opcodes: add support for eBPF

This patch adds support for the Linux kernel eBPF architecture to the
opcodes.  The port is based on CGEN.

opcodes/ChangeLog:

2019-05-23  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* configure.ac (SHARED_DEPENDENCIES): Add case for bfd_bpf_arch.
	* configure: Regenerated.
	* Makefile.am: Add rules for the files generated from cpu/bpf.cpu
	and cpu/bpf.opc.
	(HFILES): Add bpf-desc.h and bpf-opc.h.
	(TARGET_LIBOPCODES_CFILES): Add bpf-asm.c, bpf-desc.c, bpf-dis.c,
	bpf-ibld.c and bpf-opc.c.
	(BPF_DEPS): Define.
	* Makefile.in: Regenerated.
	* disassemble.c (ARCH_bpf): Define.
	(disassembler): Add case for bfd_arch_bpf.
	(disassemble_init_for_target): Likewise.
	(enum epbf_isa_attr): Define.
	* disassemble.h: extern print_insn_bpf.
	* bpf-asm.c: Generated.
	* bpf-opc.h: Likewise.
	* bpf-opc.c: Likewise.
	* bpf-ibld.c: Likewise.
	* bpf-dis.c: Likewise.
	* bpf-desc.h: Likewise.
	* bpf-desc.c: Likewise.

1 files changed, 624 insertions, 0 deletions

diff --git a/opcodes/bpf-dis.c b/opcodes/bpf-dis.c
new file mode 100644
index 0000000..c48bce8
--- /dev/null
+++ b/opcodes/bpf-dis.c
@@ -0,0 +1,624 @@
+/* DO NOT EDIT!  -*- buffer-read-only: t -*- vi:set ro:  */
+/* Disassembler interface for targets using CGEN. -*- C -*-
+   CGEN: Cpu tools GENerator
+
+   THIS FILE IS MACHINE GENERATED WITH CGEN.
+   - the resultant file is machine generated, cgen-dis.in isn't
+
+   Copyright (C) 1996-2019 Free Software Foundation, Inc.
+
+   This file is part of libopcodes.
+
+   This library is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   It is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+   License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation, Inc.,
+   51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* ??? Eventually more and more of this stuff can go to cpu-independent files.
+   Keep that in mind.  */
+
+#include "sysdep.h"
+#include <stdio.h>
+#include "ansidecl.h"
+#include "disassemble.h"
+#include "bfd.h"
+#include "symcat.h"
+#include "libiberty.h"
+#include "bpf-desc.h"
+#include "bpf-opc.h"
+#include "opintl.h"
+
+/* Default text to print if an instruction isn't recognized.  */
+#define UNKNOWN_INSN_MSG _("*unknown*")
+
+static void print_normal
+  (CGEN_CPU_DESC, void *, long, unsigned int, bfd_vma, int);
+static void print_address
+  (CGEN_CPU_DESC, void *, bfd_vma, unsigned int, bfd_vma, int) ATTRIBUTE_UNUSED;
+static void print_keyword
+  (CGEN_CPU_DESC, void *, CGEN_KEYWORD *, long, unsigned int) ATTRIBUTE_UNUSED;
+static void print_insn_normal
+  (CGEN_CPU_DESC, void *, const CGEN_INSN *, CGEN_FIELDS *, bfd_vma, int);
+static int print_insn
+  (CGEN_CPU_DESC, bfd_vma,  disassemble_info *, bfd_byte *, unsigned);
+static int default_print_insn
+  (CGEN_CPU_DESC, bfd_vma, disassemble_info *) ATTRIBUTE_UNUSED;
+static int read_insn
+  (CGEN_CPU_DESC, bfd_vma, disassemble_info *, bfd_byte *, int, CGEN_EXTRACT_INFO *,
+   unsigned long *);
+
+/* -- disassembler routines inserted here.  */
+
+/* -- dis.c */
+
+/* We need to customize the disassembler a bit:
+   - Use 8 bytes per line by default.
