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/* DWARF 2 Expression Evaluator.

   Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009, 2010

   Free Software Foundation, Inc.

   Contributed by Daniel Berlin (dan@dberlin.org)

   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 3 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, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "symtab.h"

#include "gdbtypes.h"

#include "value.h"

#include "gdbcore.h"

#include "dwarf2.h"

#include "dwarf2expr.h"

#include "gdb_assert.h"

/* Local prototypes.  */

static void execute_stack_op (struct dwarf_expr_context *,

                              const gdb_byte *, const gdb_byte *);

/* Create a new context for the expression evaluator.  */

struct dwarf_expr_context *

new_dwarf_expr_context (void)

{

  struct dwarf_expr_context *retval;

  retval = xcalloc (1, sizeof (struct dwarf_expr_context));

  retval->stack_len = 0;

  retval->stack_allocated = 10;

  retval->stack = xmalloc (retval->stack_allocated

                           * sizeof (struct dwarf_stack_value));

  retval->num_pieces = 0;

  retval->pieces = 0;

  retval->max_recursion_depth = 0x100;

  return retval;

}

/* Release the memory allocated to CTX.  */

void

free_dwarf_expr_context (struct dwarf_expr_context *ctx)

{

  xfree (ctx->stack);

  xfree (ctx->pieces);

  xfree (ctx);

}

/* Helper for make_cleanup_free_dwarf_expr_context.  */

static void

free_dwarf_expr_context_cleanup (void *arg)

{

  free_dwarf_expr_context (arg);

}

/* Return a cleanup that calls free_dwarf_expr_context.  */

struct cleanup *

make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx)

{

  return make_cleanup (free_dwarf_expr_context_cleanup, ctx);

}

/* Expand the memory allocated to CTX's stack to contain at least

   NEED more elements than are currently used.  */

static void

dwarf_expr_grow_stack (struct dwarf_expr_context *ctx, size_t need)

{

  if (ctx->stack_len + need > ctx->stack_allocated)

    {

      size_t newlen = ctx->stack_len + need + 10;

      ctx->stack = xrealloc (ctx->stack,

                             newlen * sizeof (struct dwarf_stack_value));

      ctx->stack_allocated = newlen;

    }

}

/* Push VALUE onto CTX's stack.  */

void

dwarf_expr_push (struct dwarf_expr_context *ctx, ULONGEST value,

                 int in_stack_memory)

{

  struct dwarf_stack_value *v;

  /* We keep all stack elements within the range defined by the

     DWARF address size.  */

  if (ctx->addr_size < sizeof (ULONGEST))

    value &= ((ULONGEST) 1 << (ctx->addr_size * HOST_CHAR_BIT)) - 1;

  dwarf_expr_grow_stack (ctx, 1);

  v = &ctx->stack[ctx->stack_len++];

  v->value = value;

  v->in_stack_memory = in_stack_memory;

}

/* Pop the top item off of CTX's stack.  */

void

dwarf_expr_pop (struct dwarf_expr_context *ctx)

{

  if (ctx->stack_len <= 0)

    error (_("dwarf expression stack underflow"));

  ctx->stack_len--;

}

/* Retrieve the N'th item on CTX's stack.  */

ULONGEST

dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n)

{

  if (ctx->stack_len <= n)

     error (_("Asked for position %d of stack, stack only has %d elements on it."),

            n, ctx->stack_len);

  return ctx->stack[ctx->stack_len - (1 + n)].value;

}

/* Retrieve the N'th item on CTX's stack, converted to an address.  */

CORE_ADDR

dwarf_expr_fetch_address (struct dwarf_expr_context *ctx, int n)

{

  ULONGEST result = dwarf_expr_fetch (ctx, n);

  /* For most architectures, calling extract_unsigned_integer() alone

     is sufficient for extracting an address.  However, some

     architectures (e.g. MIPS) use signed addresses and using

     extract_unsigned_integer() will not produce a correct

     result.  Make sure we invoke gdbarch_integer_to_address()

     for those architectures which require it.  */

  if (gdbarch_integer_to_address_p (ctx->gdbarch))

    {

      enum bfd_endian byte_order = gdbarch_byte_order (ctx->gdbarch);

      gdb_byte *buf = alloca (ctx->addr_size);

      struct type *int_type;

      switch (ctx->addr_size)

