decoder.hh revision 9037:2f84b98634ff 
1/*
2 * Copyright (c) 2012 Google
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Gabe Black
29 */
30
31#ifndef __ARCH_X86_DECODER_HH__
32#define __ARCH_X86_DECODER_HH__
33
34#include <cassert>
35
36#include "arch/x86/regs/misc.hh"
37#include "arch/x86/types.hh"
38#include "base/bitfield.hh"
39#include "base/misc.hh"
40#include "base/trace.hh"
41#include "base/types.hh"
42#include "cpu/decode_cache.hh"
43#include "cpu/static_inst.hh"
44#include "debug/Decoder.hh"
45
46class ThreadContext;
47
48namespace X86ISA
49{
50
51class Decoder
52{
53  private:
54    //These are defined and documented in decoder_tables.cc
55    static const uint8_t Prefixes[256];
56    static const uint8_t UsesModRM[2][256];
57    static const uint8_t ImmediateType[2][256];
58    static const uint8_t SizeTypeToSize[3][10];
59
60  protected:
61    ThreadContext * tc;
62    //The bytes to be predecoded
63    MachInst fetchChunk;
64    //The pc of the start of fetchChunk
65    Addr basePC;
66    //The pc the current instruction started at
67    Addr origPC;
68    //The offset into fetchChunk of current processing
69    int offset;
70    //The extended machine instruction being generated
71    ExtMachInst emi;
72    HandyM5Reg m5Reg;
73
74    inline uint8_t getNextByte()
75    {
76        return ((uint8_t *)&fetchChunk)[offset];
77    }
78
79    void getImmediate(int &collected, uint64_t &current, int size)
80    {
81        //Figure out how many bytes we still need to get for the
82        //immediate.
83        int toGet = size - collected;
84        //Figure out how many bytes are left in our "buffer"
85        int remaining = sizeof(MachInst) - offset;
86        //Get as much as we need, up to the amount available.
87        toGet = toGet > remaining ? remaining : toGet;
88
89        //Shift the bytes we want to be all the way to the right
90        uint64_t partialImm = fetchChunk >> (offset * 8);
91        //Mask off what we don't want
92        partialImm &= mask(toGet * 8);
93        //Shift it over to overlay with our displacement.
94        partialImm <<= (immediateCollected * 8);
95        //Put it into our displacement
96        current |= partialImm;
97        //Update how many bytes we've collected.
98        collected += toGet;
99        consumeBytes(toGet);
100    }
101
102    inline void consumeByte()
103    {
104        offset++;
105        assert(offset <= sizeof(MachInst));
106        if(offset == sizeof(MachInst))
107            outOfBytes = true;
108    }
109
110    inline void consumeBytes(int numBytes)
111    {
112        offset += numBytes;
113        assert(offset <= sizeof(MachInst));
114        if(offset == sizeof(MachInst))
115            outOfBytes = true;
116    }
117
118    void doReset();
119
120    //State machine state
121  protected:
122    //Whether or not we're out of bytes
123    bool outOfBytes;
124    //Whether we've completed generating an ExtMachInst
125    bool instDone;
126    //The size of the displacement value
127    int displacementSize;
128    //The size of the immediate value
129    int immediateSize;
130    //This is how much of any immediate value we've gotten. This is used
131    //for both the actual immediate and the displacement.
132    int immediateCollected;
133
134    enum State {
135        ResetState,
136        PrefixState,
137        OpcodeState,
138        ModRMState,
139        SIBState,
140        DisplacementState,
141        ImmediateState,
142        //We should never get to this state. Getting here is an error.
143        ErrorState
144    };
145
146    State state;
147
148    //Functions to handle each of the states
149    State doPrefixState(uint8_t);
150    State doOpcodeState(uint8_t);
151    State doModRMState(uint8_t);
152    State doSIBState(uint8_t);
153    State doDisplacementState();
154    State doImmediateState();
155
156  public:
157    Decoder(ThreadContext * _tc) :
158        tc(_tc), basePC(0), origPC(0), offset(0),
159        outOfBytes(true), instDone(false),
160        state(ResetState)
161    {
162        memset(&emi, 0, sizeof(emi));
163        emi.mode.mode = LongMode;
164        emi.mode.submode = SixtyFourBitMode;
165        m5Reg = 0;
166    }
167
168    void reset()
169    {
170        state = ResetState;
171    }
172
173    ThreadContext * getTC()
174    {
175        return tc;
176    }
177
178    void setTC(ThreadContext * _tc)
179    {
180        tc = _tc;
181    }
182
183    void process();
184
185    //Use this to give data to the decoder. This should be used
186    //when there is control flow.
187    void moreBytes(const PCState &pc, Addr fetchPC, MachInst data)
188    {
189        DPRINTF(Decoder, "Getting more bytes.\n");
190        basePC = fetchPC;
191        offset = (fetchPC >= pc.instAddr()) ? 0 : pc.instAddr() - fetchPC;
192        fetchChunk = data;
193        outOfBytes = false;
194        process();
195    }
196
197    bool needMoreBytes()
198    {
199        return outOfBytes;
200    }
201
202    bool instReady()
203    {
204        return instDone;
205    }
206
207    void
208    updateNPC(X86ISA::PCState &nextPC)
209    {
210        if (!nextPC.size()) {
211            int size = basePC + offset - origPC;
212            DPRINTF(Decoder,
213                    "Calculating the instruction size: "
214                    "basePC: %#x offset: %#x origPC: %#x size: %d\n",
215                    basePC, offset, origPC, size);
216            nextPC.size(size);
217            nextPC.npc(nextPC.pc() + size);
218        }
219    }
220
221  protected:
222    /// Caching for decoded instruction objects.
223    static DecodeCache::InstMap instMap;
224    static DecodeCache::AddrMap<StaticInstPtr> decodePages;
225
226  public:
227    StaticInstPtr decodeInst(ExtMachInst mach_inst);
228
229    /// Decode a machine instruction.
230    /// @param mach_inst The binary instruction to decode.
231    /// @retval A pointer to the corresponding StaticInst object.
232    StaticInstPtr decode(ExtMachInst mach_inst, Addr addr);
233
234    StaticInstPtr
235    decode(X86ISA::PCState &nextPC)
236    {
237        if (!instDone)
238            return NULL;
239        instDone = false;
240        updateNPC(nextPC);
241        return decode(emi, origPC);
242    }
243};
244
245} // namespace X86ISA
246
247#endif // __ARCH_X86_DECODER_HH__
248