def _initialise_segments(self, hdr, file_, prepare):
"""Initialise instance from program headers."""
# Now load all the program headers
#
# "The time has come," the developer said, "to talk of many
# things: Of section to segment mapping and scatter load, of
# cabbages and kings, and why the RVCT linker is on drugs and
# whether pigs have wings."
#
# There are two ways of determining which sections belong in a
# segment:
#
# 1) In most cases a section is in a segment if its virtual
# address range falls in the virtual address range of the
# segment. These segments tend to contain multiple
# PROGBITS sections and may end with a NOBITS section.
#
# 2) In the case of segments build with RVCT's scatter load
# support the virtual address of the included sections can
# be anywhere in memory. In this case a section is in the
# segment if its data file offset falls in the offset range
# of the segment. These segments can contain multiple
# PROGBITS and NOBITS sections in any order. The file size
# of the segment is the filesize of all of the PROGBITS
# sections. The memory size of the segment is the sum of
# the size of all of the sections, not the difference
# between the lowest and highest virtual addresses.
#
# Some other things about ELF files that you need to know:
#
# a) Segments can overlap, and sections can appear in multiple
# segments.
#
# b) Some sections do not appear in any segments. These tend
# to be the symbol table and other debugging data.
#
# c) The offsets of NOBITS sections tend to be the same as the
# offset for the next PROGBITS section, even if it is in
# the next segment. However, sometimes NOBITS sections
# appear at the beginning of a segment.
#
# d) The address offset from the start of a segment and the
# file offset from the start of the segment are not
# necessarily the same.
#
# Therefore, to map sections to segments involves two passes:
#
# 1) Find all of the sections that fall in the segment virtual
# address range.
#
# 2) Find all of the remaining sections that fall in the file
# offset range. If any are found then mark the segment as
# a scatter-load segment.
#
# The file size and memory size of a segment depends on
# whether or not it is a scatter load segment. For scatter
# load files, the section that has the latest offset from the
# beginning of the section is used, while for non-scatter-load
# segments, the section with the largest virtual address is
# used.
#
# File offsets cannot be used for both types of segments
# because broken linkers can produce sections with
# inconsistant virtual address to file offset mappings and
# this will make elfweaver produce segments with incorrect
# file sizes or memory sizes.
#
# "O Readers," said the developer, "You've had a pleasant run!
# Shall we start the code again?" But answer came there none--
# And this was scarcely odd, because no-one would read this far
# for fun.
self._ph_offset = hdr.e_phoff
self.segments = []
# Short circuit the return.
if hdr.e_phoff == 0:
return
ph_list = self._get_headers(hdr, file_, ELF_PH_CLASSES, hdr.e_phoff,
hdr.e_phentsize, hdr.e_phnum)
# Map segments to sections, pass 1.
for ph in ph_list:
if ph.p_type != PT_PHDR:
low = ph.p_vaddr
high = low + ph.p_memsz
sects = []
for section in self.sections:
# See if the section's virtual address range falls within
# the virtual address range of the segment.
addr = section.address
if low <= addr < high and addr + section.get_size() <= high:
sects.append(section)
if sects:
seg = SectionedElfSegment(self,
prog_header=ph,
sections=sects)
else:
data = file_.get_data(ph.p_offset, ph.p_filesz)
seg = DataElfSegment(self,
prog_header=ph,
data=data,
memsz=ph.p_memsz)
else:
seg = HeaderElfSegment(self, prog_header=ph)
self.segments.append(seg)
# Map segments to sections, pass 2
sheaders = self._get_section_headers(hdr, file_)
sect_offsets = [header.sh_offset for header in sheaders]
for ph, seg in zip(ph_list, self.segments):
if seg.has_sections():
low = ph.p_offset
high = low + ph.p_filesz
for (section, offset) in zip(self.sections, sect_offsets):
# Scatter-load sections do not appear in multiple segments,
# so skip sections that are already in some segment.
if section.in_segment:
continue
# See if the section's file offset range falls within the
# file offset range of the segment. Remember that the
# trailing BSS section can have the offset of the next
# section
if low <= offset <= high and \
((section.type == SHT_NOBITS and offset != low) or \
(section.type != SHT_NOBITS and section.get_size() > 0 and \
offset + section.get_size() <= high)):
seg.add_section(section)
seg.set_scatter_load()
# If we're a scatter-load segment we need to work out in segment
# offsets for our sections
if seg.is_scatter_load():
for section in seg.sections:
idx = self.sections.index(section)
offset = sect_offsets[idx]
section.set_in_segment_offset(offset - ph.p_offset)
# If need be, we now prepare the segments
if prepare:
for ph, seg in zip(ph_list, self.segments):
if ph.p_type == PT_PHDR:
prog_header_size = hdr.e_phentsize * hdr.e_phnum
else:
prog_header_size = None
seg.prepare(ph.p_offset, prog_header_size)
def _initialise_segments(self, hdr, file_, prepare):
"""Initialise instance from program headers."""
