A reader for LC_SEGMENT or LC_SEGMENT_64 load commands in Mach-O images mapped into another process. More...

#include "snapshot/mac/mach_o_image_segment_reader.h"

Public Member Functions
bool	Initialize (ProcessReaderMac *process_reader, mach_vm_address_t load_command_address, const std::string &load_command_info, const std::string &module_name, uint32_t file_type)
	Reads the segment load command from another process. More...

void	SetSlide (mach_vm_size_t slide)
	Sets the image’s slide value. More...

std::string	Name () const
	Returns the segment’s name. More...

mach_vm_address_t	Address () const

mach_vm_address_t	Size () const

mach_vm_address_t	vmaddr () const
	The segment’s preferred load address. More...

mach_vm_size_t	vmsize () const
	Returns the segment’s size as mapped into memory. More...

mach_vm_size_t	fileoff () const
	Returns the file offset of the mapped segment in the file from which it was mapped. More...

uint32_t	nsects () const
	Returns the number of sections in the segment. More...

const process_types::section *	GetSectionByName (const std::string &section_name, mach_vm_address_t *address) const
	Obtain section information by section name. More...

const process_types::section *	GetSectionAtIndex (size_t index, mach_vm_address_t *address) const
	Obtain section information by section index. More...

bool	SegmentSlides () const

Static Public Member Functions
static std::string	SegmentNameString (const char *segment_name_c)
	Returns a segment name string. More...

static std::string	SectionNameString (const char *section_name_c)
	Returns a section name string. More...

static std::string	SegmentAndSectionNameString (const char segment_name_c, const char section_name_c)
	Returns a segment and section name string. More...

Detailed Description

A reader for LC_SEGMENT or LC_SEGMENT_64 load commands in Mach-O images mapped into another process.

This class is capable of reading both LC_SEGMENT and LC_SEGMENT_64 based on the bitness of the remote process.

A MachOImageSegmentReader will normally be instantiated by a MachOImageReader.

Member Function Documentation

◆ Address()

mach_vm_address_t crashpad::MachOImageSegmentReader::Address ( ) const

Returns: The segment’s actual load address in memory, adjusted for any “slide”.

Note: For the segment’s preferred load address, not adjusted for slide, use vmaddr().

◆ fileoff()

mach_vm_size_t crashpad::MachOImageSegmentReader::fileoff ( ) const

inline

Returns the file offset of the mapped segment in the file from which it was mapped.

The file offset is the difference between the beginning of the mach_header or mach_header_64 and the beginning of the segment’s mapped region. For segments that are not mapped from a file (such as __PAGEZERO segments), this will be 0.

◆ GetSectionAtIndex()

const process_types::section * crashpad::MachOImageSegmentReader::GetSectionAtIndex	(	size_t	index,
		mach_vm_address_t *	address
	)		const

Obtain section information by section index.

Parameters

[in]	index	The index of the section to return, in the order that it appears in the segment load command. Unlike MachOImageReader::GetSectionAtIndex(), this is a 0-based index. This parameter must be in the range of valid indices aas reported by nsects().
[out]	address	The actual address that the section was loaded at in memory, taking any “slide” into account if the section did not load at its preferred address as stored in the Mach-O image file. This parameter can be `nullptr`.

Returns: A pointer to the section information. If index is out of range, execution is aborted. The caller does not take ownership; the lifetime of the returned object is scoped to the lifetime of this MachOImageSegmentReader object.

Note: The process_types::section::addr field gives the section’s preferred load address as stored in the Mach-O image file, and is not adjusted for any “slide” that may have occurred when the image was loaded.; Unlike MachOImageReader::GetSectionAtIndex(), this method does not accept out-of-range values for index, and aborts execution instead of returning nullptr upon encountering an out-of-range value. This is because this method is expected to be used in a loop that can be limited to nsects() iterations, so an out-of-range error can be treated more harshly as a logic error, as opposed to a data error.

See also: MachOImageReader::GetSectionAtIndex()

◆ GetSectionByName()

const process_types::section * crashpad::MachOImageSegmentReader::GetSectionByName	(	const std::string &	section_name,
		mach_vm_address_t *	address
	)		const

Obtain section information by section name.

Parameters

[in]	section_name	The name of the section to search for, without the leading segment name. For example, use `"__text"`, not `"__TEXT,__text"` or `"__TEXT.__text"`.
[out]	address	The actual address that the section was loaded at in memory, taking any “slide” into account if the section did not load at its preferred address as stored in the Mach-O image file. This parameter can be `nullptr`.

Returns: A pointer to the section information if it was found, or nullptr if it was not found. The caller does not take ownership; the lifetime of the returned object is scoped to the lifetime of this MachOImageSegmentReader object.

Note: The process_types::section::addr field gives the section’s preferred load address as stored in the Mach-O image file, and is not adjusted for any “slide” that may have occurred when the image was loaded.

