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Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation

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On Fri, Mar 3, 2017 at 3:30 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Fri, Mar 3, 2017 at 2:55 PM, Alexander Potapenko <glider@google.com> wrote:
>> On Fri, Mar 3, 2017 at 2:50 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>
>>>> @@ -416,6 +416,17 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
>>>>   */
>>>>  #define noinline_for_stack noinline
>>>>
>>>> +/*
>>>> + * CONFIG_KASAN can lead to extreme stack usage with certain patterns when
>>>> + * one function gets inlined many times and each instance requires a stack
>>>> + * ckeck.
>>>> + */
>>>> +#ifdef CONFIG_KASAN
>>>> +#define noinline_for_kasan noinline __maybe_unused
>>>
>>>
>>> noinline_iff_kasan might be a better name.  noinline_for_kasan gives the impression
>>> that we always noinline function for the sake of kasan, while noinline_iff_kasan
>>> clearly indicates that function is noinline only if kasan is used.
>
> Fine with me. I actually tried to come up with a name that implies that the
> symbol is actually "inline" (or even __always_inline_ without KASAN, but
> couldn't think of any good name for it.
>
>> FWIW we may be facing the same problem with other compiler-based
>> tools, e.g. KMSAN (which isn't there yet).
>> So it might be better to choose a macro name that doesn't use the name "KASAN".
>> E.g. noinline_iff_memtool (or noinline_iff_memory_tool if that's not too long).
>> WDYT?
>
> Would KMSAN also force local variables to be non-overlapping the way that
> asan-stack=1 and -fsanitize-address-use-after-scope do? As I understood it,
> KMSAN would add extra code for maintaining the uninit bits, but in an example
> like this
The thing is that KMSAN (and other tools that insert heavyweight
instrumentation) may cause heavy register spilling which will also
blow up the stack frames.
> int f(int *);
> static inline __attribute__((always_inline)) int g(void)
> {
>     int i;
>     f(&i);
>     return i;
> }
> int f(void)
> {
>      return g()+g()+g()+g();
> }
>
> each of the four copies of 'i' could have the same location on the stack
> and get marked uninitialized again before calling f(). We only need
> noinline_for_kasan (whatever we end up calling that) for compiler
> features that force each instance of 'i' to have its own stack redzone.
>
>      Arnd



-- 
Alexander Potapenko
Software Engineer

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[PATCH 00/26] bring back stack frame warning with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
    Re: [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arend Van Spriel <arend.vanspriel@broadcom.com> - 2017-03-06 10:50 +0100
      Re: [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-06 12:00 +0100
        Re: [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arend Van Spriel <arend.vanspriel@broadcom.com> - 2017-03-06 12:20 +0100
          Re: [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-06 12:20 +0100
            Re: [PATCH 07/26] brcmsmac: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-06 12:40 +0100
  [PATCH 15/26] [media] tuners: i2c: reduce stack usage for tuner_i2c_xfer_* Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 11/26] rtlwifi: reduce stack usage for KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 04/26] tty: kbd: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 12/26] wl3501_cs: reduce stack size for KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 09/26] brcmsmac: split up wlc_phy_workarounds_nphy Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
    Re: [PATCH 09/26] brcmsmac: split up wlc_phy_workarounds_nphy Arend Van Spriel <arend.vanspriel@broadcom.com> - 2017-03-06 10:40 +0100
  [PATCH 01/26] compiler: introduce noinline_for_kasan annotation Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
    Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation Alexander Potapenko <glider@google.com> - 2017-03-03 15:00 +0100
      Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation Alexander Potapenko <glider@google.com> - 2017-03-03 15:40 +0100
        Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation Arnd Bergmann <arnd@arndb.de> - 2017-03-03 16:10 +0100
      Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation Arnd Bergmann <arnd@arndb.de> - 2017-03-03 15:40 +0100
    RE: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation David Laight <David.Laight@ACULAB.COM> - 2017-03-03 18:10 +0100
  [PATCH 05/26] netlink: mark nla_put_{u8,u16,u32} noinline_for_kasan Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
  [PATCH 08/26] brcmsmac: make some local variables 'static const' to reduce stack size Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:20 +0100
    Re: [PATCH 08/26] brcmsmac: make some local variables 'static const'  to reduce stack size Arend Van Spriel <arend.vanspriel@broadcom.com> - 2017-03-06 10:40 +0100
      Re: [PATCH 08/26] brcmsmac: make some local variables 'static const' to reduce stack size Kalle Valo <kvalo@codeaurora.org> - 2017-03-06 17:40 +0100
        Re: [PATCH 08/26] brcmsmac: make some local variables 'static const'  to reduce stack size Arnd Bergmann <arnd@arndb.de> - 2017-03-06 22:40 +0100
          Re: [PATCH 08/26] brcmsmac: make some local variables 'static const' to reduce stack size Kalle Valo <kvalo@codeaurora.org> - 2017-03-07 10:50 +0100
            Re: [PATCH 08/26] brcmsmac: make some local variables 'static const'  to reduce stack size Arend Van Spriel <arend.vanspriel@broadcom.com> - 2017-03-07 11:10 +0100
  [PATCH 22/26] drm/i915/gvt: don't overflow the kernel stack with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 18:40 +0100
  Re: [PATCH 24/26] ocfs2: reduce stack size with KASAN Joe Perches <joe@perches.com> - 2017-03-02 19:00 +0100
    Re: [PATCH 24/26] ocfs2: reduce stack size with KASAN Joe Perches <joe@perches.com> - 2017-03-02 23:50 +0100
      Re: [PATCH 24/26] ocfs2: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-03 00:10 +0100
        Re: [PATCH 24/26] ocfs2: reduce stack size with KASAN Joe Perches <joe@perches.com> - 2017-03-03 01:00 +0100
    Re: [PATCH 24/26] ocfs2: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-03 00:00 +0100
  [PATCH 24/26] ocfs2: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 20:10 +0100
  [PATCH 23/26] mtd: cfi: reduce stack size with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 20:20 +0100
  [PATCH 18/26] [media] i2c: cx25840: avoid stack overflow with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-02 23:30 +0100
  Re: [PATCH 00/26] bring back stack frame warning with KASAN Alexander Potapenko <glider@google.com> - 2017-03-03 13:30 +0100
    Re: [PATCH 00/26] bring back stack frame warning with KASAN Arnd Bergmann <arnd@arndb.de> - 2017-03-03 14:00 +0100
  Re: [PATCH 10/26] brcmsmac: reindent split functions Kalle Valo <kvalo@codeaurora.org> - 2017-03-06 17:50 +0100

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