rs6000-tdep.c

早期freebsd实现

/* Target-dependent code for GDB, the GNU debugger.
   Copyright 1986, 1987, 1989, 1991, 1992 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "symtab.h"
#include "target.h"

#include <sys/param.h>
#include <sys/dir.h>
#include <sys/user.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <fcntl.h>

#include <a.out.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/core.h>
#include <sys/ldr.h>


extern struct obstack frame_cache_obstack;

extern int errno;

/* Nonzero if we just simulated a single step break. */
int one_stepped;

/* Breakpoint shadows for the single step instructions will be kept here. */

static struct sstep_breaks {
	int address;
	int data;
} stepBreaks[2];

/* Static function prototypes */

static void
add_text_to_loadinfo PARAMS ((CORE_ADDR textaddr, CORE_ADDR dataaddr));

static CORE_ADDR
find_toc_address PARAMS ((CORE_ADDR pc));

static CORE_ADDR
branch_dest PARAMS ((int opcode, int instr, CORE_ADDR pc, CORE_ADDR safety));

static void
frame_get_cache_fsr PARAMS ((struct frame_info *fi,
			     struct aix_framedata *fdatap));

/*
 * Calculate the destination of a branch/jump.  Return -1 if not a branch.
 */
static CORE_ADDR
branch_dest (opcode, instr, pc, safety)
     int opcode;
     int instr;
     CORE_ADDR pc;
     CORE_ADDR safety;
{
  register long offset;
  CORE_ADDR dest;
  int immediate;
  int absolute;
  int ext_op;

  absolute = (int) ((instr >> 1) & 1);

  switch (opcode) {
     case 18	:
	immediate = ((instr & ~3) << 6) >> 6;	/* br unconditional */

     case 16	:  
	if (opcode != 18)		        /* br conditional */
	  immediate = ((instr & ~3) << 16) >> 16;
	if (absolute)
	  dest = immediate;	
	else
	  dest = pc + immediate;
	break;

      case 19	:
	ext_op = (instr>>1) & 0x3ff;

	if (ext_op == 16)			/* br conditional register */
	  dest = read_register (LR_REGNUM) & ~3;

	else if (ext_op == 528)			/* br cond to count reg */
	  dest = read_register (CTR_REGNUM) & ~3;

	else return -1; 
	break;
	
       default: return -1;
  }
  return (dest < TEXT_SEGMENT_BASE) ? safety : dest;
}



/* AIX does not support PT_STEP. Simulate it. */

void
single_step (signal)
     int signal;
{
#define	INSNLEN(OPCODE)	 4

  static char breakp[] = BREAKPOINT;
  int ii, insn, ret, loc;
  int breaks[2], opcode;

  if (!one_stepped) {
    loc = read_pc ();

    ret = read_memory (loc, &insn, sizeof (int));
    if (ret)
      printf ("Error in single_step()!!\n");

    breaks[0] = loc + INSNLEN(insn);
    opcode = insn >> 26;
    breaks[1] = branch_dest (opcode, insn, loc, breaks[0]);

    /* Don't put two breakpoints on the same address. */
    if (breaks[1] == breaks[0])
      breaks[1] = -1;

    stepBreaks[1].address = -1;

    for (ii=0; ii < 2; ++ii) {

      /* ignore invalid breakpoint. */
      if ( breaks[ii] == -1)
        continue;

      read_memory (breaks[ii], &(stepBreaks[ii].data), sizeof(int));

      ret = write_memory (breaks[ii], breakp, sizeof(int));
      stepBreaks[ii].address = breaks[ii];
    }  

    one_stepped = 1;
  } else {

    /* remove step breakpoints. */
    for (ii=0; ii < 2; ++ii)
      if (stepBreaks[ii].address != -1)
        write_memory 
           (stepBreaks[ii].address, &(stepBreaks[ii].data), sizeof(int));

    one_stepped = 0;
  }
  errno = 0;			/* FIXME, don't ignore errors! */
}


/* return pc value after skipping a function prologue. */

skip_prologue (pc)
CORE_ADDR pc;
{
  unsigned int tmp;
  unsigned int op;    /* FIXME, assumes instruction size matches host int!!! */

  if (target_read_memory (pc, (char *)&op, sizeof (op)))
    return pc;			/* Can't access it -- assume no prologue. */
  SWAP_TARGET_AND_HOST (&op, sizeof (op));

