llvm-objcopy - object copying and editing tool¶

:::{program} llvm-objcopy :::

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.

:::{option} –add-gnu-debuglink Add a .gnu_debuglink section for <debug-file> to the output. :::

:::{option} –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>. :::

:::{option} –binary-architecture , -B Ignored for compatibility. :::

:::{option} –disable-deterministic-archives, -U Use real values for UIDs, GIDs and timestamps when updating archive member headers. :::

:::{option} –discard-all, -x Remove most local symbols not referenced by relocations 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. Additionally, remove all debug sections. :::

:::{option} –dump-section

= 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>. :::

:::{option} –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. :::

:::{option} –extract-section

= Extract the specified section <section> into the file <file> as a seperate object. Can be specified multiple times to extract multiple sections. <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. :::

:::{option} –globalize-symbol Mark any defined symbols named <symbol> as global symbols in the output. Can be specified multiple times to mark multiple symbols. :::

:::{option} –globalize-symbols 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. :::

:::{option} –help, -h Print a summary of command line options. :::

:::{option} –keep-global-symbol , -G Mark all symbols local in the output, except for symbols with the name <symbol>. Can be specified multiple times to ignore multiple symbols. :::

:::{option} –keep-global-symbols Mark 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. :::

:::{option} –localize-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. :::

:::{option} –localize-symbols 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. :::

:::{option} –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. :::

:::{option} –only-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>. :::

:::{option} –redefine-sym = Rename symbols called <old> to <new> in the output. Can be specified multiple times to rename multiple symbols. :::

:::{option} –redefine-syms 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. :::

:::{option} –regex If specified, symbol and section names specified by other switches are treated as extended POSIX regular expression patterns. :::

:::{option} –remove-symbol-prefix Remove <prefix> from the start of every symbol name. No-op for symbols that do not start with <prefix>. :::

:::{option} –remove-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>. :::

:::{option} –set-section-alignment

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

:::{option} –set-section-flags

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

Supported flag names are alloc, load, noload, readonly, exclude, debug, code, data, rom, share, contents, merge, strings, and large. Not all flags are meaningful for all object file formats or target architectures.

For ELF objects, the flags have the following 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.
exclude = add the SHF_EXCLUDE 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.
large = add the SHF_X86_64_LARGE on x86_64; rejected if the target architecture is not x86_64.

For COFF objects, the flags have the following effects:

alloc = add the IMAGE_SCN_CNT_UNINITIALIZED_DATA and IMAGE_SCN_MEM_READ flags, unless the load flag is specified.
noload = add the IMAGE_SCN_LNK_REMOVE and IMAGE_SCN_MEM_READ flags.
readonly = if this flag is not specified, add the IMAGE_SCN_MEM_WRITE flag.
exclude = add the IMAGE_SCN_LNK_REMOVE and IMAGE_SCN_MEM_READ flags.
debug = add the IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE and IMAGE_SCN_MEM_READ flags.
code = add the IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE and IMAGE_SCN_MEM_READ flags.
data = add the IMAGE_SCN_CNT_INITIALIZED_DATA and IMAGE_SCN_MEM_READ flags.
share = add the IMAGE_SCN_MEM_SHARED and IMAGE_SCN_MEM_READ flags. :::

:::{option} –skip-symbol Do not change the parameters of symbol <symbol> when executing other options that can change the symbol’s name, binding or visibility. :::

:::{option} –skip-symbols Do not change the parameters of symbols named in the file <filename> when executing other options that can change the symbol’s name, binding or visibility. 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. :::

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

:::{option} –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.

For WebAssembly objects, remove all custom sections except for those named metadata.code.*. :::

:::{option} –strip-debug, -g Remove all debug sections from the output. :::

:::{option} –strip-symbol , -N Remove all symbols named <symbol> from the output. Can be specified multiple times to remove multiple symbols. :::

:::{option} –strip-symbols 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. :::

:::{option} –strip-unneeded-symbol Remove from the output all symbols named <symbol> that are local or undefined and are not required by any relocation. :::

:::{option} –strip-unneeded-symbols 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. :::

:::{option} –strip-unneeded Remove from the output all local or undefined symbols that are not required by relocations. Also remove all debug sections. :::

:::{option} –update-section = Replace the contents of the section <name> with contents from the file <file>. If the section <name> is part of a segment, the new contents cannot be larger than the existing section. :::

:::{option} –verbose, -v Print the paths of files that are copied. :::

:::{option} –version, -V Display the version of the llvm-objcopy executable. :::

:::{option} –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 '*'. :::

:::{option} @ Read command-line options and commands from response file <FILE>. :::

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.

