path: root/usr/src/man/man1/elfedit.1

'\" te
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.TH ELFEDIT 1 "May 17, 2020"
.SH NAME
elfedit \- examine or edit ELF files
.SH SYNOPSIS
.nf
\fBelfedit\fR [\fB-adr\fR] [\fB-e\fR \fIcmd\fR] [\fB-L\fR \fIpath\fR] [\fB-o\fR \fBdefault\fR | \fBsimple\fR | \fBnum\fR]
     [\fIinfile\fR] [\fIoutfile\fR]
.fi

.SH DESCRIPTION
\fBelfedit\fR is a tool for examining or modifying the contents of an existing
ELF object. Specifically, \fBelfedit\fR is used to modify the ELF metadata
contained in the object. Access is provided to most of the ELF data contained
in an object, including the ELF header, section header table, program header
table, dynamic section, hardware and software capabilities, string tables, and
symbol tables.
.SS "Syntax"
\fBelfedit\fR processes commands from the command line (\fB-e\fR option) or
from standard input. If standard input is a terminal, \fBelfedit\fR provides
terminal editing capabilities, as well as extensive command completion. ELF
uses many standard symbolic names for special integer values and bit masks.
\fBelfedit\fR is aware of most possible completions for such names. You can
press TAB at any point while entering an \fBelfedit\fR command to cause
\fBelfedit\fR to display a usage message and any known completions for the text
at the current cursor.
.sp
.LP
\fBelfedit\fR functionality is organized in the form of modules. Each module
delivers a set of commands, focused on related functionality. A command is
specified by combining the module and command names with a colon (\fB:\fR)
delimiter, with no intervening white space. For example, \fBdyn:runpath\fR
refers to the \fBrunpath\fR command provided by the \fBdyn\fR module. Module
names must be unique. The command names within a given module are unique within
that module, but the same command names can be used in more than one module.
.sp
.LP
Some modules designate one of their commands to be the default command for that
module. This command is run when the user specifies only a module name. Most
\fBelfedit\fR modules supply a command named dump, which produces the same
information displayed by the \fBelfdump\fR utility for the part of the ELF file
covered by the module. It is common for a module to specify dump as its default
command.
.sp
.LP
The syntax used to execute an \fBelfedit\fR command is intended to be familiar
to anyone who uses UNIX command line utilities. It consists of white space
delimited tokens. The first token is the command name. Options, which are
arguments that start with the hyphen (\fB-\fR) character follow the command.
Plain arguments (operands) follow the options. There can be \fB0\fR or more
options and operands for a given command, but if they are present, options
always precede plain arguments. The special option, \fB--\fR, (two hyphens) can
be used to delimit the end of the options. When it is encountered, any
remaining arguments are considered to be plain arguments even if they start
with a \fB-\fR.
.sp
.LP
The interpretation of the characters in an \fBelfedit\fR token depends on the
style of quoting used:
.sp
.ne 2
.na
\fBUnquoted\fR
.ad
.RS 17n
Outside of single (') or double (") quotes, backslash (\) acts as an escape
character. When a backslash character is seen, \fBelfedit\fR ignores it, and
treats the character following it literally (even if the following character is
itself a backslash). This feature can be used to insert a white space character
into a string argument to a command without having it split the string into two
separate tokens. Similarly, it can be used to insert a quote or backslash as a
literal character.
.RE

.sp
.ne 2
.na
\fBSingle Quotes\fR
.ad
.RS 17n
Within single quotes ('), white space characters do not delimit tokens, and are
interpreted as literal characters within the token. Double quote (") and
backslash (\) characters are interpreted as literal characters, and have no
special meaning.
.RE

.sp
.ne 2
.na
\fBDouble Quotes\fR
.ad
.RS 17n
Within double quotes ("), white space characters do not delimit tokens. Single
quote characters are interpreted literally and do not have a quoting function.
Backslash (\) is an escape character which operates similarly to the way it is
used in the C programming language within a string literal:
.sp
.ne 2
.na
\fB\ea\fR
.ad
.RS 8n
alert (bell)
.RE

