Merge "Move files up to match upstream source structure."

1 files changed, 853 insertions, 0 deletions

diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
new file mode 100644
index 00000000..068f3853
--- /dev/null
+++ b/libdw/dwarf_getlocation.c
@@ -0,0 +1,853 @@
+/* Return location expression list.
+   Copyright (C) 2000-2010, 2013, 2014 Red Hat, Inc.
+   This file is part of elfutils.
+   Written by Ulrich Drepper <drepper@redhat.com>, 2000.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * 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
+
+   or both in parallel, as here.
+
+   elfutils 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 copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <dwarf.h>
+#include <search.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#include <libdwP.h>
+
+
+static bool
+attr_ok (Dwarf_Attribute *attr)
+{
+  if (attr == NULL)
+    return false;
+
+  /* Must be one of the attributes listed below.  */
+  switch (attr->code)
+    {
+    case DW_AT_location:
+    case DW_AT_data_member_location:
+    case DW_AT_vtable_elem_location:
+    case DW_AT_string_length:
+    case DW_AT_use_location:
+    case DW_AT_frame_base:
+    case DW_AT_return_addr:
+    case DW_AT_static_link:
+    case DW_AT_segment:
+    case DW_AT_GNU_call_site_value:
+    case DW_AT_GNU_call_site_data_value:
+    case DW_AT_GNU_call_site_target:
+    case DW_AT_GNU_call_site_target_clobbered:
+      break;
+
+    default:
+      __libdw_seterrno (DWARF_E_NO_LOCLIST);
+      return false;
+    }
+
+  return true;
+}
+
+
+struct loclist
+{
+  uint8_t atom;
+  Dwarf_Word number;
+  Dwarf_Word number2;
+  Dwarf_Word offset;
+  struct loclist *next;
+};
+
+
+static int
+loc_compare (const void *p1, const void *p2)
+{
+  const struct loc_s *l1 = (const struct loc_s *) p1;
+  const struct loc_s *l2 = (const struct loc_s *) p2;
+
+  if ((uintptr_t) l1->addr < (uintptr_t) l2->addr)
+    return -1;
+  if ((uintptr_t) l1->addr > (uintptr_t) l2->addr)
+    return 1;
+
+  return 0;
+}
+
+/* For each DW_OP_implicit_value, we store a special entry in the cache.
+   This points us directly to the block data for later fetching.  */
+static void
+store_implicit_value (Dwarf *dbg, void **cache, Dwarf_Op *op)
+{
+  struct loc_block_s *block = libdw_alloc (dbg, struct loc_block_s,
+					   sizeof (struct loc_block_s), 1);
+  const unsigned char *data = (const unsigned char *) (uintptr_t) op->number2;
+  // Ignored, equal to op->number.  And data length already checked.
+  (void) __libdw_get_uleb128 (&data, data + len_leb128 (Dwarf_Word));
+  block->addr = op;
+  block->data = (unsigned char *) data;
+  block->length = op->number;
+  (void) tsearch (block, cache, loc_compare);
+}
+
+int
+dwarf_getlocation_implicit_value (attr, op, return_block)
+     Dwarf_Attribute *attr;
+     const Dwarf_Op *op;
+     Dwarf_Block *return_block;
+{
+  if (attr == NULL)
+    return -1;
+
+  struct loc_block_s fake = { .addr = (void *) op };
+  struct loc_block_s **found = tfind (&fake, &attr->cu->locs, loc_compare);
+  if (unlikely (found == NULL))
+    {
+      __libdw_seterrno (DWARF_E_NO_BLOCK);
+      return -1;
+    }
+
+  return_block->length = (*found)->length;
+  return_block->data = (*found)->data;
+  return 0;
+}
+
+/* DW_AT_data_member_location can be a constant as well as a loclistptr.
