linux-kernel - Re: [PATCH] kasan: add __asan_report_loadN/storeN

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Date:   Tue, 23 Jan 2018 16:34:23 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kasan: add __asan_report_loadN/storeN_noabort callbacks

On Tue, Jan 23, 2018 at 11:44 AM, Andrey Ryabinin
<aryabinin@...tuozzo.com> wrote:
> On 01/19/2018 08:44 PM, Andrey Konovalov wrote:
>> Instead of __asan_report_load_n_noabort and __asan_report_store_n_noabort
>> callbacks Clang emits differently named __asan_report_loadN_noabort and
>> __asan_report_storeN_noabort (similar to __asan_loadN/storeN_noabort, whose
>> names both GCC and Clang agree on).
>>
>> Add callback implementation for __asan_report_loadN/storeN_noabort.
>>
>
> This made me wonder why this wasn't observed before. So I noticed that
> inline instrumentation with -fsanitize=kernel-addresss is broken in clang,
> and clang never calls __asan_report*() functions. I see that you guys fixed this
> just yesterday https://reviews.llvm.org/D42384 .

Correct.

>
> But it seems that you didn't fix the rest of "if (CompileKernel)" crap.
> Clang generates "__asan_report_[load,store]N*" instead of "__asan_report_[load,store]_n*"
> only because of this idiocy:
>
>         const std::string SuffixStr = CompileKernel ? "N" : "_n";
>
> See https://github.com/llvm-mirror/llvm/blob/ca19eaabd75f55865efd321b7a6f1d4ba3db8bc8/lib/Transforms/Instrumentation/AddressSanitizer.cpp#L2250
>
> Note that SuffixStr is used *only* for __asan_report_* callbacks, which makes no sense because
> we never ever had __asan_report* callbacks with "N" suffix.
>
> So I think that you should just fix the llvm here.

I think you are right.

I thought that GCC uses different and inconsistent callback names for
the kernel and user space, but that doesn't seem to be the case.

I submitted an LLVM change: https://reviews.llvm.org/D42423

Please discard this patch.

>
> And there is probably one more "if (CompileKernel)" crap in runOnModule()
> which breaks globals instrumentation.

Right, this will be fixed at some point.

>
>
>