the relocation manager for dwarf works! sdf
diff --git a/elftools/common/exceptions.py b/elftools/common/exceptions.py
index c2da24c..26f1ba0 100644
--- a/elftools/common/exceptions.py
+++ b/elftools/common/exceptions.py
@@ -9,6 +9,9 @@
class ELFError(Exception):
pass
+class ELFRelocationError(ELFError):
+ pass
+
class ELFParseError(ELFError):
pass
diff --git a/elftools/dwarf/die.py b/elftools/dwarf/die.py
index 0836aa0..f438934 100644
--- a/elftools/dwarf/die.py
+++ b/elftools/dwarf/die.py
@@ -29,7 +29,8 @@
# (e.g. for a DW_FORM_strp it's the raw string offset into the table)
#
# offset:
-# Offset of this attribute's value in the stream
+# Offset of this attribute's value in the stream (absolute offset, relative
+# the beginning of the whole stream)
#
AttributeValue = namedtuple(
'AttributeValue', 'name form value raw_value offset')
@@ -159,12 +160,34 @@
self.tag = abbrev_decl['tag']
self.has_children = abbrev_decl.has_children()
+ # The offset of the .debug_info section in the stream. Used to compute
+ # relative offset of attribute values to the beginning of the section.
+ section_offset = self.dwarfinfo.debug_info_loc.offset
+
+ # Some attribute values need relocations. These are computed with the
+ # help of a DWARFRelocationManager for .debug_info, which is held by
+ # DWARFInfo for this purpose.
+ relocation_manager = self.dwarfinfo.relocation_manager['.debug_info']
+
# Guided by the attributes listed in the abbreviation declaration, parse
# values from the stream.
#
for name, form in abbrev_decl.iter_attr_specs():
attr_offset = self.stream.tell()
raw_value = struct_parse(structs.Dwarf_dw_form[form], self.stream)
+
+ # raw_value may need to be relocated, if there's a relocation
+ # registered for this offset in the relocation manager.
+ # Relocations are listed by offset relative to the beginning of
+ # the section.
+ offset_from_section = attr_offset - section_offset
+ if relocation_manager.has_relocation(offset_from_section):
+ # Applying the relocation may change the stream, so preserve it
+ with preserve_stream_pos(self.stream):
+ raw_value = relocation_manager.apply_relocation(
+ offset=offset_from_section,
+ value=raw_value)
+
value = self._translate_attr_value(form, raw_value)
self.attributes[name] = AttributeValue(
name=name,
diff --git a/elftools/dwarf/dwarfinfo.py b/elftools/dwarf/dwarfinfo.py
index 051ea9f..1e2208b 100644
--- a/elftools/dwarf/dwarfinfo.py
+++ b/elftools/dwarf/dwarfinfo.py
@@ -14,6 +14,7 @@
from .structs import DWARFStructs
from .compileunit import CompileUnit
from .abbrevtable import AbbrevTable
+from .dwarfrelocationmanager import DWARFRelocationManager
# Describes a debug section in a stream: offset and size
@@ -27,7 +28,7 @@
"""
def __init__(self,
stream,
- little_endian,
+ elffile,
debug_info_loc,
debug_abbrev_loc,
debug_str_loc,
@@ -35,9 +36,9 @@
""" stream:
A stream (file-like object) that contains debug sections
- little_endian:
- Section contents are in little-endian data format
-
+ elffile:
+ ELFFile reference
+
debug_*_loc:
DebugSectionLocator for this section, specifying where it can
be found in the stream
@@ -48,7 +49,13 @@
self.debug_str_loc = debug_str_loc
self.debug_line_loc = debug_line_loc
- self.little_endian = little_endian
+ self.elffile = elffile
+ self.little_endian = self.elffile.little_endian
+
+ self.relocation_manager = {}
+ self.relocation_manager['.debug_info'] = DWARFRelocationManager(
+ elffile=self.elffile,
+ section_name='.debug_info')
# This is the DWARFStructs the context uses, so it doesn't depend on
# DWARF format and address_size (these are determined per CU) - set them
diff --git a/elftools/dwarf/dwarfrelocationmanager.py b/elftools/dwarf/dwarfrelocationmanager.py
index d8f7831..048e1c6 100644
--- a/elftools/dwarf/dwarfrelocationmanager.py
+++ b/elftools/dwarf/dwarfrelocationmanager.py
@@ -6,7 +6,6 @@
# Eli Bendersky (eliben@gmail.com)
# This code is in the public domain
#-------------------------------------------------------------------------------
-
from ..elf.sections import RelocationSection
@@ -20,28 +19,30 @@
self.section_name = section_name
self._section = self.elffile.get_section_by_name(section_name)
- # _relocs maps an offset in the section to a Relocation object
+ # _relocs maps an offset in the section to an index in the relocation
+ # table.
