A section of data as read from an object file. More...

#include <section.h>

Inheritance diagram for Linker::Section:

Public Types
enum	section_flags { Readable = 1 << 0 , Writable = 1 << 1 , Execable = 1 << 2 , Mergeable = 1 << 3 , ZeroFilled = 1 << 4 , Fixed = 1 << 5 , Resource = 1 << 6 , Optional = 1 << 7 , Stack = 1 << 8 , Heap = 1 << 9 , CustomFlag = 1 << 10 }
	Possible flags for the section. More...

Public Member Functions
	Section (std::string name, int flags=Readable)

void	SetFlag (unsigned newflags)
	Sets the flags of the section.

unsigned	GetFlags () const

bool	IsReadable () const

void	SetReadable (bool state)

bool	IsWritable () const

void	SetWritable (bool state)

bool	IsExecable () const

void	SetExecable (bool state)

bool	IsMergeable () const

void	SetMergeable (bool state)

bool	IsFixed () const

bool	IsZeroFilled () const

offset_t	SetZeroFilled (bool is_zero_filled)

offset_t	GetAlign () const

void	SetAlign (offset_t new_align)

offset_t	GetStartAddress () const

offset_t	SetAddress (offset_t new_address)
	For non-fixed segments, sets the starting address and makes the fixed.

void	ResetAddress (offset_t new_address)
	Forcibly alters the starting address.

offset_t	Size () const

offset_t	Expand (offset_t new_size)
	Increases the size of the section by the specified amount.

offset_t	RealignEnd (offset_t align)
	Expands the section to a size such that its end is at a specified alignment.

int	GetByte (offset_t offset) override
	Retrieve byte at a certain offset (optional, might not be defined)

uint64_t	ReadUnsigned (size_t bytes, offset_t offset, EndianType endiantype) const

uint64_t	ReadUnsigned (size_t bytes, offset_t offset) const

int64_t	ReadSigned (size_t bytes, offset_t offset, EndianType endiantype) const

uint64_t	ReadSigned (size_t bytes, offset_t offset) const

void	WriteWord (size_t bytes, offset_t offset, uint64_t value, EndianType endiantype)

void	WriteWord (size_t bytes, offset_t offset, uint64_t value)

void	WriteWord (size_t bytes, uint64_t value, EndianType endiantype)
	Writes value at the current end of the section.

void	WriteWord (size_t bytes, uint64_t value)
	Writes value at the current end of the section.

offset_t	Append (const void *new_data, size_t length)
	Appends data at the end of a section.

offset_t	Append (const char *new_data)
	Appends data at the end of a section.

offset_t	Append (const Section &other)
	Appends (or merges) another section.

offset_t	Append (Buffer &buffer)
	Appends (or merges) another writable buffer.

Position	Start () const
	Retrieves the address of the first byte of the section.

Position	Base () const
	Retrieves the address of the start of the segment of the section.

void	ReadFile (std::istream &in)
	Overwrites section data with contents of input stream.

void	ReadFile (Reader &in)
	Overwrites section data with contents of input stream.

offset_t	WriteFile (std::ostream &out, offset_t size, offset_t offset=0) const
	Writes data into file.

offset_t	WriteFile (std::ostream &out) const
	Writes data into file.

void	Reset ()
	Clear the section.

Public Member Functions inherited from Linker::Buffer
	Buffer (size_t size)

offset_t	ActualDataSize () override
	Retrieves size of stored data.

void	ReadFile (Reader &rd)

void	ReadFile (Reader &rd, offset_t count)

offset_t	WriteFile (Writer &wr, offset_t count, offset_t offset=0) override
	Writes data of non-zero filled sections.

virtual offset_t	WriteFile (Writer &wr, offset_t count, offset_t offset=0)=0
	Writes data of non-zero filled sections.

offset_t	WriteFile (Writer &wr)
	Writes data of non-zero filled sections.

Public Member Functions inherited from Linker::Writable
offset_t	WriteFile (Writer &wr)
	Writes data of non-zero filled sections.

Static Public Member Functions
static std::shared_ptr< Section >	ReadFromFile (Reader &rd, std::string name, int flags=Readable)

static std::shared_ptr< Section >	ReadFromFile (Reader &rd, offset_t count, std::string name, int flags=Readable)

Static Public Member Functions inherited from Linker::Buffer
static std::shared_ptr< Buffer >	ReadFromFile (Reader &rd)

static std::shared_ptr< Buffer >	ReadFromFile (Reader &rd, offset_t count)

Public Attributes
std::string	name
	Name of the section.

section_flags	flags
	The type of the section.

offset_t	bias = 0
	Difference between the first byte of the section and the zero address associated with the section.

std::variant< std::string, uint16_t >	resource_type = " "
	The resource type and ID for a resource section.

std::variant< std::string, uint16_t >	resource_id = uint16_t(0)

std::weak_ptr< Segment >	segment
	The segment a section belongs to.

std::string	collection_name
	Section name that collects sections.

