objcopy
copy and translate object files
see also :
ld - objdump
Synopsis
objcopy
[-F
bfdname|--target=bfdname]
[-I
bfdname|--input-target=bfdname]
[-O
bfdname|--output-target=bfdname]
[-B
bfdarch|--binary-architecture=bfdarch]
[-S|--strip-all]
[-g|--strip-debug]
[-K
symbolname|--keep-symbol=symbolname]
[-N
symbolname|--strip-symbol=symbolname]
[--strip-unneeded-symbol=symbolname]
[-G
symbolname|--keep-global-symbol=symbolname]
[--localize-hidden]
[-L
symbolname|--localize-symbol=symbolname]
[--globalize-symbol=symbolname]
[-W
symbolname|--weaken-symbol=symbolname]
[-w|--wildcard]
[-x|--discard-all]
[-X|--discard-locals]
[-b
byte|--byte=byte]
[-i
[breadth]|--interleave[=breadth]]
[--interleave-width=width]
[-j
sectionname|--only-section=sectionname]
[-R
sectionname|--remove-section=sectionname]
[-p|--preserve-dates]
[-D|--enable-deterministic-archives]
[-U|--disable-deterministic-archives]
[--debugging]
[--gap-fill=val]
[--pad-to=address]
[--set-start=val]
[--adjust-start=incr]
[--change-addresses=incr]
[--change-section-address
section{=,+,-}val]
[--change-section-lma
section{=,+,-}val]
[--change-section-vma
section{=,+,-}val]
[--change-warnings]
[--no-change-warnings]
[--set-section-flags
section=flags]
[--add-section
sectionname=filename]
[--rename-section
oldname=newname[,flags]]
[--long-section-names
{enable,disable,keep}]
[--change-leading-char]
[--remove-leading-char]
[--reverse-bytes=num]
[--srec-len=ival]
[--srec-forceS3]
[--redefine-sym
old=new]
[--redefine-syms=filename]
[--weaken]
[--keep-symbols=filename]
[--strip-symbols=filename]
[--strip-unneeded-symbols=filename]
[--keep-global-symbols=filename]
[--localize-symbols=filename]
[--globalize-symbols=filename]
[--weaken-symbols=filename]
[--alt-machine-code=index]
[--prefix-symbols=string]
[--prefix-sections=string]
[--prefix-alloc-sections=string]
[--add-gnu-debuglink=path-to-file]
[--keep-file-symbols]
[--only-keep-debug]
[--strip-dwo]
[--extract-dwo]
[--extract-symbol]
[--writable-text]
[--readonly-text]
[--pure]
[--impure]
[--file-alignment=num]
[--heap=size]
[--image-base=address]
[--section-alignment=num]
[--stack=size]
[--subsystem=which:major.minor]
[--compress-debug-sections]
[--decompress-debug-sections]
[--dwarf-depth=n]
[--dwarf-start=n]
[-v|--verbose]
[-V|--version]
[--help] [--info]
infile [outfile]
add an example, a script, a trick and tips
examples
source
objcopy --globalize-symbol=init
./simple3.ko simple3_gl.ko
objcopy --globalize-symbol=init
./simple4.ko simple4_gl.ko
source
To extract the kernel vmlinux, System.map, .config or initrd from
the zImage binary:
objcopy -j .kernel:vmlinux -O binary zImage vmlinux.gz
objcopy -j .kernel:vmlinux -O binary zImage vmlinux.gz
objcopy -j .kernel:System.map -O binary zImage
System.map.gz
description
The
GNU objcopy utility copies the
contents of an object file to another. objcopy uses
the GNU BFD Library to read and write the
object files. It can write the destination object file in a
format different from that of the source object file. The
exact behavior of objcopy is controlled by
command-line options. Note that objcopy should be
able to copy a fully linked file between any two formats.
However, copying a relocatable object file between any two
formats may not work as expected.
objcopy
creates temporary files to do its translations and deletes
them afterward. objcopy uses BFD to do
all its translation work; it has access to all the formats
described in BFD and thus is able to
recognize most formats without being told explicitly.
objcopy
can be used to generate S-records by using an output
target of srec (e.g., use -O srec).
objcopy
can be used to generate a raw binary file by using an output
target of binary (e.g., use -O binary).