# _reloc_section is the relocation section object
# ... both are loaded by _load_relocations
self._relocs = {}
self._reloc_section = None
self._load_relocations()
- # _symtable: symbol table section attached to the relocation section
- self._symtable = self.elffile.get_section(
- self._reloc_section['sh_link'])
-
def has_relocation(self, offset):
""" Does the given offset have a relocation registered for it?
The offset is relative to its section.
"""
return offset in self._relocs
- def apply_relocation(self, offset):
- """ Apply the relocation registered for the given offset. Return the
- relocated value.
+ def apply_relocation(self, offset, value):
+ """ Apply the relocation registered for the given offset. value is
+ the original value at that offset. Return the relocated value.
"""
- reloc = self._relocs[offset]
+ reloc_index = self._relocs[offset]
+ return self.elffile.apply_relocation(
+ reloc_section=self._reloc_section,
+ reloc_index=reloc_index,
+ offset=offset,
+ value=value)
def _load_relocations(self):
# Currently assume that only a single relocation section will exist
@@ -53,7 +54,8 @@
if ( isinstance(section, RelocationSection) and
section.name in reloc_section_names):
self._reloc_section = section
- for reloc in self._reloc_section.iter_relocations():
- self._relocs[reloc['r_offset']] = reloc
+ for i, reloc in enumerate(
+ self._reloc_section.iter_relocations()):
+ self._relocs[reloc['r_offset']] = i
break
diff --git a/elftools/elf/descriptions.py b/elftools/elf/descriptions.py
index f404898..b7e87ab 100644
--- a/elftools/elf/descriptions.py
+++ b/elftools/elf/descriptions.py
@@ -68,10 +68,10 @@
def describe_symbol_shndx(x):
return _DESCR_ST_SHNDX.get(x, '%3s' % x)
-def describe_reloc_type(x, e_machine):
- if e_machine in ('EM_386', 'EM_486'):
+def describe_reloc_type(x, elffile):
+ if elffile.architecture_is_x86():
return _DESCR_RELOC_TYPE_i386.get(x, _unknown)
- elif e_machine in ('EM_X86_64', 'EM_L10M'):
+ elif elffile.architecture_is_x64():
return _DESCR_RELOC_TYPE_x64.get(x, _unknown)
else:
return 'unrecognized: %-7x' % (x & 0xFFFFFFFF)
diff --git a/elftools/elf/elffile.py b/elftools/elf/elffile.py
index ebd04dd..0a12d4c 100644
--- a/elftools/elf/elffile.py
+++ b/elftools/elf/elffile.py
@@ -6,7 +6,7 @@
# Eli Bendersky (eliben@gmail.com)
# This code is in the public domain
#-------------------------------------------------------------------------------
-from ..common.exceptions import ELFError
+from ..common.exceptions import ELFError, ELFRelocationError
from ..common.utils import struct_parse, elf_assert
from ..construct import ConstructError
from .structs import ELFStructs
@@ -14,6 +14,7 @@
Section, StringTableSection, SymbolTableSection, NullSection,
RelocationSection)
from .segments import Segment, InterpSegment
+from .enums import ENUM_RELOC_TYPE_i386, ENUM_RELOC_TYPE_x64
from ..dwarf.dwarfinfo import DWARFInfo, DebugSectionLocator
@@ -124,12 +125,34 @@
return DWARFInfo(
stream=self.stream,
- little_endian=self.little_endian,
+ elffile=self,
debug_info_loc=debug_sections['.debug_info'],
debug_abbrev_loc=debug_sections['.debug_abbrev'],
debug_str_loc=debug_sections['.debug_str'],
debug_line_loc=debug_sections['.debug_line'])
+ def architecture_is_x86(self):
+ return self['e_machine'] in ('EM_386', 'EM_486')
+
+ def architecture_is_x64(self):
+ return self['e_machine'] == 'EM_X86_64'
+
+ def apply_relocation(self, reloc_section, reloc_index, offset, value):
+ """ Apply a relocation to the offset. The original value at offset is
+ also provided. Return a relocated value that should be written
+ back into the offset.