  /* Assume that subsequent fetches can fail with low probability.  */

  if (op == 0x7c0802a6) {		/* mflr r0 */
    pc += 4;
    op = read_memory_integer (pc, 4);
  }

  if ((op & 0xfc00003e) == 0x7c000026) { /* mfcr Rx */
    pc += 4;
    op = read_memory_integer (pc, 4);
  }

  if ((op & 0xfc000000) == 0x48000000) { /* bl foo, to save fprs??? */
    pc += 4;
    op = read_memory_integer (pc, 4);

    /* At this point, make sure this is not a trampoline function
       (a function that simply calls another functions, and nothing else).
       If the next is not a nop, this branch was part of the function
       prologue. */

    if (op == 0x4def7b82 ||		/* crorc 15, 15, 15 */
	op == 0x0)
      return pc - 4;			/* don't skip over this branch */
  }

  if ((op & 0xfc1f0000) == 0xbc010000) { /* stm Rx, NUM(r1) */
    pc += 4;
    op = read_memory_integer (pc, 4);
  }

  while (((tmp = op >> 16) == 0x9001) || /* st   r0, NUM(r1) */
	 (tmp == 0x9421) ||		/* stu  r1, NUM(r1) */
	 (op == 0x93e1fffc)) 		/* st   r31,-4(r1) */
  {
    pc += 4;
    op = read_memory_integer (pc, 4);
  }

  while ((tmp = (op >> 22)) == 0x20f) {	/* l	r31, ... or */
    pc += 4;				/* l	r30, ...    */
    op = read_memory_integer (pc, 4);
  }

  /* store parameters into stack */
  while(
	(op & 0xfc1f0000) == 0xd8010000 || 	/* stfd Rx,NUM(r1) */
	(op & 0xfc1f0000) == 0x90010000 ||	/* st r?, NUM(r1)  */
	(op & 0xfc000000) == 0xfc000000 ||	/* frsp, fp?, .. */
	(op & 0xd0000000) == 0xd0000000)	/* stfs, fp?, .. */
    {
      pc += 4;					/* store fpr double */
      op = read_memory_integer (pc, 4);
    }

  if (op == 0x603f0000) {			/* oril r31, r1, 0x0 */
    pc += 4;					/* this happens if r31 is used as */
    op = read_memory_integer (pc, 4);		/* frame ptr. (gcc does that)	  */

    tmp = 0;
    while ((op >> 16) == (0x907f + tmp)) {	/* st r3, NUM(r31) */
      pc += 4;					/* st r4, NUM(r31), ... */
      op = read_memory_integer (pc, 4);
      tmp += 0x20;
    }
  }
#if 0
/* I have problems with skipping over __main() that I need to address
 * sometime. Previously, I used to use misc_function_vector which
 * didn't work as well as I wanted to be.  -MGO */

  /* If the first thing after skipping a prolog is a branch to a function,
     this might be a call to an initializer in main(), introduced by gcc2.
     We'd like to skip over it as well. Fortunately, xlc does some extra
     work before calling a function right after a prologue, thus we can
     single out such gcc2 behaviour. */
     

  if ((op & 0xfc000001) == 0x48000001) { /* bl foo, an initializer function? */
    op = read_memory_integer (pc+4, 4);

    if (op == 0x4def7b82) {		/* cror 0xf, 0xf, 0xf (nop) */

      /* check and see if we are in main. If so, skip over this initializer
         function as well. */

      tmp = find_pc_misc_function (pc);
      if (tmp >= 0 && !strcmp (misc_function_vector [tmp].name, "main"))
        return pc + 8;
    }
  }
#endif /* 0 */
 
  return pc;
}


/*************************************************************************
  Support for creating pushind a dummy frame into the stack, and popping
  frames, etc. 
*************************************************************************/

/* The total size of dummy frame is 436, which is;

