Re: [kbuild-all] drivers/media/dvb-frontends/cxd2841er.c:2393:1: warning: the frame size of 2992 bytes is larger than 2048 bytes

[Fengguang Wu <fengguang.wu@intel.com>]

Hi Abylay,

> cause of this 'Kernel Address sanitizer (KASan)' is enabled in your
> config. With gcc-4.9 kasan was disabled in compile time because of:
> "scripts/Makefile.kasan:23: CONFIG_KASAN: compiler does not support
> all options. Trying minimal configuration"
> 
> but with gcc-5 it's enabled.
> 
> and
> objdump -d drivers/media/dvb-frontends/cxd2841er.o
> 
> shows that KASan adds some instructions to 'cxd2841er_sleep_tc' which
> writes necessary data to -fasan-shadow-offset=0xdffffc0000000000:
>     1476:       48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
> ...
>     14d3:       c7 00 f1 f1 f1 f1       movl   $0xf1f1f1f1,(%rax)
>     14d9:       c7 40 04 01 f4 f4 f4    movl   $0xf4f4f401,0x4(%rax)
>     14e0:       c7 40 08 f2 f2 f2 f2    movl   $0xf2f2f2f2,0x8(%rax)
>     14e7:       c7 40 0c 01 f4 f4 f4    movl   $0xf4f4f401,0xc(%rax)
> ...
> 
> and function will grow and we get '-Wframe-larger-than=2048' warnings.
> 
> So, this warning looks normal  (until they less than 8K I think) for
> configurations with KASan enabled.
> 
> I can suggest:
> * ignore this warning if KASan enabled

Yes I can easily teach the kbuild robot to ignore this warning when
KASan enabled. Thanks for the explanations!

> * Increase -Wframe-larger-than=2048 to -Wframe-larger-than=8192 if
> KASan enabled ( CONFIG_FRAME_WARN=8192 in kernel .config)

Would it be possible to auto increase the threshold (in below Kconfig) when
KASan is enabled, so that all other developers/testers won't get the warnings,
too?

lib/Kconfig.debug

config FRAME_WARN
        int "Warn for stack frames larger than (needs gcc 4.4)"
        range 0 8192
        default 1024 if !64BIT
        default 2048 if 64BIT