+
+ The relocation to apply is specified by an index and a relocation
+ section where this index points.
+
+ Throw ELFRelocationError if there's a problem with the relocation.
+ """
+ # The symbol table associated with this relocation section
+ symtab = self.get_section(reloc_section['sh_link'])
+ # Relocation object
+ reloc = reloc_section.get_relocation(reloc_index)
+ return self._do_apply_relocation(reloc, symtab, offset, value)
+
#-------------------------------- PRIVATE --------------------------------#
def __getitem__(self, name):
@@ -242,10 +265,55 @@
header=self._get_section_header(stringtable_section_num),
name='',
stream=self.stream)
-
+
def _parse_elf_header(self):
""" Parses the ELF file header and assigns the result to attributes
of this object.
"""
return struct_parse(self.structs.Elf_Ehdr, self.stream, stream_pos=0)
+ def _do_apply_relocation(self, reloc, symtab, offset, value):
+ # Only basic sanity checking here
+ if reloc['r_info_sym'] >= symtab.num_symbols():
+ raise ELFRelocationError(
+ 'Invalid symbol reference in relocation: index %s' % (
+ reloc['r_info_sym']))
+ sym_value = symtab.get_symbol(reloc['r_info_sym'])['st_value']
+ reloc_type = reloc['r_info_type']
+
+ if self.architecture_is_x86():
+ if reloc.is_RELA():
+ raise ELFRelocationError(
+ 'Unexpected RELA relocation for x86: %s' % reloc)
+ if reloc_type == ENUM_RELOC_TYPE_i386['R_386_NONE']:
+ # No relocation
+ return value
+ elif reloc_type == ENUM_RELOC_TYPE_i386['R_386_32']:
+ return sym_value + value
+ elif reloc_type == ENUM_RELOC_TYPE_i386['R_386_PC32']:
+ return sym_value + value - offset
+ else:
+ raise ELFRelocationError('Unsupported relocation type %s' % (
+ reloc_type))
+ elif self.architecture_is_x64():
+ if not reloc.is_RELA():
+ raise ELFRelocationError(
+ 'Unexpected REL relocation for x64: %s' % reloc)
+ if reloc_type == ENUM_RELOC_TYPE_x64['R_X86_64_NONE']:
+ # No relocation
+ return value
+ elif reloc_type in (
+ ENUM_RELOC_TYPE_x64['R_X86_64_64'],
+ ENUM_RELOC_TYPE_x64['R_X86_64_32'],
+ ENUM_RELOC_TYPE_x64['R_X86_64_32S']):
+ return sym_value + reloc['r_addend']
+ else:
+ raise ELFRelocationError('Unsupported relocation type %s' % (
+ reloc_type))
+ else:
+ raise ELFRelocationError(
+ 'Relocations not supported for architecture %s' % (
+ self['e_machine']))
+
+ raise ELFRelocationError('unreachable relocation code')
+
diff --git a/scripts/readelf.py b/scripts/readelf.py
index 986b7ae..efbcf21 100755
--- a/scripts/readelf.py
+++ b/scripts/readelf.py
@@ -304,7 +304,7 @@
self._format_hex(rel['r_info'],
fieldsize=hexwidth, lead0x=False),
describe_reloc_type(
- rel['r_info_type'], self.elffile['e_machine'])))
+ rel['r_info_type'], self.elffile)))
if rel['r_info_sym'] == 0:
self._emitline()
diff --git a/z.py b/z.py
index 7c09211..8bf4743 100644
--- a/z.py
+++ b/z.py
@@ -29,10 +29,10 @@
print 'CU header', cu.header
topdie = cu.get_top_DIE()
-#print topdie
+print topdie
dinfo_sec = efile.get_section_by_name('.debug_info')
relman = DWARFRelocationManager(efile, dinfo_sec.name)
print relman._reloc_section.name, relman._reloc_section['sh_offset']
-pprint.pprint(relman._relocs)
+#pprint.pprint(relman._relocs)