	32 gpr's	- 128 bytes
	32 fpr's	- 256   "
	7  the rest	- 28    "
	and 24 extra bytes for the callee's link area. The last 24 bytes
	for the link area might not be necessary, since it will be taken
	care of by push_arguments(). */

#define DUMMY_FRAME_SIZE 436

#define	DUMMY_FRAME_ADDR_SIZE 10

/* Make sure you initialize these in somewhere, in case gdb gives up what it
   was debugging and starts debugging something else. FIXMEibm */

static int dummy_frame_count = 0;
static int dummy_frame_size = 0;
static CORE_ADDR *dummy_frame_addr = 0;

extern int stop_stack_dummy;

/* push a dummy frame into stack, save all register. Currently we are saving
   only gpr's and fpr's, which is not good enough! FIXMEmgo */
   
void
push_dummy_frame ()
{
  int sp, pc;				/* stack pointer and link register */
  int ii;

  target_fetch_registers (-1);

  if (dummy_frame_count >= dummy_frame_size) {
    dummy_frame_size += DUMMY_FRAME_ADDR_SIZE;
    if (dummy_frame_addr)
      dummy_frame_addr = (CORE_ADDR*) xrealloc 
        (dummy_frame_addr, sizeof(CORE_ADDR) * (dummy_frame_size));
    else
      dummy_frame_addr = (CORE_ADDR*) 
	xmalloc (sizeof(CORE_ADDR) * (dummy_frame_size));
  }
  
  sp = read_register(SP_REGNUM);
  pc = read_register(PC_REGNUM);  

  dummy_frame_addr [dummy_frame_count++] = sp;

  /* Be careful! If the stack pointer is not decremented first, then kernel 
     thinks he is free to use the space underneath it. And kernel actually 
     uses that area for IPC purposes when executing ptrace(2) calls. So 
     before writing register values into the new frame, decrement and update
     %sp first in order to secure your frame. */

  write_register (SP_REGNUM, sp-DUMMY_FRAME_SIZE);

  /* gdb relies on the state of current_frame. We'd better update it,
     otherwise things like do_registers_info() wouldn't work properly! */

  flush_cached_frames ();
  set_current_frame (create_new_frame (sp-DUMMY_FRAME_SIZE, pc));

  /* save program counter in link register's space. */
  write_memory (sp+8, &pc, 4);

  /* save all floating point and general purpose registers here. */

  /* fpr's, f0..f31 */
  for (ii = 0; ii < 32; ++ii)
    write_memory (sp-8-(ii*8), &registers[REGISTER_BYTE (31-ii+FP0_REGNUM)], 8);

  /* gpr's r0..r31 */
  for (ii=1; ii <=32; ++ii)
    write_memory (sp-256-(ii*4), &registers[REGISTER_BYTE (32-ii)], 4);

  /* so far, 32*2 + 32 words = 384 bytes have been written. 
     7 extra registers in our register set: pc, ps, cnd, lr, cnt, xer, mq */

  for (ii=1; ii <= (LAST_SP_REGNUM-FIRST_SP_REGNUM+1); ++ii) {
    write_memory (sp-384-(ii*4), 
	       &registers[REGISTER_BYTE (FPLAST_REGNUM + ii)], 4);
  }

  /* Save sp or so called back chain right here. */
  write_memory (sp-DUMMY_FRAME_SIZE, &sp, 4);
  sp -= DUMMY_FRAME_SIZE;

  /* And finally, this is the back chain. */
  write_memory (sp+8, &pc, 4);
}


/* Pop a dummy frame.

   In rs6000 when we push a dummy frame, we save all of the registers. This
   is usually done before user calls a function explicitly.

   After a dummy frame is pushed, some instructions are copied into stack,
   and stack pointer is decremented even more.  Since we don't have a frame
   pointer to get back to the parent frame of the dummy, we start having
   trouble poping it.  Therefore, we keep a dummy frame stack, keeping
   addresses of dummy frames as such.  When poping happens and when we
   detect that was a dummy frame, we pop it back to its parent by using
   dummy frame stack (`dummy_frame_addr' array). 

FIXME:  This whole concept is broken.  You should be able to detect
a dummy stack frame *on the user's stack itself*.  When you do,
then you know the format of that stack frame -- including its