+*/
+
+#define CGEN_PRINT_INSN bpf_print_insn
+
+static int
+bpf_print_insn (CGEN_CPU_DESC cd, bfd_vma pc, disassemble_info *info)
+{
+  bfd_byte buf[CGEN_MAX_INSN_SIZE];
+  int buflen;
+  int status;
+
+  info->bytes_per_chunk = 1;
+  info->bytes_per_line = 8;
+
+  /* Attempt to read the base part of the insn.  */
+  buflen = cd->base_insn_bitsize / 8;
+  status = (*info->read_memory_func) (pc, buf, buflen, info);
+
+  /* Try again with the minimum part, if min < base.  */
+  if (status != 0 && (cd->min_insn_bitsize < cd->base_insn_bitsize))
+    {
+      buflen = cd->min_insn_bitsize / 8;
+      status = (*info->read_memory_func) (pc, buf, buflen, info);
+    }
+
+  if (status != 0)
+    {
+      (*info->memory_error_func) (status, pc, info);
+      return -1;
+    }
+
+  return print_insn (cd, pc, info, buf, buflen);
+}
+
+/* Signed immediates should be printed in hexadecimal.  */
+
+static void
+print_immediate (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+                 void *dis_info,
+                 int64_t value,
+                 unsigned int attrs ATTRIBUTE_UNUSED,
+                 bfd_vma pc ATTRIBUTE_UNUSED,
+                 int length ATTRIBUTE_UNUSED)
+{
+  disassemble_info *info = (disassemble_info *) dis_info;
+
+  if (value <= 9)
+    (*info->fprintf_func) (info->stream, "%" PRId64, value);
+  else
+    (*info->fprintf_func) (info->stream, "%#" PRIx64, value);
+
+  /* This is to avoid -Wunused-function for print_normal.  */
+  if (0)
+    print_normal (cd, dis_info, value, attrs, pc, length);
+}
+
+/* Endianness bit sizes should be printed in decimal.  */
+
+static void
+print_endsize (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+               void *dis_info,
+               unsigned long value,
+               unsigned int attrs ATTRIBUTE_UNUSED,
+               bfd_vma pc ATTRIBUTE_UNUSED,
+               int length ATTRIBUTE_UNUSED)
+{
+  disassemble_info *info = (disassemble_info *) dis_info;
+  (*info->fprintf_func) (info->stream, "%lu", value);
+}
+
+
+/* -- */
+
+void bpf_cgen_print_operand
+  (CGEN_CPU_DESC, int, PTR, CGEN_FIELDS *, void const *, bfd_vma, int);
+
+/* Main entry point for printing operands.
+   XINFO is a `void *' and not a `disassemble_info *' to not put a requirement
+   of dis-asm.h on cgen.h.
+
+   This function is basically just a big switch statement.  Earlier versions
+   used tables to look up the function to use, but
+   - if the table contains both assembler and disassembler functions then
+     the disassembler contains much of the assembler and vice-versa,
+   - there's a lot of inlining possibilities as things grow,
+   - using a switch statement avoids the function call overhead.
+
+   This function could be moved into `print_insn_normal', but keeping it
+   separate makes clear the interface between `print_insn_normal' and each of
+   the handlers.  */
+
+void
+bpf_cgen_print_operand (CGEN_CPU_DESC cd,
+			   int opindex,
+			   void * xinfo,
+			   CGEN_FIELDS *fields,
+			   void const *attrs ATTRIBUTE_UNUSED,
+			   bfd_vma pc,
+			   int length)
+{
+  disassemble_info *info = (disassemble_info *) xinfo;
+
+  switch (opindex)
+    {
+    case BPF_OPERAND_DISP16 :
+      print_normal (cd, info, fields->f_offset16, 0|(1<<CGEN_OPERAND_SIGNED)|(1<<CGEN_OPERAND_PCREL_ADDR), pc, length);
+      break;
+    case BPF_OPERAND_DISP32 :
+      print_normal (cd, info, fields->f_imm32, 0|(1<<CGEN_OPERAND_SIGNED)|(1<<CGEN_OPERAND_PCREL_ADDR), pc, length);
+      break;
+    case BPF_OPERAND_DSTBE :
+      print_keyword (cd, info, & bpf_cgen_opval_h_gpr, fields->f_dstbe, 0);
