[deliverable/binutils-gdb.git] / gdb / i386-tdep.c

/* Intel 386 target-dependent stuff.
   Copyright (C) 1988, 1989, 1991, 1994, 1995, 1996, 1998
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program 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 2 of the License, or
   (at your option) any later version.

   This program 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., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdb_string.h"
#include "frame.h"
#include "inferior.h"
#include "gdbcore.h"
#include "target.h"
#include "floatformat.h"
#include "symtab.h"
#include "gdbcmd.h"
#include "command.h"

static long i386_get_frame_setup PARAMS ((CORE_ADDR));

static void i386_follow_jump PARAMS ((void));

static void codestream_read PARAMS ((unsigned char *, int));

static void codestream_seek PARAMS ((CORE_ADDR));

static unsigned char codestream_fill PARAMS ((int));

CORE_ADDR skip_trampoline_code PARAMS ((CORE_ADDR, char *));

static int gdb_print_insn_i386 (bfd_vma, disassemble_info *);

void _initialize_i386_tdep PARAMS ((void));

/* i386_register_byte[i] is the offset into the register file of the
   start of register number i.  We initialize this from
   i386_register_raw_size.  */
int i386_register_byte[MAX_NUM_REGS];

/* i386_register_raw_size[i] is the number of bytes of storage in
   GDB's register array occupied by register i.  */
int i386_register_raw_size[MAX_NUM_REGS] = {
   4,  4,  4,  4,
   4,  4,  4,  4,
   4,  4,  4,  4,
   4,  4,  4,  4,
  10, 10, 10, 10,
  10, 10, 10, 10,
   4,  4,  4,  4,
   4,  4,  4,  4,
  16, 16, 16, 16,
  16, 16, 16, 16,
   4
};

/* i386_register_virtual_size[i] is the size in bytes of the virtual
   type of register i.  */
int i386_register_virtual_size[MAX_NUM_REGS];


/* This is the variable the is set with "set disassembly-flavor",
   and its legitimate values. */
static char att_flavor[] = "att";
static char intel_flavor[] = "intel";
static char *valid_flavors[] =
{
  att_flavor,
  intel_flavor,
  NULL
};
static char *disassembly_flavor = att_flavor;

static void i386_print_register PARAMS ((char *, int, int));

/* This is used to keep the bfd arch_info in sync with the disassembly flavor.  */
static void set_disassembly_flavor_sfunc PARAMS ((char *, int, struct cmd_list_element *));
static void set_disassembly_flavor PARAMS ((void));

/* Stdio style buffering was used to minimize calls to ptrace, but this
   buffering did not take into account that the code section being accessed
   may not be an even number of buffers long (even if the buffer is only
   sizeof(int) long).  In cases where the code section size happened to
   be a non-integral number of buffers long, attempting to read the last
   buffer would fail.  Simply using target_read_memory and ignoring errors,
   rather than read_memory, is not the correct solution, since legitimate
   access errors would then be totally ignored.  To properly handle this
   situation and continue to use buffering would require that this code
   be able to determine the minimum code section size granularity (not the
   alignment of the section itself, since the actual failing case that
   pointed out this problem had a section alignment of 4 but was not a
   multiple of 4 bytes long), on a target by target basis, and then
   adjust it's buffer size accordingly.  This is messy, but potentially
   feasible.  It probably needs the bfd library's help and support.  For
   now, the buffer size is set to 1.  (FIXME -fnf) */

#define CODESTREAM_BUFSIZ 1     /* Was sizeof(int), see note above. */
static CORE_ADDR codestream_next_addr;
static CORE_ADDR codestream_addr;
static unsigned char codestream_buf[CODESTREAM_BUFSIZ];
static int codestream_off;
static int codestream_cnt;

#define codestream_tell() (codestream_addr + codestream_off)
#define codestream_peek() (codestream_cnt == 0 ? \
                           codestream_fill(1): codestream_buf[codestream_off])
#define codestream_get() (codestream_cnt-- == 0 ? \
                         codestream_fill(0) : codestream_buf[codestream_off++])

static unsigned char
codestream_fill (peek_flag)
     int peek_flag;
{
  codestream_addr = codestream_next_addr;
  codestream_next_addr += CODESTREAM_BUFSIZ;
  codestream_off = 0;
  codestream_cnt = CODESTREAM_BUFSIZ;
  read_memory (codestream_addr, (char *) codestream_buf, CODESTREAM_BUFSIZ);

  if (peek_flag)
    return (codestream_peek ());
  else
    return (codestream_get ());
}

static void
codestream_seek (place)
     CORE_ADDR place;
{
  codestream_next_addr = place / CODESTREAM_BUFSIZ;
  codestream_next_addr *= CODESTREAM_BUFSIZ;
  codestream_cnt = 0;
  codestream_fill (1);
  while (codestream_tell () != place)
    codestream_get ();
}

static void
codestream_read (buf, count)
     unsigned char *buf;
     int count;
{
  unsigned char *p;
  int i;
  p = buf;
  for (i = 0; i < count; i++)
    *p++ = codestream_get ();
}