Thanks,
Fengguang

> 2015-09-25 12:46 GMT+03:00 Fengguang Wu <fengguang.wu@intel.com>:
> > Hi Abylay,
> >
> > This warning can be reproduced with gcc-5.2:
> >
> > =============== commit a6dc60ff1 ===============
> > /home/wfg/linux
> > HEAD is now at a6dc60ff... [media] cxd2841er: Sony CXD2841ER DVB-S/S2/T/T2/C demodulator driver
> > /home/wfg/linux/obj-compiletest
> >
> > make ARCH=x86_64 drivers/media/dvb-frontends/cxd2841er.o
> >
> > grep -a -F drivers/media/dvb-frontends/cxd2841er.c /tmp/build-err-a6dc60ff1209df29ee4668024e93d31f31421932-wfg --color
> > ../drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_sleep_tc':
> > ../drivers/media/dvb-frontends/cxd2841er.c:2393:1: warning: the frame size of 2992 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >  }
> >  ^
> > ../drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_set_frontend_tc':
> > ../drivers/media/dvb-frontends/cxd2841er.c:2274:1: warning: the frame size of 4336 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >  }
> >  ^
> >
> > =============== PREV commit e025273b86fb4a6440192b809e05332777c3faa5 ===============
> > /home/wfg/linux
> > Previous HEAD position was a6dc60ff... [media] cxd2841er: Sony CXD2841ER DVB-S/S2/T/T2/C demodulator driver
> > HEAD is now at e025273... [media] lnbh25: LNBH25 SEC controller driver
> > /home/wfg/linux/obj-compiletest
> >
> > make ARCH=x86_64 drivers/media/dvb-frontends/cxd2841er.o
> >
> > !!! BUILD ERROR !!!
> > grep -a -F drivers/media/dvb-frontends/cxd2841er.c /tmp/build-err-e025273b86fb4a6440192b809e05332777c3faa5-wfg --color
> >
> > =============== linus/master linus/master ===============
> > /home/wfg/linux
> > Previous HEAD position was e025273... [media] lnbh25: LNBH25 SEC controller driver
> > HEAD is now at 8e64a73... Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
> > /home/wfg/linux/obj-compiletest
> >
> > make ARCH=x86_64 drivers/media/dvb-frontends/cxd2841er.o
> >
> > grep -a -F drivers/media/dvb-frontends/cxd2841er.c /tmp/build-err-8e64a7331702b7888ccf84b2b9ff46ab8e167c7f-wfg --color
> > ../drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_sleep_tc':
> > ../drivers/media/dvb-frontends/cxd2841er.c:2401:1: warning: the frame size of 2984 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >  }
> >  ^
> > ../drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_set_frontend_tc':
> > ../drivers/media/dvb-frontends/cxd2841er.c:2282:1: warning: the frame size of 4336 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >  }
> >  ^
> >
> > Thanks,
> > Fengguang
> >
> > On Fri, Sep 25, 2015 at 12:21:57PM +0300, Abylay Ospan wrote:
> >> Hello,
> >>
> >> I cannot reproduce this warning. I'm compiling with your config and
> >> following commands:
> >>
> >>   git checkout a6dc60ff1209df29ee4668024e93d31f31421932
> >>   make ARCH=x86_64
> >>
> >> my gcc version is 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
> >>
> >> warning doesn't appear even if I set:
> >> CONFIG_FRAME_WARN=128
> >>
> >> Please point me if problem still exist.
> >>
> >> thanks !
> >>
> >>
> >>
> >> 2015-09-17 9:05 GMT+03:00 kbuild test robot <fengguang.wu@intel.com>:
> >> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >> > head:   72714841b705a5b9bccf37ee85a62352bee3a3ef
> >> > commit: a6dc60ff1209df29ee4668024e93d31f31421932 [media] cxd2841er: Sony CXD2841ER DVB-S/S2/T/T2/C demodulator driver
> >> > date:   5 weeks ago
> >> > config: x86_64-randconfig-b0-09171322 (attached as .config)
> >> > reproduce:
> >> >   git checkout a6dc60ff1209df29ee4668024e93d31f31421932
> >> >   # save the attached .config to linux build tree
> >> >   make ARCH=x86_64
> >> >
> >> > All warnings (new ones prefixed by >>):
> >> >
> >> >    drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_sleep_tc':
> >> >>> drivers/media/dvb-frontends/cxd2841er.c:2393:1: warning: the frame size of 2992 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >> >     }
> >> >     ^
> >> >    drivers/media/dvb-frontends/cxd2841er.c: In function 'cxd2841er_set_frontend_tc':
> >> >    drivers/media/dvb-frontends/cxd2841er.c:2274:1: warning: the frame size of 4336 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >> >     }
> >> >     ^
> >> >
> >> > vim +2393 drivers/media/dvb-frontends/cxd2841er.c
> >> >
> >> >   2377                  case SYS_DVBC_ANNEX_A:
> >> >   2378                          cxd2841er_active_c_to_sleep_tc(priv);
> >> >   2379                          break;
> >> >   2380                  default:
> >> >   2381                          dev_warn(&priv->i2c->dev,
> >> >   2382                                  "%s(): unknown delivery system %d\n",
> >> >   2383                                  __func__, priv->system);
> >> >   2384                  }
> >> >   2385          }
> >> >   2386          if (priv->state != STATE_SLEEP_TC) {
> >> >   2387                  dev_err(&priv->i2c->dev, "%s(): invalid state %d\n",
> >> >   2388                          __func__, priv->state);
> >> >   2389                  return -EINVAL;
> >> >   2390          }
> >> >   2391          cxd2841er_sleep_tc_to_shutdown(priv);
> >> >   2392          return 0;
> >> >> 2393  }
> >> >   2394
> >> >   2395  static int cxd2841er_send_burst(struct dvb_frontend *fe,
> >> >   2396                                  enum fe_sec_mini_cmd burst)
> >> >   2397  {
> >> >   2398          u8 data;
> >> >   2399          struct cxd2841er_priv *priv  = fe->demodulator_priv;
> >> >   2400
> >> >   2401          dev_dbg(&priv->i2c->dev, "%s(): burst mode %s\n", __func__,
> >> >
> >> > ---
> >> > 0-DAY kernel test infrastructure                Open Source Technology Center
> >> > https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
> >>
> >>
> >>
> >> --
> >> Abylay Ospan,
> >> NetUP Inc.
> >> http://www.netup.tv
> >> _______________________________________________
> >> kbuild-all mailing list
> >> kbuild-all@lists.01.org
> >> https://lists.01.org/mailman/listinfo/kbuild-all
> 
> 
> 
> -- 
> Abylay Ospan,
> NetUP Inc.
> http://www.netup.tv
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