+      break;
+    case BPF_OPERAND_DSTLE :
+      print_keyword (cd, info, & bpf_cgen_opval_h_gpr, fields->f_dstle, 0);
+      break;
+    case BPF_OPERAND_ENDSIZE :
+      print_endsize (cd, info, fields->f_imm32, 0, pc, length);
+      break;
+    case BPF_OPERAND_IMM32 :
+      print_immediate (cd, info, fields->f_imm32, 0|(1<<CGEN_OPERAND_SIGNED), pc, length);
+      break;
+    case BPF_OPERAND_IMM64 :
+      print_immediate (cd, info, fields->f_imm64, 0|(1<<CGEN_OPERAND_SIGNED)|(1<<CGEN_OPERAND_VIRTUAL), pc, length);
+      break;
+    case BPF_OPERAND_OFFSET16 :
+      print_immediate (cd, info, fields->f_offset16, 0|(1<<CGEN_OPERAND_SIGNED), pc, length);
+      break;
+    case BPF_OPERAND_SRCBE :
+      print_keyword (cd, info, & bpf_cgen_opval_h_gpr, fields->f_srcbe, 0);
+      break;
+    case BPF_OPERAND_SRCLE :
+      print_keyword (cd, info, & bpf_cgen_opval_h_gpr, fields->f_srcle, 0);
+      break;
+
+    default :
+      /* xgettext:c-format */
+      opcodes_error_handler
+	(_("internal error: unrecognized field %d while printing insn"),
+	 opindex);
+      abort ();
+  }
+}
+
+cgen_print_fn * const bpf_cgen_print_handlers[] =
+{
+  print_insn_normal,
+};
+
+
+void
+bpf_cgen_init_dis (CGEN_CPU_DESC cd)
+{
+  bpf_cgen_init_opcode_table (cd);
+  bpf_cgen_init_ibld_table (cd);
+  cd->print_handlers = & bpf_cgen_print_handlers[0];
+  cd->print_operand = bpf_cgen_print_operand;
+}
+
+
+/* Default print handler.  */
+
+static void
+print_normal (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+	      void *dis_info,
+	      long value,
+	      unsigned int attrs,
+	      bfd_vma pc ATTRIBUTE_UNUSED,
+	      int length ATTRIBUTE_UNUSED)
+{
+  disassemble_info *info = (disassemble_info *) dis_info;
+
+  /* Print the operand as directed by the attributes.  */
+  if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_SEM_ONLY))
+    ; /* nothing to do */
+  else if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_SIGNED))
+    (*info->fprintf_func) (info->stream, "%ld", value);
+  else
+    (*info->fprintf_func) (info->stream, "0x%lx", value);
+}
+
+/* Default address handler.  */
+
+static void
+print_address (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+	       void *dis_info,
+	       bfd_vma value,
+	       unsigned int attrs,
+	       bfd_vma pc ATTRIBUTE_UNUSED,
+	       int length ATTRIBUTE_UNUSED)
+{
+  disassemble_info *info = (disassemble_info *) dis_info;
+
+  /* Print the operand as directed by the attributes.  */
+  if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_SEM_ONLY))
+    ; /* Nothing to do.  */
+  else if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_PCREL_ADDR))
+    (*info->print_address_func) (value, info);
+  else if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_ABS_ADDR))
+    (*info->print_address_func) (value, info);
+  else if (CGEN_BOOL_ATTR (attrs, CGEN_OPERAND_SIGNED))
+    (*info->fprintf_func) (info->stream, "%ld", (long) value);
+  else
+    (*info->fprintf_func) (info->stream, "0x%lx", (long) value);
+}
+
+/* Keyword print handler.  */
+
+static void
+print_keyword (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+	       void *dis_info,
+	       CGEN_KEYWORD *keyword_table,
+	       long value,
+	       unsigned int attrs ATTRIBUTE_UNUSED)
+{
+  disassemble_info *info = (disassemble_info *) dis_info;
+  const CGEN_KEYWORD_ENTRY *ke;
+
+  ke = cgen_keyword_lookup_value (keyword_table, value);
+  if (ke != NULL)
+    (*info->fprintf_func) (info->stream, "%s", ke->name);
+  else
+    (*info->fprintf_func) (info->stream, "???");
+}
+
+/* Default insn printer.