+   Only data[48] indicate a loclistptr.  */
+static int
+check_constant_offset (Dwarf_Attribute *attr,
+		       Dwarf_Op **llbuf, size_t *listlen)
+{
+  if (attr->code != DW_AT_data_member_location)
+    return 1;
+
+  switch (attr->form)
+    {
+      /* Punt for any non-constant form.  */
+    default:
+      return 1;
+
+    case DW_FORM_data1:
+    case DW_FORM_data2:
+    case DW_FORM_data4:
+    case DW_FORM_data8:
+    case DW_FORM_sdata:
+    case DW_FORM_udata:
+      break;
+    }
+
+  /* Check whether we already cached this location.  */
+  struct loc_s fake = { .addr = attr->valp };
+  struct loc_s **found = tfind (&fake, &attr->cu->locs, loc_compare);
+
+  if (found == NULL)
+    {
+      Dwarf_Word offset;
+      if (INTUSE(dwarf_formudata) (attr, &offset) != 0)
+	return -1;
+
+      Dwarf_Op *result = libdw_alloc (attr->cu->dbg,
+				      Dwarf_Op, sizeof (Dwarf_Op), 1);
+
+      result->atom = DW_OP_plus_uconst;
+      result->number = offset;
+      result->number2 = 0;
+      result->offset = 0;
+
+      /* Insert a record in the search tree so we can find it again later.  */
+      struct loc_s *newp = libdw_alloc (attr->cu->dbg,
+					struct loc_s, sizeof (struct loc_s),
+					1);
+      newp->addr = attr->valp;
+      newp->loc = result;
+      newp->nloc = 1;
+
+      found = tsearch (newp, &attr->cu->locs, loc_compare);
+    }
+
+  assert ((*found)->nloc == 1);
+
+  if (llbuf != NULL)
+    {
+      *llbuf = (*found)->loc;
+      *listlen = 1;
+    }
+
+  return 0;
+}
+
+int
+internal_function
+__libdw_intern_expression (Dwarf *dbg, bool other_byte_order,
+			   unsigned int address_size, unsigned int ref_size,
+			   void **cache, const Dwarf_Block *block,
+			   bool cfap, bool valuep,
+			   Dwarf_Op **llbuf, size_t *listlen, int sec_index)
+{
+  /* Empty location expressions don't have any ops to intern.  */
+  if (block->length == 0)
+    {
+      *listlen = 0;
+      return 0;
+    }
+
+  /* Check whether we already looked at this list.  */
+  struct loc_s fake = { .addr = block->data };
+  struct loc_s **found = tfind (&fake, cache, loc_compare);
+  if (found != NULL)
+    {
+      /* We already saw it.  */
+      *llbuf = (*found)->loc;
+      *listlen = (*found)->nloc;
+
+      if (valuep)
+	{
+	  assert (*listlen > 1);
+	  assert ((*llbuf)[*listlen - 1].atom == DW_OP_stack_value);
+	}
+
+      return 0;
+    }
+
+  const unsigned char *data = block->data;
+  const unsigned char *const end_data = data + block->length;
+
+  const struct { bool other_byte_order; } bo = { other_byte_order };
+
+  struct loclist *loclist = NULL;
+  unsigned int n = 0;
+
+  if (cfap)
+    {
+      /* Synthesize the operation to push the CFA before the expression.  */
+      struct loclist *newloc;
+      newloc = (struct loclist *) alloca (sizeof (struct loclist));
+      newloc->atom = DW_OP_call_frame_cfa;
+      newloc->number = 0;
+      newloc->number2 = 0;
+      newloc->offset = -1;
+      newloc->next = loclist;
+      loclist = newloc;
+      ++n;
+    }
+
+  /* Decode the opcodes.  It is possible in some situations to have a
+     block of size zero.  */
+  while (data < end_data)
+    {
+      struct loclist *newloc;
+      newloc = (struct loclist *) alloca (sizeof (struct loclist));
+      newloc->number = 0;
+      newloc->number2 = 0;
+      newloc->offset = data - block->data;
+      newloc->next = loclist;
+      loclist = newloc;
+      ++n;
+
+      switch ((newloc->atom = *data++))
+	{
+	case DW_OP_addr:
+	  /* Address, depends on address size of CU.  */
+	  if (__libdw_read_address_inc (dbg, sec_index, &data,
+					address_size, &newloc->number))
+	    return -1;
+	  break;
+
+	case DW_OP_call_ref:
+	  /* DW_FORM_ref_addr, depends on offset size of CU.  */
+	  if (__libdw_read_offset_inc (dbg, sec_index, &data, ref_size,
+				       &newloc->number, IDX_debug_info, 0))
+	    return -1;
+	  break;
+
+	case DW_OP_deref:
+	case DW_OP_dup:
+	case DW_OP_drop:
+	case DW_OP_over:
+	case DW_OP_swap:
+	case DW_OP_rot:
+	case DW_OP_xderef:
+	case DW_OP_abs:
+	case DW_OP_and:
+	case DW_OP_div:
+	case DW_OP_minus:
+	case DW_OP_mod:
+	case DW_OP_mul:
+	case DW_OP_neg:
+	case DW_OP_not:
+	case DW_OP_or:
+	case DW_OP_plus:
+	case DW_OP_shl:
+	case DW_OP_shr:
+	case DW_OP_shra:
+	case DW_OP_xor:
+	case DW_OP_eq:
+	case DW_OP_ge:
+	case DW_OP_gt:
+	case DW_OP_le:
+	case DW_OP_lt:
+	case DW_OP_ne:
+	case DW_OP_lit0 ... DW_OP_lit31:
+	case DW_OP_reg0 ... DW_OP_reg31:
+	case DW_OP_nop:
+	case DW_OP_push_object_address:
+	case DW_OP_call_frame_cfa:
+	case DW_OP_form_tls_address:
+	case DW_OP_GNU_push_tls_address:
+	case DW_OP_stack_value:
+	  /* No operand.  */
+	  break;
+
+	case DW_OP_const1u:
+	case DW_OP_pick:
+	case DW_OP_deref_size:
+	case DW_OP_xderef_size:
+	  if (unlikely (data >= end_data))
+	    {
+	    invalid:
+	      __libdw_seterrno (DWARF_E_INVALID_DWARF);
+	      return -1;
+	    }
+
+	  newloc->number = *data++;
+	  break;
+
+	case DW_OP_const1s:
+	  if (unlikely (data >= end_data))
+	    goto invalid;
+
+	  newloc->number = *((int8_t *) data);
+	  ++data;
+	  break;
+
+	case DW_OP_const2u:
+	  if (unlikely (data + 2 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_2ubyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_const2s:
+	case DW_OP_skip:
+	case DW_OP_bra:
+	case DW_OP_call2:
+	  if (unlikely (data + 2 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_2sbyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_const4u:
+	  if (unlikely (data + 4 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_4ubyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_const4s:
+	case DW_OP_call4:
+	case DW_OP_GNU_parameter_ref:
+	  if (unlikely (data + 4 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_4sbyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_const8u:
+	  if (unlikely (data + 8 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_8ubyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_const8s:
+	  if (unlikely (data + 8 > end_data))
+	    goto invalid;
+
+	  newloc->number = read_8sbyte_unaligned_inc (&bo, data);
+	  break;
+
+	case DW_OP_constu:
+	case DW_OP_plus_uconst:
+	case DW_OP_regx:
+	case DW_OP_piece:
+	case DW_OP_GNU_convert:
+	case DW_OP_GNU_reinterpret:
+	  get_uleb128 (newloc->number, data, end_data);
+	  break;
+
+	case DW_OP_consts:
+	case DW_OP_breg0 ... DW_OP_breg31:
+	case DW_OP_fbreg:
+	  get_sleb128 (newloc->number, data, end_data);
+	  break;
+
+	case DW_OP_bregx:
+	  get_uleb128 (newloc->number, data, end_data);
+	  if (unlikely (data >= end_data))
+	    goto invalid;
+	  get_sleb128 (newloc->number2, data, end_data);
+	  break;
+
+	case DW_OP_bit_piece:
+	case DW_OP_GNU_regval_type:
+	  get_uleb128 (newloc->number, data, end_data);
+	  if (unlikely (data >= end_data))
+	    goto invalid;
+	  get_uleb128 (newloc->number2, data, end_data);
+	  break;
+
+	case DW_OP_implicit_value:
+	case DW_OP_GNU_entry_value:
+	  /* This cannot be used in a CFI expression.  */
+	  if (unlikely (dbg == NULL))
+	    goto invalid;
+
+	  /* start of block inc. len.  */
+	  newloc->number2 = (Dwarf_Word) (uintptr_t) data;
+	  get_uleb128 (newloc->number, data, end_data); /* Block length.  */
+	  if (unlikely ((Dwarf_Word) (end_data - data) < newloc->number))
+	    goto invalid;
+	  data += newloc->number;		/* Skip the block.  */
+	  break;
+
+	case DW_OP_GNU_implicit_pointer:
+	  /* DW_FORM_ref_addr, depends on offset size of CU.  */
+	  if (__libdw_read_offset_inc (dbg, sec_index, &data, ref_size,
+				       &newloc->number, IDX_debug_info, 0))
+	    return -1;
+	  if (unlikely (data >= end_data))
+	    goto invalid;
+	  get_uleb128 (newloc->number2, data, end_data); /* Byte offset.  */
+	  break;
+
+	case DW_OP_GNU_deref_type:
+	  if (unlikely (data + 1 >= end_data))
+	    goto invalid;
+	  newloc->number = *data++;
+	  get_uleb128 (newloc->number2, data, end_data);
+	  break;
+
+	case DW_OP_GNU_const_type:
+	  {
+	    size_t size;
+	    get_uleb128 (newloc->number, data, end_data);
+	    if (unlikely (data >= end_data))
+	      goto invalid;
+
+	    /* start of block inc. len.  */
+	    newloc->number2 = (Dwarf_Word) (uintptr_t) data;
+	    size = *data++;
+	    if (unlikely ((Dwarf_Word) (end_data - data) < size))
+	      goto invalid;
+	    data += size;		/* Skip the block.  */
+	  }
+	  break;
+
+	default:
+	  goto invalid;
+	}
+    }
+
+  if (unlikely (n == 0))
+    {
+      /* This is not allowed.
