i386-tdep.c   [plain text]

/* 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"
#include "arch-utils.h"

static long i386_get_frame_setup (CORE_ADDR);

static void i386_follow_jump (void);

static void codestream_read (unsigned char *, int);

static void codestream_seek (CORE_ADDR);

static unsigned char codestream_fill (int);

CORE_ADDR skip_trampoline_code (CORE_ADDR, char *);

static int gdb_print_insn_i386 (bfd_vma, disassemble_info *);

void _initialize_i386_tdep (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 const char att_flavor[] = "att";
static const char intel_flavor[] = "intel";
static const char *valid_flavors[] =
{
  att_flavor,
  intel_flavor,
  NULL
};
static const char *disassembly_flavor = att_flavor;

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

/* This is used to keep the bfd arch_info in sync with the disassembly flavor.  */
static void set_disassembly_flavor_sfunc (char *, int,
					  struct cmd_list_element *);
static void set_disassembly_flavor (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 (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 (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 (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 (void)
{
  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 (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 (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_unsigned_integer (retpc, 1);
      if (op == 0x59)
	/* pop %ecx */
	return 1;
      else if (op == 0x83)
	{
	  op = read_memory_unsigned_integer (retpc + 1, 1);
	  if (op == 0xc4)
	    /* addl $<signed imm 8 bits>, %esp */
	    return (read_memory_unsigned_integer (retpc + 2, 1) & 0xff) / 4;
	  else
	    return 0;
	}
      else if (op == 0x81)
	{			/* add with 32 bit immediate */
	  op = read_memory_unsigned_integer (retpc + 1, 1);
	  if (op == 0xc4)
	    /* addl $<imm 32>, %esp */
	    return read_memory_unsigned_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 (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 (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 (void)
{
  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);
}

/* Insert the (relative) function address into the call sequence
   stored at DYMMY.  */

void
i386_fix_call_dummy (char *dummy, CORE_ADDR pc, CORE_ADDR fun, int nargs,
		     value_ptr *args, struct type *type, int gcc_p)
{
  int from, to, delta, loc;

  loc = (int)(read_register (SP_REGNUM) - CALL_DUMMY_LENGTH);
  from = loc + 5;
  to = (int)(fun);
  delta = to - from;

  *((char *)(dummy) + 1) = (delta & 0xff);
  *((char *)(dummy) + 2) = ((delta >> 8) & 0xff);
  *((char *)(dummy) + 3) = ((delta >> 16) & 0xff);
  *((char *)(dummy) + 4) = ((delta >> 24) & 0xff);
}

void
i386_pop_frame (void)
{
  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_unsigned_integer (fp, 4));
  write_register (PC_REGNUM, read_memory_unsigned_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 (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 */

/* These registers are used for returning integers (and on some
   targets also for returning `struct' and `union' values when their
   size and alignment match an integer type.  */
#define LOW_RETURN_REGNUM 0	/* %eax */
#define HIGH_RETURN_REGNUM 2	/* %edx */

/* Extract from an array REGBUF containing the (raw) register state, a
   function return value of TYPE, and copy that, in virtual format,
   into VALBUF.  */

void
i386_extract_return_value (struct type *type, char *regbuf, char *valbuf)
{
  int len = TYPE_LENGTH (type);

  if (TYPE_CODE_FLT == TYPE_CODE (type))
    {
      if (NUM_FREGS == 0)
	{
	  warning ("Cannot find floating-point return value.");
	  memset (valbuf, 0, len);
	}

      /* Floating-point return values can be found in %st(0).  */
      if (len == TARGET_LONG_DOUBLE_BIT / TARGET_CHAR_BIT
	  && TARGET_LONG_DOUBLE_FORMAT == &floatformat_i387_ext)
	{
	  /* Copy straight over, but take care of the padding.  */
	  memcpy (valbuf, &regbuf[REGISTER_BYTE (FP0_REGNUM)],
		  FPU_REG_RAW_SIZE);
	  memset (valbuf + FPU_REG_RAW_SIZE, 0, len - FPU_REG_RAW_SIZE);
	}
      else
	{
	  /* Convert the extended floating-point number found in
             %st(0) to the desired type.  This is probably not exactly
             how it would happen on the target itself, but it is the
             best we can do.  */
	  DOUBLEST val;
	  floatformat_to_doublest (&floatformat_i387_ext,
				   &regbuf[REGISTER_BYTE (FP0_REGNUM)], &val);
	  store_floating (valbuf, TYPE_LENGTH (type), val);
	}
    }
  else
    {
      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
	internal_error ("Cannot extract return value of %d bytes long.", len);
    }
}

/* Convert data from raw format for register REGNUM in buffer FROM to
   virtual format with type TYPE in buffer TO.  In principle both
   formats are identical except that the virtual format has two extra
   bytes appended that aren't used.  We set these to zero.  */

void
i386_register_convert_to_virtual (int regnum, struct type *type,
				  char *from, char *to)
{
  /* Copy straight over, but take care of the padding.  */
  memcpy (to, from, FPU_REG_RAW_SIZE);
  memset (to + FPU_REG_RAW_SIZE, 0, TYPE_LENGTH (type) - FPU_REG_RAW_SIZE);
}

/* Convert data from virtual format with type TYPE in buffer FROM to
   raw format for register REGNUM in buffer TO.  Simply omit the two
   unused bytes.  */

void
i386_register_convert_to_raw (struct type *type, int regnum,
			      char *from, char *to)
{
  memcpy (to, from, FPU_REG_RAW_SIZE);
}

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

#ifdef I386_LINUX_SIGTRAMP

/* When the i386 Linux kernel calls a signal handler, 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 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.  */

#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 (pc)
     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;
}

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

int
i386_linux_sigtramp (pc)
     CORE_ADDR pc;
{
  return i386_linux_sigtramp_start (pc) != 0;
}

/* Assuming FRAME is for a Linux sigtramp routine, return the saved
   program counter.  The Linux kernel will set up a sigcontext
   structure immediately before the sigtramp routine on the stack.  */

CORE_ADDR
i386_linux_sigtramp_saved_pc (frame)
     struct frame_info *frame;
{
  CORE_ADDR pc;

  pc = i386_linux_sigtramp_start (frame->pc);
  if (pc == 0)
    error ("i386_linux_sigtramp_saved_pc called when no sigtramp");
  return read_memory_integer ((pc
			       - LINUX_SIGCONTEXT_SIZE
			       + LINUX_SIGCONTEXT_PC_OFFSET),
			      4);
}

/* Assuming FRAME is for a Linux sigtramp routine, return the saved
   stack pointer.  The Linux kernel will set up a sigcontext structure
   immediately before the sigtramp routine on the stack.  */

CORE_ADDR
i386_linux_sigtramp_saved_sp (frame)
     struct frame_info *frame;
{
  CORE_ADDR pc;

  pc = i386_linux_sigtramp_start (frame->pc);
  if (pc == 0)
    error ("i386_linux_sigtramp_saved_sp called when no sigtramp");
  return read_memory_integer ((pc
			       - LINUX_SIGCONTEXT_SIZE
			       + 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 (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 (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 (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 (char *args, int from_tty,
			      struct cmd_list_element *c)
{
  set_disassembly_flavor ();
}

static void
set_disassembly_flavor (void)
{
  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 (void)
{
  /* 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,
				&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 ();
}