1.\" $NetBSD: dwarf_init.3,v 1.2 2014/03/09 16:58:04 christos Exp $ 2.\" 3.\" Copyright (c) 2009 Joseph Koshy. All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" This software is provided by Joseph Koshy ``as is'' and 15.\" any express or implied warranties, including, but not limited to, the 16.\" implied warranties of merchantability and fitness for a particular purpose 17.\" are disclaimed. in no event shall Joseph Koshy be liable 18.\" for any direct, indirect, incidental, special, exemplary, or consequential 19.\" damages (including, but not limited to, procurement of substitute goods 20.\" or services; loss of use, data, or profits; or business interruption) 21.\" however caused and on any theory of liability, whether in contract, strict 22.\" liability, or tort (including negligence or otherwise) arising in any way 23.\" out of the use of this software, even if advised of the possibility of 24.\" such damage. 25.\" 26.\" Id: dwarf_init.3 2122 2011-11-09 15:35:14Z jkoshy 27.\" 28.Dd November 9, 2011 29.Os 30.Dt DWARF_INIT 3 31.Sh NAME 32.Nm dwarf_init , 33.Nm dwarf_elf_init 34.Nd allocate a DWARF debug descriptor 35.Sh LIBRARY 36.Lb libdwarf 37.Sh SYNOPSIS 38.In libdwarf.h 39.Ft int 40.Fo dwarf_init 41.Fa "int fd" 42.Fa "int mode" 43.Fa "Dwarf_Handler errhand" 44.Fa "Dwarf_Ptr errarg" 45.Fa "Dwarf_Debug *ret" 46.Fa "Dwarf_Error *err" 47.Fc 48.Ft in 49.Fo dwarf_elf_init 50.Fa "Elf *elf" 51.Fa "int mode" 52.Fa "Dwarf_Handler errhand" 53.Fa "Dwarf_Ptr errarg" 54.Fa "Dwarf_Debug *ret" 55.Fa "Dwarf_Error *err" 56.Fc 57.Sh DESCRIPTION 58These functions allocate and return a 59.Vt Dwarf_Debug 60instance for the object denoted by argument 61.Ar fd 62or 63.Ar elf . 64This instance would be used for subsequent access to debugging information in the object by other functions in the DWARF(3) library. 65.Pp 66For function 67.Fn dwarf_init , 68argument 69.Ar fd 70denotes an open file descriptor referencing a compilation object. 71Function 72.Fn dwarf_init 73implicitly allocates an 74.Vt Elf 75descriptor for argument 76.Ar fd . 77.Pp 78For function 79.Fn dwarf_elf_init , 80argument 81.Ar elf 82denotes a descriptor returned by 83.Xr elf_begin 3 84or 85.Xr elf_memory 3 . 86.Pp 87Argument 88.Ar mode 89specifies the access mode desired. 90It should be at least as permissive as the mode with which 91the file descriptor 92.Ar fd 93or the ELF descriptor 94.Ar elf 95was created with. 96Legal values for argument 97.Ar mode 98are: 99.Pp 100.Bl -tag -width "DW_DLC_WRITE" -compact 101.It DW_DLC_RDWR 102Permit reading and writing of DWARF information. 103.It DW_DLC_READ 104Operate in read-only mode. 105.It DW_DLC_WRITE 106Permit writing of DWARF information. 107.El 108.Pp 109Argument 110.Ar errhand 111denotes a function to be called in case of an error. 112If this argument is 113.Dv NULL 114then a default error handling scheme is used. 115See 116.Xr dwarf 3 117for a description of the error handling scheme used by the 118DWARF(3) library. 119.Pp 120Argument 121.Ar errarg 122is passed to the error handler function denoted by argument 123.Ar errhand 124when it is invoked. 125.Pp 126Argument 127.Ar ret 128points to the memory location that will hold a 129.Vt Dwarf_Debug 130reference on a successful call these functions. 131.Pp 132Argument 133.Ar err 134references a memory location that would hold a 135.Vt Dwarf_Error 136descriptor in case of an error. 137.Ss Memory Management 138The 139.Vt Dwarf_Debug 140instance returned by these functions should be freed using 141.Fn dwarf_finish . 142.Sh RETURN VALUES 143These functions return the following values: 144.Bl -tag -width ".Bq Er DW_DLV_NO_ENTRY" 145.It Bq Er DW_DLV_OK 146This return value indicates a successful return. 147.It Bq Er DW_DLV_ERROR 148The operation failed. 149.It Bq Er DW_DLV_NO_ENTRY 150The object specified by arguments 151.Ar "fd" 152or 153.Ar "elf" 154did not contain debug information. 155.El 156.Sh IMPLEMENTATION NOTES 157The current implementation does not support access modes 158.Dv DW_DLC_RDWR 159and 160.Dv DW_DLC_WRITE . 161.Sh EXAMPLES 162To initialize a 163.Vt Dwarf_Debug 164instance from a open file descriptor referencing an ELF object, and 165with the default error handler, use: 166.Bd -literal -offset indent 167Dwarf_Error err; 168Dwarf_Debug dbg; 169 170if (dwarf_init(fd, DW_DLC_READ, NULL, NULL, &dbg, &err) != 171 DW_DLV_OK) 172 errx(EXIT_FAILURE, "dwarf_init: %s", dwarf_errmsg(err)); 173.Ed 174.Sh SEE ALSO 175.Xr dwarf 3 , 176.Xr dwarf_errmsg 3 , 177.Xr dwarf_finish 3 , 178.Xr dwarf_get_elf 3 , 179.Xr elf_begin 3 , 180.Xr elf_memory 3 181