6885 CTF Everywhere Part 1

6886 Want ctfdiff
6887 ctfdump should be written in terms of libctf
6888 ctfmerge should be implemented in terms of libctf
6889 ctfconvert should be implemented in terms of libctf
6890 Want general workq
6891 Want general mergeq
6892 ctf_add_encoded assigns() incorrect byte size to types
6893 ctf_add_{struct,union,enum} can reuse forwards
6894 ctf_add_{struct,union,enum} occasionally forget to dirty the ctf_file_t
6895 ctf_add_member could better handle bitfields
6896 ctf_type_size() reports wrong size for forwards
6897 Want libctf ctf_kind_name() function
6898 Want libctf function to set struct/union size
Portions contributed by: John Levon <john.levon@joyent.com>
Portions contributed by: Richard Lowe <richlowe@richlowe.net>
Reviewed by: John Levon <john.levon@joyent.com>
Reviewed by: Andy Fiddaman <andy@omniosce.org>
Reviewed by: Gergő Doma <domag02@gmail.com>
Approved by: Dan McDonald <danmcd@joyent.com>

1 files changed, 789 insertions, 0 deletions

diff --git a/usr/src/lib/libdwarf/common/dwarf_query.c b/usr/src/lib/libdwarf/common/dwarf_query.c
new file mode 100644
index 0000000000..3f21abd039
--- /dev/null
+++ b/usr/src/lib/libdwarf/common/dwarf_query.c
@@ -0,0 +1,789 @@
+/*
+
+  Copyright (C) 2000,2002,2004 Silicon Graphics, Inc.  All Rights Reserved.
+  Portions Copyright (C) 2007-2010 David Anderson. All Rights Reserved.
+
+  This program is free software; you can redistribute it and/or modify it
+  under the terms of version 2.1 of the GNU Lesser General Public License 
+  as published by the Free Software Foundation.
+
+  This program is distributed in the hope that it would be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
+
+  Further, this software is distributed without any warranty that it is
+  free of the rightful claim of any third person regarding infringement 
+  or the like.  Any license provided herein, whether implied or 
+  otherwise, applies only to this software file.  Patent licenses, if
+  any, provided herein do not apply to combinations of this program with 
+  other software, or any other product whatsoever.  
+
+  You should have received a copy of the GNU Lesser General Public 
+  License along with this program; if not, write the Free Software 
+  Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston MA 02110-1301,
+  USA.
+
+  Contact information:  Silicon Graphics, Inc., 1500 Crittenden Lane,
+  Mountain View, CA 94043, or:
+
+  http://www.sgi.com
+
+  For further information regarding this notice, see:
+
+  http://oss.sgi.com/projects/GenInfo/NoticeExplan
+
+*/
+/* The address of the Free Software Foundation is
+   Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, 
+   Boston, MA 02110-1301, USA.
+   SGI has moved from the Crittenden Lane address.
+*/
+
+
+
+
+#include "config.h"
+#include "dwarf_incl.h"
+#include <stdio.h>
+#include "dwarf_die_deliv.h"
+
+/* This is normally reliable.
+But not always.
+If different compilation
+units have different address sizes 
+this may not give the correct value in all contexts. 
+If the Elf offset size != address_size 
+(for example if address_size = 4 but recorded in elf64 object)
+this may not give the correct value in all contexts. 
+*/
+int
+dwarf_get_address_size(Dwarf_Debug dbg,
+    Dwarf_Half * ret_addr_size, Dwarf_Error * error)
+{
+    Dwarf_Half address_size = 0;
+
+    if (dbg == 0) {
+        _dwarf_error(NULL, error, DW_DLE_DBG_NULL);
+        return (DW_DLV_ERROR);
+    }
+    address_size = dbg->de_pointer_size;
+    *ret_addr_size = address_size;
+    return DW_DLV_OK;
+}
+
+/* This will be correct in all contexts where the
+   CU context of a DIE is known.
