordPrefix(raw_ostream &OS, GOFF::RecordType Type,
147 size_t RemainingSize, uint8_t Flags) {
148 uint8_t TypeAndFlags = Flags | (Type << 4);
149 if (RemainingSize > GOFF::RecordLength)
150 TypeAndFlags |= RecContinued;
151 OS << static_cast<unsigned char>(GOFF::PTVPrefix) // Record Type
152 << static_cast<unsigned char>(TypeAndFlags) // Continuation
153 << static_cast<unsigned char>(0); // Version
154}
155
156void GOFFOstream::newRecord(GOFF::RecordType Type, size_t Size) {
157 fillRecord();
158 CurrentType = Type;
159 RemainingSize = Size;
160#ifdef NDEBUG
161 size_t Gap;
162#endif
163 Gap = (RemainingSize % GOFF::RecordContentLength);
164 if (Gap) {
165 Gap = GOFF::RecordContentLength - Gap;
166 RemainingSize += Gap;
167 }
168 NewLogicalRecord = true;
169 ++LogicalRecords;
170}
171
172void GOFFOstream::fillRecord() {
173 assert((GetNumBytesInBuffer() <= RemainingSize) &&
174 "More bytes in buffer than expected");
175 size_t Remains = RemainingSize - GetNumBytesInBuffer();
176 if (Remains) {
177 assert(Remains == Gap && "Wrong size of fill gap");
178 assert((Remains < GOFF::RecordLength) &&
179 "Attempt to fill more than one physical record");
180 raw_ostream::write_zeros(NumZeros: Remains);
181 }
182 flush();
183 assert(RemainingSize == 0 && "Not fully flushed");
184 assert(GetNumBytesInBuffer() == 0 && "Buffer not fully empty");
185}
186
187// This function is called from the raw_ostream implementation if:
188// - The internal buffer is full. Size is excactly the size of the buffer.
189// - Data larger than the internal buffer is written. Size is a multiple of the
190// buffer size.
191// - flush() has been called. Size is at most the buffer size.
192// The GOFFOstream implementation ensures that flush() is called before a new
193// logical record begins. Therefore it is sufficient to check for a new block
194// only once.
195void GOFFOstream::write_impl(const char *Ptr, size_t Size) {
196 assert((RemainingSize >= Size) && "Attempt to write too much data");
197 assert(RemainingSize && "Logical record overflow");
198 if (!(RemainingSize % GOFF::RecordContentLength)) {
199 writeRecordPrefix(OS, Type: CurrentType, RemainingSize,
200 Flags: NewLogicalRecord ? 0 : RecContinuation);
201 NewLogicalRecord = false;
202 }
203 assert(!NewLogicalRecord &&
204 "New logical record not on physical record boundary");
205
206 size_t Idx = 0;
207 while (Size > 0) {
208 size_t BytesToWrite = bytesToNextPhysicalRecord();
209 if (BytesToWrite > Size)
210 BytesToWrite = Size;
211 OS.write(Ptr: Ptr + Idx, Size: BytesToWrite);
212 Idx += BytesToWrite;
213 Size -= BytesToWrite;
214 RemainingSize -= BytesToWrite;
215 if (Size)
216 writeRecordPrefix(OS, Type: CurrentType, RemainingSize);
217 }
218}
219
220class GOFFObjectWriter : public MCObjectWriter {
221 // The target specific GOFF writer instance.
222 std::unique_ptr<MCGOFFObjectTargetWriter> TargetObjectWriter;
223
224 // The stream used to write the GOFF records.
225 GOFFOstream OS;
226
227public:
228 GOFFObjectWriter(std::unique_ptr<MCGOFFObjectTargetWriter> MOTW,
229 raw_pwrite_stream &OS)
230 : TargetObjectWriter(std::move(MOTW)), OS(OS) {}
231
232 ~GOFFObjectWriter() override {}
233
234 // Write GOFF records.
235 void writeHeader();
236 void writeEnd();
237
238 // Implementation of the MCObjectWriter interface.
239 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
240 const MCFragment *Fragment, const MCFixup &Fixup,
241 MCValue Target, uint64_t &FixedValue) override {}
242 void executePostLayoutBinding(MCAssembler &Asm,
243 const MCAsmLayout &Layout) override {}
244 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
245};
246} // end anonymous namespace
247
248void GOFFObjectWriter::writeHeader() {
249 OS.newRecord(Type: GOFF::RT_HDR, /*Size=*/57);
250 OS.write_zeros(NumZeros: 1); // Reserved
251 OS.writebe<uint32_t>(Value: 0); // Target Hardware Environment
252 OS.writebe<uint32_t>(Value: 0); // Target Operating System Environment
253 OS.write_zeros(NumZeros: 2); // Reserved
254 OS.writebe<uint16_t>(Value: 0); // CCSID
255 OS.write_zeros(NumZeros: 16); // Character Set name
256 OS.write_zeros(NumZeros: 16); // Language Product Identifier
257 OS.writebe<uint32_t>(Value: 1); // Architecture Level
258 OS.writebe<uint16_t>(Value: 0); // Module Properties Length
259 OS.write_zeros(NumZeros: 6); // Reserved
260}
261
262void GOFFObjectWriter::writeEnd() {
263 uint8_t F = GOFF::END_EPR_None;
264 uint8_t AMODE = 0;
265 uint32_t ESDID = 0;
266
267 // TODO Set Flags/AMODE/ESDID for entry point.
268
269 OS.newRecord(Type: GOFF::RT_END, /*Size=*/13);
270 OS.writebe<uint8_t>(Value: Flags(6, 2, F)); // Indicator flags
271 OS.writebe<uint8_t>(Value: AMODE); // AMODE
272 OS.write_zeros(NumZeros: 3); // Reserved
273 // The record count is the number of logical records. In principle, this value
274 // is available as OS.logicalRecords(). However, some tools rely on this field
275 // being zero.
276 OS.writebe<uint32_t>(Value: 0); // Record Count
277 OS.writebe<uint32_t>(Value: ESDID); // ESDID (of entry point)
278 OS.finalize();
279}
280
281uint64_t GOFFObjectWriter::writeObject(MCAssembler &Asm,
282 const MCAsmLayout &Layout) {
283 uint64_t StartOffset = OS.tell();
284
285 writeHeader();
286 writeEnd();
287
288 LLVM_DEBUG(dbgs() << "Wrote " << OS.logicalRecords() << " logical records.");
289
290 return OS.tell() - StartOffset;
291}
292
293std::unique_ptr<MCObjectWriter>
294llvm::createGOFFObjectWriter(std::unique_ptr<MCGOFFObjectTargetWriter> MOTW,
295 raw_pwrite_stream &OS) {
296 return std::make_unique<GOFFObjectWriter>(args: std::move(MOTW), args&: OS);
297}
298

source code of llvm/lib/MC/GOFFObjectWriter.cpp