xref: /src/usr.bin/elfctl/elfctl.1 (revision b989c1dd1e2edc8cf7597d276625b454b7b72e6d) !

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.Dd October 5, 2023
.Dt ELFCTL 1
.Os
.Sh NAME
.Nm elfctl
.Nd change an ELF binary's feature control note
.Sh SYNOPSIS
.Nm
.Op Fl h | Fl -help
.Op Fl i
.Op Fl l
.Op Fl e Ar featurelist
.Ar
.Sh DESCRIPTION
The
.Nm
utility modifies feature flags in the feature control note in an ELF binary.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl h | Fl -help
Print a usage message and exit.
.It Fl i
Ignore unknown feature flags in
.Ar featurelist .
.It Fl l
List known ELF feature flags.
.It Fl e Ar featurelist
Edit features from the given comma separated list
.Ar featurelist .
.Ar featurelist
starts with one of the three operations:
.Dq Li +
to turn on the features,
.Dq Li -
to turn off the features,
.Dq Li =
to only turn on the given features.
A comma separated list of feature names or numeric values follows the
operation.
.El
.Pp
If
.Fl e
is not specified
.Nm
displays the status of each feature in the ELF note in each
.Ar .
.Sh 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.
.Sh EXAMPLES
The following is an example of a typical usage
of the
.Nm
command:
.Bd -literal -offset indent
elfctl file
elfctl -e +noaslr file
.Ed
.Pp
Features may be specified as numerical values:
.Bd -literal -offset indent
elfctl -e =0x0001,0x0004 file
.Ed
.Pp
Features may also be specified as a single combined value:
.Bd -literal -offset indent
elfctl -e =0x5 file
.Ed
.Sh NOTES
On amd64, on a machine with LA57 (5-level paging) mode supported and
enabled, if both
.Va la57
and
.Va la48
feature flags are specified, the
.Va la57
feature has priority over
.Va la48 .
The
.Va vm.pmap.prefer_uva_la48
sysctl MIB defines the default user address space size for binaries
which do not set either of these flags.
.Sh SEE ALSO
.Xr mitigations 7
.Sh HISTORY
.Nm
first appeared in
.Fx 12.2 .
.Sh AUTHORS
.Nm
was written by
.An Bora Ozarslan Mt borako.ozarslan@gmail.com
under sponsorship from the
.Fx Foundation.