        {

        case 2:

          int_type = builtin_type (ctx->gdbarch)->builtin_uint16;

          break;

        case 4:

          int_type = builtin_type (ctx->gdbarch)->builtin_uint32;

          break;

        case 8:

          int_type = builtin_type (ctx->gdbarch)->builtin_uint64;

          break;

        default:

          internal_error (__FILE__, __LINE__,

                          _("Unsupported address size.\n"));

        }

      store_unsigned_integer (buf, ctx->addr_size, byte_order, result);

      return gdbarch_integer_to_address (ctx->gdbarch, int_type, buf);

    }

  return (CORE_ADDR) result;

}

/* Retrieve the in_stack_memory flag of the N'th item on CTX's stack.  */

int

dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n)

{

  if (ctx->stack_len <= n)

     error (_("Asked for position %d of stack, stack only has %d elements on it."),

            n, ctx->stack_len);

  return ctx->stack[ctx->stack_len - (1 + n)].in_stack_memory;

}

/* Return true if the expression stack is empty.  */

static int

dwarf_expr_stack_empty_p (struct dwarf_expr_context *ctx)

{

  return ctx->stack_len == 0;

}

/* Add a new piece to CTX's piece list.  */

static void

add_piece (struct dwarf_expr_context *ctx, ULONGEST size, ULONGEST offset)

{

  struct dwarf_expr_piece *p;

  ctx->num_pieces++;

  ctx->pieces = xrealloc (ctx->pieces,

                          (ctx->num_pieces

                           * sizeof (struct dwarf_expr_piece)));

  p = &ctx->pieces[ctx->num_pieces - 1];

  p->location = ctx->location;

  p->size = size;

  p->offset = offset;

  if (p->location == DWARF_VALUE_LITERAL)

    {

      p->v.literal.data = ctx->data;

      p->v.literal.length = ctx->len;

    }

  else if (dwarf_expr_stack_empty_p (ctx))

    {

      p->location = DWARF_VALUE_OPTIMIZED_OUT;

      /* Also reset the context's location, for our callers.  This is

         a somewhat strange approach, but this lets us avoid setting

         the location to DWARF_VALUE_MEMORY in all the individual

         cases in the evaluator.  */

      ctx->location = DWARF_VALUE_OPTIMIZED_OUT;

    }

  else if (p->location == DWARF_VALUE_MEMORY)

    {

      p->v.mem.addr = dwarf_expr_fetch_address (ctx, 0);

      p->v.mem.in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, 0);

    }

  else

    {

      p->v.value = dwarf_expr_fetch (ctx, 0);

    }

}

/* Evaluate the expression at ADDR (LEN bytes long) using the context

   CTX.  */

void

dwarf_expr_eval (struct dwarf_expr_context *ctx, const gdb_byte *addr,

                 size_t len)

{

  int old_recursion_depth = ctx->recursion_depth;

  execute_stack_op (ctx, addr, addr + len);

  /* CTX RECURSION_DEPTH becomes invalid if an exception was thrown here.  */

  gdb_assert (ctx->recursion_depth == old_recursion_depth);

}

/* Decode the unsigned LEB128 constant at BUF into the variable pointed to

   by R, and return the new value of BUF.  Verify that it doesn't extend

   past BUF_END.  */

const gdb_byte *

read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end, ULONGEST * r)

{

  unsigned shift = 0;

  ULONGEST result = 0;

  gdb_byte byte;

  while (1)

    {

      if (buf >= buf_end)

        error (_("read_uleb128: Corrupted DWARF expression."));

      byte = *buf++;

      result |= (byte & 0x7f) << shift;

      if ((byte & 0x80) == 0)

        break;

      shift += 7;

    }

  *r = result;

  return buf;

}

/* Decode the signed LEB128 constant at BUF into the variable pointed to

   by R, and return the new value of BUF.  Verify that it doesn't extend

   past BUF_END.  */

const gdb_byte *

read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end, LONGEST * r)

{

  unsigned shift = 0;

  LONGEST result = 0;

  gdb_byte byte;

  while (1)

    {

      if (buf >= buf_end)

        error (_("read_sleb128: Corrupted DWARF expression."));

      byte = *buf++;

      result |= (byte & 0x7f) << shift;

      shift += 7;

      if ((byte & 0x80) == 0)

        break;

    }

  if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)

    result |= -(1 << shift);

  *r = result;

  return buf;

