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Re: [Qemu-devel] [PATCH v3] configure: add option to disable -fstack-pro
From: |
Laurent Desnogues |
Subject: |
Re: [Qemu-devel] [PATCH v3] configure: add option to disable -fstack-protector flags |
Date: |
Fri, 28 Mar 2014 16:31:27 +0100 |
Hello,
On Mon, Jan 13, 2014 at 9:36 PM, Steven Noonan <address@hidden> wrote:
> 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, no stack
> protector.
Why did you remove -fstack-protector-all which is the current default?
That being said, I manually applied your patch (it doesn't apply any
more) and ran it on qemu-system-arm.
Env: Fedora 19 x86_64, gcc 4.8.2, Intel 4770K (no OC, HT disabled)
Soft: ARM image booting kernel and running Sunspider with Google v8
main 17.8s
prot_off 16.5s
prot_off+patch+disable 15.5s
prot_off is with --disable-stack-protector
patch is with Paolo patch to ENV_GET_CPU
disable is with --disable-qom-cast-debug
Definitely a good speed up. I think a respin of that patch is needed
and would be a good thing :)
Thanks,
Laurent
> Signed-off-by: Steven Noonan <address@hidden>
> Cc: Anthony Liguori <address@hidden>
> Reviewed-by: Stefan Weil <address@hidden>
> ---
> configure | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/configure b/configure
> index 07b6be3..09f83a7 100755
> --- a/configure
> +++ b/configure
> @@ -147,6 +147,7 @@ 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
> @@ -879,6 +880,10 @@ 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"
> @@ -1117,6 +1122,7 @@ echo " --enable-sparse enable sparse checker"
> echo " --disable-sparse disable sparse checker (default)"
> echo " --disable-strip disable stripping binaries"
> echo " --disable-werror disable compilation abort on warning"
> +echo " --disable-stack-protector disable compiler-provided stack protection"
> echo " --disable-sdl disable SDL"
> echo " --enable-sdl enable SDL"
> echo " --disable-gtk disable gtk UI"
> @@ -1298,9 +1304,15 @@ 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"
> + 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
>
> # Workaround for http://gcc.gnu.org/PR55489. Happens with -fPIE/-fPIC and
> --
> 1.8.5.2
>
>
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Laurent Desnogues <=