From: Andrey Konovalov <andreyknvl@gmail.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: andrey.konovalov@linux.dev, Marco Elver <elver@google.com>,
Alexander Potapenko <glider@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Sami Tolvanen <samitolvanen@google.com>,
Peter Collingbourne <pcc@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Florian Mayer <fmayer@google.com>,
Linux Memory Management List <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH v2 1/4] stacktrace: add interface based on shadow call stack
Date: Tue, 5 Apr 2022 17:37:06 +0200 [thread overview]
Message-ID: <CA+fCnZeVKv9iJknyHiKWF0QA3vx+SznJCDJ10Q_HmnzHmnpt=w@mail.gmail.com> (raw)
In-Reply-To: <YkVyGdniIBXf4t8/@FVFF77S0Q05N>
On Thu, Mar 31, 2022 at 11:19 AM Mark Rutland <mark.rutland@arm.com> wrote:
>
> > Collecting stack traces this way is significantly faster: boot time
> > of a defconfig build with KASAN enabled gets descreased by ~30%.
>
> Hmm... just to check, do ou know if that's just because of hte linear copy, or
> because we're skipping other work we have to do in the regular stacktrace?
No, I haven't looked into this.
> > The implementation of the added interface is not meant to use
> > stack_trace_consume_fn to avoid making a function call for each
> > collected frame to further improve performance.
>
> ... because we could easily provide an inline-optimized stack copy *without*
> having to write a distinct unwinder, and I'd *really* like to avoid having a
> bunch of distinct unwinders for arm64, as it really hinders maintenance. We're
> working on fixing/improving the arm64 unwinder for things like
> RELIABLE_STACKTRACE, and I know that some of that work is non-trivial to make
> work with an SCS-based unwind rather than an FP-based unwind, and/or will
> undermine the saving anyway.
Responded on the cover letter wrt this.
> > +int stack_trace_save_shadow(unsigned long *store, unsigned int size,
> > + unsigned int skipnr)
> > +{
> > + /*
> > + * Do not use stack_trace_consume_fn to avoid making a function
> > + * call for each collected frame to improve performance.
> > + * Skip + 1 frame to skip stack_trace_save_shadow.
> > + */
> > + return arch_stack_walk_shadow(store, size, skipnr + 1);
> > +}
> > +#endif
>
> If we really need this, can we make it an __always_inline in a header so that
> we can avoid the skip? Generally the skipping is problematic due to
> inlining/outlining and LTO, and I'd like to avoid adding more of it
> unnecessarily.
Yes, I think this should work.
However, if we keep the implementation in mm/kasan, this integration
will not be required.
Thanks!
next prev parent reply other threads:[~2022-04-05 20:15 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 15:32 [PATCH v2 0/4] kasan, arm64, scs, stacktrace: collect stack traces from Shadow Call Stack andrey.konovalov
2022-03-23 15:32 ` [PATCH v2 1/4] stacktrace: add interface based on shadow call stack andrey.konovalov
2022-03-25 20:46 ` Andrew Morton
2022-03-29 18:36 ` Andrey Konovalov
2022-03-31 9:19 ` Mark Rutland
2022-04-05 15:37 ` Andrey Konovalov [this message]
2022-03-23 15:32 ` [PATCH v2 2/4] arm64, scs: save scs_sp values per-cpu when switching stacks andrey.konovalov
2022-03-24 11:08 ` kernel test robot
2022-03-24 21:39 ` kernel test robot
2022-03-31 9:24 ` Mark Rutland
2022-04-05 15:22 ` Andrey Konovalov
2022-03-23 15:32 ` [PATCH v2 3/4] arm64: implement stack_trace_save_shadow andrey.konovalov
2022-03-24 8:35 ` kernel test robot
2022-03-31 9:32 ` Mark Rutland
2022-04-05 15:38 ` Andrey Konovalov
2022-03-23 15:32 ` [PATCH v2 4/4] kasan: use stack_trace_save_shadow andrey.konovalov
2022-03-28 12:49 ` Marco Elver
2022-03-29 18:36 ` Andrey Konovalov
2022-03-28 12:36 ` [PATCH v2 0/4] kasan, arm64, scs, stacktrace: collect stack traces from Shadow Call Stack Marco Elver
2022-03-29 18:36 ` Andrey Konovalov
2022-03-29 20:11 ` Andrey Konovalov
2022-03-31 9:54 ` Mark Rutland
2022-03-31 12:39 ` Mark Rutland
2022-04-05 15:10 ` Andrey Konovalov
2022-04-07 18:41 ` Mark Rutland
2022-04-13 19:28 ` Andrey Konovalov
2022-04-14 7:02 ` Mark Rutland
2022-04-05 15:09 ` Andrey Konovalov
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