Class: Elf::Writer::Layout

Inherits:
Object
  • Object
show all
Defined in:
lib/mithril/writer.rb

Defined Under Namespace

Classes: LoadMap

Constant Summary collapse

RESERVED_PHDRS = 
16

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(factory) ⇒ Layout

Returns a new instance of Layout.



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# File 'lib/mithril/writer.rb', line 66

def initialize(factory)
  @layout_by_flags = {}
  @layout = RBTree.new()
  @shstrtab = StringTable.new()
  @factory = factory
  @phdrs = [] #BinData::Array.new(:type => @factory.phdr)
  @unallocated =[]
  @sections = [OutputSection.new("", SHT::SHT_NULL, 0,0,0,0,0,0,0,"")]
  @sections[0].index = 0

  @pinned_sections = {} # Name to vaddr
end

Instance Attribute Details

#tbss_size ⇒ Object

Returns the value of attribute tbss_size.



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# File 'lib/mithril/writer.rb', line 157

def tbss_size
  @tbss_size
end

Instance Method Details

#[](idx) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 85

def [](idx)
  @sections[idx]
end

#add(*sections) ⇒ Object

Ordering as follows: Fixed



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# File 'lib/mithril/writer.rb', line 88

def add(*sections)       #Ordering as follows: Fixed
  #(non-nil vaddrs) go where they have to go
  # Flexible sections are added to lowest hole after section of
  # the same type
  retval = []
  return [] if sections.empty?
  sections.each{|sect|
    sect.index = @sections.size
    expect_value "Correct size", sect.data.bytesize, sect.siz
    @sections << sect
    retval << sect.index
  }
  flags = sections.first.flags
  @layout_by_flags[flags] ||= RBTree.new()
  if sections.length > 1 || sections.first.vaddr.nil?
    sections.each { |i| 
      expect_value "All adjacent sections have the same flags", i.flags,flags
      expect_value "All sections must float", i.vaddr, nil
    }
    if sections.length == 1 && @pinned_sections.include?(sections.first.name)
      sections.first.vaddr = @pinned_sections[sections.first.name]
      @layout.delete sections.first.vaddr
      @pinned_sections.delete @sections.first.name
    else
      allocate_sections(sections)
    end
  end
  #TODO: Handle the damn nobits
  if(flags & SHF::SHF_ALLOC == 0)
    sections.each {|i| @unallocated << i}
  else
    sections.each {|i|

      expect_value "Sections shouldn't overlap",  range_available?(@layout,i.vaddr,i.end), true 
      @layout[i.vaddr] = i 
      @layout_by_flags[i.flags][i.vaddr] = i
    }
  end
  retval
end

#add_with_phdr(sections, type, flags) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 128

def add_with_phdr(sections,type,flags)
  raise RuntimeError.new "need one section in phdr" if sections.empty?
  x=self.add *sections
  @phdrs << [sections,type,flags]
  x
end

#pagealign_loadmap(loadmaps) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 147

def pagealign_loadmap(loadmaps)
  #TODO: Be smarter about this..
  loadmaps.sort_by(&:vaddr).each_cons(2) do |low,high|
      if rounddown(low.vaddr + low.memsz,PAGESIZE) >= rounddown(high.vaddr,PAGESIZE)
        low.flags |= high.flags
        high.flags |= low.flags              
      end
  end
  loadmaps
end

#pin_section(name, size, vaddr) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 78

def pin_section(name,size,vaddr)
  x = OutputSection.new(".pin_dummy",SHT::SHT_NULL,0,vaddr,0,0,0,0,0,
                        BinData::Array.new(type: :int8, initial_length: size).to_binary_s)
  raise RuntimeError.new "Invalid pin" unless range_available?(@layout,vaddr,vaddr+size)
  @layout[vaddr] = x
  @pinned_sections[name] = vaddr
end

#shstrtab(buf) ⇒ Object

Last section written, TODO: Move to layout



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# File 'lib/mithril/writer.rb', line 134

def shstrtab(buf) # Last section written, TODO: Move to layout
  name = ".shstrtab"
  idx = @shstrtab.add_string name
  x=@factory.shdr.new
  x.name= idx 
  x.type = SHT::SHT_STRTAB
  x.off = buf.tell
  x.siz = @shstrtab.buf.size
  buf.write @shstrtab.buf.string
  x
end

#write_phdrs(buf, filehdr, load) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 158

def write_phdrs(buf,filehdr,load)
  phdrs = BinData::Array.new(:type => @factory.phdr)
  expect_value "Too many PHDRS",true, @phdrs.size + load.size < RESERVED_PHDRS
  @phdrs.each {|x|
    sections, type,flags =*x
    x =  @factory.phdr.new
    x.align = sections.map(&:align).max
    x.vaddr = sections.map(&:vaddr).min
    x.paddr = x.vaddr
    x.filesz = sections.map(&:end).max - x.vaddr
    if type == PT::PT_TLS and @tbss_size #HACK
      x.memsz = x.filesz + @tbss_size
    else
      x.memsz = x.filesz
    end
    x.flags = flags
    x.off = sections.map(&:off).min
    x.type = type
    phdrs.push x
  }
  #
  load.first.andand.tap{|l|
    l.vaddr -= l.off
    l.memsz += l.off
    l.off = 0
  }
  pagealign_loadmap(load)
  load.each {|l|
    phdrs.push @factory.phdr.new.tap {|x|
      x.align = [PAGESIZE,l.align].max
      x.vaddr = l.vaddr
      x.paddr = x.vaddr
      x.type = PT::PT_LOAD
      x.filesz = l.end - l.off#TODO: handle nobits
      x.memsz = x.filesz # l.memsz
      x.off = l.off
      x.flags = PF::PF_R
      x.flags |= PF::PF_W if(l.flags & SHF::SHF_WRITE != 0)
      x.flags |= PF::PF_X if(l.flags & SHF::SHF_EXECINSTR != 0)

