NAME

dwarf_get_ranges — retrieve non-contiguous address ranges

LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

#include <libdwarf.h>

int
dwarf_get_ranges(Dwarf_Debug dbg, Dwarf_Off offset, Dwarf_Ranges **ranges, Dwarf_Signed *cnt, Dwarf_Unsigned *byte_cnt, Dwarf_Error *err);

int
dwarf_get_ranges_a(Dwarf_Debug dbg, Dwarf_Off offset, Dwarf_Die die, Dwarf_Ranges **ranges, Dwarf_Signed *cnt, Dwarf_Unsigned *byte_cnt, Dwarf_Error *err);

DESCRIPTION

Function dwarf_get_ranges() retrieves information about the non-contiguous address ranges associated with a DWARF debugging information entry. Information about address ranges is returned as an array of descriptors of type Dwarf_Ranges, with each Dwarf_Ranges descriptor describing one address range entry.

Argument dbg should reference a DWARF debug context allocated using dwarf_init(3).

Argument offset is an offset, relative to the “.debug_ranges” section, to the start of the desired list of address ranges. The offset of an address ranges list is indicated by the DW_AT_ranges attribute of a debugging information entry.

Argument die (function dwarf_get_ranges_a() only) is ignored in this implementation; see the section Compatibility Notes below.

Argument ranges should point to a location that will be set to a pointer to an array of Dwarf_Ranges descriptors.

Argument cnt should point to a location that will be set to the number of entries returned. If argument byte_cnt is not NULL, it will be set to the number of bytes occupied by the returned entries in the “.debug_ranges” section.

If argument err is not NULL, it will be used to store error information in case of an error.

Dwarf_Ranges descriptors are defined in the header file <libdwarf.h>, and consists of the following fields:

dwr_addr1

The first address offset, whose meaning depends on the type of the entry.

dwr_addr2

The second address offset, whose meaning depends on the type of the entry.

dwr_type

The type of this address range entry:

DW_RANGES_ENTRY: A range list entry. For this type of entry, the fields dwr_addr1 and dwr_addr2 hold the beginning and ending offsets of the address range, respectively.
DW_RANGES_ADDRESS_SELECTION: A base address selection entry. For this type of entry, the field dwr_addr1 is the value of the largest representable address offset, and dwr_addr2 is a base address for the beginning and ending address offsets of subsequent address range entries in the list.
DW_RANGES_END: An end of list mark. Both dwr_addr1 and dwr_addr2 are set to 0.

Memory Management

The memory area used for the array of Dwarf_Ranges descriptors returned in argument ranges is owned by the DWARF Access Library (libdwarf, -ldwarf). The application should not attempt to directly free this pointer. Portable code should instead use dwarf_ranges_dealloc() to indicate that the memory may be freed.

RETURN VALUES

These functions return DW_DLV_OK when they succeed. They return DW_DLV_NO_ENTRY if there is no address range list at the specified offset offset. In case of an error, they return DW_DLV_ERROR and set the argument err.

EXAMPLES

To retrieve the address range list associated with a debugging information entry, use:

Dwarf_Debug dbg;
Dwarf_Die die;
Dwarf_Error de;
Dwarf_Addr base;
Dwarf_Attribute *attr_list;
Dwarf_Ranges *ranges;
Dwarf_Signed cnt;
Dwarf_Unsigned off, attr_count, bytecnt;
int i, j;

if ((ret = dwarf_attrlist(die, &attr_list, &attr_count, &de)) !=
    DW_DLV_OK)
	errx(EXIT_FAILURE, "dwarf_attrlist failed: %s",
	    dwarf_errmsg(de));

for (i = 0; (Dwarf_Unsigned) i < attr_count; i++) {
	if (dwarf_whatattr(attr_list[i], &attr, &de) != DW_DLV_OK) {
		warnx("dwarf_whatattr failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (attr != DW_AT_ranges)
		continue;
	if (dwarf_formudata(attr_list[i], &off, &de) != DW_DLV_OK) {
		warnx("dwarf_formudata failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (dwarf_get_ranges(dbg, (Dwarf_Off) off, &ranges, &cnt,
	    &bytecnt, &de) != DW_DLV_OK)
		continue;
	for (j = 0; j < cnt; j++) {
		if (ranges[j].dwr_type == DW_RANGES_END)
			break;
		else if (ranges[j].dwr_type ==
		    DW_RANGES_ADDRESS_SELECTION)
			base = ranges[j].dwr_addr2;
		else {
			/*
			 * DW_RANGES_ENTRY entry.
			 * .. Use dwr_addr1 and dwr_addr2 ..
			 */
		}
	}
}

COMPATIBILITY

Function dwarf_get_ranges_a() is identical to dwarf_get_ranges(), except that it requires one additional argument die denoting the debugging information entry associated with the address range list. In this implementation of the DWARF Access Library (libdwarf, -ldwarf), the argument die is ignored, and function dwarf_get_ranges_a() is only provided for compatibility with other implementations of the DWARF(3) API.

ERRORS

These function can fail with:

[DW_DLE_ARGUMENT]: One of the arguments dbg, ranges or cnt was NULL.
[DW_DLE_NO_ENTRY]: There is no address range list at the specified offset offset.