llvm-objcopy - object copying and editing tool

SYNOPSIS

llvm-objcopy [options] input [output]

DESCRIPTION

llvm-objcopy is a tool to copy and manipulate objects. In basic usage, it makes a semantic copy of the input to the output. If any options are specified, the output may be modified along the way, e.g. by removing sections.

If no output file is specified, the input file is modified in-place. If “-” is specified for the input file, the input is read from the program’s standard input stream. If “-” is specified for the output file, the output is written to the standard output stream of the program.

If the input is an archive, any requested operations will be applied to each archive member individually.

The tool is still in active development, but in most scenarios it works as a drop-in replacement for GNU’s objcopy.

GENERIC AND CROSS-PLATFORM OPTIONS

The following options are either agnostic of the file format, or apply to multiple file formats.

Add a .gnu_debuglink section for <debug-file> to the output.

--add-section <section=file>

Add a section named <section> with the contents of <file> to the output. For ELF objects the section will be of type SHT_NOTE, if the name starts with “.note”. Otherwise, it will have type SHT_PROGBITS. Can be specified multiple times to add multiple sections.

For MachO objects, <section> must be formatted as <segment name>,<section name>.

--binary-architecture <arch>, -B

Ignored for compatibility.

--disable-deterministic-archives, -U

Use real values for UIDs, GIDs and timestamps when updating archive member headers.

--discard-all, -x

Remove most local symbols from the output. Different file formats may limit this to a subset of the local symbols. For example, file and section symbols in ELF objects will not be discarded.

--dump-section <section>=<file>

Dump the contents of section <section> into the file <file>. Can be specified multiple times to dump multiple sections to different files. <file> is unrelated to the input and output files provided to llvm-objcopy and as such the normal copying and editing operations will still be performed. No operations are performed on the sections prior to dumping them.

For MachO objects, <section> must be formatted as <segment name>,<section name>.

--enable-deterministic-archives, -D

Enable deterministic mode when copying archives, i.e. use 0 for archive member header UIDs, GIDs and timestamp fields. On by default.

--help, -h

Print a summary of command line options.

--only-keep-debug

Produce a debug file as the output that only preserves contents of sections useful for debugging purposes.

For ELF objects, this removes the contents of SHF_ALLOC sections that are not SHT_NOTE by making them SHT_NOBITS and shrinking the program headers where possible.

--only-section <section>, -j

Remove all sections from the output, except for sections named <section>. Can be specified multiple times to keep multiple sections.

For MachO objects, <section> must be formatted as <segment name>,<section name>.

--redefine-sym <old>=<new>

Rename symbols called <old> to <new> in the output. Can be specified multiple times to rename multiple symbols.

--redefine-syms <filename>

Rename symbols in the output as described in the file <filename>. In the file, each line represents a single symbol to rename, with the old name and new name separated by whitespace. Leading and trailing whitespace is ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--regex

If specified, symbol and section names specified by other switches are treated as extended POSIX regular expression patterns.

--remove-section <section>, -R

Remove the specified section from the output. Can be specified multiple times to remove multiple sections simultaneously.

For MachO objects, <section> must be formatted as <segment name>,<section name>.

--set-section-alignment <section>=<align>

Set the alignment of section <section> to <align>`. Can be specified multiple times to update multiple sections.

--strip-all-gnu

Remove all symbols, debug sections and relocations from the output. This option is equivalent to GNU objcopy’s --strip-all switch.

--strip-all, -S

For ELF objects, remove from the output all symbols and non-alloc sections not within segments, except for .gnu.warning, .ARM.attribute sections and the section name table.

For COFF and Mach-O objects, remove all symbols, debug sections, and relocations from the output.

--strip-debug, -g

Remove all debug sections from the output.

--strip-symbol <symbol>, -N

Remove all symbols named <symbol> from the output. Can be specified multiple times to remove multiple symbols.

--strip-symbols <filename>

Remove all symbols whose names appear in the file <filename>, from the output. In the file, each line represents a single symbol name, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--strip-unneeded-symbol <symbol>

Remove from the output all symbols named <symbol> that are local or undefined and are not required by any relocation.

--strip-unneeded-symbols <filename>

Remove all symbols whose names appear in the file <filename>, from the output, if they are local or undefined and are not required by any relocation. In the file, each line represents a single symbol name, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--strip-unneeded

Remove from the output all local or undefined symbols that are not required by relocations. Also remove all debug sections.

--version, -V

Display the version of the llvm-objcopy executable.

@<FILE>

Read command-line options and commands from response file <FILE>.

--wildcard, -w

Allow wildcard syntax for symbol-related flags. On by default for section-related flags. Incompatible with –regex.