.sp
.ne 2
.na
\fB\\b\fR
.ad
.RS 8n
backspace
.RE

.sp
.ne 2
.na
\fB\ef\fR
.ad
.RS 8n
form feed
.RE

.sp
.ne 2
.na
\fB\en\fR
.ad
.RS 8n
newline
.RE

.sp
.ne 2
.na
\fB\er\fR
.ad
.RS 8n
return
.RE

.sp
.ne 2
.na
\fB\et\fR
.ad
.RS 8n
horizontal tab
.RE

.sp
.ne 2
.na
\fB\\v\fR
.ad
.RS 8n
vertical tab
.RE

.sp
.ne 2
.na
\fB\\\fR
.ad
.RS 8n
backslash
.RE

.sp
.ne 2
.na
\fB\'\fR
.ad
.RS 8n
single quote
.RE

.sp
.ne 2
.na
\fB\e"\fR
.ad
.RS 8n
double quote
.RE

.sp
.ne 2
.na
\fB\\ooo\fR
.ad
.RS 8n
An octal constant, where ooo is one to three octal digits (0...7)
.RE

Any other character following a backslash is an error.
.RE

.sp
.LP
The core commands belong to an internal module named \fBsys\fR. All other
modules are packaged as dynamically loadable sharable objects. \fBelfedit\fR
loads modules on demand, when a command that requires it is executed, or as the
result of executing the \fBsys:load\fR command. Due to its special built in
status, and because its commands are used heavily, \fBelfedit\fR allows you to
specify commands from the \fBsys\fR module without including the \fBsys:\fR
prefix, for example, \fBload\fR rather than \fBsys:load\fR. To access a command
from any other module, you must specify the full \fImodule\fR\fB:\fR\fIcmd\fR
form.
.sp
.LP
\fBelfedit\fR is delivered with the following standard modules:
.sp
.ne 2
.na
\fB\fBcap\fR\fR
.ad
.RS 11n
Capabilities Section
.RE

.sp
.ne 2
.na
\fB\fBdyn\fR\fR
.ad
.RS 11n
Dynamic Section
.RE

.sp
.ne 2
.na
\fB\fBehdr\fR\fR
.ad
.RS 11n
ELF Header
.RE

.sp
.ne 2
.na
\fB\fBphdr\fR\fR
.ad
.RS 11n
Program Header Array
.RE

.sp
.ne 2
.na
\fB\fBshdr\fR\fR
.ad
.RS 11n
Section Header Array
.RE

.sp
.ne 2
.na
\fB\fBstr\fR\fR
.ad
.RS 11n
String Table Section
.RE

.sp
.ne 2
.na
\fB\fBsym\fR\fR
.ad
.RS 11n
Symbol Table Section
.RE

.sp
.ne 2
.na
\fB\fBsyminfo\fR\fR
.ad
.RS 11n
\fBSyminfo\fR Section
.RE

.sp
.ne 2
.na
\fB\fBsys\fR\fR
.ad
.RS 11n
Core built in \fBelfedit\fR commands
.RE

.SS "Status And Command Documentation"
Status And Command Documentation
.sp
.LP
The status (\fBsys:status\fR) command displays information about the current
\fBelfedit\fR session:
.RS +4
.TP
.ie t \(bu
.el o
Input and output files
.RE
.RS +4
.TP
.ie t \(bu
.el o
Option setting
.RE
.RS +4
.TP
.ie t \(bu
.el o
Module search path
.RE
.RS +4
.TP
.ie t \(bu
.el o
Modules loaded
.RE
.sp
.LP
Included with every \fBelfedit\fR module is extensive online documentation for
every command, in a format similar to UNIX manual pages. The \fBhelp\fR
(\fBsys:help\fR) command is used to display this information. To learn more
about \fBelfedit\fR, start \fBelfedit\fR and use the help command without
arguments:
.sp
.in +2
.nf
% elfedit
> help
.fi
.in -2
.sp

.sp
.LP
\fBelfedit\fR displays a welcome message with more information about
\fBelfedit\fR, and on how to use the help system.
.sp
.LP
To obtain summary information for a module:
.sp
.in +2
.nf
> help module
.fi
.in -2
.sp

.sp
.LP
To obtain the full documentation for a specific command provided by a module:
.sp
.in +2
.nf
> help module:command
.fi
.in -2
.sp

.sp
.LP
Using the \fBdyn\fR module and \fBdyn:runpath\fR commands as examples:
.sp
.in +2
.nf
> help dyn
> help dyn:runpath
.fi
.in -2
.sp

.sp
.LP
help (\fBsys:help\fR) can be used to obtain help on itself:
.sp
.in +2
.nf
> help help
.fi
.in -2
.sp