/* next instruction is a jump, move to target */

static void
i386_follow_jump ()
{
  unsigned char buf[4];
  long delta;

  int data16;
  CORE_ADDR pos;

  pos = codestream_tell ();

  data16 = 0;
  if (codestream_peek () == 0x66)
    {
      codestream_get ();
      data16 = 1;
    }

  switch (codestream_get ())
    {
    case 0xe9:
      /* relative jump: if data16 == 0, disp32, else disp16 */
      if (data16)
        {
          codestream_read (buf, 2);
          delta = extract_signed_integer (buf, 2);

          /* include size of jmp inst (including the 0x66 prefix).  */
          pos += delta + 4;
        }
      else
        {
          codestream_read (buf, 4);
          delta = extract_signed_integer (buf, 4);

          pos += delta + 5;
        }
      break;
    case 0xeb:
      /* relative jump, disp8 (ignore data16) */
      codestream_read (buf, 1);
      /* Sign-extend it.  */
      delta = extract_signed_integer (buf, 1);

      pos += delta + 2;
      break;
    }
  codestream_seek (pos);
}

/*
 * find & return amound a local space allocated, and advance codestream to
 * first register push (if any)
 *
 * if entry sequence doesn't make sense, return -1, and leave 
 * codestream pointer random
 */

static long
i386_get_frame_setup (pc)
     CORE_ADDR pc;
{
  unsigned char op;

  codestream_seek (pc);

  i386_follow_jump ();

  op = codestream_get ();

  if (op == 0x58)               /* popl %eax */
    {
      /*
       * this function must start with
       * 
       *    popl %eax             0x58
       *    xchgl %eax, (%esp)  0x87 0x04 0x24
       * or xchgl %eax, 0(%esp) 0x87 0x44 0x24 0x00
       *
       * (the system 5 compiler puts out the second xchg
       * inst, and the assembler doesn't try to optimize it,
       * so the 'sib' form gets generated)
       * 
       * this sequence is used to get the address of the return
       * buffer for a function that returns a structure
       */
      int pos;
      unsigned char buf[4];
      static unsigned char proto1[3] =
      {0x87, 0x04, 0x24};
      static unsigned char proto2[4] =
      {0x87, 0x44, 0x24, 0x00};
      pos = codestream_tell ();
      codestream_read (buf, 4);
      if (memcmp (buf, proto1, 3) == 0)
        pos += 3;
      else if (memcmp (buf, proto2, 4) == 0)
        pos += 4;

      codestream_seek (pos);
      op = codestream_get ();   /* update next opcode */
    }

  if (op == 0x68 || op == 0x6a)
    {
      /*
       * this function may start with
       *
       *   pushl constant
       *   call _probe
       *   addl $4, %esp
       *      followed by 
       *     pushl %ebp
       *     etc.
       */
      int pos;
      unsigned char buf[8];

      /* Skip past the pushl instruction; it has either a one-byte 
         or a four-byte operand, depending on the opcode.  */
      pos = codestream_tell ();
      if (op == 0x68)
        pos += 4;
      else
        pos += 1;
      codestream_seek (pos);

      /* Read the following 8 bytes, which should be "call _probe" (6 bytes)
         followed by "addl $4,%esp" (2 bytes).  */
      codestream_read (buf, sizeof (buf));
      if (buf[0] == 0xe8 && buf[6] == 0xc4 && buf[7] == 0x4)
        pos += sizeof (buf);
      codestream_seek (pos);
      op = codestream_get ();   /* update next opcode */
    }

  if (op == 0x55)               /* pushl %ebp */
    {
      /* check for movl %esp, %ebp - can be written two ways */
      switch (codestream_get ())
        {
        case 0x8b:
          if (codestream_get () != 0xec)
            return (-1);
          break;
        case 0x89:
          if (codestream_get () != 0xe5)
            return (-1);
          break;
        default:
          return (-1);
        }
      /* check for stack adjustment 