}

/* Check that the current operator is either at the end of an

   expression, or that it is followed by a composition operator.  */

void

dwarf_expr_require_composition (const gdb_byte *op_ptr, const gdb_byte *op_end,

                                const char *op_name)

{

  /* It seems like DW_OP_GNU_uninit should be handled here.  However,

     it doesn't seem to make sense for DW_OP_*_value, and it was not

     checked at the other place that this function is called.  */

  if (op_ptr != op_end && *op_ptr != DW_OP_piece && *op_ptr != DW_OP_bit_piece)

    error (_("DWARF-2 expression error: `%s' operations must be "

             "used either alone or in conjuction with DW_OP_piece "

             "or DW_OP_bit_piece."),

           op_name);

}

/* The engine for the expression evaluator.  Using the context in CTX,

   evaluate the expression between OP_PTR and OP_END.  */

static void

execute_stack_op (struct dwarf_expr_context *ctx,

                  const gdb_byte *op_ptr, const gdb_byte *op_end)

{

#define sign_ext(x) ((LONGEST) (((x) ^ sign_bit) - sign_bit))

  ULONGEST sign_bit = (ctx->addr_size >= sizeof (ULONGEST) ? 0

                       : ((ULONGEST) 1) << (ctx->addr_size * 8 - 1));

  enum bfd_endian byte_order = gdbarch_byte_order (ctx->gdbarch);

  ctx->location = DWARF_VALUE_MEMORY;

  ctx->initialized = 1;  /* Default is initialized.  */

  if (ctx->recursion_depth > ctx->max_recursion_depth)

    error (_("DWARF-2 expression error: Loop detected (%d)."),

           ctx->recursion_depth);

  ctx->recursion_depth++;

  while (op_ptr < op_end)

    {

      enum dwarf_location_atom op = *op_ptr++;

      ULONGEST result;

      /* Assume the value is not in stack memory.

         Code that knows otherwise sets this to 1.

         Some arithmetic on stack addresses can probably be assumed to still

         be a stack address, but we skip this complication for now.

         This is just an optimization, so it's always ok to punt

         and leave this as 0.  */

      int in_stack_memory = 0;

      ULONGEST uoffset, reg;

      LONGEST offset;

      switch (op)

        {

        case DW_OP_lit0:

        case DW_OP_lit1:

        case DW_OP_lit2:

        case DW_OP_lit3:

        case DW_OP_lit4:

        case DW_OP_lit5:

        case DW_OP_lit6:

        case DW_OP_lit7:

        case DW_OP_lit8:

        case DW_OP_lit9:

        case DW_OP_lit10:

        case DW_OP_lit11:

        case DW_OP_lit12:

        case DW_OP_lit13:

        case DW_OP_lit14:

        case DW_OP_lit15:

        case DW_OP_lit16:

        case DW_OP_lit17:

        case DW_OP_lit18:

        case DW_OP_lit19:

        case DW_OP_lit20:

        case DW_OP_lit21:

        case DW_OP_lit22:

        case DW_OP_lit23:

        case DW_OP_lit24:

        case DW_OP_lit25:

        case DW_OP_lit26:

        case DW_OP_lit27:

        case DW_OP_lit28:

        case DW_OP_lit29:

        case DW_OP_lit30:

        case DW_OP_lit31:

          result = op - DW_OP_lit0;

          break;

        case DW_OP_addr:

          result = extract_unsigned_integer (op_ptr,

                                             ctx->addr_size, byte_order);

          op_ptr += ctx->addr_size;

          /* Some versions of GCC emit DW_OP_addr before

             DW_OP_GNU_push_tls_address.  In this case the value is an

             index, not an address.  We don't support things like

             branching between the address and the TLS op.  */

          if (op_ptr >= op_end || *op_ptr != DW_OP_GNU_push_tls_address)

            result += ctx->offset;

          break;

        case DW_OP_const1u:

          result = extract_unsigned_integer (op_ptr, 1, byte_order);

          op_ptr += 1;

          break;

        case DW_OP_const1s:

          result = extract_signed_integer (op_ptr, 1, byte_order);

          op_ptr += 1;

          break;

        case DW_OP_const2u:

          result = extract_unsigned_integer (op_ptr, 2, byte_order);

          op_ptr += 2;

          break;

        case DW_OP_const2s:

          result = extract_signed_integer (op_ptr, 2, byte_order);

          op_ptr += 2;

          break;

        case DW_OP_const4u:

