linux-kernel - Re: [PATCH v2 2/2] kernel.h: Disable -Wreturn-stack-address for _THIS_IP

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Date:   Tue, 31 Jul 2018 10:02:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     kbuild test robot <lkp@...el.com>, kbuild-all@...org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>, paul.burton@...s.com,
        Christophe Leroy <christophe.leroy@....fr>,
        Stafford Horne <shorne@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Ingo Molnar <mingo@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Borislav Petkov <bp@...e.de>, NeilBrown <neilb@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        sandipan@...ux.vnet.ibm.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Paul Lawrence <paullawrence@...gle.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Will Deacon <will.deacon@....com>, ghackmann@...roid.com,
        "# 3.4.x" <stable@...r.kernel.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Wei Wang <wvw@...gle.com>, Andrew Vagin <avagin@...nvz.org>
Subject: Re: [PATCH v2 2/2] kernel.h: Disable -Wreturn-stack-address for _THIS_IP_

On Tue, Jul 31, 2018 at 9:48 AM, Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
> Does anyone understand this error?  The code looks just fine to me,
> and the source file doesn't conflict with any of the macros I've added
> (certainly not in any way that could cause an indentation error as
> reported here).

It does _use_ the macro, but yeah, I'm stumped...

> On Tue, Jul 31, 2018 at 3:27 AM kbuild test robot <lkp@...el.com> wrote:
>>    drivers/net//wireless/intel/iwlwifi/iwl-trans.c: In function 'iwl_trans_send_cmd':
>> >> drivers/net//wireless/intel/iwlwifi/iwl-trans.c:137:2: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
>>      if (!(cmd->flags & CMD_ASYNC))
>>      ^~
>>    drivers/net//wireless/intel/iwlwifi/iwl-trans.c:138:1: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
>>       lock_map_acquire_read(&trans->sync_cmd_lockdep_map);
>>     ^ ~
>>
>> vim +/if +137 drivers/net//wireless/intel/iwlwifi/iwl-trans.c
>>
>> 92fe8343 Emmanuel Grumbach 2015-12-01 @137      if (!(cmd->flags & CMD_ASYNC))
>> 92fe8343 Emmanuel Grumbach 2015-12-01  138              lock_map_acquire_read(&trans->sync_cmd_lockdep_map);

#define lock_map_acquire_read(l)
lock_acquire_shared_recursive(l, 0, 0, NULL, _THIS_IP_)

#define lock_acquire_shared_recursive(l, s, t, n, i)
lock_acquire(l, s, t, 2, 1, n, i)

The config doesn't have CONFIG_LOCKDEP, so it's not:

extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                         int trylock, int read, int check,
                         struct lockdep_map *nest_lock, unsigned long ip);

but rather:

# define lock_acquire(l, s, t, r, c, n, i)      do { } while (0)

If you build with the same gcc and config, does it reproduce for you?

-Kees

-- 
Kees Cook
Pixel Security