       *  subl $XXX, %esp
       *
       * note: you can't subtract a 16 bit immediate
       * from a 32 bit reg, so we don't have to worry
       * about a data16 prefix 
       */
      op = codestream_peek ();
      if (op == 0x83)
        {
          /* subl with 8 bit immed */
          codestream_get ();
          if (codestream_get () != 0xec)
            /* Some instruction starting with 0x83 other than subl.  */
            {
              codestream_seek (codestream_tell () - 2);
              return 0;
            }
          /* subl with signed byte immediate 
           * (though it wouldn't make sense to be negative)
           */
          return (codestream_get ());
        }
      else if (op == 0x81)
        {
          char buf[4];
          /* Maybe it is subl with 32 bit immedediate.  */
          codestream_get ();
          if (codestream_get () != 0xec)
            /* Some instruction starting with 0x81 other than subl.  */
            {
              codestream_seek (codestream_tell () - 2);
              return 0;
            }
          /* It is subl with 32 bit immediate.  */
          codestream_read ((unsigned char *) buf, 4);
          return extract_signed_integer (buf, 4);
        }
      else
        {
          return (0);
        }
    }
  else if (op == 0xc8)
    {
      char buf[2];
      /* enter instruction: arg is 16 bit unsigned immed */
      codestream_read ((unsigned char *) buf, 2);
      codestream_get ();        /* flush final byte of enter instruction */
      return extract_unsigned_integer (buf, 2);
    }
  return (-1);
}

/* Return number of args passed to a frame.
   Can return -1, meaning no way to tell.  */

int
i386_frame_num_args (fi)
     struct frame_info *fi;
{
#if 1
  return -1;
#else
  /* This loses because not only might the compiler not be popping the
     args right after the function call, it might be popping args from both
     this call and a previous one, and we would say there are more args
     than there really are.  */

  int retpc;
  unsigned char op;
  struct frame_info *pfi;

  /* on the 386, the instruction following the call could be:
     popl %ecx        -  one arg
     addl $imm, %esp  -  imm/4 args; imm may be 8 or 32 bits
     anything else    -  zero args  */

  int frameless;

  frameless = FRAMELESS_FUNCTION_INVOCATION (fi);
  if (frameless)
    /* In the absence of a frame pointer, GDB doesn't get correct values
       for nameless arguments.  Return -1, so it doesn't print any
       nameless arguments.  */
    return -1;

  pfi = get_prev_frame (fi);
  if (pfi == 0)
    {
      /* Note:  this can happen if we are looking at the frame for
         main, because FRAME_CHAIN_VALID won't let us go into
         start.  If we have debugging symbols, that's not really
         a big deal; it just means it will only show as many arguments
         to main as are declared.  */
      return -1;
    }
  else
    {
      retpc = pfi->pc;
      op = read_memory_integer (retpc, 1);
      if (op == 0x59)
        /* pop %ecx */
        return 1;
      else if (op == 0x83)
        {
          op = read_memory_integer (retpc + 1, 1);
          if (op == 0xc4)
            /* addl $<signed imm 8 bits>, %esp */
            return (read_memory_integer (retpc + 2, 1) & 0xff) / 4;
          else
            return 0;
        }
      else if (op == 0x81)
        {                       /* add with 32 bit immediate */
          op = read_memory_integer (retpc + 1, 1);
          if (op == 0xc4)
            /* addl $<imm 32>, %esp */
            return read_memory_integer (retpc + 2, 4) / 4;
          else
            return 0;
        }
      else
        {
          return 0;
        }
    }
#endif
}

/*
 * parse the first few instructions of the function to see
 * what registers were stored.
 *
 * We handle these cases:
 *
 * The startup sequence can be at the start of the function,
 * or the function can start with a branch to startup code at the end.
 *
 * %ebp can be set up with either the 'enter' instruction, or 
 * 'pushl %ebp, movl %esp, %ebp' (enter is too slow to be useful,
 * but was once used in the sys5 compiler)
 *
 * Local space is allocated just below the saved %ebp by either the
 * 'enter' instruction, or by 'subl $<size>, %esp'.  'enter' has
 * a 16 bit unsigned argument for space to allocate, and the
 * 'addl' instruction could have either a signed byte, or
 * 32 bit immediate.
 *
 * Next, the registers used by this function are pushed.  In
 * the sys5 compiler they will always be in the order: %edi, %esi, %ebx
 * (and sometimes a harmless bug causes it to also save but not restore %eax);
 * however, the code below is willing to see the pushes in any order,
 * and will handle up to 8 of them.
 *
 * If the setup sequence is at the end of the function, then the
 * next instruction will be a branch back to the start.
 */

void
i386_frame_init_saved_regs (fip)
     struct frame_info *fip;
{
  long locals = -1;
  unsigned char op;
  CORE_ADDR dummy_bottom;
  CORE_ADDR adr;
  CORE_ADDR pc;
  int i;

  if (fip->saved_regs)
    return;

  frame_saved_regs_zalloc (fip);