+
+   DIS_INFO is defined as `void *' so the disassembler needn't know anything
+   about disassemble_info.  */
+
+static void
+print_insn_normal (CGEN_CPU_DESC cd,
+		   void *dis_info,
+		   const CGEN_INSN *insn,
+		   CGEN_FIELDS *fields,
+		   bfd_vma pc,
+		   int length)
+{
+  const CGEN_SYNTAX *syntax = CGEN_INSN_SYNTAX (insn);
+  disassemble_info *info = (disassemble_info *) dis_info;
+  const CGEN_SYNTAX_CHAR_TYPE *syn;
+
+  CGEN_INIT_PRINT (cd);
+
+  for (syn = CGEN_SYNTAX_STRING (syntax); *syn; ++syn)
+    {
+      if (CGEN_SYNTAX_MNEMONIC_P (*syn))
+	{
+	  (*info->fprintf_func) (info->stream, "%s", CGEN_INSN_MNEMONIC (insn));
+	  continue;
+	}
+      if (CGEN_SYNTAX_CHAR_P (*syn))
+	{
+	  (*info->fprintf_func) (info->stream, "%c", CGEN_SYNTAX_CHAR (*syn));
+	  continue;
+	}
+
+      /* We have an operand.  */
+      bpf_cgen_print_operand (cd, CGEN_SYNTAX_FIELD (*syn), info,
+				 fields, CGEN_INSN_ATTRS (insn), pc, length);
+    }
+}
+
+/* Subroutine of print_insn. Reads an insn into the given buffers and updates
+   the extract info.
+   Returns 0 if all is well, non-zero otherwise.  */
+
+static int
+read_insn (CGEN_CPU_DESC cd ATTRIBUTE_UNUSED,
+	   bfd_vma pc,
+	   disassemble_info *info,
+	   bfd_byte *buf,
+	   int buflen,
+	   CGEN_EXTRACT_INFO *ex_info,
+	   unsigned long *insn_value)
+{
+  int status = (*info->read_memory_func) (pc, buf, buflen, info);
+
+  if (status != 0)
+    {
+      (*info->memory_error_func) (status, pc, info);
+      return -1;
+    }
+
+  ex_info->dis_info = info;
+  ex_info->valid = (1 << buflen) - 1;
+  ex_info->insn_bytes = buf;
+
+  *insn_value = bfd_get_bits (buf, buflen * 8, info->endian == BFD_ENDIAN_BIG);
+  return 0;
+}
+
+/* Utility to print an insn.
+   BUF is the base part of the insn, target byte order, BUFLEN bytes long.
+   The result is the size of the insn in bytes or zero for an unknown insn
+   or -1 if an error occurs fetching data (memory_error_func will have
+   been called).  */
+
+static int
+print_insn (CGEN_CPU_DESC cd,
+	    bfd_vma pc,
+	    disassemble_info *info,
+	    bfd_byte *buf,
+	    unsigned int buflen)
+{
+  CGEN_INSN_INT insn_value;
+  const CGEN_INSN_LIST *insn_list;
+  CGEN_EXTRACT_INFO ex_info;
+  int basesize;
+
+  /* Extract base part of instruction, just in case CGEN_DIS_* uses it. */
+  basesize = cd->base_insn_bitsize < buflen * 8 ?
+                                     cd->base_insn_bitsize : buflen * 8;
+  insn_value = cgen_get_insn_value (cd, buf, basesize);
+
+
+  /* Fill in ex_info fields like read_insn would.  Don't actually call
+     read_insn, since the incoming buffer is already read (and possibly
+     modified a la m32r).  */
+  ex_info.valid = (1 << buflen) - 1;
+  ex_info.dis_info = info;
+  ex_info.insn_bytes = buf;
+
+  /* The instructions are stored in hash lists.