.SS "Module Search Path"
\fBelfedit\fR modules are implemented as sharable objects which are loaded on
demand. When a module is required, \fBelfedit\fR searches a module path in
order to locate the sharable object that implements the module. The path is a
sequence of directory names delimited by colon (\fB:\fR) characters. In
addition to normal characters, the path can also contain any of the following
tokens:
.sp
.ne 2
.na
\fB\fB%i\fR\fR
.ad
.RS 6n
Expands to the current instruction set architecture (ISA) name (\fBsparc\fR,
\fBsparcv9\fR, \fBi386\fR, \fBamd64\fR).
.RE

.sp
.ne 2
.na
\fB\fB%I\fR\fR
.ad
.RS 6n
Expands to the 64-bit ISA. This is the same thing as \fB%i\fR for 64-bit
versions of \fBelfedit\fR, but expands to the empty string for 32-bit versions.
.RE

.sp
.ne 2
.na
\fB\fB%o\fR\fR
.ad
.RS 6n
Expands to the old value of the path being modified. This is useful for
appending or prepending directories to the default path.
.RE

.sp
.ne 2
.na
\fB\fB%r\fR\fR
.ad
.RS 6n
Root of file system tree holding the \fBelfedit\fR program, assuming that
\fBelfedit\fR is installed as \fBusr/bin/elfedit\fR within the tree. On a
standard system, this is simply the standard system root directory (\fB/\fR).
On a development system, where the copy of \fBelfedit\fR can be installed
elsewhere, the use of \fB%r\fR can be used to ensure that the matching set of
modules are used.
.RE

.sp
.ne 2
.na
\fB\fB%%\fR\fR
.ad
.RS 6n
Expands to a single \fB%\fR character
.RE

.sp
.LP
The default module search path for \fBelfedit\fR is:
.sp
.in +2
.nf
%r/usr/lib/elfedit/%I
.fi
.in -2
.sp

.sp
.LP
Expanding the tokens, this is:
.sp
.ne 2
.na
\fB\fB/usr/lib/elfedit\fR\fR
.ad
.RS 28n
32-bit \fBelfedit\fR
.RE

.sp
.ne 2
.na
\fB\fB/usr/lib/elfedit/sparcv9\fR\fR
.ad
.RS 28n
64-bit \fBelfedit\fR (\fBsparc\fR)
.RE

.sp
.ne 2
.na
\fB\fB/usr/lib/elfedit/amd64\fR\fR
.ad
.RS 28n
64-bit \fBelfedit\fR (\fBx86\fR)
.RE

.sp
.LP
The default search path can be changed by setting the \fBELFEDIT_PATH\fR
environment variable, or by using the \fB-L\fR command line option. If you
specify both, the \fB-L\fR option supersedes the environment variable.
.SH OPTIONS
The following options are supported:
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.RS 29n
Enable \fBautoprint\fR mode. When \fBautoprint\fR is enabled, \fBelfedit\fR
prints the modified values that result when the ELF file is modified. This
output is shown in the current output style, which can be changed using the
\fB-o\fR option. The default output style is the style used by the
\fBelfdump\fR(1) utility. \fBautoprint\fR mode is the default when
\fBelfedit\fR is used interactively (when \fBstdin\fR and \fBstdout\fR are
terminals). Therefore, the \fB-a\fR option only has meaning when \fBelfedit\fR
is used in non-interactive contexts. To disable \fBautoprint\fR in an
interactive session, use the \fBelfedit\fR command:
.sp
.in +2
.nf
> set a off
.fi
.in -2
.sp

.RE

.sp
.ne 2
.na
\fB\fB-d\fR\fR
.ad
.RS 29n
If set, this option causes \fBelfedit\fR to issue informational messages
describing its internal operations and details of the ELF object being
processed. This can be useful when a deep understanding of the operation being
carried out is desired.
.RE

.sp
.ne 2
.na
\fB\fB-e\fR \fIcmd\fR\fR
.ad
.RS 29n
Specifies an edit command. Multiple \fB-e\fR options can be specified. If edit
commands are present on the command line, \fBelfedit\fR operates in batch mode.
After opening the file, \fBelfedit\fR executes each command in the order given,
after which the modified file is saved and \fBelfedit\fR exits. Batch mode is
useful for performing simple operations from shell scripts and makefiles.
.RE

.sp
.ne 2
.na
\fB\fB-L\fR \fIpath\fR\fR
.ad
.RS 29n
Sets default path for locating \fBelfedit\fR modules. Modules are described in
\fBModule Search Path\fR section of this manual page..
.RE