+	 It would mean an empty location expression, which we handled
+	 already as a special case above.  */
+      goto invalid;
+    }
+
+  if (valuep)
+    {
+      struct loclist *newloc;
+      newloc = (struct loclist *) alloca (sizeof (struct loclist));
+      newloc->atom = DW_OP_stack_value;
+      newloc->number = 0;
+      newloc->number2 = 0;
+      newloc->offset = data - block->data;
+      newloc->next = loclist;
+      loclist = newloc;
+      ++n;
+    }
+
+  /* Allocate the array.  */
+  Dwarf_Op *result;
+  if (dbg != NULL)
+    result = libdw_alloc (dbg, Dwarf_Op, sizeof (Dwarf_Op), n);
+  else
+    {
+      result = malloc (sizeof *result * n);
+      if (result == NULL)
+	{
+	nomem:
+	  __libdw_seterrno (DWARF_E_NOMEM);
+	  return -1;
+	}
+    }
+
+  /* Store the result.  */
+  *llbuf = result;
+  *listlen = n;
+
+  do
+    {
+      /* We populate the array from the back since the list is backwards.  */
+      --n;
+      result[n].atom = loclist->atom;
+      result[n].number = loclist->number;
+      result[n].number2 = loclist->number2;
+      result[n].offset = loclist->offset;
+
+      if (result[n].atom == DW_OP_implicit_value)
+	store_implicit_value (dbg, cache, &result[n]);
+
+      loclist = loclist->next;
+    }
+  while (n > 0);
+
+  /* Insert a record in the search tree so that we can find it again later.  */
+  struct loc_s *newp;
+  if (dbg != NULL)
+    newp = libdw_alloc (dbg, struct loc_s, sizeof (struct loc_s), 1);
+  else
+    {
+      newp = malloc (sizeof *newp);
+      if (newp == NULL)
+	{
+	  free (result);
+	  goto nomem;
+	}
+    }
+
+  newp->addr = block->data;
+  newp->loc = result;
+  newp->nloc = *listlen;
+  (void) tsearch (newp, cache, loc_compare);
+
+  /* We did it.  */
+  return 0;
+}
+
+static int
+getlocation (struct Dwarf_CU *cu, const Dwarf_Block *block,
+	     Dwarf_Op **llbuf, size_t *listlen, int sec_index)
+{
+  /* Empty location expressions don't have any ops to intern.