:::{option} –add-symbol =[

:][,] 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. :::

:::{option} –allow-broken-links Allow llvm-objcopy to remove sections even if it would leave invalid section references. Any invalid sh_link fields will be set to zero. :::

:::{option} –change-section-lma *{+-} Shift LMA of non-zero-sized segments by <val>. :::

:::{option} –change-section-address

{=+-}, –adjust-section-vma Change the address of sections that match <section> pattern to the specified value, or apply +<val>/-<val> to the current value. Can be specified multiple times to specify multiple patterns. Each section is only modified by one --change-section-address argument. If a section name matches multiple patterns, the rightmost change applies. The object file needs to be of ET_REL type. :::

:::{option} –change-start , –adjust-start Add <incr> to the program’s start address. Can be specified multiple times, in which case the values will be applied cumulatively. :::

:::{option} –compress-debug-sections [] Compress DWARF debug sections in the output, using the specified format. Supported formats are zlib and zstd. Use zlib if <format> is omitted. :::

:::{option} –compress-sections

= Compress or decompress sections matched by <section> using the specified format. Supported formats are zlib and zstd. Specify none for decompression. When a section is matched by multiple options, the last one wins. A wildcard <section> starting with ‘!’ is disallowed. Sections within a segment cannot be (de)compressed. :::

:::{option} –decompress-debug-sections Decompress any compressed DWARF debug sections in the output. :::

:::{option} –discard-locals, -X Remove local symbols starting with “.L” not referenced by relocations from the output. :::

:::{option} –extract-dwo Remove all sections that are not DWARF .dwo sections from the output. :::

:::{option} –extract-main-partition Extract the main partition from the output. :::

:::{option} –extract-partition Extract the named partition from the output. :::

:::{option} –gap-fill For binary outputs, fill the gaps between sections with <value> instead of zero. The value must be an unsigned 8-bit integer. :::

:::{option} –input-target , -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. :::

:::{option} –keep-file-symbols Keep symbols of type STT_FILE, even if they would otherwise be stripped. :::

:::{option} –keep-section

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

:::{option} –keep-symbol , -K When removing symbols from the output, do not remove symbols named <symbol>. Can be specified multiple times to keep multiple symbols. :::

:::{option} –keep-symbols 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. :::

:::{option} –localize-hidden Mark all symbols with hidden or internal visibility local in the output. :::

:::{option} –new-symbol-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. :::

:::{option} –no-verify-note-sections When adding note sections, do not verify if the section format is valid. :::

:::{option} –output-target , -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 value specified for --input-target or the input file’s format if that option is also unspecified. :::

:::{option} –pad-to

For binary outputs, pad the output to the load address <address> using a value of zero or the value specified by --gap-fill. :::

:::{option} –prefix-alloc-sections Add <prefix> to the front of the names of all allocatable sections in the output. :::

:::{option} –prefix-symbols Add <prefix> to the front of every symbol name in the output. :::

:::{option} –preserve-dates, -p Preserve access and modification timestamps in the output. :::

:::{option} –remove-note [/] Remove notes of integer type <type> and name <name> from SHT_NOTE sections that are not in a segment. Can be specified multiple times. :::

:::{option} –rename-section =[,,…] 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. :::

:::{option} –set-section-type

= Set the type of section <section> to the integer <type>. Can be specified multiple times to update multiple sections. :::

:::{option} –set-start Set the start address of the output to <addr>. Overrides any previously specified --change-start or --adjust-start options. :::

:::{option} –set-symbol-visibility = Change the visibility of a symbol to the specified value. :::

:::{option} –set-symbols-visibility = Read a list of symbols from <filename> and change their visibility to the specified value. Visibility values: default, internal, hidden, protected. :::

:::{option} –split-dwo 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. :::

:::{option} –strip-dwo Remove all DWARF .dwo sections from the output. :::

:::{option} –strip-non-alloc Remove from the output all non-allocatable sections that are not within segments. :::

:::{option} –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. :::

:::{option} –target , -F Equivalent to --input-target and --output-target for the specified format. See [SUPPORTED FORMATS] for a list of valid <format> values. :::

:::{option} –verify-note-sections When adding note sections, verify if the section format is valid. On by default. :::

:::{option} –weaken-symbol , -W Mark global symbols named <symbol> as weak symbols in the output. Can be specified multiple times to mark multiple symbols as weak. :::

:::{option} –weaken-symbols 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. :::

:::{option} –weaken Mark all defined global symbols as weak in the output. :::

MACH-O-SPECIFIC OPTIONS¶

:::{option} –keep-undefined Keep undefined symbols, even if they would otherwise be stripped. :::

COFF-SPECIFIC OPTIONS¶

:::{option} –subsystem [:] Set the PE subsystem, and optionally subsystem version. :::

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
elf32-hexagon
elf32-loongarch
elf64-loongarch
elf64-s390
elf64-amdgpu

The following formats are supported by llvm-objcopy for the --output-target only:

srec

Additionally, all targets except binary, ihex, and srec 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 <https://github.com/llvm/llvm-project/labels/tools:llvm-objcopy/strip/>.

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.

LLVM