  /* if frame is the end of a dummy, compute where the
   * beginning would be
   */
  dummy_bottom = fip->frame - 4 - REGISTER_BYTES - CALL_DUMMY_LENGTH;

  /* check if the PC is in the stack, in a dummy frame */
  if (dummy_bottom <= fip->pc && fip->pc <= fip->frame)
    {
      /* all regs were saved by push_call_dummy () */
      adr = fip->frame;
      for (i = 0; i < NUM_REGS; i++)
        {
          adr -= REGISTER_RAW_SIZE (i);
          fip->saved_regs[i] = adr;
        }
      return;
    }

  pc = get_pc_function_start (fip->pc);
  if (pc != 0)
    locals = i386_get_frame_setup (pc);

  if (locals >= 0)
    {
      adr = fip->frame - 4 - locals;
      for (i = 0; i < 8; i++)
        {
          op = codestream_get ();
          if (op < 0x50 || op > 0x57)
            break;
#ifdef I386_REGNO_TO_SYMMETRY
          /* Dynix uses different internal numbering.  Ick.  */
          fip->saved_regs[I386_REGNO_TO_SYMMETRY (op - 0x50)] = adr;
#else
          fip->saved_regs[op - 0x50] = adr;
#endif
          adr -= 4;
        }
    }

  fip->saved_regs[PC_REGNUM] = fip->frame + 4;
  fip->saved_regs[FP_REGNUM] = fip->frame;
}

/* return pc of first real instruction */

int
i386_skip_prologue (pc)
     int pc;
{
  unsigned char op;
  int i;
  static unsigned char pic_pat[6] =
  {0xe8, 0, 0, 0, 0,            /* call   0x0 */
   0x5b,                        /* popl   %ebx */
  };
  CORE_ADDR pos;

  if (i386_get_frame_setup (pc) < 0)
    return (pc);

  /* found valid frame setup - codestream now points to 
   * start of push instructions for saving registers
   */

  /* skip over register saves */
  for (i = 0; i < 8; i++)
    {
      op = codestream_peek ();
      /* break if not pushl inst */
      if (op < 0x50 || op > 0x57)
        break;
      codestream_get ();
    }

  /* The native cc on SVR4 in -K PIC mode inserts the following code to get
     the address of the global offset table (GOT) into register %ebx.
     call       0x0
     popl       %ebx
     movl       %ebx,x(%ebp)    (optional)
     addl       y,%ebx
     This code is with the rest of the prologue (at the end of the
     function), so we have to skip it to get to the first real
     instruction at the start of the function.  */

  pos = codestream_tell ();
  for (i = 0; i < 6; i++)
    {
      op = codestream_get ();
      if (pic_pat[i] != op)
        break;
    }
  if (i == 6)
    {
      unsigned char buf[4];
      long delta = 6;

      op = codestream_get ();
      if (op == 0x89)           /* movl %ebx, x(%ebp) */
        {
          op = codestream_get ();
          if (op == 0x5d)       /* one byte offset from %ebp */
            {
              delta += 3;
              codestream_read (buf, 1);
            }
          else if (op == 0x9d)  /* four byte offset from %ebp */
            {
              delta += 6;
              codestream_read (buf, 4);
            }
          else                  /* unexpected instruction */
            delta = -1;
          op = codestream_get ();
        }
      /* addl y,%ebx */
      if (delta > 0 && op == 0x81 && codestream_get () == 0xc3)
        {
          pos += delta + 6;
        }
    }
  codestream_seek (pos);

  i386_follow_jump ();

  return (codestream_tell ());
}

void
i386_push_dummy_frame ()
{
  CORE_ADDR sp = read_register (SP_REGNUM);
  int regnum;
  char regbuf[MAX_REGISTER_RAW_SIZE];

