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Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init

From Brian Gerst <brgerst@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init
Date 2016-01-18 18:00 +0100
Message-ID <qSljR-3pb-13@gated-at.bofh.it> (permalink)
References <qREHU-i0-3@gated-at.bofh.it> <qRERA-mf-1@gated-at.bofh.it> <qRFaV-v0-1@gated-at.bofh.it> <qRSUx-1gy-15@gated-at.bofh.it>
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On Sun, Jan 17, 2016 at 5:33 AM, Borislav Petkov <bp@suse.de> wrote:
> On Sat, Jan 16, 2016 at 02:58:21PM -0500, Brian Gerst wrote:
>> It saves space.  The only thing left in main text is one jump
>> instruction (5 bytes).
>
> How do I measure this?
>
> Because with my tailored config here, the only thing I'm seeing is a growth of
> text by 730 bytes:
>
> before:
>    text    data     bss     dec     hex filename
> 10926552        3598944 16642048        31167544        1db9438 vmlinux
>
> [    0.056552] Freeing SMP alternatives memory: 24K (ffffffff81dd7000 - ffffffff81ddd000)
> [    2.883728] Freeing unused kernel memory: 2904K (ffffffff81b01000 - ffffffff81dd7000)
>
>
> after:
>    text    data     bss     dec     hex filename
> 10927282        3598944 16642048        31168274        1db9712 vmlinux
>
> [    0.052559] Freeing SMP alternatives memory: 24K (ffffffff81dd7000 - ffffffff81ddd000)
> [    3.225318] Freeing unused kernel memory: 2904K (ffffffff81b01000 - ffffffff81dd7000)

It is due to page alignment padding.  It was not enough to lose a
whole page from .text in your case.

The size command includes any section that is marked executable in the
text count, including init text.  If you use readelf -S vmlinux.o
instead you will notice that .text is the same size or smaller, and
.static_cpu_has (which is freed after boot) is the difference.

--
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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