.sp
.ne 2
.na
\fB\fB-o\fR \fBdefault\fR | \fBsimple\fR | \fBnum\fR\fR
.ad
.RS 29n
The style used to display ELF data. This option establishes the current style
for the session. It can be changed from within the \fBelfedit\fR session by
using the set (\fBsys:set\fR) command, or by providing \fB-o\fR options to the
individual commands executed within the session.
.sp
.ne 2
.na
\fB\fBdefault\fR\fR
.ad
.RS 11n
The default style is to display output in a format intended for human viewing.
This style is similar to that used by the \fBelfdump\fR utility.
.RE

.sp
.ne 2
.na
\fB\fBnum\fR\fR
.ad
.RS 11n
Integer values are always shown in integer form. Strings are shown as the
integer offset into the containing string table.
.RE

.sp
.ne 2
.na
\fB\fBsimple\fR\fR
.ad
.RS 11n
When displaying strings from within the ELF file, only the string is displayed.
Integer values are displayed as symbolic constants if possible, and in integer
form otherwise. No titles, headers, or other supplemental output is shown.
.RE

.RE

.sp
.ne 2
.na
\fB\fB-r\fR\fR
.ad
.RS 29n
Read-only mode. The input file is opened for read-only access, and the results
of the edit session are not saved. \fBelfedit\fR does not allow the
\fIoutfile\fR argument when \fB-r\fR is specified. Read-only mode is highly
recommended when there is no intention to modify the file. In addition to
providing extra protection against accidental modification, it allows for the
examination of files for which the user does not have write permission.
.RE

.SH OPERANDS
The following operands are supported:
.sp
.ne 2
.na
\fB\fIinfile\fR\fR
.ad
.RS 11n
Input file containing an ELF object to process.
.sp
This can be an executable (\fBET_EXEC\fR), shared object (\fBET_DYN\fR), or
relocatable object file, (\fBET_REL\fR). Archives are not directly supported.
To edit an object in an archive, you must extract the object, edit the copy,
and then insert it back into the archive.
.sp
If no \fIinfile\fR is present, \fBelfedit\fR runs in a limited mode that only
allows executing commands from the \fBsys:\fR module. This mode is primarily to
allow access to the command documentation available from the help
(\fBsys:help\fR) command.
.sp
If \fIinfile\fR is present, and no \fIoutfile\fR is given, \fBelfedit\fR edits
the file in place, and writes the results into the same file, causing the
original file contents to be overwritten. It is usually recommended that
\fBelfedit\fR not be used in this mode, and that an output file be specified.
Once the resulting file has been tested and validated, it can be moved into the
place of the original file.
.sp
The \fB-r\fR option can be used to open \fIinfile\fR for read-only access. This
can be useful for examining an existing file that you do not wish to modify.
.RE

.sp
.ne 2
.na
\fB\fIoutfile\fR\fR
.ad
.RS 11n
Output file. If both \fIinfile\fR and \fIoutfile\fR are present, \fIinfile\fR
is opened for read-only access, and the modified object contents are written to
\fIoutfile\fR.
.RE

.SH USAGE
When supported by the system, \fBelfedit\fR runs as a 64-bit application,
capable of processing files greater than or equal to 2 Gbytes (2^31 bytes).
.sp
.LP
At startup, \fBelfedit\fR uses \fBlibelf\fR to open the input file and cache a
copy of its contents in memory for editing. It can then execute one or more
commands. A session finishes by optionally writing the modified object to the
output file, and then exiting.
.sp
.LP
If no \fIinfile\fR is present, \fBelfedit\fR runs in a limited mode that only
allows executing commands from the \fBsys\fR module. This mode is primarily to
allow access to the command documentation available from the help
(\fBsys:help\fR) command.
.sp
.LP
If one or more \fB-e\fR options are specified, the commands they supply are
executed in the order given. \fBelfedit\fR adds implicit calls to write
(\fBsys:write\fR) and quit (\fBsys:qui\fRt) immediately following the given
commands, causing the output file to be written and the \fBelfedit\fR process
to exit. This form of use is convenient in shell scripts and makefiles.
.sp
.LP
If no \fB-e\fR options are specified, \fBelfedit\fR reads commands from
\fBstdin\fR and executes them in the order given. The caller must explicitly
issue the write (\fBsys:write\fR) and quit (\fBsys:quit\fR) commands to save
their work and exit when running in this mode.
.SH EXIT STATUS
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 5n
Successful completion.
.RE