  sp = push_word (sp, read_register (PC_REGNUM));
  sp = push_word (sp, read_register (FP_REGNUM));
  write_register (FP_REGNUM, sp);
  for (regnum = 0; regnum < NUM_REGS; regnum++)
    {
      read_register_gen (regnum, regbuf);
      sp = push_bytes (sp, regbuf, REGISTER_RAW_SIZE (regnum));
    }
  write_register (SP_REGNUM, sp);
}

void
i386_pop_frame ()
{
  struct frame_info *frame = get_current_frame ();
  CORE_ADDR fp;
  int regnum;
  char regbuf[MAX_REGISTER_RAW_SIZE];

  fp = FRAME_FP (frame);
  i386_frame_init_saved_regs (frame);

  for (regnum = 0; regnum < NUM_REGS; regnum++)
    {
      CORE_ADDR adr;
      adr = frame->saved_regs[regnum];
      if (adr)
        {
          read_memory (adr, regbuf, REGISTER_RAW_SIZE (regnum));
          write_register_bytes (REGISTER_BYTE (regnum), regbuf,
                                REGISTER_RAW_SIZE (regnum));
        }
    }
  write_register (FP_REGNUM, read_memory_integer (fp, 4));
  write_register (PC_REGNUM, read_memory_integer (fp + 4, 4));
  write_register (SP_REGNUM, fp + 8);
  flush_cached_frames ();
}

#ifdef GET_LONGJMP_TARGET

/* Figure out where the longjmp will land.  Slurp the args out of the stack.
   We expect the first arg to be a pointer to the jmp_buf structure from which
   we extract the pc (JB_PC) that we will land at.  The pc is copied into PC.
   This routine returns true on success. */

int
get_longjmp_target (pc)
     CORE_ADDR *pc;
{
  char buf[TARGET_PTR_BIT / TARGET_CHAR_BIT];
  CORE_ADDR sp, jb_addr;

  sp = read_register (SP_REGNUM);

  if (target_read_memory (sp + SP_ARG0,         /* Offset of first arg on stack */
                          buf,
                          TARGET_PTR_BIT / TARGET_CHAR_BIT))
    return 0;

  jb_addr = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);

  if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf,
                          TARGET_PTR_BIT / TARGET_CHAR_BIT))
    return 0;

  *pc = extract_address (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);

  return 1;
}

#endif /* GET_LONGJMP_TARGET */

void
i386_extract_return_value (type, regbuf, valbuf)
     struct type *type;
     char regbuf[REGISTER_BYTES];
     char *valbuf;
{
  /* On AIX, i386 GNU/Linux and DJGPP, floating point values are
     returned in floating point registers.  */
  /* FIXME: cagney/2000-02-29: This function needs to be rewritten
     using multi-arch. Please don't keep adding to this #ifdef
     spaghetti. */
#if defined(I386_AIX_TARGET) || defined(I386_GNULINUX_TARGET) || defined(I386_DJGPP_TARGET)
  if (TYPE_CODE_FLT == TYPE_CODE (type))
    {
      double d;
      /* 387 %st(0), gcc uses this */
      floatformat_to_double (&floatformat_i387_ext,
#if defined(FPDATA_REGNUM)
                             &regbuf[REGISTER_BYTE (FPDATA_REGNUM)],
#else /* !FPDATA_REGNUM */
                             &regbuf[REGISTER_BYTE (FP0_REGNUM)],
#endif /* FPDATA_REGNUM */

                             &d);
      store_floating (valbuf, TYPE_LENGTH (type), d);
    }
  else
#endif /* I386_AIX_TARGET || I386_GNULINUX_TARGET || I386_DJGPP_TARGET */
    {
#if defined(LOW_RETURN_REGNUM)
      int len = TYPE_LENGTH (type);
      int low_size = REGISTER_RAW_SIZE (LOW_RETURN_REGNUM);
      int high_size = REGISTER_RAW_SIZE (HIGH_RETURN_REGNUM);

      if (len <= low_size)
        memcpy (valbuf, regbuf + REGISTER_BYTE (LOW_RETURN_REGNUM), len);
      else if (len <= (low_size + high_size))
        {
          memcpy (valbuf,
                  regbuf + REGISTER_BYTE (LOW_RETURN_REGNUM),
                  low_size);
          memcpy (valbuf + low_size,
                  regbuf + REGISTER_BYTE (HIGH_RETURN_REGNUM),
                  len - low_size);
        }
      else
        error ("GDB bug: i386-tdep.c (i386_extract_return_value): Don't know how to find a return value %d bytes long", len);
#else /* !LOW_RETURN_REGNUM */
      memcpy (valbuf, regbuf, TYPE_LENGTH (type));
#endif /* LOW_RETURN_REGNUM */
    }
}