When objcopy generates a raw binary file, it will
essentially produce a memory dump of the contents of the
input object file. All symbols and relocation information
will be discarded. The memory dump will start at the load
address of the lowest section copied into the output
file.
When generating
an S-record or a raw binary file, it may be helpful to
use -S to remove sections containing debugging
information. In some cases -R will be useful to
remove sections which contain information that is not needed
by the binary file.
Note---objcopy
is not able to change the endianness of its input files. If
the input format has an endianness (some formats do not),
objcopy can only copy the inputs into file formats
that have the same endianness or which have no endianness
(e.g., srec). (However, see the
--reverse-bytes option.)
options
infile
outfile
The input and output files,
respectively. If you do not specify outfile,
objcopy creates a temporary file and destructively
renames the result with the name of infile.
-I bfdname
--input-target=bfdname
Consider the source
file’s object format to be bfdname, rather than
attempting to deduce it.
-O bfdname
--output-target=bfdname
Write the output file using the
object format bfdname.
-F bfdname
--target=bfdname
Use bfdname as the
object format for both the input and the output file; i.e.,
simply transfer data from source to destination with no
translation.
-B bfdarch
--binary-architecture=bfdarch
Useful when transforming a
architecture-less input file into an object file. In this
case the output architecture can be set to bfdarch.
This option will be ignored if the input file has a known
bfdarch. You can access this binary data inside a
program by referencing the special symbols that are created
by the conversion process. These symbols are called
_binary_objfile_start, _binary_objfile_end and
_binary_objfile_size. e.g. you can transform a
picture file into an object file and then access it in your
code using these symbols.
-j
sectionname
--only-section=sectionname
Copy only the named section
from the input file to the output file. This option may be
given more than once. Note that using this option
inappropriately may make the output file unusable.
-R
sectionname
--remove-section=sectionname
Remove any section named
sectionname from the output file. This option may be
given more than once. Note that using this option
inappropriately may make the output file unusable.
--strip-all
Do not copy relocation and
symbol information from the source file.
--strip-debug
Do not copy debugging symbols
or sections from the source file.
--strip-unneeded
Strip all symbols that are not
needed for relocation processing.
-K
symbolname
--keep-symbol=symbolname
When stripping symbols, keep
symbol symbolname even if it would normally be
stripped. This option may be given more than once.
-N
symbolname
--strip-symbol=symbolname
Do not copy symbol
symbolname from the source file. This option may be
given more than once.
--strip-unneeded-symbol=symbolname
Do not copy symbol
symbolname from the source file unless it is needed
by a relocation. This option may be given more than
once.
-G
symbolname
--keep-global-symbol=symbolname
Keep only symbol
symbolname global. Make all other symbols local to
the file, so that they are not visible externally. This
option may be given more than once.
--localize-hidden
In an ELF
object, mark all symbols that have hidden or internal
visibility as local. This option applies on top of
symbol-specific localization options such as
-L.
-L
symbolname
--localize-symbol=symbolname
Make symbol symbolname
local to the file, so that it is not visible externally.
This option may be given more than once.
-W
symbolname
--weaken-symbol=symbolname
Make symbol symbolname
weak. This option may be given more than once.
--globalize-symbol=symbolname
Give symbol symbolname
global scoping so that it is visible outside of the file in
which it is defined. This option may be given more than
once.
--wildcard
Permit regular expressions in
symbolnames used in other command line options. The
question mark (?), asterisk (*), backslash (\) and square
brackets ([]) operators can be used anywhere in the symbol
name. If the first character of the symbol name is the
exclamation point (!) then the sense of the switch is
reversed for that symbol. For example:
-w -W !foo -W fo*
would cause
objcopy to weaken all symbols that start with "fo"
except for the symbol "foo".
--discard-all
Do not copy non-global symbols
from the source file.
--discard-locals
Do not copy compiler-generated
local symbols. (These usually start with L or
..)
-b byte
--byte=byte
If interleaving has been
enabled via the --interleave option then
start the range of bytes to keep at the byteth byte.
byte can be in the range from 0 to
breadth-1, where breadth is the value
given by the --interleave option.