+     Note that synthetic empty_cu doesn't have an associated DWARF dbg.  */
+  if (block->length == 0)
+    {
+      *listlen = 0;
+      return 0;
+    }
+
+  return __libdw_intern_expression (cu->dbg, cu->dbg->other_byte_order,
+				    cu->address_size, (cu->version == 2
+						       ? cu->address_size
+						       : cu->offset_size),
+				    &cu->locs, block,
+				    false, false,
+				    llbuf, listlen, sec_index);
+}
+
+int
+dwarf_getlocation (attr, llbuf, listlen)
+     Dwarf_Attribute *attr;
+     Dwarf_Op **llbuf;
+     size_t *listlen;
+{
+  if (! attr_ok (attr))
+    return -1;
+
+  int result = check_constant_offset (attr, llbuf, listlen);
+  if (result != 1)
+    return result;
+
+  /* If it has a block form, it's a single location expression.  */
+  Dwarf_Block block;
+  if (INTUSE(dwarf_formblock) (attr, &block) != 0)
+    return -1;
+
+  return getlocation (attr->cu, &block, llbuf, listlen, cu_sec_idx (attr->cu));
+}
+
+static int
+attr_base_address (attr, basep)
+     Dwarf_Attribute *attr;
+     Dwarf_Addr *basep;
+{
+  /* Fetch the CU's base address.  */
+  Dwarf_Die cudie = CUDIE (attr->cu);
+
+  /* Find the base address of the compilation unit.  It will
+     normally be specified by DW_AT_low_pc.  In DWARF-3 draft 4,
+     the base address could be overridden by DW_AT_entry_pc.  It's
+     been removed, but GCC emits DW_AT_entry_pc and not DW_AT_lowpc
+     for compilation units with discontinuous ranges.  */
+  Dwarf_Attribute attr_mem;
+  if (unlikely (INTUSE(dwarf_lowpc) (&cudie, basep) != 0)
+      && INTUSE(dwarf_formaddr) (INTUSE(dwarf_attr) (&cudie,
+						     DW_AT_entry_pc,
+						     &attr_mem),
+				 basep) != 0)
+    {
+      if (INTUSE(dwarf_errno) () != 0)
+	return -1;
+
+      /* The compiler provided no base address when it should
+	 have.  Buggy GCC does this when it used absolute
+	 addresses in the location list and no DW_AT_ranges.  */
+      *basep = 0;
+    }
+  return 0;
+}
+
+static int
+initial_offset_base (attr, offset, basep)
+     Dwarf_Attribute *attr;
+     ptrdiff_t *offset;
+     Dwarf_Addr *basep;
+{
+  if (attr_base_address (attr, basep) != 0)
+    return -1;
+
+  Dwarf_Word start_offset;
+  if (__libdw_formptr (attr, IDX_debug_loc,
+		       DWARF_E_NO_LOCLIST,
+		       NULL, &start_offset) == NULL)
+    return -1;
+
+  *offset = start_offset;
+  return 0;
+}
+
+static ptrdiff_t
+getlocations_addr (attr, offset, basep, startp, endp, address,
+		   locs, expr, exprlen)
+     Dwarf_Attribute *attr;
+     ptrdiff_t offset;
+     Dwarf_Addr *basep;
+     Dwarf_Addr *startp;
+     Dwarf_Addr *endp;
+     Dwarf_Addr address;
+     Elf_Data *locs;
+     Dwarf_Op **expr;
+     size_t *exprlen;
+{
+  unsigned char *readp = locs->d_buf + offset;
+  unsigned char *readendp = locs->d_buf + locs->d_size;
+
+ next:
+  if (readendp - readp < attr->cu->address_size * 2)
+    {
+    invalid:
+      __libdw_seterrno (DWARF_E_INVALID_DWARF);
+      return -1;
+    }
+
+  Dwarf_Addr begin;
+  Dwarf_Addr end;
+
+  switch (__libdw_read_begin_end_pair_inc (attr->cu->dbg, IDX_debug_loc,
+					   &readp, attr->cu->address_size,
+					   &begin, &end, basep))
+    {
+    case 0: /* got location range. */
+      break;
+    case 1: /* base address setup. */
+      goto next;
+    case 2: /* end of loclist */
+      return 0;
+    default: /* error */
+      return -1;
+    }
+
+  if (readendp - readp < 2)
+    goto invalid;
+
+  /* We have a location expression.  */
+  Dwarf_Block block;
+  block.length = read_2ubyte_unaligned_inc (attr->cu->dbg, readp);
+  block.data = readp;
+  if (readendp - readp < (ptrdiff_t) block.length)
+    goto invalid;
+  readp += block.length;
+
+  *startp = *basep + begin;
+  *endp = *basep + end;
+
+  /* If address is minus one we want them all, otherwise only matching.  */
