Subject: Re: [GIT PULL] Compiler Attributes for v4.20-rc1
To: Linus Torvalds <torvalds@linux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: dan.carpenter@oracle.com, adilger.kernel@dilger.ca,
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        rostedt@goodmis.org, mchehab+samsung@kernel.org, olof@lxom.net,
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        Nick Desaulniers <ndesaulniers@google.com>,
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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
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Date: Fri, 2 Nov 2018 16:17:23 +0300
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On 11/02/2018 04:46 AM, Linus Torvalds wrote:
> On Thu, Nov 1, 2018 at 10:06 AM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> The logic for using __no_sanitize_address *used* to be
>>
>>     #if GCC_VERSION >= 40902
> 
> Ok, looking around, I think this has less to do with the attribute
> being recognized, and simply just being because KASAN itself wants
> gcc-4.9.2.
> 
> I'm actually not seeing that KASAN dependency in the Kconfig scripts
> (and it probably _should_ be now that we can just add compiler version
> dependencies there), but that explains why the gcc version check is
> different from "gcc supports the attribute".
> 
> Anyway, I decided to do the merge by just getting rid of the
> GCC_VERSION check around __no_sanitize_address_or_inline entirely. If
> you enable KASAN, then a function with that marking just won't be
> marked inline.
> 
> End result: pulled. I'm as confused as you are as to why
> __no_sanitize_address_or_inline is in the gcc header, but I guess it
> ends up being the same issue: KASAN depends on gcc even if that
> dependency doesn't seem to be spelled out in lib/Kconfig.kasan.
> 
> So I _think_ the KASAN config should have a
> 
>     depends on CC_IS_GCC && GCC_VERSION >= 40902
> 
> on it, but maybe there is something I'm missing.
> 

I'd rather use cc-option instead of version check, since we also support clang.

It should be possible to express compiler requirements for subfeatures
like stack/inline instrumentation in Kconfig. But that would be not that trivial, 
see the scripts/Makefile.kasan

> But from a pull standpoint, I don't want to mess with those
> (unrelated) issues, so I just kept the merge resolution as simple and
> straightforward as possible.
> 
> Miguel, please do double-check the merge (it's not pushed out yet, I'm
> doing the usual build tests etc first).
> 
>                     Linus
>