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From: Kees Cook <keescook@chromium.org>
Date: Wed, 30 May 2018 20:53:45 -0700
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Subject: Re: linux-next: build warnings after merge of the kbuild tree
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, May 30, 2018 at 6:26 PM, Kees Cook <keescook@chromium.org> wrote:
> On Wed, May 30, 2018 at 6:12 PM, Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> Hi.
>> (+CC Kees)
>>
>> 2018-05-31 7:40 GMT+09:00 Stephen Rothwell <sfr@canb.auug.org.au>:
>>> Hi Masahiro,
>>>
>>> After merging the kbuild tree, today's linux-next build (x86_64
>>> allmodconfig) produced these warnings:
>>>
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c: In function 'wlc_phy_workarounds_nphy_rev7':
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c:16563:1: warning: the frame size of 3136 bytes is larger than 2048 bytes [-Wframe-larger-than=]
>>>  }
>>>  ^
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c: In function 'wlc_phy_workarounds_nphy_rev3':
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c:16905:1: warning: the frame size of 2872 bytes is larger than 2048 bytes [-Wframe-larger-than=]
>>>  }
>>>  ^
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c: In function 'wlc_phy_cal_txiqlo_nphy':
>>> drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c:26033:1: warning: the frame size of 2432 bytes is larger than 2048 bytes [-Wframe-larger-than=]
>>>  }
>>>  ^
>>>
>>> I have no idea what caused these warnings to appear ... nothing in those
>>> functions looks too bad.
>>
>>
>> This has been triggered by the following commit:
>>
>>
>> commit 0e461945f3504e09b8ecf947b6398adce1287a28
>> Author: Masahiro Yamada <yamada.masahiro@socionext.com>
>> Date:   Mon May 28 18:22:07 2018 +0900
>>
>>     gcc-plugins: allow to enable GCC_PLUGINS for COMPILE_TEST
>>
>>
>>
>> CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL was previously disabled
>> for COMPILE_TEST, which is now enabled.
>
> Weird -- I do build tests with plugins enabled pretty regularly. I
> hadn't seen this before. I'll see if I can figure out what the
> combination is...

Weirdly, I only see this after merging kbuild/for-next into
next-20180530. (I don't get the warning if I just force the plugins
on.)

Regardless, I can confirm that CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
trips it. I'll investigate more tomorrow...

-Kees

-- 
Kees Cook
Pixel Security