linux-kernel - Re: [PATCH v2] objtool,ftrace: Implement UNWIND_HINT_RET

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: <20200401142015.60ac0a28@gandalf.local.home>
Date:   Wed, 1 Apr 2020 14:20:15 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Julien Thierry <jthierry@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, x86@...nel.org, mhiramat@...nel.org,
        mbenes@...e.cz
Subject: Re: [PATCH v2] objtool,ftrace: Implement UNWIND_HINT_RET_OFFSET

On Wed, 1 Apr 2020 19:45:44 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> > I believe what Julien is saying is the above logic is equivalent:
> > 
> > 	if (x != y &&
> > 	    !(z && x == y + z))
> > 
> > is the same as:
> > 
> > 	if (x != y + z)  
> 
> It is not, the former will accept either x==y || x==y+z, while the
> latter will only accept x==y+z.

No, the former accepts:

	x==y || (z && x == y + z)

Which is the same as: x == y + z

As the second condition is only tested if z != 0, and x ==  y is the same
as x == y + 0

-- Steve