#ifdef I386V4_SIGTRAMP_SAVED_PC
/* Get saved user PC for sigtramp from the pushed ucontext on the stack
   for all three variants of SVR4 sigtramps.  */

CORE_ADDR
i386v4_sigtramp_saved_pc (frame)
     struct frame_info *frame;
{
  CORE_ADDR saved_pc_offset = 4;
  char *name = NULL;

  find_pc_partial_function (frame->pc, &name, NULL, NULL);
  if (name)
    {
      if (STREQ (name, "_sigreturn"))
        saved_pc_offset = 132 + 14 * 4;
      else if (STREQ (name, "_sigacthandler"))
        saved_pc_offset = 80 + 14 * 4;
      else if (STREQ (name, "sigvechandler"))
        saved_pc_offset = 120 + 14 * 4;
    }

  if (frame->next)
    return read_memory_integer (frame->next->frame + saved_pc_offset, 4);
  return read_memory_integer (read_register (SP_REGNUM) + saved_pc_offset, 4);
}
#endif /* I386V4_SIGTRAMP_SAVED_PC */

#ifdef I386_LINUX_SIGTRAMP

/* Linux has two flavors of signals.  Normal signal handlers, and
   "realtime" (RT) signals.  The RT signals can provide additional
   information to the signal handler if the SA_SIGINFO flag is set
   when establishing a signal handler using `sigaction'.  It is not
   unlikely that future versions of Linux will support SA_SIGINFO for
   normal signals too.  */

/* When the i386 Linux kernel calls a signal handler and the
   SA_RESTORER flag isn't set, the return address points to a bit of
   code on the stack.  This function returns whether the PC appears to
   be within this bit of code.

   The instruction sequence for normal signals is
       pop    %eax
       mov    $0x77,%eax
       int    $0x80
   or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80.

   Checking for the code sequence should be somewhat reliable, because
   the effect is to call the system call sigreturn.  This is unlikely
   to occur anywhere other than a signal trampoline.

   It kind of sucks that we have to read memory from the process in
   order to identify a signal trampoline, but there doesn't seem to be
   any other way.  The IN_SIGTRAMP macro in tm-linux.h arranges to
   only call us if no function name could be identified, which should
   be the case since the code is on the stack.

   Detection of signal trampolines for handlers that set the
   SA_RESTORER flag is in general not possible.  Unfortunately this is
   what the GNU C Library has been doing for quite some time now.
   However, as of version 2.1.2, the GNU C Library uses signal
   trampolines (named __restore and __restore_rt) that are identical
   to the ones used by the kernel.  Therefore, these trampolines are
   supported too.  */

#define LINUX_SIGTRAMP_INSN0 (0x58)     /* pop %eax */
#define LINUX_SIGTRAMP_OFFSET0 (0)
#define LINUX_SIGTRAMP_INSN1 (0xb8)     /* mov $NNNN,%eax */
#define LINUX_SIGTRAMP_OFFSET1 (1)
#define LINUX_SIGTRAMP_INSN2 (0xcd)     /* int */
#define LINUX_SIGTRAMP_OFFSET2 (6)

static const unsigned char linux_sigtramp_code[] =
{
  LINUX_SIGTRAMP_INSN0,                                 /* pop %eax */
  LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00,         /* mov $0x77,%eax */
  LINUX_SIGTRAMP_INSN2, 0x80                            /* int $0x80 */
};

#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)

/* If PC is in a sigtramp routine, return the address of the start of
   the routine.  Otherwise, return 0.  */

static CORE_ADDR
i386_linux_sigtramp_start (CORE_ADDR pc)
{
  unsigned char buf[LINUX_SIGTRAMP_LEN];

  /* We only recognize a signal trampoline if PC is at the start of
     one of the three instructions.  We optimize for finding the PC at
     the start, as will be the case when the trampoline is not the
     first frame on the stack.  We assume that in the case where the
     PC is not at the start of the instruction sequence, there will be
     a few trailing readable bytes on the stack.  */

  if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
    return 0;

  if (buf[0] != LINUX_SIGTRAMP_INSN0)
    {
      int adjust;

      switch (buf[0])
        {
        case LINUX_SIGTRAMP_INSN1:
          adjust = LINUX_SIGTRAMP_OFFSET1;
          break;
        case LINUX_SIGTRAMP_INSN2:
          adjust = LINUX_SIGTRAMP_OFFSET2;
          break;
        default:
          return 0;
        }

      pc -= adjust;

      if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
        return 0;
    }

  if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
    return 0;

  return pc;
}

/* This function does the same for RT signals.  Here the instruction
   sequence is
       mov    $0xad,%eax
       int    $0x80
   or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.