Additional Inherited Members
Protected Attributes inherited from Linker::Buffer
std::vector< uint8_t >	data

Detailed Description

A section of data as read from an object file.

A section represents a series of bytes within an object file, executable or memory image. For segmented architectures such as the 8086, it also represents a segment group at the final stages of linking (once all similar sections have been combined), where each symbol belonging to the same segment will have the same preferred segment base.

Member Enumeration Documentation

◆ section_flags

enum Linker::Section::section_flags

Possible flags for the section.

Enumerator
Readable	The data in the section can be read at runtime.
Writable	The section can be written to at runtime.
Execable	The section data can be used as instruction.
Mergeable	Sections of the same name with this flag are overlayed instead of appended. When the sections are zero filled, merged sections will have a size that is the maximum of the merged sections instead of their sum. For sections with data, only the longer one is kept. They are assumed to have identical data. TODO: unimplemented
ZeroFilled	Section is filled with zeros. Most formats do not require sections that are zero filled to be stored in the binary image. We keep track of which sections are zero filled using this flag.
Fixed	Section resides at a fixed address and cannot be moved. When generating code, all sections are assigned starting addresses and are converted to fixed sections.
Resource	Section data represents a resource that has to be handled differently. The NE, LE/LX, PE and classic Macintosh file formats support storing resources within their binary images. To ease usage, these resources can be stored in the object file instead of requiring a separate resource file.
Optional	Section data may be unallocated if necessary. Reserved for file formats such as MZFormat and CPM86Format where additional memory can be requested.
Stack	Stack section.
Heap	Heap section.
CustomFlag	Other flags.

Member Function Documentation

◆ Base()

Position Section::Base ( ) const

Retrieves the address of the start of the segment of the section.

For Intel 8086, it is expected that the data in a segment does not begin at the same location as the base of the segment.

◆ Expand()

offset_t Section::Expand ( offset_t new_size )

Increases the size of the section by the specified amount.

Parameters

new_size The new size for the section. If it is smaller than the current size, nothing is changed.

Returns: The actual amount of bytes the section was increased by.

◆ GetByte()

int Section::GetByte ( offset_t offset )

overridevirtual

Retrieve byte at a certain offset (optional, might not be defined)

Reimplemented from Linker::Buffer.

◆ ReadFile() [1/2]

void Section::ReadFile ( Reader & in )

Overwrites section data with contents of input stream.

Note that only as many bytes are read in as the size of the section.

◆ ReadFile() [2/2]

void Section::ReadFile ( std::istream & in )

Overwrites section data with contents of input stream.

Note that only as many bytes are read in as the size of the section.

◆ SetAddress()

offset_t Section::SetAddress ( offset_t new_address )

For non-fixed segments, sets the starting address and makes the fixed.

If the segment is already fixed, the address is not changed. Alignment requirements might cause the new address to be incremented.

Parameters

new_address Attempted starting address

Returns: The new starting address

◆ SetFlag()

void Section::SetFlag ( unsigned newflags )

Sets the flags of the section.

Certain flags require special handling.

◆ WriteFile() [1/2]

offset_t Section::WriteFile ( std::ostream & out ) const

Writes data into file.

Note that zero filled sections do not write anything.

Parameters

out	Output stream

Returns: Count of actual number of bytes written

◆ WriteFile() [2/2]

offset_t Section::WriteFile	(	std::ostream &	out,
		offset_t	size,
		offset_t	offset = 0 ) const

Writes data into file.

Note that zero filled sections do not write anything.

Parameters

out	Output stream
size	Maximum number of bytes to write

Returns: Count of actual number of bytes written

Member Data Documentation

◆ bias

offset_t Linker::Section::bias = 0

Difference between the first byte of the section and the zero address associated with the section.

On the Intel 8086, addresses consist of two parts: a segment address and an offset within that segment. The linker collects sections and assigns them to segments, which often map to hardware segments. On some platforms, the address of the first byte of a section will not be the same as the address of the beginning of the hardware segment it belongs to. The bias field stores this difference.

For example, the first byte of a .com file will have an address 0x100. This is represented by setting the bias to -0x100.

◆ resource_type

std::variant<std::string, uint16_t> Linker::Section::resource_type = " "

The resource type and ID for a resource section.

All resources can have a resource type and a resource ID that can usually be a string or an integer. Some platforms specify which one is which (for example, Macintosh resources have a 4-character type but a 16-bit ID). For others (for example, the NE format), they can be either.

◆ segment

std::weak_ptr<Segment> Linker::Section::segment

The segment a section belongs to.

This field is assigned as part of the linking process.

The documentation for this class was generated from the following files:

src/linker/section.h
src/linker/section.cc

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

◆ section_flags

Member Function Documentation

◆ Base()

◆ Expand()

◆ GetByte()

◆ ReadFile() [1/2]

◆ ReadFile() [2/2]

◆ SetAddress()

◆ SetFlag()

◆ WriteFile() [1/2]

◆ WriteFile() [2/2]

Member Data Documentation

◆ bias

◆ resource_type

◆ segment