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Groups > linux.kernel > #1312869
| From | Brian Gerst <brgerst@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init |
| Date | 2016-01-20 05:40 +0100 |
| Message-ID | <qSSIO-1jE-65@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <qSnbY-4FZ-15@gated-at.bofh.it> <qSt7I-vW-11@gated-at.bofh.it> <qStr4-D8-1@gated-at.bofh.it> <qSALU-5Mg-9@gated-at.bofh.it> <qSSfM-16M-41@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Jan 19, 2016 at 11:02 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 01/19/16 01:22, Borislav Petkov wrote:
>> On Mon, Jan 18, 2016 at 05:33:03PM -0800, H. Peter Anvin wrote:
>>> Why the f do we call a subroutine for what amounts to a single bt or
>>> test instruction?
>>
>> No real reason. You can kick me when you see me next time:
>>
>> 4a90a99c4f80 ("x86: Add a static_cpu_has_safe variant")
>>
>
> So, here is my suggestion:
>
> 1. Just get rid of static_cpu_has_safe() and make static_cpu_has() safe.
>
> 2. Get rid of the non-asm goto variant and just fall back to dynamic if
> asm goto is unavailable. It doesn't make any sense, really, if it is
> supposed to be safe, and by now the asm goto-capable gcc is in more wide
> use. (Originally the gcc 3.x fallback to pure dynamic didn't exist,
> either.)
>
> 3. Put the dynamic test in the .init.text section and inline it:
>
> .section .init.text,"ax"
> testb %2,%3
> jnz %[t_yes]
> jmp %[t_no]
> .previous
>
> ... "i" (1 << (bit & 7)),
> "m" (((const char *)boot_cpu_data->x86_capability)[bit >> 3]) ...
Can't put it in .init.text or else you get:
WARNING: arch/x86/kernel/built-in.o(.text+0x4b9): Section mismatch in
reference from the function __switch_to() to the (unknown reference)
.init.text:(unknown)
The function __switch_to() references
the (unknown reference) __init (unknown).
This is often because __switch_to lacks a __init
annotation or the annotation of (unknown) is wrong.
We want to override that because we know that the reference will be
removed after alternatives run. That's why I created a new section.
--
Brian Gerst
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[PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-16 20:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-16 20:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-16 21:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-17 11:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-18 18:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-18 18:50 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-18 19:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-18 19:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-18 19:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-18 20:50 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 00:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-19 00:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 00:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 15:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 17:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 00:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Andy Lutomirski <luto@amacapital.net> - 2016-01-20 00:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Boris Petkov <bp@suse.de> - 2016-01-20 01:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 11:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 11:50 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-21 23:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-21 23:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-22 00:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-22 00:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-22 00:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-22 11:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-18 20:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 02:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-19 02:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-19 10:30 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Brian Gerst <brgerst@gmail.com> - 2016-01-20 05:40 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 05:50 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 12:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 12:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 15:50 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 12:00 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 16:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 16:20 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init Borislav Petkov <bp@suse.de> - 2016-01-20 17:10 +0100
Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init "H. Peter Anvin" <hpa@zytor.com> - 2016-01-20 17:20 +0100
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