mips-tdep.c

早期freebsd实现

    int reg30; /* Value of $r30. Used by gcc for frame-pointer */
    unsigned long reg_mask = 0;

    if (start_pc == 0) return NULL;
    bzero(&temp_proc_desc, sizeof(temp_proc_desc));
    bzero(&temp_saved_regs, sizeof(struct frame_saved_regs));
    PROC_LOW_ADDR(&temp_proc_desc) = start_pc;

    if (start_pc + 200 < limit_pc) limit_pc = start_pc + 200;
  restart:
    frame_size = 0;
    for (cur_pc = start_pc; cur_pc < limit_pc; cur_pc += 4) {
	unsigned long word;
	int status;

	status = read_memory_nobpt (cur_pc, (char *)&word, 4); 
	if (status) memory_error (status, cur_pc); 
	SWAP_TARGET_AND_HOST (&word, sizeof (word));
	if ((word & 0xFFFF0000) == 0x27bd0000) /* addiu $sp,$sp,-i */
	    frame_size += (-word) & 0xFFFF;
	else if ((word & 0xFFFF0000) == 0x23bd0000) /* addu $sp,$sp,-i */
	    frame_size += (-word) & 0xFFFF;
	else if ((word & 0xFFE00000) == 0xafa00000) { /* sw reg,offset($sp) */
	    int reg = (word & 0x001F0000) >> 16;
	    reg_mask |= 1 << reg;
	    temp_saved_regs.regs[reg] = sp + (short)word;
	}
	else if ((word & 0xFFFF0000) == 0x27be0000) { /* addiu $30,$sp,size */
	    if ((unsigned short)word != frame_size)
		reg30 = sp + (unsigned short)word;
	    else if (!has_frame_reg) {
		int alloca_adjust;
		has_frame_reg = 1;
		reg30 = read_next_frame_reg(next_frame, 30);
		alloca_adjust = reg30 - (sp + (unsigned short)word);
		if (alloca_adjust > 0) {
		    /* FP > SP + frame_size. This may be because
		    /* of an alloca or somethings similar.
		     * Fix sp to "pre-alloca" value, and try again.
		     */
		    sp += alloca_adjust;
		    goto restart;
		}
	    }
	}
	else if ((word & 0xFFE00000) == 0xafc00000) { /* sw reg,offset($30) */
	    int reg = (word & 0x001F0000) >> 16;
	    reg_mask |= 1 << reg;
	    temp_saved_regs.regs[reg] = reg30 + (short)word;
	}
    }
    if (has_frame_reg) {
	PROC_FRAME_REG(&temp_proc_desc) = 30;
	PROC_FRAME_OFFSET(&temp_proc_desc) = 0;
    }
    else {
	PROC_FRAME_REG(&temp_proc_desc) = SP_REGNUM;
	PROC_FRAME_OFFSET(&temp_proc_desc) = frame_size;
    }
    PROC_REG_MASK(&temp_proc_desc) = reg_mask;
    PROC_PC_REG(&temp_proc_desc) = RA_REGNUM;
    return &temp_proc_desc;
}

static mips_extra_func_info_t
find_proc_desc(pc, next_frame)
    CORE_ADDR pc;
    FRAME next_frame;
{
  mips_extra_func_info_t proc_desc;
  struct block *b = block_for_pc(pc);
  struct symbol *sym =
      b ? lookup_symbol(MIPS_EFI_SYMBOL_NAME, b, LABEL_NAMESPACE, 0, NULL) : NULL;

  if (sym)
    {
	/* IF this is the topmost frame AND
	 * (this proc does not have debugging information OR
	 * the PC is in the procedure prologue)
	 * THEN create a "heuristic" proc_desc (by analyzing
	 * the actual code) to replace the "official" proc_desc.
	 */
	proc_desc = (mips_extra_func_info_t)SYMBOL_VALUE(sym);
	if (next_frame == NULL) {
	    struct symtab_and_line val;
	    struct symbol *proc_symbol =
		PROC_DESC_IS_DUMMY(proc_desc) ? 0 : PROC_SYMBOL(proc_desc);

