111 lines
3.1 KiB
Ruby
111 lines
3.1 KiB
Ruby
require_relative "constants"
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require_relative "null_section"
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module Elf
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class ObjectFile
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include Constants
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def initialize(target)
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@target = target
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@sections = []
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add_section NullSection.new
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end
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def add_section(section)
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@sections << section
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section.index = @sections.length - 1
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end
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def write(io)
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write_preamble(io)
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sh_offset_pos = io.tell
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write_header(io)
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string_table = write_string_table(io)
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io.write_unsigned_int_16 @sections.length # section header count
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io.write_unsigned_int_16 @sections.length-1 # section name string table index
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section_data = write_sections(io)
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sh_offset = io.tell
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write_section_data(section_data, string_table , io)
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io.seek sh_offset_pos
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io.write_unsigned_int_32 sh_offset
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end
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def write_string_table(io)
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string_table = StringTableSection.new(".shstrtab")
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@sections << string_table
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@sections.each { |section|
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string_table.add_string section.name
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}
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string_table
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end
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def write_section_data(section_data, string_table,io)
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section_data.each { |data|
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section, offset, size = data[:section], data[:offset], data[:size]
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# write header first
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io.write_unsigned_int_32 string_table.index_for(section.name)
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io.write_unsigned_int_32 section.type
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io.write_unsigned_int_32 section.flags
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io.write_unsigned_int_32 section.addr
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if (section.type == SHT_NOBITS)
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raise 'SHT_NOBITS not handled yet'
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elsif (section.type == SHT_NULL)
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io.write_unsigned_int_32 0
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io.write_unsigned_int_32 0
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else
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io.write_unsigned_int_32 offset
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io.write_unsigned_int_32 size
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end
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io.write_unsigned_int_32 section.link
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io.write_unsigned_int_32 section.info
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io.write_unsigned_int_32 section.alignment
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io.write_unsigned_int_32 section.ent_size
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}
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end
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def write_sections(io)
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section_data = []
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@sections.each { |section|
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offset = io.tell
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section.write(io)
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size = io.tell - offset
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section_data << {:section => section, :offset => offset, :size => size}
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}
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section_data
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end
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def write_header(io)
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io.write_unsigned_int_32 0 # section header table offset
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io.write_unsigned_int_32 0 # no flags
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io.write_unsigned_int_16 52 # header length
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io.write_unsigned_int_16 0 # program header length
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io.write_unsigned_int_16 0 # program header count
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io.write_unsigned_int_16 40 # section header length
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end
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def write_preamble(io)
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io << "\x7fELF"
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io.write_unsigned_int_8 @target[0]
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io.write_unsigned_int_8 @target[1]
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io.write_unsigned_int_8 EV_CURRENT
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io.write_unsigned_int_8 @target[2]
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io << "\x00" * 8 # pad
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io.write_unsigned_int_16 ET_REL
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io.write_unsigned_int_16 @target[3]
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io.write_unsigned_int_32 EV_CURRENT
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io.write_unsigned_int_32 0 # entry point
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io.write_unsigned_int_32 0 # no program header table
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end
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end
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end
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