linux-kernel - Re: [GIT PULL] x86/alternatives padding

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Message-ID: <20150304210243.GH3516@pd.tnic>
Date:	Wed, 4 Mar 2015 22:02:43 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	x86-ml <x86@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/alternatives padding

On Wed, Mar 04, 2015 at 09:22:27PM +0100, Ingo Molnar wrote:
> So you could have a look at the detailed section dump itself via:
> 
>    objdump -h vmlinux
> 
> there .text will be the raw text and .alt* will be listed separately. 
> The 'size' tool will add up executable sections IIRC, mixing these 
> sections.

Right.

> .alt* is freed after init, so it's not really a kernel image size 
> increase, right?

Exactly:

void free_initmem(void)
{
        free_init_pages("unused kernel",
                        (unsigned long)(&__init_begin),
                        (unsigned long)(&__init_end));
}

which are:

 69708: ffffffff81ee9000     0 NOTYPE  GLOBAL DEFAULT   16 __init_begin
 72679: ffffffff81ff9000     0 NOTYPE  GLOBAL DEFAULT   25 __init_end

and there's a bunch of stuff between ffffffff81ee9000 and ffffffff81ff9000:

  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [17] .init.text        PROGBITS         ffffffff81efe000  012fe000
       0000000000066c98  0000000000000000  AX       0     0     16
  [18] .init.data        PROGBITS         ffffffff81f65000  01365000
       0000000000086d18  0000000000000000  WA       0     0     4096
  [19] .x86_cpu_dev.init PROGBITS         ffffffff81febd18  013ebd18
       0000000000000018  0000000000000000   A       0     0     8
  [20] .altinstructions  PROGBITS         ffffffff81febd30  013ebd30
       0000000000007e4b  0000000000000000   A       0     0     1
  [21] .altinstr_replace PROGBITS         ffffffff81ff3b7b  013f3b7b
       0000000000002044  0000000000000000  AX       0     0     1
  [22] .iommu_table      PROGBITS         ffffffff81ff5bc0  013f5bc0
       00000000000000c8  0000000000000000   A       0     0     8
  [23] .apicdrivers      PROGBITS         ffffffff81ff5c88  013f5c88
       0000000000000010  0000000000000000  WA       0     0     8
  [24] .exit.text        PROGBITS         ffffffff81ff5c98  013f5c98
       0000000000002412  0000000000000000  AX       0     0     1

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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