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support relocation info

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Sami Samhuri 2010-01-19 23:19:47 -08:00
parent 0269598c16
commit ce1f5bb4dc
1 changed files with 57 additions and 50 deletions
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107
asm/machofile.rb
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@ -8,16 +8,20 @@ module Assembler
attr_accessor :header, :load_commands, :sections, :data
attr_accessor :current_segment
attr_accessor :text_offset
def initialize(filetype=MH_OBJECT)
@header = MachHeader.new(MH_MAGIC, CPU_TYPE_X86, CPU_SUBTYPE_X86_ALL, filetype, 0, 0, 0)
@load_commands = [] # All defined segments.
@sections = {} # Map of segment names to lists of segments.
@sections = {} # Map of segment names to lists of sections.
@section_disk_size = Hash.new(0) # Sections store their VM size so we need their sizes on disk.
@section_offset = 0 # Offset of the next section's data, in bytes.
@data = [] # Blobs of data that appear at the end of the file.
# (text, data, symtab, ...)
# (text, data, relocation info, symtab, ...)
@current_segment = nil # An alias for the last defined segment.
@text_segname = nil # Name of __TEXT segement
@text_sect_index = nil # Index of __text section
@text_data_index = nil # Index into @data of __text section data
@reloc_info = nil # Copy of relocation info array
end
@ -82,11 +86,12 @@ module Assembler
segment=@current_segment, type=S_REGULAR)
# Create the new section.
section = Section.new(name, segname, 0, vmsize, 0, 0, 0, 0, 0, 0, type)
section = Section.new(name, segname, @section_offset, vmsize, 0, 0, 0, 0, 0, 0, type)
# Add this section to the map of segment names to sections.
(@sections[segment[:segname]] ||= []) << section
@section_disk_size[name] = data.size
@section_offset += data.size
@data << data if data.size > 0
# Update the header.
@ -116,20 +121,32 @@ module Assembler
# name given (__TEXT).
def text(data, sectname='__text', segname='__TEXT')
real_segname = nil
unless @current_segment
segment(segname_based_on_filetype(segname)) do |seg|
real_segname = segname_based_on_filetype(segname)
segment(real_segname) do |seg|
seg[:maxprot] = VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE
seg[:initprot] = VM_PROT_READ | VM_PROT_EXECUTE
end
end
end
section(sectname, segname, data) do |sect|
# reloff and nreloc are calculated later (in calculate_offsets)
sect[:flags] = 0x400 # S_ATTR_SOME_INSTRUCTIONS
end
# Remember where section and data are so we can update them later.
@text_segname = real_segname || segname
@text_sect_index = @sections[@text_segname].length-1
@text_data_index = @data.length-1
return self
end
def update_text(data)
raise 'no __text segment defined yet' unless @text_data_index
@data[@text_data_index] = data
end
# Basis for #data, #const, and #bss methods.
def segment_based_on_filetype(segname, options={})
@ -173,6 +190,19 @@ module Assembler
end
end
# Define a relocation table. Usually between segments and the
# symbol table.
#
# Accepts an array of relocation info structs.
def reloc(reloc_info)
@data << if reloc_info.respond_to?(:join)
reloc_info.map {|r| r.serialize}.join
else
reloc_info
end
@reloc_info = reloc_info.map {|x| x.clone}
return self
end
# Define a symbol table. This should usually be placed at the end of the
# file.
@ -204,7 +234,6 @@ module Assembler
@data << nlist_ary.map {|n| n.serialize}.join
@data << stab
return self
end
@ -218,63 +247,34 @@ module Assembler
# Now that we have all the pieces of the file defined we can calculate
# the file offsets of segments and sections.
recalculate_offsets
# |------------------|
# | Mach Header | Part 1
# |------------------|
# | Segment 1 | Part 2
# | Section 1 | ---
# | Section 2 | --|--
# | ... | | |
# | Segment 2 | | |
# | Section 4 | | |
# | Section 5 | | |
# | ... | | |
# | ... | | |
# | [Symtab cmd] | | |
# |------------------| | |
# | Section data 1 | <-- | Part 3
# | Section data 2 | <----
# | ... |
# | [Symtab data] |
# |------------------|
calculate_offsets
###################################
# Mach-O file Part 1: Mach Header #
###################################
@header.serialize +
obj = @header.serialize
#####################################
# Mach-O file Part 2: Load Commands #
#####################################
# dump each load command (which include the section headers under them)
obj += @load_commands.map do |cmd|
sects = @sections[cmd[:segname]] rescue []
sects.inject(cmd.serialize) do |data, sect|
data + sect.serialize
end
end.join
@load_commands.map do |cmd|
sects = @sections[cmd[:segname]] rescue []
sects.inject(cmd.serialize) do |data, sect|
data + sect.serialize
end
end.join +
###################################
# Mach-O file Part 3: Binary data #
###################################
obj += @data.join
return obj
@data.join
end
# Update the file offsets in segments and sections.
def recalculate_offsets
def calculate_offsets
# Maintain the offset into the the file on disk. This is used
# to update the various structures.
@ -317,7 +317,7 @@ module Assembler
# Second pass over load commands. Fill in file offsets.
@load_commands.each do |cmd|
case cmd[:cmd]\
case cmd[:cmd]
when LC_SEGMENT
seg = cmd
@ -329,6 +329,13 @@ module Assembler
end
when LC_SYMTAB
if @reloc_info
# update text section with relocation info
__text = @sections[@text_segname][@text_sect_index]
__text[:reloff] = offset
__text[:nreloc] = @reloc_info.length
offset += @reloc_info.first.bytesize * @reloc_info.length
end
st = cmd
st[:symoff] = offset
offset += st[:nsyms] * Nlist.bytesize
@ -341,8 +348,8 @@ module Assembler
end
end # @load_commands.each
end # def recalculate_offsets
end # def calculate_offsets
#######
@ -354,7 +361,7 @@ module Assembler
when MH_OBJECT: ''
when MH_EXECUTE: segname
else
raise "unsupported MachO file type! #{@header.inspect}"
raise "unsupported MachO file type: #{@header.inspect}"
end
end