See also: MachOImageReader::GetSectionByName()

◆ Initialize()

bool crashpad::MachOImageSegmentReader::Initialize	(	ProcessReaderMac *	process_reader,
		mach_vm_address_t	load_command_address,
		const std::string &	load_command_info,
		const std::string &	module_name,
		uint32_t	file_type
	)

Reads the segment load command from another process.

This method must only be called once on an object. This method must be called successfully before any other method in this class may be called.

Parameters

[in]	process_reader	The reader for the remote process.
[in]	load_command_address	The address, in the remote process’ address space, where the `LC_SEGMENT` or `LC_SEGMENT_64` load command to be read is located. This address is determined by a Mach-O image reader, such as MachOImageReader, as it walks Mach-O load commands.
[in]	load_command_info	A string to be used in logged messages. This string is for diagnostic purposes only, and may be empty.
[in]	module_name	The path used to load the module. This string is used to relax otherwise strict parsing rules for common modules with known defects.
[in]	file_type	The module’s Mach-O file type. This is used to relax otherwise strict parsing rules for common modules with known defects.

Returns: true if the load command was read successfully. false otherwise, with an appropriate message logged.

◆ Name()

std::string crashpad::MachOImageSegmentReader::Name ( ) const

Returns the segment’s name.

The segment’s name is taken from the load command’s segname field. Common segment names are "__TEXT", "__DATA", and "__LINKEDIT". Symbolic constants for these common names are defined in <mach-o/loader.h>.

◆ nsects()

uint32_t crashpad::MachOImageSegmentReader::nsects ( ) const

inline

Returns the number of sections in the segment.

This will return 0 for a segment without any sections, typical for __PAGEZERO and __LINKEDIT segments.

Although the Mach-O file format uses a uint32_t for this field, there is an overall limit of 255 sections in an entire Mach-O image file (not just in a single segment) imposed by the symbol table format. Symbols will not be able to reference anything in a section beyond the first 255 in a Mach-O image file.

◆ SectionNameString()

std::string crashpad::MachOImageSegmentReader::SectionNameString ( const char * section_name_c )

static

Returns a section name string.

Section names may be 16 characters long, and are not necessarily NUL-terminated. This function will return a section name based on up to the first 16 characters found at section_name_c.

◆ SegmentAndSectionNameString()

std::string crashpad::MachOImageSegmentReader::SegmentAndSectionNameString	(	const char *	segment_name_c,
		const char *	section_name_c
	)

static

Returns a segment and section name string.

A segment and section name string is composed of a segment name string (see SegmentNameString()) and a section name string (see SectionNameString()) separated by a comma. An example is "__TEXT,__text".

◆ SegmentNameString()

std::string crashpad::MachOImageSegmentReader::SegmentNameString ( const char * segment_name_c )

static

Returns a segment name string.

Segment names may be 16 characters long, and are not necessarily NUL-terminated. This function will return a segment name based on up to the first 16 characters found at segment_name_c.

◆ SegmentSlides()

bool crashpad::MachOImageSegmentReader::SegmentSlides ( ) const

Returns whether the segment slides.

Most segments slide, but the __PAGEZERO segment does not, it grows instead. This method identifies non-sliding segments in the same way that the kernel does.

◆ SetSlide()

void crashpad::MachOImageSegmentReader::SetSlide ( mach_vm_size_t slide )

Sets the image’s slide value.

This method must only be called once on an object, after Initialize() is called successfully. It must be called before Address(), Size(), GetSectionByName(), or GetSectionAtIndex() can be called.

This method is provided because slide is a property of the image that cannot be determined until at least some segments have been read. As such, it is not necessarily known at the time that Initialize() is called.

◆ Size()

mach_vm_size_t crashpad::MachOImageSegmentReader::Size ( ) const

Returns: The segment’s actual size address in memory, adjusted for any growth in the case of a nonsliding segment.

Note: For the segment’s preferred size, not adjusted for growth, use vmsize().

◆ vmaddr()

mach_vm_address_t crashpad::MachOImageSegmentReader::vmaddr ( ) const

inline

The segment’s preferred load address.

Returns: The segment’s preferred load address as stored in the Mach-O file.

Note: This value is not adjusted for any “slide” that may have occurred when the image was loaded. Use Address() for a value adjusted for slide.

See also: MachOImageReader::GetSegmentByName()

◆ vmsize()

mach_vm_size_t crashpad::MachOImageSegmentReader::vmsize ( ) const

inline

Returns the segment’s size as mapped into memory.

Note: For non-sliding segments, this value is not adjusted for any growth that may have occurred when the image was loaded. Use Size() for a value adjusted for growth.

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

snapshot/mac/mach_o_image_segment_reader.h
snapshot/mac/mach_o_image_segment_reader.cc

Public Member Functions

Static Public Member Functions

Detailed Description

Member Function Documentation

◆ Address()

◆ fileoff()

◆ GetSectionAtIndex()

◆ GetSectionByName()

◆ Initialize()

◆ Name()

◆ nsects()

◆ SectionNameString()

◆ SegmentAndSectionNameString()

◆ SegmentNameString()

◆ SegmentSlides()

◆ SetSlide()

◆ Size()

◆ vmaddr()

◆ vmsize()