	    if (proc_symbol) {
		val = find_pc_line (BLOCK_START
				    (SYMBOL_BLOCK_VALUE(proc_symbol)),
				    0);
		val.pc = val.end ? val.end : pc;
	    }
	    if (!proc_symbol || pc < val.pc) {
		mips_extra_func_info_t found_heuristic =
		    heuristic_proc_desc(PROC_LOW_ADDR(proc_desc),
					pc, next_frame);
		if (found_heuristic) proc_desc = found_heuristic;
	    }
	}
    }
  else
    {
      /* Is linked_proc_desc_table really necessary?  It only seems to be used
	 by procedure call dummys.  However, the procedures being called ought
	 to have their own proc_descs, and even if they don't,
	 heuristic_proc_desc knows how to create them! */

      register struct linked_proc_info *link;
      for (link = linked_proc_desc_table; link; link = link->next)
	  if (PROC_LOW_ADDR(&link->info) <= pc
	      && PROC_HIGH_ADDR(&link->info) > pc)
	      return &link->info;
      proc_desc =
	  heuristic_proc_desc(heuristic_proc_start(pc), pc, next_frame);
    }
  return proc_desc;
}

/* XXX this is not a cache (i.e., you don't invalidate it) */
mips_extra_func_info_t cached_proc_desc;

FRAME_ADDR
mips_frame_chain(frame)
    FRAME frame;
{
    mips_extra_func_info_t proc_desc;
    CORE_ADDR saved_pc = FRAME_SAVED_PC(frame);

#ifdef KERNELDEBUG
    if (kernel_debugging) {
	    if (!inside_kernstack(frame->frame))
		    return (0);
	    if (in_trap_handler(saved_pc)) {
		    /* XXX this works? */
		    cached_proc_desc = find_proc_desc(saved_pc, frame);
		    /*XXX need to lookup frame of parent */
		    return read_memory_integer(frame->frame + 4 * 32, 4);
	    }
    } else
#endif
	    if (saved_pc == 0 || inside_entry_file (saved_pc))
		    return 0;

    proc_desc = find_proc_desc(saved_pc, frame);
    if (!proc_desc)
      return 0;

    cached_proc_desc = proc_desc;
    return read_next_frame_reg(frame, PROC_FRAME_REG(proc_desc))
      + PROC_FRAME_OFFSET(proc_desc);
}

void
init_extra_frame_info(fci)
     struct frame_info *fci;
{
  extern struct obstack frame_cache_obstack;
  /* Use proc_desc calculated in frame_chain */
  mips_extra_func_info_t proc_desc = fci->next ? cached_proc_desc :
      find_proc_desc(fci->pc, fci->next);

  fci->saved_regs = (struct frame_saved_regs*)
    obstack_alloc (&frame_cache_obstack, sizeof(struct frame_saved_regs));
  bzero(fci->saved_regs, sizeof(struct frame_saved_regs));
  fci->proc_desc =
      proc_desc == &temp_proc_desc ? 0 : proc_desc;

#ifdef KERNELDEBUG
  if (kernel_debugging && in_trap_handler(fci->pc)) {
	  int i;
	  if (fci->next != 0)
		  fci->frame = READ_FRAME_REG(fci, SP_REGNUM);
	  else
		  fci->frame = read_register(SP_REGNUM);
	  for (i = 1; i <= 32; ++i)
		  fci->saved_regs->regs[i] = fci->frame + 4 * (3 + i);
	  return;
  }
#endif
  if (proc_desc)
    {
      int ireg;
      CORE_ADDR reg_position;
      unsigned long mask;
      /* r0 bit means kernel trap */
      int kernel_trap = PROC_REG_MASK(proc_desc) & 1;

