On Tue, Sep 10, 2013 at 4:49 PM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> On Mon, Sep 9, 2013 at 10:06 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>>> [*] Why does m68k allmodconfig still succeed on kissb???
>>> It does fail for me, as m68k's copy_from_user_page() calls
>>> flush_icache_user_range(), which is not exported.
>>>
>> I don't see a build failure in m68k:allmodconfig either.
>>
>> flush_icache_user_range() is called from copy_to_user_page(), not from
>> copy_from_user_page(). copy_from_user_page() calls flush_cache_page()
>> which calls __flush_cache_030(). The first is inline, the second is
>> assembler, so I would expect it to work. Which doesn't answer
>> the question why it fails for you.
>
> Sorry, I meant copy_to_user_page().
>
> I tried with 2.6.3 from crosstool, and it succeeded, too.
>
> Turns out cfs_access_process_vm() is called with write=0 only.
> Gcc 2.6.3 optimizes away the write != 0 branch (which calls copy_to_user_page()
> and thus flush_icache_user_range()), while gcc 4.1.2 doesn't do that.
> Mystery solved.
>
Thanks for chasing down the root cause. I was also wondering why I
didn't see this when building on MIPS some time ago.
Thanks,
Tao
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
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