   The effect is to call the system call rt_sigreturn.  */

#define LINUX_RT_SIGTRAMP_INSN0 (0xb8)  /* mov $NNNN,%eax */
#define LINUX_RT_SIGTRAMP_OFFSET0 (0)
#define LINUX_RT_SIGTRAMP_INSN1 (0xcd)  /* int */
#define LINUX_RT_SIGTRAMP_OFFSET1 (5)

static const unsigned char linux_rt_sigtramp_code[] =
{
  LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00,      /* mov $0xad,%eax */
  LINUX_RT_SIGTRAMP_INSN1, 0x80                         /* int $0x80 */
};

#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)

/* If PC is in a RT sigtramp routine, return the address of the start
   of the routine.  Otherwise, return 0.  */

static CORE_ADDR
i386_linux_rt_sigtramp_start (CORE_ADDR pc)
{
  unsigned char buf[LINUX_RT_SIGTRAMP_LEN];

  /* We only recognize a signal trampoline if PC is at the start of
     one of the two instructions.  We optimize for finding the PC at
     the start, as will be the case when the trampoline is not the
     first frame on the stack.  We assume that in the case where the
     PC is not at the start of the instruction sequence, there will be
     a few trailing readable bytes on the stack.  */

  if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
    return 0;

  if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
    {
      if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
        return 0;

      pc -= LINUX_RT_SIGTRAMP_OFFSET1;

      if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
        return 0;
    }

  if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
    return 0;

  return pc;
}

/* Return whether PC is in a Linux sigtramp routine.  */

int
i386_linux_in_sigtramp (CORE_ADDR pc, char *name)
{
  if (name)
    return STREQ ("__restore", name) || STREQ ("__restore_rt", name);
  
  return (i386_linux_sigtramp_start (pc) != 0
          || i386_linux_rt_sigtramp_start (pc) != 0);
}

/* Assuming FRAME is for a Linux sigtramp routine, return the address
   of the associated sigcontext structure.  */

CORE_ADDR
i386_linux_sigcontext_addr (struct frame_info *frame)
{
  CORE_ADDR pc;

  pc = i386_linux_sigtramp_start (frame->pc);
  if (pc)
    {
      CORE_ADDR sp;

      if (frame->next)
        /* If this isn't the top frame, the next frame must be for the
           signal handler itself.  The sigcontext structure lives on
           the stack, right after the signum argument.  */
        return frame->next->frame + 12;

      /* This is the top frame.  We'll have to find the address of the
         sigcontext structure by looking at the stack pointer.  Keep
         in mind that the first instruction of the sigtramp code is
         "pop %eax".  If the PC is at this instruction, adjust the
         returned value accordingly.  */
      sp = read_register (SP_REGNUM);
      if (pc == frame->pc)
        return sp + 4;
      return sp;
    }

  pc = i386_linux_rt_sigtramp_start (frame->pc);
  if (pc)
    {
      if (frame->next)
        /* If this isn't the top frame, the next frame must be for the
           signal handler itself.  The sigcontext structure is part of
           the user context.  A pointer to the user context is passed
           as the third argument to the signal handler.  */
        return read_memory_integer (frame->next->frame + 16, 4) + 20;

      /* This is the top frame.  Again, use the stack pointer to find
         the address of the sigcontext structure.  */
      return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20;
    }

  error ("Couldn't recognize signal trampoline.");
  return 0;
}

/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>.  */
#define LINUX_SIGCONTEXT_PC_OFFSET (56)

/* Assuming FRAME is for a Linux sigtramp routine, return the saved
   program counter.  */

CORE_ADDR
i386_linux_sigtramp_saved_pc (struct frame_info *frame)
{
  CORE_ADDR addr;
  addr = i386_linux_sigcontext_addr (frame);
  return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4);
}

/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>.  */
#define LINUX_SIGCONTEXT_SP_OFFSET (28)

/* Assuming FRAME is for a Linux sigtramp routine, return the saved
   stack pointer.  */

