Object Access Functions

The data structures used to specify object access methods are defined in <libdwarf.h>.

Dwarf_Obj_Access_Interface

This structure bundles together a set of file access methods along with a pointer to application-private state.

typedef struct {
	void *object;
	const Dwarf_Obj_Access_Methods *methods;
} Dwarf_Obj_Access_Interface;

object

This field points to application-specific state that will be passed as the first parameter to the actual access object methods.

methods

This structure contains pointers to the functions implementing the access methods, as described below.

Dwarf_Obj_Access_Methods

This structure specifies the functions implementing low-level access.

typedef struct {
	int (*get_section_info)(void *obj, Dwarf_Half index,
	    Dwarf_Obj_Access_Section *ret, int *error);
	Dwarf_Endianness (*get_byte_order)(void *obj);
	Dwarf_Small (*get_length_size)(void *obj);
	Dwarf_Small (*get_pointer_size)(void *obj);
	Dwarf_Unsigned (*get_section_count)(void *obj);
	int (*load_section)(void *obj, Dwarf_Half ndx,
	    Dwarf_Small **ret_data, int *error);
} Dwarf_Obj_Access_Methods;

get_byte_order

This function should return the endianness of the DWARF object by returning one of the constants DW_OBJECT_MSB or DW_OBJECT_LSB.

get_length_size

This function should return the number of bytes needed to represent a DWARF offset in the object being debugged.

get_pointer_size

This function should return the size in bytes, in the object being debugged, of a memory address.

get_section_count

This function should return the number of sections in the object being debugged.

get_section_info

This function should return information about the section at the index ndx by filling in the structure of type Dwarf_Obj_Access_Section pointed to by argument ret. The Dwarf_Obj_Access_Section structure is described below.

load_section

This function should load the section specified by argument ndx into memory and place a pointer to the section's data into the location pointed to by argument ret_data.

The argument obj passed to these functions will be set to the pointer value in the object field of the associated Dwarf_Obj_Access_Interface structure.

The argument error is used to return an error code in case of an error.

Dwarf_Obj_Access_Section

This structure describes the layout of a section in the DWARF object.

typedef struct {
	Dwarf_Addr addr;
	Dwarf_Unsigned size;
	const char *name;
} Dwarf_Obj_Access_Section;

addr

A pointer to the start of the section's data.

size

The size of the section in bytes.

name

A pointer to a NUL-terminated string containing the name of the section.