execstack(8) — Linux manual page


execstack(8)             System Manager's Manual            execstack(8)

NAME         top

       execstack - tool to set, clear, or query executable stack flag of
       ELF binaries and shared libraries

SYNOPSIS         top

       execstack [OPTION...] [FILES]

DESCRIPTION         top

       execstack is a program which sets, clears, or queries executable
       stack flag of ELF binaries and shared libraries.  Linux has in
       the past allowed execution of instructions on the stack and there
       are lots of binaries and shared libraries assuming this
       behaviour.  Furthermore, GCC trampoline code for e.g. nested
       functions requires executable stack on many architectures.  To
       avoid breaking binaries and shared libraries which need
       executable stack, ELF binaries and shared libraries now can be
       marked as requiring executable stack or not requiring it.  This
       marking is done through the p_flags field in the PT_GNU_STACK
       program header entry.  If the marking is missing, kernel or
       dynamic linker need to assume it might need executable stack.
       The marking is done automatically by recent GCC versions (objects
       using trampolines on the stack are marked as requiring executable
       stack, all other newly built objects are marked as not requiring
       it) and linker collects these markings into marking of the whole
       binary or shared library.  The user can override this at assembly
       time (through --execstack or --noexecstack assembler options), at
       link time (through -z execstack or -z noexecstack linker options)
       and using the execstack tool also on an already linker binary or
       shared library.  This tool is especially useful for third party
       shared libraries where it is known that they don't need
       executable stack or testing proves it.

OPTIONS         top

       -s --set-execstack
              Mark binary or shared library as requiring executable

       -c --clear-execstack
              Mark binary or shared library as not requiring executable

       -q --query
              Query executable stack marking of binaries and shared
              libraries.  For each file it prints either - when
              executable stack is not required, X when executable stack
              is required or ?  when it is unknown whether the object
              requires or doesn't require executable stack (the marking
              is missing).

       -V     Print execstack version and exit.

       -? --help
              Print help message.

              Print a short usage message.

ARGUMENTS         top

       Command line arguments should be names of ELF binaries and shared
       libraries which should be modified or queried.

EXAMPLES         top

              # execstack -s ~/lib/libfoo.so.1
       will mark ~/lib/libfoo.so.1 as requiring executable stack.
              # execstack -c ~/bin/bar
       will mark ~/bin/bar as not requiring executable stack.
              # execstack -q ~/lib/libfoo.so.1 ~/bin/bar
       will query executable stack marking of the given files.

SEE ALSO         top


BUGS         top

       execstack doesn't support yet marking of executables if they do
       not have PT_GNU_STACK program header entry nor they have room for
       program segment header table growth.

AUTHORS         top

       Jakub Jelinek <jakub@redhat.com>.

COLOPHON         top

       This page is part of the prelink (prelink ELF shared libraries
       and binaries) project.  Information about the project can be
       found at ⟨http://people.redhat.com/jakub/prelink/⟩.  It is not
       known how to report bugs for this man page; if you know, please
       send a mail to man-pages@man7.org.  This page was obtained from
       the tarball prelink-20130503.tar.bz2 fetched from
       ⟨http://people.redhat.com/jakub/prelink/⟩ on 2023-12-22.  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

                             28 October 2003                execstack(8)