gld-pinsn.c

/* Print GOULD RISC instructions for GDB, the GNU debugger.
   Copyright (C) 1986, 1987 Free Software Foundation, Inc.

GDB is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY.  No author or distributor accepts responsibility to anyone
for the consequences of using it or for whether it serves any
particular purpose or works at all, unless he says so in writing.
Refer to the GDB General Public License for full details.

Everyone is granted permission to copy, modify and redistribute GDB,
but only under the conditions described in the GDB General Public
License.  A copy of this license is supposed to have been given to you
along with GDB so you can know your rights and responsibilities.  It
should be in a file named COPYING.  Among other things, the copyright
notice and this notice must be preserved on all copies.

In other words, go ahead and share GDB, but don't try to stop
anyone else from sharing it farther.  Help stamp out software hoarding!
*/

#include <stdio.h>
#include <a.out.h>

#include "defs.h"
#include "param.h"
#include "symtab.h"
#include "frame.h"
#include "opcode.h"

/* GOULD RISC instructions are never longer than this many bytes.  */
#define MAXLEN 4

/* Number of elements in the opcode table.  */
#define NOPCODES (sizeof gld_opcodes / sizeof gld_opcodes[0])


/* Print the GOULD instruction at address MEMADDR in debugged memory,
   on STREAM.  Returns length of the instruction, in bytes.  */

int
print_insn (memaddr, stream)
	CORE_ADDR memaddr;
	FILE *stream;
{
	unsigned char buffer[MAXLEN];
	register int i;
	register char *d;
	register int bestmask;
	unsigned best;
	int temp, index, bestlen;

	read_memory (memaddr, buffer, MAXLEN);

	bestmask = 0;
	index = -1;
	best = 0xffffffff;
	for (i = 0; i < NOPCODES; i++)
	{
		register unsigned int opcode = gld_opcodes[i].opcode;
		register unsigned int mask = gld_opcodes[i].mask;
		register unsigned int len = gld_opcodes[i].length;
		register unsigned int test;

		/* Get possible opcode bytes into integer */
		test = buffer[0] << 24;
		test |= buffer[1] << 16;
		test |= buffer[2] << 8;
		test |= buffer[3];

		/* Mask with opcode and see if match */
		if ((opcode & mask) == (test & mask))
		{
			/* See if second or third match */
			if (index >= 0)
			{
				/* Take new one if it looks good */
				if (bestlen == MAXLEN && len == MAXLEN)
				{
					/* See if lower bits matched */
					if (((bestmask & 3) == 0) &&
					    ((mask & 3) != 0))
					{
						bestmask = mask;
						bestlen = len;
						best = test;
						index = i;
					}
				}
			}
			else
			{
				/* First match, save it */
				bestmask = mask;
				bestlen = len;
				best = test;
				index = i;
			}
		}
	}

	/* Handle undefined instructions.  */
	if (index < 0)
	{
		fprintf (stream, "undefined   0%o",(buffer[0]<<8)+buffer[1]);
		return 2;
	}

	/* Print instruction name */
	fprintf (stream, "%-12s", gld_opcodes[index].name);

	/* Adjust if short instruction */
	if (gld_opcodes[index].length < 4)
	{
		best >>= 16;
		i = 0;
	}
	else
	{
		i = 16;
	}

	/* Dump out instruction arguments */
  	for (d = gld_opcodes[index].args; *d; ++d)
	{
	    switch (*d)
	    {
		case 'f':
		    fprintf (stream, "%d",  (best >> (7 + i)) & 7);
		    break;
		case 'r':
		    fprintf (stream, "r%d", (best >> (7 + i)) & 7);
		    break;
		case 'R':
		    fprintf (stream, "r%d", (best >> (4 + i)) & 7);
		    break;
		case 'b':
		    fprintf (stream, "b%d", (best >> (7 + i)) & 7);
		    break;
		case 'B':
		    fprintf (stream, "b%d", (best >> (4 + i)) & 7);
		    break;
		case 'v':
		    fprintf (stream, "b%d", (best >> (7 + i)) & 7);
		    break;
		case 'V':
		    fprintf (stream, "b%d", (best >> (4 + i)) & 7);
		    break;
		case 'X':
		    temp = (best >> 20) & 7;
		    if (temp)
			fprintf (stream, "r%d", temp);
		    else
			putc ('0', stream);
		    break;
		case 'A':
		    temp = (best >> 16) & 7;
		    if (temp)
			fprintf (stream, "(b%d)", temp);
		    break;
		case 'S':
		    fprintf (stream, "#%d", best & 0x1f);
		    break;
		case 'I':
		    fprintf (stream, "#%x", best & 0xffff);
		    break;
		case 'O':
		    fprintf (stream, "%x", best & 0xffff);
		    break;
		case 'h':
		    fprintf (stream, "%d", best & 0xfffe);
		    break;
		case 'd':
		    fprintf (stream, "%d", best & 0xfffc);
		    break;
		case 'T':
		    fprintf (stream, "%d", (best >> 8) & 0xff);
		    break;
		case 'N':
		    fprintf (stream, "%d", best & 0xff);
		    break;
		default:
		    putc (*d, stream);
		    break;
	    }
	}

	/* Return length of instruction */
  	return (gld_opcodes[index].length);
}

/*
 * Find the number of arguments to a function.
 */
findarg(frame)
	struct frame_info *frame;
{
	register struct symbol *func;
	register unsigned pc;

#ifdef notdef
	/* find starting address of frame function */
	pc = get_pc_function_start (frame->pc);

	/* find function symbol info */
	func = find_pc_function (pc);

	/* call blockframe code to look for match */
	if (func != NULL)
                return (func->value.block->nsyms / sizeof(int));
#endif

        return (-1);
} 

/*
 * In the case of the NPL, the frame's norminal address is Br2 and the 
 * previous routines frame is up the stack X bytes.  Finding out what
 * 'X' is can be tricky.
 *
 *    1.) stored in the code function header xA(Br1).
 *    2.) must be careful of recurssion.
 */
FRAME_ADDR
findframe(thisframe)
    FRAME thisframe;
{
    register FRAME_ADDR pointer;
#if 0    
    struct frame_info *frame;
    FRAME_ADDR framechain();

    /* Setup toplevel frame structure */
    frame->pc = read_pc();
    frame->next_frame = 0;
    frame->frame = read_register (SP_REGNUM);	/* Br2 */

    /* Search for this frame (start at current Br2) */
    do
    {
	pointer = framechain(frame);
	frame->next_frame = frame->frame;
	frame->frame = pointer;
	frame->pc = FRAME_SAVED_PC(frame);
    }
    while (frame->next_frame != thisframe);
#endif

    pointer = framechain (thisframe);

    /* stop gap for now, end at __base3 */
    if (thisframe->pc == 0)
	return 0;

    return pointer;
}

/*
 * Gdb front-end and internal framechain routine.
 * Go back up stack one level.  Tricky...
 */
FRAME_ADDR
framechain(frame)
    register struct frame_info *frame;
{
    register CORE_ADDR func, prevsp;
    register unsigned value;

    /* Get real function start address from internal frame address */
    func = get_pc_function_start(frame->pc);

    /* If no stack given, read register Br1 "(sp)" */
    if (!frame->frame)
	prevsp = read_register (SP_REGNUM);
    else
	prevsp = frame->frame;

    /* Check function header, case #2 */
    value = read_memory_integer (func, 4);
    if (value)
    {
	/* 32bit call push value stored in function header */
	prevsp += value;
    }
    else
    {
	/* read half-word from suabr at start of function */
	prevsp += read_memory_integer (func + 10, 2);
    }

    return (prevsp);
}