---
name: "elfctl"
section: "1"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/elfctl"
---

# elfctl(1)

change an ELF binary's feature control note

## NAME

**elfctl** – change an ELF binary's feature control note

## SYNOPSIS

**elfctl** \[**-h** \| **--help**\] \[**-i**\] \[**-l**\] \[**-e** *featurelist*\] *file ...*

## DESCRIPTION

The **elfctl** utility modifies feature flags in the feature control note in an ELF binary.

The options are as follows:

- **-h** \| **--help**

  Print a usage message and exit.

- **-i**

  Ignore unknown feature flags in *featurelist*.

- **-l**

  List known ELF feature flags.

- **-e** *featurelist*

  Edit features from the given comma separated list *featurelist*. *featurelist* starts with one of the three operations: “+” to turn on the features, “-” to turn off the features, “=” to only turn on the given features. A comma separated list of feature names or numeric values follows the operation.

If **-e** is not specified **elfctl** displays the status of each feature in the ELF note in each *file ...*.

## EXIT STATUS

Exit status is 0 on success, and 1 if the command fails if a file does not exist, is too short, or fails to find or edit features note.

## EXAMPLES

The following is an example of a typical usage of the **elfctl** command:

```
elfctl file
elfctl -e +noaslr file
```

Features may be specified as numerical values:

```
elfctl -e =0x0001,0x0004 file
```

Features may also be specified as a single combined value:

```
elfctl -e =0x5 file
```

## NOTES

On amd64, on a machine with LA57 (5-level paging) mode supported and enabled, if both *la57* and *la48* feature flags are specified, the *la57* feature has priority over *la48*. The *vm.pmap.prefer\_uva\_la48* sysctl MIB defines the default user address space size for binaries which do not set either of these flags.

## SEE ALSO

[mitigations(7)](/mitigations/7.md)

## HISTORY

**elfctl** first appeared in FreeBSD 12.2.

## AUTHORS

**elfctl** was written by Bora Ozarslan ⟨*borako.ozarslan@gmail.com*⟩ under sponsorship from the FreeBSD Foundation.