NAME

dwarf_get_fde_list —

retrieve frame information

LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

#include <libdwarf.h>

int
dwarf_get_fde_list(Dwarf_Debug dbg, Dwarf_Cie **cie_list, Dwarf_Signed *cie_count, Dwarf_Fde **fde_list, Dwarf_Signed *fde_count, Dwarf_Error *err);

int
dwarf_get_fde_list_eh(Dwarf_Debug dbg, Dwarf_Cie **cie_list, Dwarf_Signed *cie_count, Dwarf_Fde **fde_list, Dwarf_Signed *fde_count, Dwarf_Error *err);

DESCRIPTION

These functions retrieve frame related information for the specified DWARF debug context.

Function dwarf_get_fde_list() retrieves frame information from the DWARF section named “.debug_frame”. For objects containing GNU style C++ exception handling information, the function dwarf_get_fde_list_eh() retrieves frame information from the section named “.eh_frame”.

Frame information is returned using opaque descriptors of type Dwarf_Cie and Dwarf_Fde. Applications need to use the other frame related functions in the DWARF(3) API set to retrieve the information contained in these descriptors.

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

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

Argument cie_count should point to a location that will be set to the number of Dwarf_Cie descriptors returned.

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

Argument fde_count should point to a location that will be set to the number of Dwarf_Fde descriptors returned.

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

Memory Management

The memory areas used for the arrays returned in arguments cie_list and fde_list are owned by the DWARF Access Library (libdwarf, -ldwarf). Application code should not attempt to directly free these areas. Portable applications should instead use the dwarf_fde_cie_list_dealloc(3) function to indicate that these memory areas may be freed.

RETURN VALUES

On success, these functions returns DW_DLV_OK. They return DW_DLV_NO_ENTRY if there is no frame information associated with the given DWARF debug context. In case of an error, they return DW_DLV_ERROR and set the argument err.

EXAMPLES

To obtain frame information from the “.debug_frame” section, use:

Dwarf_Debug dbg;
Dwarf_Cie *cie_list, cie;
Dwarf_Fde *fde_list, fde;
Dwarf_Off fde_offset, cie_offset;
Dwarf_Unsigned func_len, fde_length, fde_instlen;
Dwarf_Signed cie_count, fde_count, cie_index;
Dwarf_Addr low_pc;
Dwarf_Ptr fde_addr, fde_inst, cie_inst;
Dwarf_Error de;
int i;

if (dwarf_get_fde_list(dbg, &cie_list, &cie_count,
    &fde_list, &fde_count, &de) != DW_DLV_OK) {
	errx(EXIT_FAILURE, "dwarf_get_fde_list failed: %s",
	    dwarf_errmsg(de));
}

for (i = 0; i < fde_count; i++) {
	if (dwarf_get_fde_n(fde_list, i, &fde, &de) != DW_DLV_OK) {
		warnx("dwarf_get_fde_n failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (dwarf_get_cie_of_fde(fde, &cie, &de) != DW_DLV_OK) {
		warnx("dwarf_get_fde_n failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (dwarf_get_fde_range(fde, &low_pc, &func_len, &fde_addr,
	    &fde_length, &cie_offset, &cie_index, &fde_offset,
	    &de) != DW_DLV_OK) {
		warnx("dwarf_get_fde_range failed: %s",
		    dwarf_errmsg(de));
		continue;
	}
	if (dwarf_get_fde_instr_bytes(fde, &fde_inst, &fde_instlen,
	    &de) != DW_DLV_OK) {
		warnx("dwarf_get_fde_instr_bytes failed: %s",
		    dwarf_errmsg(de));
		continue;
	}

	/* ... Use the retrieved frame information ... */
}

/* Indicate that the returned arrays may be freed. */
dwarf_fde_cie_list_dealloc(dbg, cie_list, cie_count, fde_list,
    fde_count);

ERRORS

These functions may fail with the following errors:

[DW_DLE_ARGUMENT]: One of the arguments dbg, cie_list, cie_count, fde_list or fde_count was NULL.
[DW_DLE_NO_ENTRY]: There is no frame information associated with the giving DWARF debug context.