linux-kernel - Re: [PATCHv2 1/4] x86_64: cleanup THREAD

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20150121180429.GB31527@pd.tnic>
Date:	Wed, 21 Jan 2015 19:04:30 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>,
	Andy Lutomirski <luto@...capital.net>, X86 ML <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCHv2 1/4] x86_64: cleanup THREAD_INFO(reg,offset) macro

On Wed, Jan 21, 2015 at 05:20:09PM +0100, Alexander van Heukelum wrote:
> On Wed, Jan 21, 2015, at 14:40, Denys Vlasenko wrote:
> > On Sun, Jan 18, 2015 at 12:45 PM, Alexander van Heukelum
> > <heukelum@...tmail.fm> wrote:
> > > The macro THREAD_INFO(reg,offset) is used in assembly to compute the
> > > offset between the user ptregs and the thread_info struct. Change
> > > the macro and all its uses so that offset is given as the current
> > > top of stack in the pt_regs frame. The generated code is identical.
> > 
> > What is the purpose of doing this?
> > 
> > I don't mean to say that it's pointless, but it is also not obvious
> > why it's better than the code before patch.
> 
> Just because I had a hard time understanding what the offset
> parameter means. Turns out Borislav did another variant in his
> patchset. Quoting him from the commit message which made
> that the change:
> > Semi-mysterious expressions THREAD_INFO(%rsp,RIP) - "why RIP??"
> > are now replaced by more logical THREAD_INFO(%rsp,SIZEOF_PTREGS) -
> > "rsp is SIZEOF_PTREGS bytes below the top, calculate
> > thread_info's address using that information"
> 
> Borislav expresses "offset" as an offset from the stack's page
> boundary,while I chose the offset from the start of struct
> pt_regs on the stack.

I've never done any such thing :-)

s/Borislav/Denys/g.

-- 
Regards/Gruss,
    Boris.

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