+*/
+int
+dwarf_get_die_address_size(Dwarf_Die die,
+    Dwarf_Half * ret_addr_size, Dwarf_Error * error)
+{
+    Dwarf_Half address_size = 0;
+    CHECK_DIE(die, DW_DLV_ERROR);
+    address_size = die->di_cu_context->cc_address_size;
+    *ret_addr_size = address_size;
+    return DW_DLV_OK;
+}
+
+int
+dwarf_dieoffset(Dwarf_Die die,
+    Dwarf_Off * ret_offset, Dwarf_Error * error)
+{
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    *ret_offset = (die->di_debug_info_ptr -
+        die->di_cu_context->cc_dbg->de_debug_info.dss_data);
+    return DW_DLV_OK;
+}
+
+
+/*
+    This function returns the offset of
+    the die relative to the start of its
+    compilation-unit rather than .debug_info.
+    Returns DW_DLV_ERROR on error.
+*/
+int
+dwarf_die_CU_offset(Dwarf_Die die,
+    Dwarf_Off * cu_off, Dwarf_Error * error)
+{
+    Dwarf_CU_Context cu_context = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+    cu_context = die->di_cu_context;
+
+    *cu_off =
+        (die->di_debug_info_ptr - cu_context->cc_dbg->de_debug_info.dss_data -
+         cu_context->cc_debug_info_offset);
+    return DW_DLV_OK;
+}
+
+/*
+    This function returns the global offset 
+    (meaning the section offset) and length of
+    the CU that this die is a part of.
+    Used for correctness checking by dwarfdump.
+*/
+int
+dwarf_die_CU_offset_range(Dwarf_Die die,
+     Dwarf_Off * cu_off, 
+     Dwarf_Off * cu_length,
+     Dwarf_Error * error)
+{
+    Dwarf_CU_Context cu_context = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+    cu_context = die->di_cu_context;
+
+    *cu_off = cu_context->cc_debug_info_offset;
+    *cu_length = cu_context->cc_length + cu_context->cc_length_size
+            + cu_context->cc_extension_size;
+    return DW_DLV_OK;
+}
+
+
+
+int
+dwarf_tag(Dwarf_Die die, Dwarf_Half * tag, Dwarf_Error * error)
+{
+    CHECK_DIE(die, DW_DLV_ERROR);
+    *tag = (die->di_abbrev_list->ab_tag);
+    return DW_DLV_OK;
+}
+
+
+int
+dwarf_attrlist(Dwarf_Die die,
+    Dwarf_Attribute ** attrbuf,
+    Dwarf_Signed * attrcnt, Dwarf_Error * error)
+{
+    Dwarf_Word attr_count = 0;
+    Dwarf_Word i = 0;
+    Dwarf_Half attr = 0;
+    Dwarf_Half attr_form = 0;
+    Dwarf_Byte_Ptr abbrev_ptr = 0;
+    Dwarf_Abbrev_List abbrev_list = 0;
+    Dwarf_Attribute new_attr = 0;
+    Dwarf_Attribute head_attr = NULL;
+    Dwarf_Attribute curr_attr = NULL;
+    Dwarf_Attribute *attr_ptr = 0;
+    Dwarf_Debug dbg = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+    dbg = die->di_cu_context->cc_dbg;
+
+    abbrev_list = _dwarf_get_abbrev_for_code(die->di_cu_context,
+                                             die->di_abbrev_list->
+                                             ab_code);
+    if (abbrev_list == NULL) {
+        _dwarf_error(dbg, error, DW_DLE_DIE_ABBREV_BAD);
+        return (DW_DLV_ERROR);
+    }
+    abbrev_ptr = abbrev_list->ab_abbrev_ptr;
+
+    info_ptr = die->di_debug_info_ptr;
+    SKIP_LEB128_WORD(info_ptr);
+
+    do {
+        Dwarf_Unsigned utmp2;
+
+        DECODE_LEB128_UWORD(abbrev_ptr, utmp2);
+        attr = (Dwarf_Half) utmp2;
+        DECODE_LEB128_UWORD(abbrev_ptr, utmp2);
+        attr_form = (Dwarf_Half) utmp2;
+
+        if (attr != 0) {
+            new_attr =
+                (Dwarf_Attribute) _dwarf_get_alloc(dbg, DW_DLA_ATTR, 1);
+            if (new_attr == NULL) {
+                _dwarf_error(dbg, error, DW_DLE_ALLOC_FAIL);