+     Pick the first one and keep trying until we find the right one.  */
+
+  insn_list = CGEN_DIS_LOOKUP_INSN (cd, (char *) buf, insn_value);
+  while (insn_list != NULL)
+    {
+      const CGEN_INSN *insn = insn_list->insn;
+      CGEN_FIELDS fields;
+      int length;
+      unsigned long insn_value_cropped;
+
+#ifdef CGEN_VALIDATE_INSN_SUPPORTED
+      /* Not needed as insn shouldn't be in hash lists if not supported.  */
+      /* Supported by this cpu?  */
+      if (! bpf_cgen_insn_supported (cd, insn))
+        {
+          insn_list = CGEN_DIS_NEXT_INSN (insn_list);
+	  continue;
+        }
+#endif
+
+      /* Basic bit mask must be correct.  */
+      /* ??? May wish to allow target to defer this check until the extract
+	 handler.  */
+
+      /* Base size may exceed this instruction's size.  Extract the
+         relevant part from the buffer. */
+      if ((unsigned) (CGEN_INSN_BITSIZE (insn) / 8) < buflen &&
+	  (unsigned) (CGEN_INSN_BITSIZE (insn) / 8) <= sizeof (unsigned long))
+	insn_value_cropped = bfd_get_bits (buf, CGEN_INSN_BITSIZE (insn),
+					   info->endian == BFD_ENDIAN_BIG);
+      else
+	insn_value_cropped = insn_value;
+
+      if ((insn_value_cropped & CGEN_INSN_BASE_MASK (insn))
+	  == CGEN_INSN_BASE_VALUE (insn))
+	{
+	  /* Printing is handled in two passes.  The first pass parses the
+	     machine insn and extracts the fields.  The second pass prints
+	     them.  */
+
+	  /* Make sure the entire insn is loaded into insn_value, if it
+	     can fit.  */
+	  if (((unsigned) CGEN_INSN_BITSIZE (insn) > cd->base_insn_bitsize) &&
+	      (unsigned) (CGEN_INSN_BITSIZE (insn) / 8) <= sizeof (unsigned long))
+	    {
+	      unsigned long full_insn_value;
+	      int rc = read_insn (cd, pc, info, buf,
+				  CGEN_INSN_BITSIZE (insn) / 8,
+				  & ex_info, & full_insn_value);
+	      if (rc != 0)
+		return rc;
+	      length = CGEN_EXTRACT_FN (cd, insn)
+		(cd, insn, &ex_info, full_insn_value, &fields, pc);
+	    }
+	  else
+	    length = CGEN_EXTRACT_FN (cd, insn)
+	      (cd, insn, &ex_info, insn_value_cropped, &fields, pc);
+
+	  /* Length < 0 -> error.  */
+	  if (length < 0)
+	    return length;
+	  if (length > 0)
+	    {
+	      CGEN_PRINT_FN (cd, insn) (cd, info, insn, &fields, pc, length);
+	      /* Length is in bits, result is in bytes.  */
+	      return length / 8;
+	    }
+	}
+
+      insn_list = CGEN_DIS_NEXT_INSN (insn_list);
+    }
+
+  return 0;
+}
+
+/* Default value for CGEN_PRINT_INSN.
+   The result is the size of the insn in bytes or zero for an unknown insn
+   or -1 if an error occured fetching bytes.  */
+
+#ifndef CGEN_PRINT_INSN
+#define CGEN_PRINT_INSN default_print_insn
+#endif
+
+static int
+default_print_insn (CGEN_CPU_DESC cd, bfd_vma pc, disassemble_info *info)
+{
+  bfd_byte buf[CGEN_MAX_INSN_SIZE];
+  int buflen;
+  int status;
+
+  /* Attempt to read the base part of the insn.  */
+  buflen = cd->base_insn_bitsize / 8;
+  status = (*info->read_memory_func) (pc, buf, buflen, info);
+
+  /* Try again with the minimum part, if min < base.  */
+  if (status != 0 && (cd->min_insn_bitsize < cd->base_insn_bitsize))
+    {
+      buflen = cd->min_insn_bitsize / 8;
+      status = (*info->read_memory_func) (pc, buf, buflen, info);
+    }
+
+  if (status != 0)
+    {
+      (*info->memory_error_func) (status, pc, info);
+      return -1;
+    }
+
+  return print_insn (cd, pc, info, buf, buflen);
+}
+
+/* Main entry point.
+   Print one instruction from PC on INFO->STREAM.