# Now load all the program headers
#
# "The time has come," the developer said, "to talk of many
# things: Of section to segment mapping and scatter load, of
# cabbages and kings, and why the RVCT linker is on drugs and
# whether pigs have wings."
#
# There are two ways of determining which sections belong in a
# segment:
#
# 1) In most cases a section is in a segment if its virtual
# address range falls in the virtual address range of the
# segment. These segments tend to contain multiple
# PROGBITS sections and may end with a NOBITS section.
#
# 2) In the case of segments build with RVCT's scatter load
# support the virtual address of the included sections can
# be anywhere in memory. In this case a section is in the
# segment if its data file offset falls in the offset range
# of the segment. These segments can contain multiple
# PROGBITS and NOBITS sections in any order. The file size
# of the segment is the filesize of all of the PROGBITS
# sections. The memory size of the segment is the sum of
# the size of all of the sections, not the difference
# between the lowest and highest virtual addresses.
#
# Some other things about ELF files that you need to know:
#
# a) Segments can overlap, and sections can appear in multiple
# segments.
#
# b) Some sections do not appear in any segments. These tend
# to be the symbol table and other debugging data.
#
# c) The offsets of NOBITS sections tend to be the same as the
# offset for the next PROGBITS section, even if it is in
# the next segment. However, sometimes NOBITS sections
# appear at the beginning of a segment.
#
# d) The address offset from the start of a segment and the
# file offset from the start of the segment are not
# necessarily the same.
#
# Therefore, to map sections to segments involves two passes:
#
# 1) Find all of the sections that fall in the segment virtual
# address range.
#
# 2) Find all of the remaining sections that fall in the file
# offset range. If any are found then mark the segment as
# a scatter-load segment.
#
# The file size and memory size of a segment depends on
# whether or not it is a scatter load segment. For scatter
# load files, the section that has the latest offset from the
# beginning of the section is used, while for non-scatter-load
# segments, the section with the largest virtual address is
# used.
#
# File offsets cannot be used for both types of segments
# because broken linkers can produce sections with
# inconsistant virtual address to file offset mappings and
# this will make elfweaver produce segments with incorrect
# file sizes or memory sizes.
#
# "O Readers," said the developer, "You've had a pleasant run!
# Shall we start the code again?" But answer came there none--
# And this was scarcely odd, because no-one would read this far
# for fun.
self._ph_offset = hdr.e_phoff
self.segments = []
# Short circuit the return.
if hdr.e_phoff == 0:
return
ph_list = self._get_headers(hdr, file_, ELF_PH_CLASSES, hdr.e_phoff,
hdr.e_phentsize, hdr.e_phnum)
# Map segments to sections, pass 1.
for ph in ph_list:
if ph.p_type != PT_PHDR:
low = ph.p_vaddr
high = low + ph.p_memsz
sects = []
for section in self.sections:
# See if the section's virtual address range falls within
# the virtual address range of the segment.
addr = section.address
if low <= addr < high and addr + section.get_size() <= high:
sects.append(section)
if sects:
seg = SectionedElfSegment(self, prog_header=ph,
sections=sects)
else:
data = file_.get_data(ph.p_offset, ph.p_filesz)
seg = DataElfSegment(self, prog_header=ph, data=data,
memsz=ph.p_memsz)
else:
seg = HeaderElfSegment(self, prog_header=ph)
self.segments.append(seg)
# Map segments to sections, pass 2
sheaders = self._get_section_headers(hdr, file_)
sect_offsets = [header.sh_offset for header in sheaders]
for ph, seg in zip(ph_list, self.segments):
if seg.has_sections():
low = ph.p_offset
high = low + ph.p_filesz
for (section, offset) in zip(self.sections, sect_offsets):
# Scatter-load sections do not appear in multiple segments,
# so skip sections that are already in some segment.
if section.in_segment:
continue
# See if the section's file offset range falls within the
# file offset range of the segment. Remember that the
# trailing BSS section can have the offset of the next
# section
if low <= offset <= high and \
((section.type == SHT_NOBITS and offset != low) or \
(section.type != SHT_NOBITS and section.get_size() > 0 and \
offset + section.get_size() <= high)):
seg.add_section(section)
seg.set_scatter_load()
# If we're a scatter-load segment we need to work out in segment
# offsets for our sections
if seg.is_scatter_load():
for section in seg.sections:
idx = self.sections.index(section)
offset = sect_offsets[idx]
section.set_in_segment_offset(offset - ph.p_offset)
# If need be, we now prepare the segments
if prepare:
for ph, seg in zip(ph_list, self.segments):
if ph.p_type == PT_PHDR:
prog_header_size = hdr.e_phentsize * hdr.e_phnum
else:
prog_header_size = None
seg.prepare(ph.p_offset, prog_header_size)