+                return (DW_DLV_ERROR);
+            }
+
+            new_attr->ar_attribute = attr;
+            new_attr->ar_attribute_form_direct = attr_form;
+            new_attr->ar_attribute_form = attr_form;
+            if (attr_form == DW_FORM_indirect) {
+                Dwarf_Unsigned utmp6;
+
+                /* DECODE_LEB128_UWORD does info_ptr update */
+                DECODE_LEB128_UWORD(info_ptr, utmp6);
+                attr_form = (Dwarf_Half) utmp6;
+                new_attr->ar_attribute_form = attr_form;
+            }
+            new_attr->ar_cu_context = die->di_cu_context;
+            new_attr->ar_debug_info_ptr = info_ptr;
+
+            {
+                Dwarf_Unsigned sov = _dwarf_get_size_of_val(dbg, 
+                    attr_form, 
+                    die->di_cu_context->cc_address_size,
+                    info_ptr,
+                    die->di_cu_context->cc_length_size);
+                info_ptr += sov;
+            }
+ 
+
+            if (head_attr == NULL)
+                head_attr = curr_attr = new_attr;
+            else {
+                curr_attr->ar_next = new_attr;
+                curr_attr = new_attr;
+            }
+            attr_count++;
+        }
+    } while (attr != 0 || attr_form != 0);
+
+    if (attr_count == 0) {
+        *attrbuf = NULL;
+        *attrcnt = 0;
+        return (DW_DLV_NO_ENTRY);
+    }
+
+    attr_ptr = (Dwarf_Attribute *)
+        _dwarf_get_alloc(dbg, DW_DLA_LIST, attr_count);
+    if (attr_ptr == NULL) {
+        _dwarf_error(dbg, error, DW_DLE_ALLOC_FAIL);
+        return (DW_DLV_ERROR);
+    }
+
+    curr_attr = head_attr;
+    for (i = 0; i < attr_count; i++) {
+        *(attr_ptr + i) = curr_attr;
+        curr_attr = curr_attr->ar_next;
+    }
+
+    *attrbuf = attr_ptr;
+    *attrcnt = attr_count;
+    return (DW_DLV_OK);
+}
+
+
+/*
+    This function takes a die, and an attr, and returns
+    a pointer to the start of the value of that attr in
+    the given die in the .debug_info section.  The form
+    is returned in *attr_form.
+
+    Returns NULL on error, or if attr is not found.
+    However, *attr_form is 0 on error, and positive 
+    otherwise.
+*/
+static Dwarf_Byte_Ptr
+_dwarf_get_value_ptr(Dwarf_Die die,
+    Dwarf_Half attr, Dwarf_Half * attr_form)
+{
+    Dwarf_Byte_Ptr abbrev_ptr = 0;
+    Dwarf_Abbrev_List abbrev_list;
+    Dwarf_Half curr_attr = 0;
+    Dwarf_Half curr_attr_form = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+
+    abbrev_list = _dwarf_get_abbrev_for_code(die->di_cu_context,
+        die->di_abbrev_list->ab_code);
+    if (abbrev_list == NULL) {
+        *attr_form = 0;
+        return (NULL);
+    }
+    abbrev_ptr = abbrev_list->ab_abbrev_ptr;
+
+    info_ptr = die->di_debug_info_ptr;
+    SKIP_LEB128_WORD(info_ptr);
+
+    do {
+        Dwarf_Unsigned utmp3;
+
+        DECODE_LEB128_UWORD(abbrev_ptr, utmp3);
+        curr_attr = (Dwarf_Half) utmp3;
+        DECODE_LEB128_UWORD(abbrev_ptr, utmp3);
+        curr_attr_form = (Dwarf_Half) utmp3;
+        if (curr_attr_form == DW_FORM_indirect) {
+            Dwarf_Unsigned utmp6;
+
+            /* DECODE_LEB128_UWORD updates info_ptr */
+            DECODE_LEB128_UWORD(info_ptr, utmp6);
+            curr_attr_form = (Dwarf_Half) utmp6;
+        }
+
+        if (curr_attr == attr) {
+            *attr_form = curr_attr_form;
+            return (info_ptr);
+        }
+