+  if (address != (Dwarf_Word) -1 && (address < *startp || address >= *endp))
+    goto next;
+
+  if (getlocation (attr->cu, &block, expr, exprlen, IDX_debug_loc) != 0)
+    return -1;
+
+  return readp - (unsigned char *) locs->d_buf;
+}
+
+int
+dwarf_getlocation_addr (attr, address, llbufs, listlens, maxlocs)
+     Dwarf_Attribute *attr;
+     Dwarf_Addr address;
+     Dwarf_Op **llbufs;
+     size_t *listlens;
+     size_t maxlocs;
+{
+  if (! attr_ok (attr))
+    return -1;
+
+  if (llbufs == NULL)
+    maxlocs = SIZE_MAX;
+
+  /* If it has a block form, it's a single location expression.  */
+  Dwarf_Block block;
+  if (INTUSE(dwarf_formblock) (attr, &block) == 0)
+    {
+      if (maxlocs == 0)
+	return 0;
+      if (llbufs != NULL &&
+	  getlocation (attr->cu, &block, &llbufs[0], &listlens[0],
+		       cu_sec_idx (attr->cu)) != 0)
+	return -1;
+      return listlens[0] == 0 ? 0 : 1;
+    }
+
+  int error = INTUSE(dwarf_errno) ();
+  if (unlikely (error != DWARF_E_NO_BLOCK))
+    {
+      __libdw_seterrno (error);
+      return -1;
+    }
+
+  int result = check_constant_offset (attr, &llbufs[0], &listlens[0]);
+  if (result != 1)
+    return result ?: 1;
+
+  Dwarf_Addr base, start, end;
+  Dwarf_Op *expr;
+  size_t expr_len;
+  ptrdiff_t off = 0;
+  size_t got = 0;
+
+  /* This is a true loclistptr, fetch the initial base address and offset.  */
+  if (initial_offset_base (attr, &off, &base) != 0)
+    return -1;
+
+  const Elf_Data *d = attr->cu->dbg->sectiondata[IDX_debug_loc];
+  if (d == NULL)
+    {
+      __libdw_seterrno (DWARF_E_NO_LOCLIST);
+      return -1;
+    }
+
+  while (got < maxlocs
+         && (off = getlocations_addr (attr, off, &base, &start, &end,
+				   address, d, &expr, &expr_len)) > 0)
+    {
+      /* This one matches the address.  */
+      if (llbufs != NULL)
+	{
+	  llbufs[got] = expr;
+	  listlens[got] = expr_len;
+	}
+      ++got;
+    }
+
+  /* We might stop early, so off can be zero or positive on success.  */
+  if (off < 0)
+    return -1;
+
+  return got;
+}
+
+ptrdiff_t
+dwarf_getlocations (attr, offset, basep, startp, endp, expr, exprlen)
+     Dwarf_Attribute *attr;
+     ptrdiff_t offset;
+     Dwarf_Addr *basep;
+     Dwarf_Addr *startp;
+     Dwarf_Addr *endp;
+     Dwarf_Op **expr;
+     size_t *exprlen;
+{
+  if (! attr_ok (attr))
+    return -1;
+
+  /* 1 is an invalid offset, meaning no more locations. */
+  if (offset == 1)
+    return 0;
+
+  if (offset == 0)
+    {
+      /* If it has a block form, it's a single location expression.  */
+      Dwarf_Block block;
+      if (INTUSE(dwarf_formblock) (attr, &block) == 0)
+	{
+	  if (getlocation (attr->cu, &block, expr, exprlen,
+			   cu_sec_idx (attr->cu)) != 0)
+	    return -1;
+
+	  /* This is the one and only location covering everything. */
+	  *startp = 0;
+	  *endp = -1;
+	  return 1;
+	}
+
+      int error = INTUSE(dwarf_errno) ();
+      if (unlikely (error != DWARF_E_NO_BLOCK))
+	{
+	  __libdw_seterrno (error);
+	  return -1;
+	}
+
+      int result = check_constant_offset (attr, expr, exprlen);
+      if (result != 1)
+	{
+	  if (result == 0)
+	    {
+	      /* This is the one and only location covering everything. */
+	      *startp = 0;
+	      *endp = -1;
+	      return 1;
+	    }
+	  return result;
+	}
+
+      /* We must be looking at a true loclistptr, fetch the initial
+	 base address and offset.  */
+      if (initial_offset_base (attr, &offset, basep) != 0)
+	return -1;
+    }
+
+  const Elf_Data *d = attr->cu->dbg->sectiondata[IDX_debug_loc];
+  if (d == NULL)
+    {
+      __libdw_seterrno (DWARF_E_NO_LOCLIST);
+      return -1;
+    }
+
+  return getlocations_addr (attr, offset, basep, startp, endp,
+			    (Dwarf_Word) -1, d, expr, exprlen);
+}