    }
  }
  
  #phdrs.unshift @factory.phdr.new.tap {|x|
  #  x.align = 4
  #  x.vaddr = 
  # x.type = PT::PT_PHDRS
  #}
  #      pp load
  filehdr.phoff = buf.tell
  filehdr.phentsize = @factory.phdr.new.num_bytes
  filehdr.phnum = phdrs.size
  phdrs.write buf

end

#write_sections(buf, filehdr) ⇒ Object 



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# File 'lib/mithril/writer.rb', line 214

def write_sections(buf,filehdr)
  first_shdr = @sections.first 
  first_shdr.index = 0
  
  #Get more clever about mapping files
  # We put actual program headers right at the beginning.
  phdr_off = buf.tell
  buf.seek phdr_off + RESERVED_PHDRS * @factory.phdr.new.num_bytes
  offset = buf.tell
  @sections[0].off = 0
  (@layout.to_a.sort_by(&:first).map(&:last) + @unallocated).each {|s|
    if s.flags & SHF::SHF_ALLOC != 0
      offset = align_mod(offset,s.vaddr, PAGESIZE)     
    end
    s.off = offset
    offset += s.data.bytesize
    
  }
  idx = 0
  @sections.each{|s|  expect_value "Size field correct", s.siz, s.data.bytesize}
  @sections.sort_by(&:off).each_cons(2){|low,high|
    expect_value "Offsets should not overlap", true, low.off + low.data.bytesize <= high.off
  }
  shdrs = BinData::Array.new(:type=>@factory.shdr).push *@sections.map{ |s|
    expect_value "aligned to vaddr", 0,s.vaddr % s.align if s.align != 0
    expect_value "idx", idx,s.index
    idx +=1 
    #expect_value "aligned to pagesize",0, PAGESIZE % s.align
    
    buf.seek s.off
    old_off = buf.tell 
    buf.write(s.data)
#          pp "#{idx }#{s.name} written to offset #{old_off} to #{buf.tell}"

    
    expect_value "size", s.data.bytesize, s.siz
    link_value = lambda do |name|
      if name.is_a? String
        @sections.to_enum.with_index.select {|sect,idx| sect.name == name}.first.last rescue raise RuntimeError.new("Invalid Section reference #{name}") #Index of first match TODO: check unique
      else
        name || 0
      end
    end
    x=  @factory.shdr.new
    x.name   = @shstrtab.add_string(s.name)
    x.type   = s.type
    x.flags  = s.flags
    x.vaddr  = s.vaddr
    x.off    = s.off
    x.siz    = s.siz
    x.link   = link_value.call(s.link) 
    x.info   = link_value.call(s.info)
    x.addralign  = s.align
    x.entsize= s.entsize
   # x.flags |= SHF::SHF_ALLOC if(@file.gnu_tls.tbss == s)
    x
  }
  #remove
  mapped = @sections.select{|x| x.flags & SHF::SHF_ALLOC != 0}.sort_by(&:vaddr)
  mapped.each_cons(2){|low,high| expect_value "Mapped sections should not overlap", true,low.vaddr + low.siz<= high.vaddr}
  load = mapped.group_by(&:flags).map{|flags,sections| 
    sections.group_by{|x| x.vaddr - x.off}.map do |align,sections|
      memsize = sections.last.off + sections.last.siz - sections.first.off
     # if sections.last.type == SHT::SHT_            end
    # sections.select{|x| x.type == SHT::SHT_NOBITS}.tap {|nobits|
    #    if nobits.size > 0
     #     expect_value "At most one NOBITS", nobits.size,1
     #     expect_value "NOBITS is the last section",sections.last.type, SHT::SHT_NOBITS
     #     last_file_addr = nobits.first.vaddr
     #     memsize = sections.last.off - sections.first.off
     #   end
     # } 
      LoadMap.new(sections.first.off,  sections.last.off + sections.last.siz,
                  sections.first.vaddr, memsize ,flags,sections.map(&:align).max) #TODO: LCM?
    end
  }.flatten     
  buf.seek 0,IO::SEEK_END
  
  shdrs << shstrtab(buf)
  filehdr.shstrndx = shdrs.size - 1
  filehdr.shoff = buf.tell 
  filehdr.shentsize = shdrs[0].num_bytes
  filehdr.shnum = shdrs.size
  shdrs.write buf      
  
  buf.seek roundup(buf.tell, PAGESIZE)-1
  buf.write '\0' # pad to pagesize
  buf.seek phdr_off
  write_phdrs(buf,filehdr,load)
end