-i
[breadth]
--interleave[=breadth]
Only copy a range out of every
breadth bytes. (Header data is not affected). Select
which byte in the range begins the copy with the
--byte option. Select the width of the
range with the --interleave-width
option.
This option is
useful for creating files to program ROM . It
is typically used with an "srec" output
target. Note that objcopy will complain if you do not
specify the --byte option as well.
The default
interleave breadth is 4, so with --byte
set to 0, objcopy would copy the first byte out of
every four bytes from the input to the output.
--interleave-width=width
When used with the
--interleave option, copy width
bytes at a time. The start of the range of bytes to be
copied is set by the --byte option, and
the extent of the range is set with the
--interleave option.
The default
value for this option is 1. The value of width plus
the byte value set by the --byte
option must not exceed the interleave breadth set by the
--interleave option.
This option can
be used to create images for two 16-bit flashes
interleaved in a 32-bit bus by passing -b 0
-i 4 --interleave-width=2 and
-b 2 -i 4
--interleave-width=2 to two
objcopy commands. If the input was
’12345678’ then the outputs would be
’1256’ and ’3478’ respectively.
--preserve-dates
Set the access and modification
dates of the output file to be the same as those of the
input file.
--enable-deterministic-archives
Operate in deterministic
mode. When copying archive members and writing the archive
index, use zero for UIDs, GIDs, timestamps, and use
consistent file modes for all files.
If
binutils was configured with
--enable-deterministic-archives,
then this mode is on by default. It can be disabled with the
-U option, below.
--disable-deterministic-archives
Do not operate in
deterministic mode. This is the inverse of the
-D option, above: when copying archive members
and writing the archive index, use their actual
UID , GID , timestamp, and
file mode values.
This is the
default unless binutils was configured with
--enable-deterministic-archives.
--debugging
Convert debugging information,
if possible. This is not the default because only certain
debugging formats are supported, and the conversion process
can be time consuming.
--gap-fill
val
Fill gaps between sections with
val. This operation applies to the load
address ( LMA ) of the sections. It is
done by increasing the size of the section with the lower
address, and filling in the extra space created with
val.
--pad-to
address
Pad the output file up to the
load address address. This is done by increasing the
size of the last section. The extra space is filled in with
the value specified by --gap-fill
(default zero).
--set-start
val
Set the start address of the
new file to val. Not all object file formats support
setting the start address.
--change-start
incr
--adjust-start incr
Change the start address by
adding incr. Not all object file formats support
setting the start address.
--change-addresses
incr
--adjust-vma incr
Change the VMA
and LMA addresses of all sections, as well as
the start address, by adding incr. Some object file
formats do not permit section addresses to be changed
arbitrarily. Note that this does not relocate the sections;
if the program expects sections to be loaded at a certain
address, and this option is used to change the sections such
that they are loaded at a different address, the program may
fail.
--change-section-address
section{=,+,-}val
--adjust-section-vma
section{=,+,-}val
Set or change both the
VMA address and the LMA
address of the named section. If = is used,
the section address is set to val. Otherwise,
val is added to or subtracted from the section
address. See the comments under
--change-addresses, above. If
section does not exist in the input file, a warning
will be issued, unless
--no-change-warnings is
used.
--change-section-lma
section{=,+,-}val
Set or change the
LMA address of the named section. The
LMA address is the address where the section
will be loaded into memory at program load time. Normally
this is the same as the VMA address, which is
the address of the section at program run time, but on some
systems, especially those where a program is held in
ROM , the two can be different. If =
is used, the section address is set to val.
Otherwise, val is added to or subtracted from the
section address. See the comments under
--change-addresses, above. If
section does not exist in the input file, a warning
will be issued, unless
--no-change-warnings is
used.
--change-section-vma
section{=,+,-}val
Set or change the
VMA address of the named section. The
VMA address is the address where the section
will be located once the program has started executing.
Normally this is the same as the LMA address,
which is the address where the section will be loaded into
memory, but on some systems, especially those where a
program is held in ROM , the two can be
different. If = is used, the section address is set
to val. Otherwise, val is added to or
subtracted from the section address. See the comments under
--change-addresses, above. If
section does not exist in the input file, a warning
will be issued, unless
--no-change-warnings is
used.