Wildcard syntax allows the following special symbols:

Character Meaning Equivalent
* Any number of characters .*
? Any single character .
\ Escape the next character \
[a-z] Character class [a-z]
[!a-z], [^a-z] Negated character class [^a-z]

Additionally, starting a wildcard with ‘!’ will prevent a match, even if another flag matches. For example -w -N '*' -N '!x' will strip all symbols except for x.

The order of wildcards does not matter. For example, -w -N '*' -N '!x' is the same as -w -N '!x' -N '*'.

COFF-SPECIFIC OPTIONS

The following options are implemented only for COFF objects. If used with other objects, llvm-objcopy will either emit an error or silently ignore them.

ELF-SPECIFIC OPTIONS

The following options are implemented only for ELF objects. If used with other objects, llvm-objcopy will either emit an error or silently ignore them.

--add-symbol <name>=[<section>:]<value>[,<flags>]

Add a new symbol called <name> to the output symbol table, in the section named <section>, with value <value>. If <section> is not specified, the symbol is added as an absolute symbol. The <flags> affect the symbol properties. Accepted values are:

  • global = the symbol will have global binding.
  • local = the symbol will have local binding.
  • weak = the symbol will have weak binding.
  • default = the symbol will have default visibility.
  • hidden = the symbol will have hidden visibility.
  • protected = the symbol will have protected visibility.
  • file = the symbol will be an STT_FILE symbol.
  • section = the symbol will be an STT_SECTION symbol.
  • object = the symbol will be an STT_OBJECT symbol.
  • function = the symbol will be an STT_FUNC symbol.
  • indirect-function = the symbol will be an STT_GNU_IFUNC symbol.

Additionally, the following flags are accepted but ignored: debug, constructor, warning, indirect, synthetic, unique-object, before.

Can be specified multiple times to add multiple symbols.

Allow llvm-objcopy to remove sections even if it would leave invalid section references. Any invalid sh_link fields will be set to zero.

Set the directory used by --build-id-link-input and --build-id-link-output.

Hard-link the input to <dir>/xx/xxx<suffix>, where <dir> is the directory specified by --build-id-link-dir. The path used is derived from the hex build ID.

Hard-link the output to <dir>/xx/xxx<suffix>, where <dir> is the directory specified by --build-id-link-dir. The path used is derived from the hex build ID.

--change-start <incr>, --adjust-start

Add <incr> to the program’s start address. Can be specified multiple times, in which case the values will be applied cumulatively.

--compress-debug-sections [<style>]

Compress DWARF debug sections in the output, using the specified style. Supported styles are zlib-gnu and zlib. Defaults to zlib if no style is specified.

--decompress-debug-sections

Decompress any compressed DWARF debug sections in the output.

--discard-locals, -X

Remove local symbols starting with “.L” from the output.

--extract-dwo

Remove all sections that are not DWARF .dwo sections from the output.

--extract-main-partition

Extract the main partition from the output.

--extract-partition <name>

Extract the named partition from the output.

--globalize-symbol <symbol>

Mark any defined symbols named <symbol> as global symbols in the output. Can be specified multiple times to mark multiple symbols.

--globalize-symbols <filename>

Read a list of names from the file <filename> and mark defined symbols with those names as global in the output. In the file, each line represents a single symbol, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--input-target <format>, -I

Read the input as the specified format. See SUPPORTED FORMATS for a list of valid <format> values. If unspecified, llvm-objcopy will attempt to determine the format automatically.

--keep-file-symbols

Keep symbols of type STT_FILE, even if they would otherwise be stripped.

--keep-global-symbol <symbol>

Make all symbols local in the output, except for symbols with the name <symbol>. Can be specified multiple times to ignore multiple symbols.

--keep-global-symbols <filename>

Make all symbols local in the output, except for symbols named in the file <filename>. In the file, each line represents a single symbol, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--keep-section <section>

When removing sections from the output, do not remove sections named <section>. Can be specified multiple times to keep multiple sections.

--keep-symbol <symbol>, -K

When removing symbols from the output, do not remove symbols named <symbol>. Can be specified multiple times to keep multiple symbols.

--keep-symbols <filename>

When removing symbols from the output do not remove symbols named in the file <filename>. In the file, each line represents a single symbol, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--localize-hidden

Make all symbols with hidden or internal visibility local in the output.

--localize-symbol <symbol>, -L

Mark any defined non-common symbol named <symbol> as a local symbol in the output. Can be specified multiple times to mark multiple symbols as local.

--localize-symbols <filename>

Read a list of names from the file <filename> and mark defined non-common symbols with those names as local in the output. In the file, each line represents a single symbol, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--new-symbol-visibility <visibility>

Specify the visibility of the symbols automatically created when using binary input or --add-symbol. Valid options are:

  • default
  • hidden
  • internal
  • protected

The default is default.

