linux-kernel - Re: [PATCH v7 3/3] x86, mce: Add __mcsafe

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAPcyv4j3uvN4S=okc36N7PaMGf3HtUOwCf75-Vs9OtmA2nhKuw@mail.gmail.com>
Date:	Wed, 6 Jan 2016 09:05:01 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	"Elliott, Robert (Persistent Memory)" <elliott@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>,
	linux-nvdimm <linux-nvdimm@...1.01.org>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v7 3/3] x86, mce: Add __mcsafe_copy()

On Wed, Jan 6, 2016 at 8:57 AM, Luck, Tony <tony.luck@...el.com> wrote:
>>> I do select it, but by randconfig I still need to handle the
>>> CONFIG_X86_MCE=n case.
>>>
>>>> I'm seriously wondering whether the ifdef still makes sense. Now I don't have an extra exception table and routines to sort/search/fixup, it doesn't seem as useful as it was a few iterations ago.
>>>
>>> Either way is ok with me.  That said, the extra definitions to allow
>>> it compile out when not enabled don't seem too onerous.
>>
>> This works for me, because all we need is the definitions.  As long as
>> we don't attempt to link to mcsafe_copy() we get the benefit of
>> compiling this out when de-selected:
>
> It seems  that Kconfig's "select" statement doesn't auto-select other things
> that are dependencies of the symbol you choose.
>
> CONFIG_MCE_KERNEL_RECOVERY really is dependent on
> CONFIG_X86_MCE ... having the code for the __mcsafe_copy()
> linked into the kernel won't do you any good without a machine
> check handler that jumps to the fixup code.
>
> So I think you have to select X86_MCE as well (or Kconfig needs
> to be taught to do it automatically ... but I have a nagging feeling
> that this is known behavior).
>

I don't want to force it on, otherwise we might as well remove the
ability to configure it.  Instead I have this:

config BLK_DEV_PMEM
       select MCE_KERNEL_RECOVERY if X86_MCE && X86_64

...that way if you turn on X86_MCE and BLK_DEV_PMEM you get
MCE_KERNEL_RECOVERY by default.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/