CORE_ADDR
i386_linux_sigtramp_saved_sp (struct frame_info *frame)
{
  CORE_ADDR addr;
  addr = i386_linux_sigcontext_addr (frame);
  return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4);
}

#endif /* I386_LINUX_SIGTRAMP */

#ifdef STATIC_TRANSFORM_NAME
/* SunPRO encodes the static variables.  This is not related to C++ mangling,
   it is done for C too.  */

char *
sunpro_static_transform_name (name)
     char *name;
{
  char *p;
  if (IS_STATIC_TRANSFORM_NAME (name))
    {
      /* For file-local statics there will be a period, a bunch
         of junk (the contents of which match a string given in the
         N_OPT), a period and the name.  For function-local statics
         there will be a bunch of junk (which seems to change the
         second character from 'A' to 'B'), a period, the name of the
         function, and the name.  So just skip everything before the
         last period.  */
      p = strrchr (name, '.');
      if (p != NULL)
        name = p + 1;
    }
  return name;
}
#endif /* STATIC_TRANSFORM_NAME */



/* Stuff for WIN32 PE style DLL's but is pretty generic really. */

CORE_ADDR
skip_trampoline_code (pc, name)
     CORE_ADDR pc;
     char *name;
{
  if (pc && read_memory_unsigned_integer (pc, 2) == 0x25ff)     /* jmp *(dest) */
    {
      unsigned long indirect = read_memory_unsigned_integer (pc + 2, 4);
      struct minimal_symbol *indsym =
      indirect ? lookup_minimal_symbol_by_pc (indirect) : 0;
      char *symname = indsym ? SYMBOL_NAME (indsym) : 0;

      if (symname)
        {
          if (strncmp (symname, "__imp_", 6) == 0
              || strncmp (symname, "_imp_", 5) == 0)
            return name ? 1 : read_memory_unsigned_integer (indirect, 4);
        }
    }
  return 0;                     /* not a trampoline */
}

static int
gdb_print_insn_i386 (memaddr, info)
     bfd_vma memaddr;
     disassemble_info *info;
{
  if (disassembly_flavor == att_flavor)
    return print_insn_i386_att (memaddr, info);
  else if (disassembly_flavor == intel_flavor)
    return print_insn_i386_intel (memaddr, info);
  /* Never reached - disassembly_flavour is always either att_flavor
     or intel_flavor */
  abort ();
}

/* If the disassembly mode is intel, we have to also switch the
   bfd mach_type.  This function is run in the set disassembly_flavor
   command, and does that.  */

static void
set_disassembly_flavor_sfunc (args, from_tty, c)
     char *args;
     int from_tty;
     struct cmd_list_element *c;
{
  set_disassembly_flavor ();
}

static void
set_disassembly_flavor ()
{
  if (disassembly_flavor == att_flavor)
    set_architecture_from_arch_mach (bfd_arch_i386, bfd_mach_i386_i386);
  else if (disassembly_flavor == intel_flavor)
    set_architecture_from_arch_mach (bfd_arch_i386, bfd_mach_i386_i386_intel_syntax);
}


void
_initialize_i386_tdep ()
{
  /* Initialize the table saying where each register starts in the
     register file.  */
  {
    int i, offset;

    offset = 0;
    for (i = 0; i < MAX_NUM_REGS; i++)
      {
        i386_register_byte[i] = offset;
        offset += i386_register_raw_size[i];
      }
  }

  /* Initialize the table of virtual register sizes.  */
  {
    int i;

    for (i = 0; i < MAX_NUM_REGS; i++)
      i386_register_virtual_size[i] = TYPE_LENGTH (REGISTER_VIRTUAL_TYPE (i));
  }

  tm_print_insn = gdb_print_insn_i386;
  tm_print_insn_info.mach = bfd_lookup_arch (bfd_arch_i386, 0)->mach;

  /* Add the variable that controls the disassembly flavor */
  {
    struct cmd_list_element *new_cmd;

    new_cmd = add_set_enum_cmd ("disassembly-flavor", no_class,
                                valid_flavors,
                                (char *) &disassembly_flavor,
                                "Set the disassembly flavor, the valid values are \"att\" and \"intel\", \
and the default value is \"att\".",
                                &setlist);
    new_cmd->function.sfunc = set_disassembly_flavor_sfunc;
    add_show_from_set (new_cmd, &showlist);
  }

  /* Finally, initialize the disassembly flavor to the default given
     in the disassembly_flavor variable */

  set_disassembly_flavor ();
}