+        info_ptr += _dwarf_get_size_of_val(die->di_cu_context->cc_dbg,
+                         curr_attr_form, 
+                         die->di_cu_context->cc_address_size,
+                         info_ptr, 
+                         die->di_cu_context->cc_length_size);
+    } while (curr_attr != 0 || curr_attr_form != 0);
+
+    *attr_form = 1;
+    return (NULL);
+}
+
+
+int
+dwarf_diename(Dwarf_Die die, char **ret_name, Dwarf_Error * error)
+{
+    Dwarf_Half attr_form = 0;
+    Dwarf_Debug dbg = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+    Dwarf_Unsigned string_offset = 0;
+    int res = DW_DLV_ERROR;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    info_ptr = _dwarf_get_value_ptr(die, DW_AT_name, &attr_form);
+    if (info_ptr == NULL) {
+        if (attr_form == 0) {
+            _dwarf_error(die->di_cu_context->cc_dbg, error,
+                         DW_DLE_DIE_BAD);
+            return (DW_DLV_ERROR);
+        }
+        return DW_DLV_NO_ENTRY;
+    }
+
+    if (attr_form == DW_FORM_string) {
+        *ret_name = (char *) (info_ptr);
+        return DW_DLV_OK;
+    }
+
+    dbg = die->di_cu_context->cc_dbg;
+    if (attr_form != DW_FORM_strp) {
+        _dwarf_error(dbg, error, DW_DLE_ATTR_FORM_BAD);
+        return (DW_DLV_ERROR);
+    }
+
+    READ_UNALIGNED(dbg, string_offset, Dwarf_Unsigned,
+        info_ptr, die->di_cu_context->cc_length_size);
+
+    if (string_offset >= dbg->de_debug_str.dss_size) {
+        _dwarf_error(dbg, error, DW_DLE_STRING_OFFSET_BAD);
+        return (DW_DLV_ERROR);
+    }
+
+    res = _dwarf_load_section(dbg, &dbg->de_debug_str,error);
+    if (res != DW_DLV_OK) {
+        return res;
+    }
+
+    *ret_name = (char *) (dbg->de_debug_str.dss_data + string_offset);
+    return DW_DLV_OK;
+}
+
+
+int
+dwarf_hasattr(Dwarf_Die die,
+    Dwarf_Half attr,
+    Dwarf_Bool * return_bool, Dwarf_Error * error)
+{
+    Dwarf_Half attr_form = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    if (_dwarf_get_value_ptr(die, attr, &attr_form) == NULL) {
+        if (attr_form == 0) {
+            _dwarf_error(die->di_cu_context->cc_dbg, error,
+                DW_DLE_DIE_BAD);
+            return (DW_DLV_ERROR);
+        }
+        *return_bool = false;
+        return DW_DLV_OK;
+    }
+
+    *return_bool = (true);
+    return DW_DLV_OK;
+}
+
+
+int
+dwarf_attr(Dwarf_Die die,
+    Dwarf_Half attr,
+    Dwarf_Attribute * ret_attr, Dwarf_Error * error)
+{
+    Dwarf_Half attr_form = 0;
+    Dwarf_Attribute attrib = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+    Dwarf_Debug dbg = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+    dbg = die->di_cu_context->cc_dbg;
+
+    info_ptr = _dwarf_get_value_ptr(die, attr, &attr_form);
+    if (info_ptr == NULL) {
+        if (attr_form == 0) {
+            _dwarf_error(dbg, error, DW_DLE_DIE_BAD);
+            return (DW_DLV_ERROR);
+        }
+        return DW_DLV_NO_ENTRY;
+    }
+
+    attrib = (Dwarf_Attribute) _dwarf_get_alloc(dbg, DW_DLA_ATTR, 1);
+    if (attrib == NULL) {
+        _dwarf_error(dbg, error, DW_DLE_ALLOC_FAIL);
+        return (DW_DLV_ERROR);
+    }
+
+    attrib->ar_attribute = attr;
+    attrib->ar_attribute_form = attr_form;
+    attrib->ar_attribute_form_direct = attr_form;
+    attrib->ar_cu_context = die->di_cu_context;
+    attrib->ar_debug_info_ptr = info_ptr;
+    *ret_attr = (attrib);
+    return DW_DLV_OK;
+}
+
+
+int
+dwarf_lowpc(Dwarf_Die die,