.sp
.ne 2
.na
\fB\fB1\fR\fR
.ad
.RS 5n
A fatal error occurred.
.RE

.sp
.ne 2
.na
\fB\fB2\fR\fR
.ad
.RS 5n
Invalid command line options were specified.
.RE

.SH EXAMPLES
In the following examples, interactive use of \fBelfedit\fR is shown with the
shell prompt (\fB%\fR) and the \fBelfedit\fR prompt (\fB>\fR). Neither of these
characters should be entered by the user.
.LP
\fBExample 1 \fRChanging the Runpath of an Executable
.sp
.LP
The following example presupposes an executable named \fBprog\fR, installed in
a bin directory that has an adjacent lib directory for sharable objects. The
following command sets the \fBrunpath\fR of that executable to the \fBlib\fR
directory:

.sp
.in +2
.nf
elfedit -e 'dyn:runpath $ORIGIN/../lib'
.fi
.in -2
.sp

.sp
.LP
The use of single quotes with the argument to the \fB-e\fR option is necessary
to ensure that the shell passes the entire command as a single argument to
\fBelfedit\fR.

.sp
.LP
Alternatively, the same operation can be done using \fBelfedit\fR in its
non-batch mode:

.sp
.in +2
.nf
% elfedit prog
> dyn:runpath $ORIGIN/../lib
     index  tag         value
       [30]  RUNPATH     0x3e6      $ORIGIN/../lib
> write
> quit
.fi
.in -2
.sp

.sp
.LP
The addition or modification of elements such as \fBrunpath\fR or needed
entries might only be achievable when \fBpadding\fR exists within the objects.
See \fBNotes\fR.

.LP
\fBExample 2 \fRRemoving a Hardware Capability Bit
.sp
.LP
Objects that require optional hardware support to run are built with a
capability section that contains a mask of bits specifying which capabilities
they need. The runtime linker (\fBld.so.1\fR) checks this mask against the
attributes of the running system to determine whether a given object is able to
be run by the current system. Programs that require abilities not available on
the system are prevented from running.

.sp
.LP
This check prevents a naive program that does not explicitly check for the
hardware support it requires from crashing in a confusing manner. However, it
can be inconvenient for a program that is written to explicitly check the
system capabilities at runtime. Such a program might have optimized code to use
when the hardware supports it while providing a generic fallback version that
can be run, albeit more slowly, otherwise. In this case, the hardware
compatibility mask prevents such a program from running on the older hardware.
In such a case, removing the relevant bit from the mask allows the program to
run.

.sp
.LP
The following example removes the \fBAV_386_SSE\fR3 hardware capability from an
x86 binary that uses the SSE3 CPU extension. This transfers responsibility for
validating the ability to use SSE3 from the runtime linker to the program
itself:

.sp
.in +2
.nf
elfedit -e 'cap:hw1 -and -cmp sse3' prog
.fi
.in -2
.sp

.LP
\fBExample 3 \fRReading Information From an Object
.sp
.LP
\fBelfedit\fR can be used to extract specific targeted information from an
object. The following shell command reads the number of section headers
contained in the file \fB/usr/bin/ls\fR:

.sp
.in +2
.nf
% SHNUM=`elfedit -r -onum -e 'ehdr:e_shnum' /usr/bin/ls`
% echo $SHNUM
29
.fi
.in -2
.sp

.sp
.LP
You might get a different value, depending on the version of Solaris and type
of machine that you are using. The \fB-r\fR option causes the file to be opened
read-only, allowing a user with ordinary access permissions to open the file,
and protecting against accidental damage to an important system executable. The
\fBnum\fR output style is used in order to obtain only the desired value,
without any extraneous text.

.sp
.LP
Similarly, the following extracts the symbol type of the symbol \fBunlink\fR
from the C runtime library:

.sp
.in +2
.nf
% TYPE=`elfedit -r -osimple -e 'sym:st_type unlink' /lib/libc.so`
% echo $TYPE
STT_FUNC
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.ne 2
.na
\fB\fBELFEDIT_PATH\fR\fR
.ad
.RS 16n
Alters the default module search path. Module search paths are discussed in the
\fBModule Search Path\fR section of this manual page.
.RE

.sp
.ne 2
.na
\fB\fBLD_NOEXEC_64\fR\fR
.ad
.RS 16n
Suppresses the automatic execution of the 64-bit \fBelfedit\fR. By default, the
64-bit version of \fBelfedit\fR runs if the system is 64-bit capable.
.RE

