On Fri, Mar 28, 2014 at 5:19 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: > From: Steven Noonan <ste...@uplinklabs.net> > > The -fstack-protector flag family is useful for ensuring safety and for > debugging, but has a performance impact. Here are some boot time comparisons > of > the various versions of -fstack-protector using qemu-system-arm on an x86_64 > host: > > # -fstack-protector-all > Startup finished in 1.810s (kernel) + 12.331s (initrd) + 49.016s > (userspace) = 1min 3.159s > Startup finished in 1.801s (kernel) + 12.287s (initrd) + 47.925s > (userspace) = 1min 2.013s > Startup finished in 1.812s (kernel) + 12.302s (initrd) + 47.995s > (userspace) = 1min 2.111s > > # -fstack-protector-strong > Startup finished in 1.744s (kernel) + 11.223s (initrd) + 44.688s > (userspace) = 57.657s > Startup finished in 1.721s (kernel) + 11.222s (initrd) + 44.194s > (userspace) = 57.138s > Startup finished in 1.693s (kernel) + 11.250s (initrd) + 44.426s > (userspace) = 57.370s > > # -fstack-protector > Startup finished in 1.705s (kernel) + 11.409s (initrd) + 43.563s > (userspace) = 56.677s > Startup finished in 1.877s (kernel) + 11.137s (initrd) + 43.719s > (userspace) = 56.734s > Startup finished in 1.708s (kernel) + 11.141s (initrd) + 43.628s > (userspace) = 56.478s > > # no stack protector > Startup finished in 1.743s (kernel) + 11.190s (initrd) + 43.709s > (userspace) = 56.643s > Startup finished in 1.763s (kernel) + 11.216s (initrd) + 43.767s > (userspace) = 56.747s > Startup finished in 1.711s (kernel) + 11.283s (initrd) + 43.878s > (userspace) = 56.873s > > This patch introduces a configure option to disable the stack protector > entirely, and conditional stack protector flag selection (in order, > based on availability): -fstack-protector-strong, -fstack-protector-all, > no stack protector. > > Signed-off-by: Steven Noonan <snoo...@amazon.com> > Cc: Anthony Liguori <aligu...@amazon.com> > Reviewed-by: Stefan Weil <s...@weilnetz.de> > [Prefer -fstack-protector-all to -fstack-protector, suggested by > Laurent Desnogues. - Paolo] > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > configure | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/configure b/configure > index fb3bd05..eb0e7bb 100755 > --- a/configure > +++ b/configure > @@ -198,6 +198,7 @@ audio_win_int="" > cc_i386=i386-pc-linux-gnu-gcc > libs_qga="" > debug_info="yes" > +stack_protector="" > > # Don't accept a target_list environment variable. > unset target_list > @@ -950,6 +951,10 @@ for opt do > ;; > --disable-werror) werror="no" > ;; > + --enable-stack-protector) stack_protector="yes" > + ;; > + --disable-stack-protector) stack_protector="no" > + ;; > --disable-curses) curses="no" > ;; > --enable-curses) curses="yes" > @@ -1219,6 +1224,7 @@ Advanced options (experts only): > --disable-sparse disable sparse checker (default) > --disable-strip disable stripping binaries > --disable-werror disable compilation abort on warning > + --disable-stack-protector disable compiler-provided stack protection > --disable-sdl disable SDL > --enable-sdl enable SDL > --with-sdlabi select preferred SDL ABI 1.2 or 2.0 > @@ -1439,9 +1445,15 @@ for flag in $gcc_flags; do > fi > done > > -if compile_prog "-Werror -fstack-protector-all" "" ; then > - QEMU_CFLAGS="$QEMU_CFLAGS -fstack-protector-all" > - LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,-fstack-protector-all" > +if test "$stack_protector" != "no" ; then > + gcc_flags="-fstack-protector-strong -fstack-protector-all" > + for flag in $gcc_flags; do > + if compile_prog "-Werror $flag" "" ; then > + QEMU_CFLAGS="$QEMU_CFLAGS $flag" > + LIBTOOLFLAGS="$LIBTOOLFLAGS -Wc,$flag" > + break > + fi > + done > fi
My understanding is that -fstack-protector, -fstack-protector-strong, and -fstack-protector-all are strictly ordered in terms of the number of functions that are checked, so you have changed the default behavior to check less functions for compilers that support -fstack-protector-strong. Is that what you had in mind? Also aren't there some versions of gcc that have -fstack-protector but not the other two options? Thanks, Laurent > # Workaround for http://gcc.gnu.org/PR55489. Happens with -fPIE/-fPIC and > -- > 1.8.5.3 >
