1/* s390-dis.c -- Disassemble S390 instructions
2   Copyright (C) 2000-2017 Free Software Foundation, Inc.
3   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
4
5   This file is part of the GNU opcodes library.
6
7   This library is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3, or (at your option)
10   any later version.
11
12   It is distributed in the hope that it will be useful, but WITHOUT
13   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
15   License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this file; see the file COPYING.  If not, write to the
19   Free Software Foundation, 51 Franklin Street - Fifth Floor, Boston,
20   MA 02110-1301, USA.  */
21
22#include "sysdep.h"
23#include <stdio.h>
24#include "ansidecl.h"
25#include "dis-asm.h"
26#include "opintl.h"
27#include "opcode/s390.h"
28
29static int init_flag = 0;
30static int opc_index[256];
31static int current_arch_mask = 0;
32static int option_use_insn_len_bits_p = 0;
33
34/* Set up index table for first opcode byte.  */
35
36static void
37init_disasm (struct disassemble_info *info)
38{
39  int i;
40  const char *p;
41
42  memset (opc_index, 0, sizeof (opc_index));
43
44  /* Reverse order, such that each opc_index ends up pointing to the
45     first matching entry instead of the last.  */
46  for (i = s390_num_opcodes; i--; )
47    opc_index[s390_opcodes[i].opcode[0]] = i;
48
49  for (p = info->disassembler_options; p != NULL; )
50    {
51      if (CONST_STRNEQ (p, "esa"))
52	current_arch_mask = 1 << S390_OPCODE_ESA;
53      else if (CONST_STRNEQ (p, "zarch"))
54	current_arch_mask = 1 << S390_OPCODE_ZARCH;
55      else if (CONST_STRNEQ (p, "insnlength"))
56	option_use_insn_len_bits_p = 1;
57      else
58	fprintf (stderr, "Unknown S/390 disassembler option: %s\n", p);
59
60      p = strchr (p, ',');
61      if (p != NULL)
62	p++;
63    }
64
65  if (!current_arch_mask)
66    current_arch_mask = 1 << S390_OPCODE_ZARCH;
67
68  init_flag = 1;
69}
70
71/* Derive the length of an instruction from its first byte.  */
72
73static inline int
74s390_insn_length (const bfd_byte *buffer)
75{
76  /* 00xxxxxx -> 2, 01xxxxxx/10xxxxxx -> 4, 11xxxxxx -> 6.  */
77  return ((buffer[0] >> 6) + 3) & ~1U;
78}
79
80/* Match the instruction in BUFFER against the given OPCODE, excluding
81   the first byte.  */
82
83static inline int
84s390_insn_matches_opcode (const bfd_byte *buffer,
85			  const struct s390_opcode *opcode)
86{
87  return (buffer[1] & opcode->mask[1]) == opcode->opcode[1]
88    && (buffer[2] & opcode->mask[2]) == opcode->opcode[2]
89    && (buffer[3] & opcode->mask[3]) == opcode->opcode[3]
90    && (buffer[4] & opcode->mask[4]) == opcode->opcode[4]
91    && (buffer[5] & opcode->mask[5]) == opcode->opcode[5];
92}
93
94union operand_value
95{
96  int i;
97  unsigned int u;
98};
99
100/* Extracts an operand value from an instruction.  */
101/* We do not perform the shift operation for larl-type address
102   operands here since that would lead to an overflow of the 32 bit
103   integer value.  Instead the shift operation is done when printing
104   the operand.  */
105
106static inline union operand_value
107s390_extract_operand (const bfd_byte *insn,
108		      const struct s390_operand *operand)
109{
110  union operand_value ret;
111  unsigned int val;
112  int bits;
113  const bfd_byte *orig_insn = insn;
114
115  /* Extract fragments of the operand byte for byte.  */
116  insn += operand->shift / 8;
117  bits = (operand->shift & 7) + operand->bits;
118  val = 0;
119  do
120    {
121      val <<= 8;
122      val |= (unsigned int) *insn++;
123      bits -= 8;
124    }
125  while (bits > 0);
126  val >>= -bits;
127  val &= ((1U << (operand->bits - 1)) << 1) - 1;
128
129  /* Check for special long displacement case.  */
130  if (operand->bits == 20 && operand->shift == 20)
131    val = (val & 0xff) << 12 | (val & 0xfff00) >> 8;