.sp
.ne 2
.na
\fB\fBPAGER\fR\fR
.ad
.RS 16n
Interactively delivers output from \fBelfedit\fR to the screen. If not set,
\fBmore\fR is used. See \fBmore\fR(1).
.RE

.SH FILES
.ne 2
.na
\fB\fB/usr/lib/elfedit\fR\fR
.ad
.RS 20n
Default directory for \fBelfedit\fR modules that are loaded on demand to supply
editing commands.
.RE

.sp
.ne 2
.na
\fB\fB~/.teclarc\fR\fR
.ad
.RS 20n
Personal \fBtecla\fR customization file for command line editing. See
\fBtecla\fR(5).
.RE

.SH ATTRIBUTES
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
.TE

.SH SEE ALSO
\fBdump\fR(1), \fBelfdump\fR(1), \fBld.so.1\fR(1), \fBmore\fR(1), \fBnm\fR(1),
\fBpvs\fR(1), \fBelf\fR(3ELF), \fBlibelf\fR(3LIB), \fBtecla\fR(5),
\fBattributes\fR(5)
.sp
.LP
\fILinker and Libraries Guide\fR
.SH WARNINGS
\fBelfedit\fR is designed to be a tool for testing and development of the ELF
system. It offers the ability to examine and change nearly every piece of ELF
metadata in the object. It quietly allows edits that can produce an invalid or
unusable ELF file. The user is expected to have knowledge of the ELF format and
of the rules and conventions that govern them. The \fILinker and Libraries
Guide\fR can be helpful when using \fBelfedit\fR.
.sp
.LP
\fBelfedit\fR allows the user to alter the ELF metadata in an object, but
cannot understand or alter the code of the actual program. Setting ELF
attributes such as types, sizes, alignments, and so forth in a manner that does
not agree with the actual contents of the file is therefore likely to yield a
broken and unusable output object. Such changes might be useful for testing of
linker components, but should be avoided otherwise.
.sp
.LP
Higher level operations, such as the use of the \fBdyn:runpath\fR command to
change the \fBrunpath\fR of an object, are safe, and can be carried out without
the sort of risk detailed in this section.
.SH NOTES
Not every ELF operation supported by \fBelfedit\fR can be successfully carried
out on every ELF object. \fBelfedit\fR is constrained by the existing sections
found in the file.
.sp
.LP
One area of particular interest is that \fBelfedit\fR might not be able to
modify the \fBrunpath\fR of a given object. To modify a \fBrunpath\fR, the
following must be true:
.RS +4
.TP
.ie t \(bu
.el o
The desired string must already exist in the dynamic string table, or there
must be enough reserved space within this section for the new string to be
added. If your object has a string table reservation area, the value of the
\fB\&.dynamic DT_SUNW_STRPAD\fR element indicates the size of the area. The
following \fBelfedit\fR command can be used to check this:
.sp
.in +2
.nf
% elfedit -r -e 'dyn:tag DT_SUNW_STRPAD' file
.fi
.in -2
.sp

.RE
.RS +4
.TP
.ie t \(bu
.el o
The dynamic section must already have a \fBrunpath\fR element, or there must be
an unused dynamic slot available where one can be inserted. To test for the
presence of an existing \fBrunpath\fR:
.sp
.in +2
.nf
% elfedit -r -e 'dyn:runpath' file
.fi
.in -2
.sp

A dynamic section uses an element of type \fBDT_NULL\fR to terminate the array
found in that section. The final \fBDT_NULL\fR cannot be changed, but if there
are more than one of these, \fBelfedit\fR can convert one of them into a
\fBrunpath\fR element. To test for extra dynamic slots:
.sp
.in +2
.nf
% elfedit -r -e 'dyn:tag DT_NULL' file
.fi
.in -2
.sp

.RE
.sp
.LP
Older objects do not have the extra space necessary to complete such
operations. The space necessary to do so was introduced in the Solaris Express
Community Edition release.
.sp
.LP
When an operation fails, the detailed information printed using the \fB-d\fR
(debug) option can be very helpful in uncovering the reason why.
.sp
.LP
\fBelfedit\fR modules follow a convention by which commands that directly
manipulate a field in an ELF structure have the same name as the field, while
commands that implement higher level concepts do not. For instance, the command
to manipulate the \fBe_flags\fR field in the ELF header is named
\fBehdr:e_flags\fR. Therefore, you generally find the command to modify ELF
fields by identifying the module and looking for a command with the name of the
field.