--change-warnings
--adjust-warnings
If
--change-section-address or
--change-section-lma or
--change-section-vma is used,
and the named section does not exist, issue a warning. This
is the default.
--no-change-warnings
--no-adjust-warnings
Do not issue a warning if
--change-section-address or
--adjust-section-lma or
--adjust-section-vma is used,
even if the named section does not exist.
--set-section-flags
section=flags
Set the flags for the named
section. The flags argument is a comma separated
string of flag names. The recognized names are alloc,
contents, load, noload,
readonly, code, data, rom,
share, and debug. You can set the
contents flag for a section which does not have
contents, but it is not meaningful to clear the
contents flag of a section which does have
contents--just remove the section instead. Not all flags are
meaningful for all object file formats.
--add-section
sectionname=filename
Add a new section named
sectionname while copying the file. The contents of
the new section are taken from the file filename. The
size of the section will be the size of the file. This
option only works on file formats which can support sections
with arbitrary names.
--rename-section
oldname=newname[,flags]
Rename a section from
oldname to newname, optionally changing the
section’s flags to flags in the process. This
has the advantage over usng a linker script to perform the
rename in that the output stays as an object file and does
not become a linked executable.
This option is
particularly helpful when the input format is binary, since
this will always create a section called .data. If for
example, you wanted instead to create a section called
.rodata containing binary data you could use the following
command line to achieve it:
objcopy -I binary -O <output_format> -B <architecture> \
--rename-section .data=.rodata,alloc,load,readonly,data,contents \
<input_binary_file> <output_object_file>
--long-section-names
{enable,disable,keep}
Controls the handling of long
section names when processing "COFF" and
"PE-COFF" object formats. The
default behaviour, keep, is to preserve long section
names if any are present in the input file. The
enable and disable options forcibly enable or
disable the use of long section names in the output object;
when disable is in effect, any long section names in
the input object will be truncated. The enable option
will only emit long section names if any are present in the
inputs; this is mostly the same as keep, but it is
left undefined whether the enable option might force
the creation of an empty string table in the output
file.
--change-leading-char
Some object file formats use
special characters at the start of symbols. The most common
such character is underscore, which compilers often add
before every symbol. This option tells objcopy to
change the leading character of every symbol when it
converts between object file formats. If the object file
formats use the same leading character, this option has no
effect. Otherwise, it will add a character, or remove a
character, or change a character, as appropriate.
--remove-leading-char
If the first character of a
global symbol is a special symbol leading character used by
the object file format, remove the character. The most
common symbol leading character is underscore. This option
will remove a leading underscore from all global symbols.
This can be useful if you want to link together objects of
different file formats with different conventions for symbol
names. This is different from
--change-leading-char because
it always changes the symbol name when appropriate,
regardless of the object file format of the output file.
--reverse-bytes=num
Reverse the bytes in a section
with output contents. A section length must be evenly
divisible by the value given in order for the swap to be
able to take place. Reversing takes place before the
interleaving is performed.
This option is
used typically in generating ROM images for
problematic target systems. For example, on some target
boards, the 32-bit words fetched from 8-bit ROMs
are re-assembled in little-endian byte order regardless of
the CPU byte order. Depending on the
programming model, the endianness of the ROM
may need to be modified.
Consider a
simple file with a section containing the following eight
bytes: 12345678.
Using
--reverse-bytes=2 for the above
example, the bytes in the output file would be ordered
21436587.
Using
--reverse-bytes=4 for the above
example, the bytes in the output file would be ordered
43218765.
By using
--reverse-bytes=2 for the above
example, followed by
--reverse-bytes=4 on the output
file, the bytes in the second output file would be ordered
34127856.
--srec-len=ival
Meaningful only for srec
output. Set the maximum length of the Srecords being
produced to ival. This length covers both address,
data and crc fields.
--srec-forceS3
Meaningful only for srec
output. Avoid generation of S1/S2 records, creating
S3-only record format.
--redefine-sym
old=new
Change the name of a symbol
old, to new. This can be useful when one is
trying link two things together for which you have no
source, and there are name collisions.