132
133  /* Sign extend value if the operand is signed or pc relative.  Avoid
134     integer overflows.  */
135  if (operand->flags & (S390_OPERAND_SIGNED | S390_OPERAND_PCREL))
136    {
137      unsigned int m = 1U << (operand->bits - 1);
138
139      if (val >= m)
140	ret.i = (int) (val - m) - 1 - (int) (m - 1U);
141      else
142	ret.i = (int) val;
143    }
144  else if (operand->flags & S390_OPERAND_LENGTH)
145    /* Length x in an instruction has real length x + 1.  */
146    ret.u = val + 1;
147
148  else if (operand->flags & S390_OPERAND_VR)
149    {
150      /* Extract the extra bits for a vector register operand stored
151	 in the RXB field.  */
152      unsigned vr = operand->shift == 32 ? 3
153	: (unsigned) operand->shift / 4 - 2;
154
155      ret.u = val | ((orig_insn[4] & (1 << (3 - vr))) << (vr + 1));
156    }
157  else
158    ret.u = val;
159
160  return ret;
161}
162
163/* Print the S390 instruction in BUFFER, assuming that it matches the
164   given OPCODE.  */
165
166static void
167s390_print_insn_with_opcode (bfd_vma memaddr,
168			     struct disassemble_info *info,
169			     const bfd_byte *buffer,
170			     const struct s390_opcode *opcode)
171{
172  const unsigned char *opindex;
173  char separator;
174
175  /* Mnemonic.  */
176  info->fprintf_func (info->stream, "%s", opcode->name);
177
178  /* Operands.  */
179  separator = '\t';
180  for (opindex = opcode->operands; *opindex != 0; opindex++)
181    {
182      const struct s390_operand *operand = s390_operands + *opindex;
183      union operand_value val = s390_extract_operand (buffer, operand);
184      unsigned long flags = operand->flags;
185
186      if ((flags & S390_OPERAND_INDEX) && val.u == 0)
187	continue;
188      if ((flags & S390_OPERAND_BASE) &&
189	  val.u == 0 && separator == '(')
190	{
191	  separator = ',';
192	  continue;
193	}
194
195      /* For instructions with a last optional operand don't print it
196	 if zero.  */
197      if ((opcode->flags & S390_INSTR_FLAG_OPTPARM)
198	  && val.u == 0
199	  && opindex[1] == 0)
200	break;
201
202      if (flags & S390_OPERAND_GPR)
203	info->fprintf_func (info->stream, "%c%%r%u", separator, val.u);
204      else if (flags & S390_OPERAND_FPR)
205	info->fprintf_func (info->stream, "%c%%f%u", separator, val.u);
206      else if (flags & S390_OPERAND_VR)
207	info->fprintf_func (info->stream, "%c%%v%i", separator, val.u);
208      else if (flags & S390_OPERAND_AR)
209	info->fprintf_func (info->stream, "%c%%a%u", separator, val.u);
210      else if (flags & S390_OPERAND_CR)
211	info->fprintf_func (info->stream, "%c%%c%u", separator, val.u);
212      else if (flags & S390_OPERAND_PCREL)
213	{
214	  info->fprintf_func (info->stream, "%c", separator);
215	  info->print_address_func (memaddr + val.i + val.i, info);
216	}
217      else if (flags & S390_OPERAND_SIGNED)
218	info->fprintf_func (info->stream, "%c%i", separator, val.i);
219      else
220	{
221	  if (flags & S390_OPERAND_OR1)
222	    val.u &= ~1;
223	  if (flags & S390_OPERAND_OR2)
224	    val.u &= ~2;
225	  if (flags & S390_OPERAND_OR8)
226	    val.u &= ~8;
227
228	  if ((opcode->flags & S390_INSTR_FLAG_OPTPARM)
229	      && val.u == 0
230	      && opindex[1] == 0)
231	    break;
232	  info->fprintf_func (info->stream, "%c%u", separator, val.u);
233	}
234
235      if (flags & S390_OPERAND_DISP)
236	separator = '(';
237      else if (flags & S390_OPERAND_BASE)
238	{
239	  info->fprintf_func (info->stream, ")");
240	  separator = ',';
241	}
242      else
243	separator = ',';
244    }
245}
246
247/* Check whether opcode A's mask is more specific than that of B.  */
248
249static int
250opcode_mask_more_specific (const struct s390_opcode *a,
251			   const struct s390_opcode *b)
252{
253  return (((int) a->mask[0] + a->mask[1] + a->mask[2]
254	   + a->mask[3] + a->mask[4] + a->mask[5])