      /* Fixup frame-pointer - only needed for top frame */
      /* This may not be quite right, if proc has a real frame register */
      if (fci->pc == PROC_LOW_ADDR(proc_desc))
	fci->frame = read_register (SP_REGNUM);
      else if (fci->next == 0)
	fci->frame = read_register (SP_REGNUM) + PROC_FRAME_OFFSET(proc_desc);
      else
	fci->frame = READ_FRAME_REG(fci, PROC_FRAME_REG(proc_desc))
	              + PROC_FRAME_OFFSET(proc_desc);
      if (proc_desc == &temp_proc_desc)
	  *fci->saved_regs = temp_saved_regs;
      else
      {
	  /* find which general-purpose registers were saved */
	  reg_position = fci->frame + PROC_REG_OFFSET(proc_desc);
	  mask = kernel_trap ? 0xFFFFFFFF : PROC_REG_MASK(proc_desc);
	  for (ireg= 31; mask; --ireg, mask <<= 1)
	      if (mask & 0x80000000)
	      {
		  fci->saved_regs->regs[ireg] = reg_position;
		  reg_position -= 4;
	      }
	  /* find which floating-point registers were saved */
	  reg_position = fci->frame + PROC_FREG_OFFSET(proc_desc);
	  /* The freg_offset points to where the first *double* register is saved.
	   * So skip to the high-order word. */
	  reg_position += 4;
	  mask = kernel_trap ? 0xFFFFFFFF : PROC_FREG_MASK(proc_desc);
	  for (ireg = 31; mask; --ireg, mask <<= 1)
	      if (mask & 0x80000000)
	      {
		  fci->saved_regs->regs[FP0_REGNUM+ireg] = reg_position;
		  reg_position -= 4;
	      }
      }

      /* hack: if argument regs are saved, guess these contain args */
      if ((PROC_REG_MASK(proc_desc) & 0xF0) == 0) fci->num_args = -1;
      else if ((PROC_REG_MASK(proc_desc) & 0x80) == 0) fci->num_args = 4;
      else if ((PROC_REG_MASK(proc_desc) & 0x40) == 0) fci->num_args = 3;
      else if ((PROC_REG_MASK(proc_desc) & 0x20) == 0) fci->num_args = 2;
      else if ((PROC_REG_MASK(proc_desc) & 0x10) == 0) fci->num_args = 1;

      fci->saved_regs->regs[PC_REGNUM] = fci->saved_regs->regs[RA_REGNUM];
    }
}

/* MIPS stack frames are almost impenetrable.  When execution stops,
   we basically have to look at symbol information for the function
   that we stopped in, which tells us *which* register (if any) is
   the base of the frame pointer, and what offset from that register
   the frame itself is at.  

   This presents a problem when trying to examine a stack in memory
   (that isn't executing at the moment), using the "frame" command.  We
   don't have a PC, nor do we have any registers except SP.

   This routine takes two arguments, SP and PC, and tries to make the
   cached frames look as if these two arguments defined a frame on the
   cache.  This allows the rest of info frame to extract the important
   arguments without difficulty.  */

FRAME
setup_arbitrary_frame (stack, pc)
     FRAME_ADDR stack;
     CORE_ADDR pc;
{
  return create_new_frame (stack, pc);
}


CORE_ADDR
mips_push_arguments(nargs, args, sp, struct_return, struct_addr)
  int nargs;
  value *args;
  CORE_ADDR sp;
  int struct_return;
  CORE_ADDR struct_addr;
{
  CORE_ADDR buf;
  register i;
  int accumulate_size = struct_return ? 4 : 0;
  struct mips_arg { char *contents; int len; int offset; };
  struct mips_arg *mips_args =
      (struct mips_arg*)alloca(nargs * sizeof(struct mips_arg));
  register struct mips_arg *m_arg;
  for (i = 0, m_arg = mips_args; i < nargs; i++, m_arg++) {
    extern value value_arg_coerce();
    value arg = value_arg_coerce (args[i]);
    m_arg->len = TYPE_LENGTH (VALUE_TYPE (arg));
    /* This entire mips-specific routine is because doubles must be aligned
     * on 8-byte boundaries. It still isn't quite right, because MIPS decided
     * to align 'struct {int a, b}' on 4-byte boundaries (even though this
     * breaks their varargs implementation...). A correct solution
     * requires an simulation of gcc's 'alignof' (and use of 'alignof'
     * in stdarg.h/varargs.h).
     */
    if (m_arg->len > 4) accumulate_size = (accumulate_size + 7) & -8;
    m_arg->offset = accumulate_size;
    accumulate_size = (accumulate_size + m_arg->len + 3) & -4;
    m_arg->contents = VALUE_CONTENTS(arg);
  }
  accumulate_size = (accumulate_size + 7) & (-8);
  if (accumulate_size < 16) accumulate_size = 16; 
  sp -= accumulate_size;
  for (i = nargs; m_arg--, --i >= 0; )
    write_memory(sp + m_arg->offset, m_arg->contents, m_arg->len);
  if (struct_return) {
    buf = struct_addr;
    write_memory(sp, (char *)&buf, sizeof(CORE_ADDR));
  }
  return sp;
}