--redefine-syms=filename
Apply
--redefine-sym to each symbol pair
"old new" listed in the file
filename. filename is simply a flat file, with
one symbol pair per line. Line comments may be introduced by
the hash character. This option may be given more than
once.
--weaken
Change all global symbols in
the file to be weak. This can be useful when building an
object which will be linked against other objects using the
-R option to the linker. This option is only
effective when using an object file format which supports
weak symbols.
--keep-symbols=filename
Apply
--keep-symbol option to each symbol
listed in the file filename. filename is
simply a flat file, with one symbol name per line. Line
comments may be introduced by the hash character. This
option may be given more than once.
--strip-symbols=filename
Apply
--strip-symbol option to each
symbol listed in the file filename. filename
is simply a flat file, with one symbol name per line. Line
comments may be introduced by the hash character. This
option may be given more than once.
--strip-unneeded-symbols=filename
Apply
--strip-unneeded-symbol
option to each symbol listed in the file filename.
filename is simply a flat file, with one symbol name
per line. Line comments may be introduced by the hash
character. This option may be given more than once.
--keep-global-symbols=filename
Apply
--keep-global-symbol option
to each symbol listed in the file filename.
filename is simply a flat file, with one symbol name
per line. Line comments may be introduced by the hash
character. This option may be given more than once.
--localize-symbols=filename
Apply
--localize-symbol option to each
symbol listed in the file filename. filename
is simply a flat file, with one symbol name per line. Line
comments may be introduced by the hash character. This
option may be given more than once.
--globalize-symbols=filename
Apply
--globalize-symbol option to each
symbol listed in the file filename. filename
is simply a flat file, with one symbol name per line. Line
comments may be introduced by the hash character. This
option may be given more than once.
--weaken-symbols=filename
Apply
--weaken-symbol option to each
symbol listed in the file filename. filename
is simply a flat file, with one symbol name per line. Line
comments may be introduced by the hash character. This
option may be given more than once.
--alt-machine-code=index
If the output architecture has
alternate machine codes, use the indexth code instead
of the default one. This is useful in case a machine is
assigned an official code and the tool-chain adopts the new
code, but other applications still depend on the original
code being used. For ELF based architectures
if the index alternative does not exist then the
value is treated as an absolute number to be stored in the
e_machine field of the ELF header.
--writable-text
Mark the output text as
writable. This option isn’t meaningful for all object
file formats.
--readonly-text
Make the output text write
protected. This option isn’t meaningful for all object
file formats.
--pure
Mark the output file as demand
paged. This option isn’t meaningful for all object
file formats.
--impure
Mark the output file as impure.
This option isn’t meaningful for all object file
formats.
--prefix-symbols=string
Prefix all symbols in the
output file with string.
--prefix-sections=string
Prefix all section names in the
output file with string.
--prefix-alloc-sections=string
Prefix all the names of all
allocated sections in the output file with
string.
--add-gnu-debuglink=path-to-file
Creates a .gnu_debuglink
section which contains a reference to path-to-file
and adds it to the output file.
--keep-file-symbols
When stripping a file, perhaps
with --strip-debug or
--strip-unneeded, retain any
symbols specifying source file names, which would otherwise
get stripped.
--only-keep-debug
Strip a file, removing contents
of any sections that would not be stripped by
--strip-debug and leaving the
debugging sections intact. In ELF files, this
preserves all note sections in the output.
The intention
is that this option will be used in conjunction with
--add-gnu-debuglink to create
a two part executable. One a stripped binary which will
occupy less space in RAM and in a
distribution and the second a debugging information file
which is only needed if debugging abilities are required.
The suggested procedure to create these files is as follows:
1.<Link the executable as normal. Assuming that is is
called>
"foo"
then...
1.<Run "objcopy
--only-keep-debug foo foo.dbg"
to>
create a file containing the
debugging info.
1.<Run "objcopy
--strip-debug foo" to create
a>
stripped executable.
1.<Run "objcopy
--add-gnu-debuglink=foo.dbg
foo">
to add a link to the debugging
info into the stripped executable.
