linux-kernel - RE:[PATCH 2/2] mm/kasan: proc interface to read KASAN errors at any time

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Date:   Fri, 30 Apr 2021 15:24:33 +0530
From:   Maninder Singh <maninder1.s@...sung.com>
To:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
CC:     Marco Elver <elver@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        AMIT SAHRAWAT <a.sahrawat@...sung.com>,
        Vaneet Narang <v.narang@...sung.com>
Subject: RE:[PATCH 2/2] mm/kasan: proc interface to read KASAN errors at any
 time

Hi Alex,
 
 
>We've recently attempted to build a universal library capturing every
>error report, but then were pointed to tracefs, which was just enough
>for our purpose (https://protect2.fireeye.com/v1/url?k=36bfb191-6924888b-36be3ade-0cc47a6cba04-0e7fd520f09636ee&q=1&e=a6b7f23a-98d4-4084-af0a-a88af0b4c9d0&u=https%3A%2F%2Flkml.org%2Flkml%2F2021%2F1%2F15%2F609).
>Greg also stated that procfs is a bad place for storing reports:
>https://protect2.fireeye.com/v1/url?k=924a3ffc-cdd106e6-924bb4b3-0cc47a6cba04-882467cbf9e8b46f&q=1&e=a6b7f23a-98d4-4084-af0a-a88af0b4c9d0&u=https%3A%2F%2Flkml.org%2Flkml%2F2021%2F1%2F15%2F929.
> 
>Maninder, which exactly problem are you trying to solve?
 
 
We focussed on 2 problems, 1 is to remove duplicate error reporting
from KASAN when multishot is ON
 
and second was to save KASAN metadata (minimal) to regenerate same KASAN warnings
when user reads new proc interface.
 
>Note that KASAN already triggers a trace_error_report_end tracepoint
>on every error report:
>https://protect2.fireeye.com/v1/url?k=2d128c9c-7289b586-2d1307d3-0cc47a6cba04-3e939a06aa0346db&q=1&e=a6b7f23a-98d4-4084-af0a-a88af0b4c9d0&u=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv5.12-rc8%2Fsource%2Fmm%2Fkasan%2Freport.c%23L90
>Would it help if you used that one? It could probably be extended with
>more parameters.
> 
>Another option if you want verbatim reports is to use the console
>tracepoints, as this is done in
>https://protect2.fireeye.com/v1/url?k=5f368dc2-00adb4d8-5f37068d-0cc47a6cba04-fe4efc4f73dbea2f&q=1&e=a6b7f23a-98d4-4084-af0a-a88af0b4c9d0&u=https%3A%2F%2Felixir.bootlin.com%2Flinux%2Fv5.12-rc8%2Fsource%2Fmm%2Fkfence%2Fkfence_test.c
>Note that there are many caveats with error report collection (see the
>links above), but for testing purpose it might be enough.
> 
 
Ok We will check these tracing methods also.
 
Thanks
Maninder Singh