/* MASK(i,j) == (1<<i) + (1<<(i+1)) + ... + (1<<j)). Assume i<=j<31. */
#define MASK(i,j) ((1 << (j)+1)-1 ^ (1 << (i))-1)

void
mips_push_dummy_frame()
{
  int ireg;
  struct linked_proc_info *link = (struct linked_proc_info*)
      xmalloc(sizeof(struct linked_proc_info));
  mips_extra_func_info_t proc_desc = &link->info;
  CORE_ADDR sp = read_register (SP_REGNUM);
  CORE_ADDR save_address;
  REGISTER_TYPE buffer;
  link->next = linked_proc_desc_table;
  linked_proc_desc_table = link;
#define PUSH_FP_REGNUM 16 /* must be a register preserved across calls */
#define GEN_REG_SAVE_MASK MASK(1,16)|MASK(24,28)|(1<<31)
#define GEN_REG_SAVE_COUNT 22
#define FLOAT_REG_SAVE_MASK MASK(0,19)
#define FLOAT_REG_SAVE_COUNT 20
#define SPECIAL_REG_SAVE_COUNT 4
  /*
   * The registers we must save are all those not preserved across
   * procedure calls. Dest_Reg (see tm-mips.h) must also be saved.
   * In addition, we must save the PC, and PUSH_FP_REGNUM.
   * (Ideally, we should also save MDLO/-HI and FP Control/Status reg.)
   *
   * Dummy frame layout:
   *  (high memory)
   * 	Saved PC
   *	Saved MMHI, MMLO, FPC_CSR
   *	Saved R31
   *	Saved R28
   *	...
   *	Saved R1
   *    Saved D18 (i.e. F19, F18)
   *    ...
   *    Saved D0 (i.e. F1, F0)
   *	CALL_DUMMY (subroutine stub; see tm-mips.h)
   *	Parameter build area (not yet implemented)
   *  (low memory)
   */
  PROC_REG_MASK(proc_desc) = GEN_REG_SAVE_MASK;
  PROC_FREG_MASK(proc_desc) = FLOAT_REG_SAVE_MASK;
  PROC_REG_OFFSET(proc_desc) = /* offset of (Saved R31) from FP */
      -sizeof(long) - 4 * SPECIAL_REG_SAVE_COUNT;
  PROC_FREG_OFFSET(proc_desc) = /* offset of (Saved D18) from FP */
      -sizeof(double) - 4 * (SPECIAL_REG_SAVE_COUNT + GEN_REG_SAVE_COUNT);
  /* save general registers */
  save_address = sp + PROC_REG_OFFSET(proc_desc);
  for (ireg = 32; --ireg >= 0; )
    if (PROC_REG_MASK(proc_desc) & (1 << ireg))
      {
	buffer = read_register (ireg);
	write_memory (save_address, (char *)&buffer, sizeof(REGISTER_TYPE));
	save_address -= 4;
      }
  /* save floating-points registers */
  save_address = sp + PROC_FREG_OFFSET(proc_desc);
  for (ireg = 32; --ireg >= 0; )
    if (PROC_FREG_MASK(proc_desc) & (1 << ireg))
      {
	buffer = read_register (ireg + FP0_REGNUM);