          result = extract_unsigned_integer (op_ptr, 4, byte_order);

          op_ptr += 4;

          break;

        case DW_OP_const4s:

          result = extract_signed_integer (op_ptr, 4, byte_order);

          op_ptr += 4;

          break;

        case DW_OP_const8u:

          result = extract_unsigned_integer (op_ptr, 8, byte_order);

          op_ptr += 8;

          break;

        case DW_OP_const8s:

          result = extract_signed_integer (op_ptr, 8, byte_order);

          op_ptr += 8;

          break;

        case DW_OP_constu:

          op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);

          result = uoffset;

          break;

        case DW_OP_consts:

          op_ptr = read_sleb128 (op_ptr, op_end, &offset);

          result = offset;

          break;

        /* The DW_OP_reg operations are required to occur alone in

           location expressions.  */

        case DW_OP_reg0:

        case DW_OP_reg1:

        case DW_OP_reg2:

        case DW_OP_reg3:

        case DW_OP_reg4:

        case DW_OP_reg5:

        case DW_OP_reg6:

        case DW_OP_reg7:

        case DW_OP_reg8:

        case DW_OP_reg9:

        case DW_OP_reg10:

        case DW_OP_reg11:

        case DW_OP_reg12:

        case DW_OP_reg13:

        case DW_OP_reg14:

        case DW_OP_reg15:

        case DW_OP_reg16:

        case DW_OP_reg17:

        case DW_OP_reg18:

        case DW_OP_reg19:

        case DW_OP_reg20:

        case DW_OP_reg21:

        case DW_OP_reg22:

        case DW_OP_reg23:

        case DW_OP_reg24:

        case DW_OP_reg25:

        case DW_OP_reg26:

        case DW_OP_reg27:

        case DW_OP_reg28:

        case DW_OP_reg29:

        case DW_OP_reg30:

        case DW_OP_reg31:

          if (op_ptr != op_end

              && *op_ptr != DW_OP_piece

              && *op_ptr != DW_OP_bit_piece

              && *op_ptr != DW_OP_GNU_uninit)

            error (_("DWARF-2 expression error: DW_OP_reg operations must be "

                     "used either alone or in conjuction with DW_OP_piece "

                     "or DW_OP_bit_piece."));

          result = op - DW_OP_reg0;

          ctx->location = DWARF_VALUE_REGISTER;

          break;

        case DW_OP_regx:

          op_ptr = read_uleb128 (op_ptr, op_end, &reg);

          dwarf_expr_require_composition (op_ptr, op_end, "DW_OP_regx");

          result = reg;

          ctx->location = DWARF_VALUE_REGISTER;

          break;

        case DW_OP_implicit_value:

          {

            ULONGEST len;

            op_ptr = read_uleb128 (op_ptr, op_end, &len);

            if (op_ptr + len > op_end)

              error (_("DW_OP_implicit_value: too few bytes available."));

            ctx->len = len;

            ctx->data = op_ptr;

            ctx->location = DWARF_VALUE_LITERAL;

            op_ptr += len;

            dwarf_expr_require_composition (op_ptr, op_end,

                                            "DW_OP_implicit_value");

          }

          goto no_push;

        case DW_OP_stack_value:

          ctx->location = DWARF_VALUE_STACK;

          dwarf_expr_require_composition (op_ptr, op_end, "DW_OP_stack_value");

          goto no_push;

        case DW_OP_breg0:

        case DW_OP_breg1:

        case DW_OP_breg2:

        case DW_OP_breg3:

        case DW_OP_breg4:

        case DW_OP_breg5:

        case DW_OP_breg6:

        case DW_OP_breg7:

        case DW_OP_breg8:

        case DW_OP_breg9:

        case DW_OP_breg10:

        case DW_OP_breg11:

        case DW_OP_breg12:

        case DW_OP_breg13:

        case DW_OP_breg14:

        case DW_OP_breg15:

        case DW_OP_breg16:

        case DW_OP_breg17:

        case DW_OP_breg18:

        case DW_OP_breg19:

        case DW_OP_breg20:

        case DW_OP_breg21:

        case DW_OP_breg22:

        case DW_OP_breg23:

        case DW_OP_breg24:

        case DW_OP_breg25:

        case DW_OP_breg26:

        case DW_OP_breg27:

        case DW_OP_breg28:

        case DW_OP_breg29:

        case DW_OP_breg30:

        case DW_OP_breg31:

