mem.c

用汇编语言编程源代码

/* SPIM S20 MIPS simulator.
   Code to create, maintain and access memory.

   Copyright (C) 1990-2003 by James Larus ([e-mail]).
   ALL RIGHTS RESERVED.

   SPIM is distributed under the following conditions:

     You may make copies of SPIM for your own use and modify those copies.

     All copies of SPIM must retain my name and copyright notice.

     You may not sell SPIM or distributed SPIM in conjunction with a
     commerical product or service without the expressed written consent of
     James Larus.

   THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
   IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   PURPOSE. */


/* $Header: /Software/SPIM/src/mem.c 10    1/01/03 7:45p Larus $
*/


#include "spim.h"
#include "spim-utils.h"
#include "inst.h"
#include "mem.h"
#include "reg.h"

/* Exported Variables: */

reg_word R[32];
reg_word HI, LO;
int HI_present, LO_present;
mem_addr PC, nPC;
double *FPR;			/* Dynamically allocate so overlay */
float *FGR;			/* is possible */
int *FWR;			/* is possible */
int FP_reg_present;		/* Presence bits for FP registers */
int FP_reg_poison;		/* Poison bits for FP registers */
int FP_spec_load;		/* Is register waiting for a speculative ld */
reg_word CpCond[4], CCR[4][32], CPR[4][32];

instruction **text_seg;
int text_modified;		/* Non-zero means text segment was written */
mem_addr text_top;
mem_word *data_seg;
int data_modified;		/* Non-zero means a data segment was written */
short *data_seg_h;		/* Points to same vector as DATA_SEG */
BYTE_TYPE *data_seg_b;		/* Ditto */
mem_addr data_top;
mem_addr gp_midpoint;		/* Middle of $gp area */
mem_word *stack_seg;
short *stack_seg_h;		/* Points to same vector as STACK_SEG */
BYTE_TYPE *stack_seg_b;		/* Ditto */
mem_addr stack_bot;
instruction **k_text_seg;
mem_addr k_text_top;
mem_word *k_data_seg;
short *k_data_seg_h;
BYTE_TYPE *k_data_seg_b;
mem_addr k_data_top;


/* Local functions: */

#ifdef __STDC__
static void free_instructions (register instruction **inst, int n);
static mem_word read_memory_mapped_IO (mem_addr addr);
static void write_memory_mapped_IO (mem_addr addr, mem_word value);
#else
static void free_instructions ();
static mem_word read_memory_mapped_IO ();
static void write_memory_mapped_IO ();
#endif


/* Local variables: */

static int32 data_size_limit, stack_size_limit, k_data_size_limit;



/* Memory is allocated in five chunks:
	text, data, stack, kernel text, and kernel data.

   The arrays are independent and have different semantics.

   text is allocated from 0x400000 up and only contains INSTRUCTIONs.
   It does not expand.

   data is allocated from 0x10000000 up.  It can be extended by the
   SBRK system call.  Programs can only read and write this segment.

   stack grows from 0x7fffefff down.  It is automatically extended.
   Programs can only read and write this segment.

   k_text is like text, except its is allocated from 0x80000000 up.

   k_data is like data, but is allocated from 0x90000000 up.

   Both kernel text and kernel data can only be accessed in kernel mode.
*/

/* The text segments contain pointers to instructions, not actual
   instructions, so they must be allocated large enough to hold as many
   pointers as there would be instructions (the two differ on machines in
   which pointers are not 32 bits long).  The following calculations round
   up in case size is not a multiple of BYTES_PER_WORD.  */

#define BYTES_TO_INST(N) (((N) + BYTES_PER_WORD - 1) / BYTES_PER_WORD * sizeof(instruction*))


#ifdef __STDC__
void
make_memory (int text_size, int data_size, int data_limit,
	     int stack_size, int stack_limit, int k_text_size,
	     int k_data_size, int k_data_limit)
#else
void
make_memory (text_size,
	     data_size, data_limit,
	     stack_size, stack_limit,
	     k_text_size,
	     k_data_size, k_data_limit)
     int text_size, data_size, data_limit, stack_size, stack_limit,
       k_text_size, k_data_size, k_data_limit;
#endif
{
  if (data_size <= 65536)
    data_size = 65536;

  if (text_seg == NULL)
    text_seg = (instruction **) xmalloc (BYTES_TO_INST(text_size));
  else
    {
      free_instructions (text_seg, (text_top - TEXT_BOT) / BYTES_PER_WORD);
      text_seg = (instruction **) realloc (text_seg, BYTES_TO_INST(text_size));
    }
  memclr (text_seg, BYTES_TO_INST(text_size));
  text_top = TEXT_BOT + text_size;

  if (data_seg == NULL)
    data_seg = (mem_word *) xmalloc (data_size);
  else
    data_seg = (mem_word *) realloc (data_seg, data_size);
  memclr (data_seg, data_size);
  data_seg_b = (BYTE_TYPE *) data_seg;
  data_seg_h = (short *) data_seg;
  data_top = DATA_BOT + data_size;
  data_size_limit = data_limit;

  if (stack_seg == NULL)
    stack_seg = (mem_word *) xmalloc (stack_size);
  else
    stack_seg = (mem_word *) realloc (stack_seg, stack_size);
  memclr (stack_seg, stack_size);
  stack_seg_b = (BYTE_TYPE *) stack_seg;
  stack_seg_h = (short *) stack_seg;
  stack_bot = STACK_TOP - stack_size;
  stack_size_limit = stack_limit;