Note---the
choice of ".dbg" as an extension for the
debug info file is arbitrary. Also the
"--only-keep-debug"
step is optional. You could instead do this:
1.<Link the executable as normal.>
1.<Copy "foo" to "foo.full">
1.<Run "objcopy --strip-debug
foo">
1.<Run "objcopy
--add-gnu-debuglink=foo.full
foo">
i.e., the file
pointed to by the
--add-gnu-debuglink can be
the full executable. It does not have to be a file created
by the --only-keep-debug
switch.
Note---this
switch is only intended for use on fully linked files. It
does not make sense to use it on object files where the
debugging information may be incomplete. Besides the
gnu_debuglink feature currently only supports the presence
of one filename containing debugging information, not
multiple filenames on a one-per-object-file basis.
--strip-dwo
Remove the contents of all
DWARF .dwo sections, leaving the remaining
debugging sections and all symbols intact. This option is
intended for use by the compiler as part of the
-gsplit-dwarf option, which splits debug
information between the .o file and a separate .dwo file.
The compiler generates all debug information in the same
file, then uses the --extract-dwo
option to copy the .dwo sections to the .dwo file, then the
--strip-dwo option to remove those
sections from the original .o file.
--extract-dwo
Extract the contents of all
DWARF .dwo sections. See the
--strip-dwo option for more
information.
--file-alignment
num
Specify the file alignment.
Sections in the file will always begin at file offsets which
are multiples of this number. This defaults to 512. [This
option is specific to PE targets.]
--heap
reserve
--heap
reserve,commit
Specify the number of bytes of
memory to reserve (and optionally commit) to be used as heap
for this program. [This option is specific to
PE targets.]
--image-base
value
Use value as the base
address of your program or dll. This is the lowest memory
location that will be used when your program or dll is
loaded. To reduce the need to relocate and improve
performance of your dlls, each should have a unique base
address and not overlap any other dlls. The default is
0x400000 for executables, and 0x10000000 for dlls. [This
option is specific to PE targets.]
--section-alignment
num
Sets the section alignment.
Sections in memory will always begin at addresses which are
a multiple of this number. Defaults to 0x1000. [This option
is specific to PE targets.]
--stack
reserve
--stack
reserve,commit
Specify the number of bytes of
memory to reserve (and optionally commit) to be used as
stack for this program. [This option is specific to
PE targets.]
--subsystem
which
--subsystem which:major
--subsystem
which:major.minor
Specifies the subsystem under
which your program will execute. The legal values for
which are "native",
"windows", "console",
"posix",
"efi-app",
"efi-bsd",
"efi-rtd",
"sal-rtd", and
"xbox". You may optionally set the
subsystem version also. Numeric values are also accepted for
which. [This option is specific to PE
targets.]
--extract-symbol
Keep the file’s section
flags and symbols but remove all section data. Specifically,
the option:
*<removes the contents of all sections;>
*<sets the size of every section to zero; and>
*<sets the file’s start address to zero.>
This option is
used to build a .sym file for a VxWorks kernel. It
can also be a useful way of reducing the size of a
--just-symbols linker input
file.
--compress-debug-sections
Compress DWARF
debug sections using zlib.
--decompress-debug-sections
Decompress DWARF
debug sections using zlib.
--version
Show the version number of
objcopy.
--verbose
Verbose output: list all object
files modified. In the case of archives, objcopy
-V lists all members of the archive.
--help
Show a summary of the options
to objcopy.
--info
Display a list showing all
architectures and object formats available.
@file
Read command-line options from
file. The options read are inserted in place of the
original @file option. If file does not exist,
or cannot be read, then the option will be treated
literally, and not removed.
Options in
file are separated by whitespace. A whitespace
character may be included in an option by surrounding the
entire option in either single or double quotes. Any
character (including a backslash) may be included by
prefixing the character to be included with a backslash. The
file may itself contain additional @file
options; any such options will be processed recursively.
copyright
Copyright (c) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011, 2012, 2013 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free
Documentation License, Version 1.3 or any later version published
by the Free Software Foundation; with no Invariant Sections, with
no Front-Cover Texts, and with no Back-Cover Texts. A copy of the
license is included in the section entitled " GNU
Free Documentation License".
see also
ld ,
objdump , and the Info entries for
binutils.