          {

            op_ptr = read_sleb128 (op_ptr, op_end, &offset);

            result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);

            result += offset;

          }

          break;

        case DW_OP_bregx:

          {

            op_ptr = read_uleb128 (op_ptr, op_end, &reg);

            op_ptr = read_sleb128 (op_ptr, op_end, &offset);

            result = (ctx->read_reg) (ctx->baton, reg);

            result += offset;

          }

          break;

        case DW_OP_fbreg:

          {

            const gdb_byte *datastart;

            size_t datalen;

            unsigned int before_stack_len;

            op_ptr = read_sleb128 (op_ptr, op_end, &offset);

            /* Rather than create a whole new context, we simply

               record the stack length before execution, then reset it

               afterwards, effectively erasing whatever the recursive

               call put there.  */

            before_stack_len = ctx->stack_len;

            /* FIXME: cagney/2003-03-26: This code should be using

               get_frame_base_address(), and then implement a dwarf2

               specific this_base method.  */

            (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);

            dwarf_expr_eval (ctx, datastart, datalen);

            if (ctx->location == DWARF_VALUE_MEMORY)

              result = dwarf_expr_fetch_address (ctx, 0);

            else if (ctx->location == DWARF_VALUE_REGISTER)

              result = (ctx->read_reg) (ctx->baton, dwarf_expr_fetch (ctx, 0));

            else

              error (_("Not implemented: computing frame base using explicit value operator"));

            result = result + offset;

            in_stack_memory = 1;

            ctx->stack_len = before_stack_len;

            ctx->location = DWARF_VALUE_MEMORY;

          }

          break;

        case DW_OP_dup:

          result = dwarf_expr_fetch (ctx, 0);

          in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, 0);

          break;

        case DW_OP_drop:

          dwarf_expr_pop (ctx);

          goto no_push;

        case DW_OP_pick:

          offset = *op_ptr++;

          result = dwarf_expr_fetch (ctx, offset);

          in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, offset);

          break;

        case DW_OP_swap:

          {

            struct dwarf_stack_value t1, t2;

            if (ctx->stack_len < 2)

               error (_("Not enough elements for DW_OP_swap. Need 2, have %d."),

                      ctx->stack_len);

            t1 = ctx->stack[ctx->stack_len - 1];

            t2 = ctx->stack[ctx->stack_len - 2];

            ctx->stack[ctx->stack_len - 1] = t2;

            ctx->stack[ctx->stack_len - 2] = t1;

            goto no_push;

          }

        case DW_OP_over:

          result = dwarf_expr_fetch (ctx, 1);

          in_stack_memory = dwarf_expr_fetch_in_stack_memory (ctx, 1);

          break;

        case DW_OP_rot:

          {

            struct dwarf_stack_value t1, t2, t3;

            if (ctx->stack_len < 3)

               error (_("Not enough elements for DW_OP_rot. Need 3, have %d."),

                      ctx->stack_len);

            t1 = ctx->stack[ctx->stack_len - 1];

            t2 = ctx->stack[ctx->stack_len - 2];

            t3 = ctx->stack[ctx->stack_len - 3];

            ctx->stack[ctx->stack_len - 1] = t2;

            ctx->stack[ctx->stack_len - 2] = t3;

            ctx->stack[ctx->stack_len - 3] = t1;

            goto no_push;

          }

        case DW_OP_deref:

        case DW_OP_deref_size:

          {

            int addr_size = (op == DW_OP_deref ? ctx->addr_size : *op_ptr++);

            gdb_byte *buf = alloca (addr_size);

            CORE_ADDR addr = dwarf_expr_fetch_address (ctx, 0);

            dwarf_expr_pop (ctx);

            (ctx->read_mem) (ctx->baton, buf, addr, addr_size);

            result = extract_unsigned_integer (buf, addr_size, byte_order);

            break;

          }

        case DW_OP_abs:

        case DW_OP_neg:

        case DW_OP_not:

        case DW_OP_plus_uconst:

          /* Unary operations.  */

          result = dwarf_expr_fetch (ctx, 0);

          dwarf_expr_pop (ctx);

          switch (op)

            {

            case DW_OP_abs:

              if (sign_ext (result) < 0)

                result = -result;

              break;

            case DW_OP_neg:

              result = -result;

              break;

            case DW_OP_not:

              result = ~result;

              break;