From: Andy Lutomirski <luto@amacapital.net>
To: Stefani Seibold <stefani@seibold.net>
Cc: linux-kernel@vger.kernel.org, ak@linux.intel.com,
aarcange@redhat.com, john.stultz@linaro.org,
Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH] Add VDSO time function support for x86 32-bit kernel
Date: Tue, 11 Dec 2012 17:29:44 -0800 [thread overview]
Message-ID: <CALCETrU6KporkvG8Pgx9jS3P_tPT5yDQE=tSktnn1RwDip-yTg@mail.gmail.com> (raw)
In-Reply-To: <1355258415.30831.2.camel@wall-e>
[cc: Jeremy Fitzhardinge -- you wrote some of this]
On Tue, Dec 11, 2012 at 12:40 PM, Stefani Seibold <stefani@seibold.net> wrote:
> Am Dienstag, den 11.12.2012, 11:37 -0800 schrieb Andy Lutomirski:
>> On Tue, Dec 11, 2012 at 8:11 AM, <stefani@seibold.net> wrote:
>> > --- a/arch/x86/vdso/vclock_gettime.c
>> > +++ b/arch/x86/vdso/vclock_gettime.c
>> > @@ -59,14 +59,23 @@ notrace static cycle_t vread_tsc(void)
>> >
>> > static notrace cycle_t vread_hpet(void)
>> > {
>> > +#ifdef CONFIG_X86_64
>> > return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
>> > +#else
>> > + return readl(VVAR(vsyscall_hpet) + HPET_COUNTER);
>> > +#endif
>> > }
>>
>> Is 0xf0 not equal to HPET_COUNTER?
>>
>
> Yes, but HPET_COUNTER is more readable.
Sorry -- read it backwards. Can you change the 64-bit one as well?
>
>> >
>> > notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
>> > {
>> > long ret;
>> > +#ifdef CONFIG_X86_64
>> > asm("syscall" : "=a" (ret) :
>> > "0" (__NR_clock_gettime),"D" (clock), "S" (ts) : "memory");
>> > +#else
>> > + asm("int $0x80" : "=a" (ret) :
>> > + "a" (__NR_clock_gettime), "b" (clock), "c" (ts) : "memory");
>> > +#endif
>> > return ret;
>> > }
>>
>> __kernel_vsyscall is probably much faster if you can figure out how to
>> call it from here :)
>>
>
> Yes i know. Thats one of my problems, because i cannot call
> __kernel_vsyscall directly due the relocation. Any idea?
What actually goes wrong? I think that if calling __kernel_vsyscall
like a normal symbol doesn't work then it's a bug in the relocation.
What's the point of this relocation? It appears thoroughly useless in
the !compat case.
--Andy
next prev parent reply other threads:[~2012-12-12 1:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 16:11 [PATCH] Add VDSO time function support for x86 32-bit kernel stefani
2012-12-11 19:27 ` John Stultz
2012-12-11 19:37 ` Andy Lutomirski
2012-12-11 20:54 ` Stefani Seibold
2012-12-11 21:18 ` Andy Lutomirski
2012-12-11 21:28 ` Stefani Seibold
2012-12-11 19:37 ` Andy Lutomirski
2012-12-11 20:40 ` Stefani Seibold
2012-12-12 1:29 ` Andy Lutomirski [this message]
2012-12-12 20:19 stefani
2012-12-12 23:34 ` H. Peter Anvin
2012-12-13 5:53 ` Stefani Seibold
2012-12-13 6:10 ` H. Peter Anvin
2012-12-13 6:14 ` H. Peter Anvin
2012-12-13 6:17 ` Stefani Seibold
2012-12-13 6:47 ` H. Peter Anvin
2012-12-13 7:17 ` Stefani Seibold
2012-12-13 19:32 ` Andy Lutomirski
2012-12-14 0:09 ` H. Peter Anvin
2012-12-14 0:20 ` Andy Lutomirski
2012-12-14 0:36 ` H. Peter Anvin
2012-12-14 1:32 ` H. Peter Anvin
2012-12-14 1:42 ` Andy Lutomirski
2012-12-14 1:49 ` H. Peter Anvin
2012-12-14 2:11 ` Andy Lutomirski
2012-12-14 2:18 ` H. Peter Anvin
2012-12-14 2:20 ` Andy Lutomirski
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