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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ARGUMENTS | EXAMPLES | SEE ALSO | BUGS | AUTHORS | COLOPHON |
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execstack(8) System Manager's Manual execstack(8)
execstack - tool to set, clear, or query executable stack flag of ELF
binaries and shared libraries
execstack [OPTION...] [FILES]
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.
-s --set-execstack
Mark binary or shared library as requiring executable stack.
-c --clear-execstack
Mark binary or shared library as not requiring executable
stack.
-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.
--usage
Print a short usage message.
Command line arguments should be names of ELF binaries and shared
libraries which should be modified or queried.
# 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.
ld.so(8).
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.
Jakub Jelinek <jakub@redhat.com>.
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 pre‐
link-20130503.tar.bz2 fetched from
⟨http://people.redhat.com/jakub/prelink/⟩ on 2018-02-02. If you dis‐
cover 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)
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