+    Dwarf_Addr * return_addr, Dwarf_Error * error)
+{
+    Dwarf_Addr ret_addr = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+    Dwarf_Half attr_form = 0;
+    Dwarf_Debug dbg = 0;
+    Dwarf_Half address_size = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    dbg = die->di_cu_context->cc_dbg;
+    address_size = die->di_cu_context->cc_address_size;
+    info_ptr = _dwarf_get_value_ptr(die, DW_AT_low_pc, &attr_form);
+    if ((info_ptr == NULL && attr_form == 0) ||
+        (info_ptr != NULL && attr_form != DW_FORM_addr)) {
+        _dwarf_error(dbg, error, DW_DLE_DIE_BAD);
+        return (DW_DLV_ERROR);
+    }
+    if (info_ptr == NULL) {
+        return (DW_DLV_NO_ENTRY);
+    }
+
+
+    READ_UNALIGNED(dbg, ret_addr, Dwarf_Addr,
+                   info_ptr, address_size);
+
+    *return_addr = ret_addr;
+    return (DW_DLV_OK);
+}
+
+
+int
+dwarf_highpc(Dwarf_Die die,
+    Dwarf_Addr * return_addr, Dwarf_Error * error)
+{
+    Dwarf_Addr ret_addr = 0;
+    Dwarf_Byte_Ptr info_ptr = 0;
+    Dwarf_Half attr_form = 0;
+    Dwarf_Debug dbg = 0;
+    Dwarf_Half address_size = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+    dbg = die->di_cu_context->cc_dbg;
+    address_size = die->di_cu_context->cc_address_size;
+    info_ptr = _dwarf_get_value_ptr(die, DW_AT_high_pc, &attr_form);
+    if ((info_ptr == NULL && attr_form == 0) ||
+        (info_ptr != NULL && attr_form != DW_FORM_addr)) {
+        _dwarf_error(dbg, error, DW_DLE_DIE_BAD);
+        return (DW_DLV_ERROR);
+    }
+    if (info_ptr == NULL) {
+        return (DW_DLV_NO_ENTRY);
+    }
+
+    READ_UNALIGNED(dbg, ret_addr, Dwarf_Addr,
+                   info_ptr, address_size);
+
+    *return_addr = ret_addr;
+    return (DW_DLV_OK);
+}
+
+
+/*
+    Takes a die, an attribute attr, and checks if attr 
+    occurs in die.  Attr is required to be an attribute
+    whose form is in the "constant" class.  If attr occurs 
+    in die, the value is returned.  
+  Returns DW_DLV_OK, DW_DLV_ERROR, or DW_DLV_NO_ENTRY as
+    appropriate. Sets the value thru the pointer return_val.
+    This function is meant to do all the 
+    processing for dwarf_bytesize, dwarf_bitsize, dwarf_bitoffset, 
+    and dwarf_srclang.
+*/
+static int
+_dwarf_die_attr_unsigned_constant(Dwarf_Die die,
+    Dwarf_Half attr,
+    Dwarf_Unsigned * return_val,
+    Dwarf_Error * error)
+{
+    Dwarf_Byte_Ptr info_ptr;
+    Dwarf_Half attr_form;
+    Dwarf_Unsigned ret_value;
+    Dwarf_Debug dbg;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    dbg = die->di_cu_context->cc_dbg;
+    info_ptr = _dwarf_get_value_ptr(die, attr, &attr_form);
+    if (info_ptr != NULL) {
+        switch (attr_form) {
+
+        case DW_FORM_data1:
+            *return_val = (*(Dwarf_Small *) info_ptr);
+            return (DW_DLV_OK);
+
+        case DW_FORM_data2:
+            READ_UNALIGNED(dbg, ret_value, Dwarf_Unsigned,
+                           info_ptr, sizeof(Dwarf_Shalf));
+            *return_val = ret_value;
+            return (DW_DLV_OK);
+
+        case DW_FORM_data4:
+            READ_UNALIGNED(dbg, ret_value, Dwarf_Unsigned,
+                           info_ptr, sizeof(Dwarf_sfixed));
+            *return_val = ret_value;
+            return (DW_DLV_OK);
+
+        case DW_FORM_data8:
+            READ_UNALIGNED(dbg, ret_value, Dwarf_Unsigned,
+                           info_ptr, sizeof(Dwarf_Unsigned));