  if (k_text_seg == NULL)
    k_text_seg = (instruction **) xmalloc (BYTES_TO_INST(k_text_size));
  else
    {
      free_instructions (k_text_seg,
			 (k_text_top - K_TEXT_BOT) / BYTES_PER_WORD);
      k_text_seg = (instruction **) realloc(k_text_seg,
					    BYTES_TO_INST(k_text_size));
    }
  memclr (k_text_seg, BYTES_TO_INST(k_text_size));
  k_text_top = K_TEXT_BOT + k_text_size;

  if (k_data_seg == NULL)
    k_data_seg = (mem_word *) xmalloc (k_data_size);
  else
    k_data_seg = (mem_word *) realloc (k_data_seg, k_data_size);
  memclr (k_data_seg, k_data_size);
  k_data_seg_b = (BYTE_TYPE *) k_data_seg;
  k_data_seg_h = (short *) k_data_seg;
  k_data_top = K_DATA_BOT + k_data_size;
  k_data_size_limit = k_data_limit;

  text_modified = 1;
  data_modified = 1;
}


/* Free the storage used by the old instructions in memory. */

#ifdef __STDC__
static void
free_instructions (register instruction **inst, int n)
#else
static void
free_instructions (inst, n)
     register instruction **inst;
     int n;
#endif
{
  for ( ; n > 0; n --, inst ++)
    if (*inst)
      free_inst (*inst);
}


/* Expand the data segment by adding N bytes. */

#ifdef __STDC__
void
expand_data (int addl_bytes)
#else
void
expand_data (addl_bytes)
     int addl_bytes;
#endif
{
  int old_size = data_top - DATA_BOT;
  int new_size = old_size + addl_bytes;
  register BYTE_TYPE *p;

  if (addl_bytes < 0 || (source_file && new_size > data_size_limit))
    {
      error ("Can't expand data segment by %d bytes to %d bytes\n",
	     addl_bytes, new_size);
      run_error ("Use -ldata # with # > %d\n", new_size);
    }
  data_seg = (mem_word *) realloc (data_seg, new_size);
  if (data_seg == NULL)
    fatal_error ("realloc failed in expand_data\n");

  data_seg_b = (BYTE_TYPE *) data_seg;
  data_seg_h = (short *) data_seg;
  data_top += addl_bytes;

  /* Zero new memory */
  for (p = data_seg_b + old_size; p < data_seg_b + new_size; )
    *p ++ = 0;
}


/* Expand the stack segment by adding N bytes.  Can't use REALLOC
   since it copies from bottom of memory blocks and stack grows down from
   top of its block. */

#ifdef __STDC__
void
expand_stack (int addl_bytes)
#else
void
expand_stack (addl_bytes)
     int addl_bytes;
#endif
{
  int old_size = STACK_TOP - stack_bot;
  int new_size = old_size + MAX (addl_bytes, old_size);
  mem_word *new_seg;
  register mem_word *po, *pn;

  if (addl_bytes < 0 || (source_file && new_size > stack_size_limit))
    {
      error ("Can't expand stack segment by %d bytes to %d bytes\n",
	     addl_bytes, new_size);
      run_error ("Use -lstack # with # > %d\n", new_size);
    }

  new_seg = (mem_word *) xmalloc (new_size);
  po = stack_seg + (old_size / BYTES_PER_WORD - 1);
  pn = new_seg + (new_size / BYTES_PER_WORD - 1);

  for ( ; po >= stack_seg ; ) *pn -- = *po --;
  for ( ; pn >= new_seg ; ) *pn -- = 0;

  free (stack_seg);
  stack_seg = new_seg;
  stack_seg_b = (BYTE_TYPE *) stack_seg;
  stack_seg_h = (short *) stack_seg;
  stack_bot -= (new_size - old_size);
}


/* Expand the kernel data segment by adding N bytes. */

#ifdef __STDC__
void
expand_k_data (int addl_bytes)
#else
void
expand_k_data (addl_bytes)
     int addl_bytes;
#endif
{
  int old_size = k_data_top - K_DATA_BOT;
  int new_size = old_size + addl_bytes;
  register BYTE_TYPE *p;

  if (addl_bytes < 0 || (source_file && new_size > k_data_size_limit))
    {
      error ("Can't expand kernel data segment by %d bytes to %d bytes\n",
	     addl_bytes, new_size);
      run_error ("Use -lkdata # with # > %d\n", new_size);
    }
  k_data_seg = (mem_word *) realloc (k_data_seg, new_size);
  if (k_data_seg == NULL)
    fatal_error ("realloc failed in expand_k_data\n");

  k_data_seg_b = (BYTE_TYPE *) k_data_seg;
  k_data_seg_h = (short *) k_data_seg;
  k_data_top += addl_bytes;

  /* Zero new memory */
  for (p = k_data_seg_b + old_size / BYTES_PER_WORD;
       p < k_data_seg_b + new_size / BYTES_PER_WORD; )
    *p ++ = 0;
}



/* Handle the infrequent and erroneous cases in the memory access macros. */

#ifdef __STDC__
instruction *
bad_text_read (mem_addr addr)
#else
instruction *
bad_text_read (addr)
     mem_addr addr;
#endif
{
  RAISE_EXCEPTION (IBUS_EXCPT, BadVAddr = addr);
  return (inst_decode (0));
}


#ifdef __STDC__
void
bad_text_write (mem_addr addr, instruction *inst)
#else
void
bad_text_write (addr, inst)
     mem_addr addr;
     instruction *inst;
#endif