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Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN

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On Wed, Jun 14, 2017 at 11:15:38PM +0200, Arnd Bergmann wrote:
> As reported by kernelci, some functions in the VT code use significant
> amounts of kernel stack when local variables get inlined into the caller
> multiple times:
> 
> drivers/tty/vt/keyboard.c: In function 'kbd_keycode':
> drivers/tty/vt/keyboard.c:1452:1: error: the frame size of 2240 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
> 
> Annotating those functions as noinline_if_stackbloat prevents the inlining
> and reduces the overall stack usage in this driver.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/tty/vt/keyboard.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> index f4166263bb3a..c0d111444a0e 100644
> --- a/drivers/tty/vt/keyboard.c
> +++ b/drivers/tty/vt/keyboard.c
> @@ -301,13 +301,13 @@ int kbd_rate(struct kbd_repeat *rpt)
>  /*
>   * Helper Functions.
>   */
> -static void put_queue(struct vc_data *vc, int ch)
> +static noinline_if_stackbloat void put_queue(struct vc_data *vc, int ch)
>  {
>  	tty_insert_flip_char(&vc->port, ch, 0);
>  	tty_schedule_flip(&vc->port);
>  }

Ugh, really?  We have to start telling gcc not to be stupid here?
That's not going to be easy, and will just entail us doing this all over
the place, right?

The code isn't asking to be inlined, so why is gcc allowing it to be
done that way?  Doesn't that imply gcc is the problem here?

thanks,

greg k-h

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[PATCH v2 00/11] bring back stack frame warning with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:20 +0200
  [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:20 +0200
    Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-06-14 23:30 +0200
      Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-15 00:00 +0200
        Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-06-15 00:20 +0200
    Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 07:00 +0200
      Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-15 07:00 +0200
        Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-16 14:10 +0200
          Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-16 15:10 +0200
            Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-16 17:50 +0200
              Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-06-16 18:00 +0200
                Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-06-16 19:30 +0200
                Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-16 23:00 +0200
                Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-06-16 23:10 +0200
  [PATCH v2 04/11] rocker: mark rocker_tlv_put_* functions as noinline_if_stackbloat Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:20 +0200
  [PATCH v2 01/11] compiler: introduce noinline_if_stackbloat annotation Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:20 +0200
  [PATCH v2 09/11] brcmsmac: split up wlc_phy_workarounds_nphy Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200
  [PATCH v2 06/11] dvb-frontends: reduce stack size in i2c access Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200
  [PATCH v2 11/11] kasan: rework Kconfig settings Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200
    Re: [PATCH v2 11/11] kasan: rework Kconfig settings Dmitry Vyukov <dvyukov@google.com> - 2017-06-15 09:10 +0200
      Re: [PATCH v2 11/11] kasan: rework Kconfig settings Dmitry Vyukov <dvyukov@google.com> - 2017-06-16 13:50 +0200
      Re: [PATCH v2 11/11] kasan: rework Kconfig settings Arnd Bergmann <arnd@arndb.de> - 2017-06-16 13:50 +0200
  [PATCH v2 08/11] brcmsmac: make some local variables 'static const' to reduce stack size Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200
    Re: [PATCH v2 08/11] brcmsmac: make some local variables 'static const' to reduce stack size Kalle Valo <kvalo@codeaurora.org> - 2017-06-15 17:00 +0200
  [PATCH v2 07/11] r820t: mark register functions as noinline_if_stackbloat Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200
  [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-06-14 23:30 +0200

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