--output-target <format>, -O

Write the output as the specified format. See SUPPORTED FORMATS for a list of valid <format> values. If unspecified, the output format is assumed to be the same as the input file’s format.

--prefix-alloc-sections <prefix>

Add <prefix> to the front of the names of all allocatable sections in the output.

--prefix-symbols <prefix>

Add <prefix> to the front of every symbol name in the output.

--preserve-dates, -p

Preserve access and modification timestamps in the output.

--rename-section <old>=<new>[,<flag>,...]

Rename sections called <old> to <new> in the output, and apply any specified <flag> values. See --set-section-flags for a list of supported flags. Can be specified multiple times to rename multiple sections.

--set-section-flags <section>=<flag>[,<flag>,...]

Set section properties in the output of section <section> based on the specified <flag> values. Can be specified multiple times to update multiple sections.

Following is a list of supported flags and their effects:

  • alloc = add the SHF_ALLOC flag.
  • load = if the section has SHT_NOBITS type, mark it as a SHT_PROGBITS section.
  • readonly = if this flag is not specified, add the SHF_WRITE flag.
  • code = add the SHF_EXECINSTR flag.
  • merge = add the SHF_MERGE flag.
  • strings = add the SHF_STRINGS flag.
  • contents = if the section has SHT_NOBITS type, mark it as a SHT_PROGBITS section.

The following flags are also accepted, but are ignored for GNU compatibility: noload, debug, data, rom, share.

--set-start-addr <addr>

Set the start address of the output to <addr>. Overrides any previously specified --change-start or --adjust-start options.

--split-dwo <dwo-file>

Equivalent to running llvm-objcopy with --extract-dwo and <dwo-file> as the output file and no other options, and then with --strip-dwo on the input file.

--strip-dwo

Remove all DWARF .dwo sections from the output.

--strip-non-alloc

Remove from the output all non-allocatable sections that are not within segments.

--strip-sections

Remove from the output all section headers and all section data not within segments. Note that many tools will not be able to use an object without section headers.

--target <format>, -F

Equivalent to --input-target and --output-target for the specified format. See SUPPORTED FORMATS for a list of valid <format> values.

--weaken-symbol <symbol>, -W

Mark any global symbol named <symbol> as a weak symbol in the output. Can be specified multiple times to mark multiple symbols as weak.

--weaken-symbols <filename>

Read a list of names from the file <filename> and mark global symbols with those names as weak in the output. In the file, each line represents a single symbol, with leading and trailing whitespace ignored, as is anything following a ‘#’. Can be specified multiple times to read names from multiple files.

--weaken

Mark all defined global symbols as weak in the output.

SUPPORTED FORMATS

The following values are currently supported by llvm-objcopy for the --input-target, --output-target, and --target options. For GNU objcopy compatibility, the values are all bfdnames.

  • binary
  • ihex
  • elf32-i386
  • elf32-x86-64
  • elf64-x86-64
  • elf32-iamcu
  • elf32-littlearm
  • elf64-aarch64
  • elf64-littleaarch64
  • elf32-littleriscv
  • elf64-littleriscv
  • elf32-powerpc
  • elf32-powerpcle
  • elf64-powerpc
  • elf64-powerpcle
  • elf32-bigmips
  • elf32-ntradbigmips
  • elf32-ntradlittlemips
  • elf32-tradbigmips
  • elf32-tradlittlemips
  • elf64-tradbigmips
  • elf64-tradlittlemips
  • elf32-sparc
  • elf32-sparcel

Additionally, all targets except binary and ihex can have -freebsd as a suffix.

BINARY INPUT AND OUTPUT

If binary is used as the value for --input-target, the input file will be embedded as a data section in an ELF relocatable object, with symbols _binary_<file_name>_start, _binary_<file_name>_end, and _binary_<file_name>_size representing the start, end and size of the data, where <file_name> is the path of the input file as specified on the command line with non-alphanumeric characters converted to _.

If binary is used as the value for --output-target, the output file will be a raw binary file, containing the memory image of the input file. Symbols and relocation information will be discarded. The image will start at the address of the first loadable section in the output.

EXIT STATUS

llvm-objcopy exits with a non-zero exit code if there is an error. Otherwise, it exits with code 0.

BUGS

To report bugs, please visit <http://llvm.org/bugs/>.

There is a known issue with --input-target and --target causing only binary and ihex formats to have any effect. Other values will be ignored and llvm-objcopy will attempt to guess the input format.

SEE ALSO

llvm-strip(1)