+   Return the size of the instruction (in bytes).  */
+
+typedef struct cpu_desc_list
+{
+  struct cpu_desc_list *next;
+  CGEN_BITSET *isa;
+  int mach;
+  int endian;
+  CGEN_CPU_DESC cd;
+} cpu_desc_list;
+
+int
+print_insn_bpf (bfd_vma pc, disassemble_info *info)
+{
+  static cpu_desc_list *cd_list = 0;
+  cpu_desc_list *cl = 0;
+  static CGEN_CPU_DESC cd = 0;
+  static CGEN_BITSET *prev_isa;
+  static int prev_mach;
+  static int prev_endian;
+  int length;
+  CGEN_BITSET *isa;
+  int mach;
+  int endian = (info->endian == BFD_ENDIAN_BIG
+		? CGEN_ENDIAN_BIG
+		: CGEN_ENDIAN_LITTLE);
+  enum bfd_architecture arch;
+
+  /* ??? gdb will set mach but leave the architecture as "unknown" */
+#ifndef CGEN_BFD_ARCH
+#define CGEN_BFD_ARCH bfd_arch_bpf
+#endif
+  arch = info->arch;
+  if (arch == bfd_arch_unknown)
+    arch = CGEN_BFD_ARCH;
+
+  /* There's no standard way to compute the machine or isa number
+     so we leave it to the target.  */
+#ifdef CGEN_COMPUTE_MACH
+  mach = CGEN_COMPUTE_MACH (info);
+#else
+  mach = info->mach;
+#endif
+
+#ifdef CGEN_COMPUTE_ISA
+  {
+    static CGEN_BITSET *permanent_isa;
+
+    if (!permanent_isa)
+      permanent_isa = cgen_bitset_create (MAX_ISAS);
+    isa = permanent_isa;
+    cgen_bitset_clear (isa);
+    cgen_bitset_add (isa, CGEN_COMPUTE_ISA (info));
+  }
+#else
+  isa = info->insn_sets;
+#endif
+
+  /* If we've switched cpu's, try to find a handle we've used before */
+  if (cd
+      && (cgen_bitset_compare (isa, prev_isa) != 0
+	  || mach != prev_mach
+	  || endian != prev_endian))
+    {
+      cd = 0;
+      for (cl = cd_list; cl; cl = cl->next)
+	{
+	  if (cgen_bitset_compare (cl->isa, isa) == 0 &&
+	      cl->mach == mach &&
+	      cl->endian == endian)
+	    {
+	      cd = cl->cd;
+ 	      prev_isa = cd->isas;
+	      break;
+	    }
+	}
+    }
+
+  /* If we haven't initialized yet, initialize the opcode table.  */
+  if (! cd)
+    {
+      const bfd_arch_info_type *arch_type = bfd_lookup_arch (arch, mach);
+      const char *mach_name;
+
+      if (!arch_type)
+	abort ();
+      mach_name = arch_type->printable_name;
+
+      prev_isa = cgen_bitset_copy (isa);
+      prev_mach = mach;
+      prev_endian = endian;
+      cd = bpf_cgen_cpu_open (CGEN_CPU_OPEN_ISAS, prev_isa,
+				 CGEN_CPU_OPEN_BFDMACH, mach_name,
+				 CGEN_CPU_OPEN_ENDIAN, prev_endian,
+				 CGEN_CPU_OPEN_END);
+      if (!cd)
+	abort ();
+
+      /* Save this away for future reference.  */
+      cl = xmalloc (sizeof (struct cpu_desc_list));
+      cl->cd = cd;
+      cl->isa = prev_isa;
+      cl->mach = mach;
+      cl->endian = endian;
+      cl->next = cd_list;
+      cd_list = cl;
+
+      bpf_cgen_init_dis (cd);
+    }
+
+  /* We try to have as much common code as possible.
+     But at this point some targets need to take over.  */
+  /* ??? Some targets may need a hook elsewhere.  Try to avoid this,
+     but if not possible try to move this hook elsewhere rather than
+     have two hooks.  */
+  length = CGEN_PRINT_INSN (cd, pc, info);
+  if (length > 0)
+    return length;
+  if (length < 0)
+    return -1;
+
+  (*info->fprintf_func) (info->stream, UNKNOWN_INSN_MSG);
+  return cd->default_insn_bitsize / 8;
+}