255	  > ((int) b->mask[0] + b->mask[1] + b->mask[2]
256	     + b->mask[3] + b->mask[4] + b->mask[5]));
257}
258
259/* Print a S390 instruction.  */
260
261int
262print_insn_s390 (bfd_vma memaddr, struct disassemble_info *info)
263{
264  bfd_byte buffer[6];
265  const struct s390_opcode *opcode = NULL;
266  unsigned int value;
267  int status, opsize, bufsize, bytes_to_dump, i;
268
269  if (init_flag == 0)
270    init_disasm (info);
271
272  /* The output looks better if we put 6 bytes on a line.  */
273  info->bytes_per_line = 6;
274
275  /* Every S390 instruction is max 6 bytes long.  */
276  memset (buffer, 0, 6);
277  status = info->read_memory_func (memaddr, buffer, 6, info);
278  if (status != 0)
279    {
280      for (bufsize = 0; bufsize < 6; bufsize++)
281	if (info->read_memory_func (memaddr, buffer, bufsize + 1, info) != 0)
282	  break;
283      if (bufsize <= 0)
284	{
285	  info->memory_error_func (status, memaddr, info);
286	  return -1;
287	}
288      opsize = s390_insn_length (buffer);
289      status = opsize > bufsize;
290    }
291  else
292    {
293      bufsize = 6;
294      opsize = s390_insn_length (buffer);
295    }
296
297  if (status == 0)
298    {
299      const struct s390_opcode *op;
300
301      /* Find the "best match" in the opcode table.  */
302      for (op = s390_opcodes + opc_index[buffer[0]];
303	   op != s390_opcodes + s390_num_opcodes
304	     && op->opcode[0] == buffer[0];
305	   op++)
306	{
307	  if ((op->modes & current_arch_mask)
308	      && s390_insn_matches_opcode (buffer, op)
309	      && (opcode == NULL
310		  || opcode_mask_more_specific (op, opcode)))
311	    opcode = op;
312	}
313
314      if (opcode != NULL)
315	{
316	  /* The instruction is valid.  Print it and return its size.  */
317	  s390_print_insn_with_opcode (memaddr, info, buffer, opcode);
318	  return opsize;
319	}
320    }
321
322  /* For code sections it makes sense to skip unknown instructions
323     according to their length bits.  */
324  if (status == 0
325      && option_use_insn_len_bits_p
326      && info->section != NULL
327      && (info->section->flags & SEC_CODE))
328    bytes_to_dump = opsize;
329  else
330    /* By default unknown instructions are printed as .long's/.short'
331       depending on how many bytes are available.  */
332    bytes_to_dump = bufsize >= 4 ? 4 : bufsize;
333
334  if (bytes_to_dump == 0)
335    return 0;
336
337  /* Fall back to hex print.  */
338  switch (bytes_to_dump)
339    {
340    case 4:
341      value = (unsigned int) buffer[0];
342      value = (value << 8) + (unsigned int) buffer[1];
343      value = (value << 8) + (unsigned int) buffer[2];
344      value = (value << 8) + (unsigned int) buffer[3];
345      info->fprintf_func (info->stream, ".long\t0x%08x", value);
346      return 4;
347    case 2:
348      value = (unsigned int) buffer[0];
349      value = (value << 8) + (unsigned int) buffer[1];
350      info->fprintf_func (info->stream, ".short\t0x%04x", value);
351      return 2;
352    default:
353      info->fprintf_func (info->stream, ".byte\t0x%02x",
354			  (unsigned int) buffer[0]);
355      for (i = 1; i < bytes_to_dump; i++)
356	info->fprintf_func (info->stream, ",0x%02x",
357			  (unsigned int) buffer[i]);
358      return bytes_to_dump;
359    }
360  return 0;
361}
362
363void
364print_s390_disassembler_options (FILE *stream)
365{
366  fprintf (stream, _("\n\
367The following S/390 specific disassembler options are supported for use\n\
368with the -M switch (multiple options should be separated by commas):\n"));
369
370  fprintf (stream, _("  esa         Disassemble in ESA architecture mode\n"));
371  fprintf (stream, _("  zarch       Disassemble in z/Architecture mode\n"));
372  fprintf (stream, _("  insnlength  Print unknown instructions according "
373		     "to length from first two bits\n"));
374}
375