linux-kernel - Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode

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Message-ID: <20141126144457.GB29982@pd.tnic>
Date:	Wed, 26 Nov 2014 15:44:57 +0100
From:	Borislav Petkov <bp@...e.de>
To:	boris ostrovsky <boris.ostrovsky@...cle.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Richard Hendershot <rshendershot@...si.com>,
	David Vrabel <david.vrabel@...rix.com>, x86-ml <x86@...nel.org>
Subject: Re: [PATCH 3.17 100/141] x86, microcode: Fix accessing dis_ucode_ldr
 on 32-bit

On Wed, Nov 26, 2014 at 07:39:26AM -0500, boris ostrovsky wrote:
> https://lkml.org/lkml/2014/11/25/973 is all I have right now.

Ok, so the Code: section from this splat says:

  25:   55                      push   %ebp
  26:   89 e5                   mov    %esp,%ebp
  28:   83 ec 08                sub    $0x8,%esp
  2b:*  80 3d c0 ee 97 01 00    cmpb   $0x0,0x197eec0           <-- trapping instruction
  32:   89 1c 24                mov    %ebx,(%esp)
  35:   89 74 24 04             mov    %esi,0x4(%esp)
  39:   74 12                   je     0x4d
  3b:   8b 1c 24                mov    (%esp),%ebx
  3e:   8b                      .byte 0x8b
  3f:   74                      .byte 0x74

which I can correlate to the dis_ucode_ldr test here:

        .loc 1 134 0
        .loc 1 137 0
        cmpb    $0, dis_ucode_ldr+1073741824    #, *_11
        je      .L46    #,


so we must be faulting when accessing that dis_ucode_ldr thing. But you
said that accessing it through its virtual address doesn't fix the issue
either. Which is very very strange...

Hmmm.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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