+            *return_val = ret_value;
+            return (DW_DLV_OK);
+
+        case DW_FORM_udata:
+            *return_val = (_dwarf_decode_u_leb128(info_ptr, NULL));
+            return (DW_DLV_OK);
+
+        default:
+            _dwarf_error(dbg, error, DW_DLE_DIE_BAD);
+            return (DW_DLV_ERROR);
+        }
+    }
+    if (attr_form == 0) {
+        _dwarf_error(dbg, error, DW_DLE_DIE_BAD);
+        return (DW_DLV_ERROR);
+    }
+    return DW_DLV_NO_ENTRY;
+}
+
+
+int
+dwarf_bytesize(Dwarf_Die die,
+    Dwarf_Unsigned * ret_size, Dwarf_Error * error)
+{
+    Dwarf_Unsigned luns = 0;
+    int res = _dwarf_die_attr_unsigned_constant(die, DW_AT_byte_size, 
+        &luns, error);
+    *ret_size = luns;
+    return res;
+}
+
+
+int
+dwarf_bitsize(Dwarf_Die die,
+    Dwarf_Unsigned * ret_size, Dwarf_Error * error)
+{
+    Dwarf_Unsigned luns = 0;
+    int res = _dwarf_die_attr_unsigned_constant(die, DW_AT_bit_size, 
+        &luns, error);
+    *ret_size = luns;
+    return res;
+}
+
+
+int
+dwarf_bitoffset(Dwarf_Die die,
+    Dwarf_Unsigned * ret_size, Dwarf_Error * error)
+{
+    Dwarf_Unsigned luns = 0;
+    int res = _dwarf_die_attr_unsigned_constant(die, 
+        DW_AT_bit_offset, &luns, error);
+    *ret_size = luns;
+    return res;
+}
+
+
+/* Refer section 3.1, page 21 in Dwarf Definition. */
+int
+dwarf_srclang(Dwarf_Die die,
+    Dwarf_Unsigned * ret_size, Dwarf_Error * error)
+{
+    Dwarf_Unsigned luns = 0;
+    int res = _dwarf_die_attr_unsigned_constant(die, DW_AT_language, 
+        &luns, error);
+    *ret_size = luns;
+    return res;
+}
+
+
+/* Refer section 5.4, page 37 in Dwarf Definition. */
+int
+dwarf_arrayorder(Dwarf_Die die,
+    Dwarf_Unsigned * ret_size, Dwarf_Error * error)
+{
+    Dwarf_Unsigned luns = 0;
+    int res = _dwarf_die_attr_unsigned_constant(die, DW_AT_ordering, 
+        &luns, error);
+    *ret_size = luns;
+    return res;
+}
+
+/*
+        Return DW_DLV_OK if ok
+        DW_DLV_ERROR if failure.
+
+        If the die and the attr are not related the result is
+        meaningless.
+*/
+int
+dwarf_attr_offset(Dwarf_Die die, Dwarf_Attribute attr, 
+    Dwarf_Off * offset /* return offset thru this ptr */,
+    Dwarf_Error * error)
+{
+    Dwarf_Off attroff = 0;
+
+    CHECK_DIE(die, DW_DLV_ERROR);
+
+    attroff = (attr->ar_debug_info_ptr -
+               die->di_cu_context->cc_dbg->de_debug_info.dss_data);
+    *offset = attroff;
+    return DW_DLV_OK;
+}
+
+int
+dwarf_die_abbrev_code(Dwarf_Die die)
+{
+    return die->di_abbrev_code;
+}
+
+/* Helper function for finding form class. */
+static enum Dwarf_Form_Class 
+dw_get_special_offset(Dwarf_Half attrnum)
+{
+    switch(attrnum) {
+    case DW_AT_stmt_list:
+             return DW_FORM_CLASS_LINEPTR;
+    case DW_AT_macro_info:
+             return DW_FORM_CLASS_MACPTR;
+    case DW_AT_ranges:
+             return DW_FORM_CLASS_RANGELISTPTR;
+    case DW_AT_location:
+    case DW_AT_string_length:
+    case DW_AT_return_addr:
+    case DW_AT_data_member_location:
+    case DW_AT_frame_base:
+    case DW_AT_segment:
+    case DW_AT_static_link:
+    case DW_AT_use_location:
+    case DW_AT_vtable_elem_location:
+             return DW_FORM_CLASS_LOCLISTPTR;
+    case DW_AT_sibling:
+    case DW_AT_byte_size :
+    case DW_AT_bit_offset :
+    case DW_AT_bit_size :
+    case DW_AT_discr :
+    case DW_AT_import :
+    case DW_AT_common_reference:
+    case DW_AT_containing_type:
+    case DW_AT_default_value:
+    case DW_AT_lower_bound:
+    case DW_AT_bit_stride:
+    case DW_AT_upper_bound:
+    case DW_AT_abstract_origin:
+    case DW_AT_base_types:
+    case DW_AT_count:
+    case DW_AT_friend:
+    case DW_AT_namelist_item:
+    case DW_AT_priority:
+    case DW_AT_specification:
+    case DW_AT_type:
+    case DW_AT_allocated:
+    case DW_AT_associated:
+    case DW_AT_byte_stride:
+    case DW_AT_extension:
+    case DW_AT_trampoline:
+    case DW_AT_small:
+    case DW_AT_object_pointer:
+    case DW_AT_signature:
+                return DW_FORM_CLASS_REFERENCE;
+    case DW_AT_MIPS_fde: /* SGI/IRIX extension */
+                return DW_FORM_CLASS_FRAMEPTR;
+    }
+    return DW_FORM_CLASS_UNKNOWN;
+}
+
+/* It takes 4 pieces of data (including the FORM)
+   to accurately determine the form 'class' as documented
+   in the DWARF spec. This is per DWARF4, but will work
+   for DWARF2 or 3 as well.  */
+enum Dwarf_Form_Class dwarf_get_form_class(
+    Dwarf_Half dwversion,
+    Dwarf_Half attrnum, 
+    Dwarf_Half offset_size, 
+    Dwarf_Half form)
+{
+    switch(form) {
+    case  DW_FORM_addr: return DW_FORM_CLASS_ADDRESS;
+
+    case  DW_FORM_data2:  return DW_FORM_CLASS_CONSTANT;
+
+    case  DW_FORM_data4: 
+        if(dwversion <= 3 && offset_size == 4) {
+            enum Dwarf_Form_Class class = dw_get_special_offset(attrnum);
+            if(class != DW_FORM_CLASS_UNKNOWN) {
+                return class;
+            }
+        }
+        return DW_FORM_CLASS_CONSTANT;
+    case  DW_FORM_data8:
+        if(dwversion <= 3 && offset_size == 8) {
+            enum Dwarf_Form_Class class = dw_get_special_offset(attrnum);
+            if(class != DW_FORM_CLASS_UNKNOWN) {
+                return class;
+            }
+        }
+        return DW_FORM_CLASS_CONSTANT;
+
+    case  DW_FORM_sec_offset:
+        {
+            enum Dwarf_Form_Class class = dw_get_special_offset(attrnum);
+            if(class != DW_FORM_CLASS_UNKNOWN) {
+                return class;
+            }
+        }
+        /* We do not know what this is. */
+        break;
+
+    case  DW_FORM_string: return DW_FORM_CLASS_STRING;
+    case  DW_FORM_strp:   return DW_FORM_CLASS_STRING;
+
+    case  DW_FORM_block:  return DW_FORM_CLASS_BLOCK;
+    case  DW_FORM_block1: return DW_FORM_CLASS_BLOCK;
+    case  DW_FORM_block2: return DW_FORM_CLASS_BLOCK;
+    case  DW_FORM_block4: return DW_FORM_CLASS_BLOCK;
+
+    case  DW_FORM_data1:  return DW_FORM_CLASS_CONSTANT;
+    case  DW_FORM_sdata:  return DW_FORM_CLASS_CONSTANT;
+    case  DW_FORM_udata:  return DW_FORM_CLASS_CONSTANT;
+
+    case  DW_FORM_ref_addr:    return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref1:        return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref2:        return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref4:        return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref8:        return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref_udata:   return DW_FORM_CLASS_REFERENCE;
+    case  DW_FORM_ref_sig8:    return DW_FORM_CLASS_REFERENCE;
+
+    case  DW_FORM_exprloc:      return DW_FORM_CLASS_EXPRLOC;
+
+    case  DW_FORM_flag:         return DW_FORM_CLASS_FLAG;
+    case  DW_FORM_flag_present: return DW_FORM_CLASS_FLAG;
+
+   
+    case  DW_FORM_indirect: 
+    default: 
+        break;
+    };
+    return DW_FORM_CLASS_UNKNOWN;
+}
+