Message-ID: <55C2B36C.20001@caviumnetworks.com>
Date: Wed, 5 Aug 2015 18:07:56 -0700
From: David Daney <ddaney@caviumnetworks.com>
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To: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
CC: Paul Burton <paul.burton@imgtec.com>, <daniel.sanders@imgtec.com>,
        <linux-mips@linux-mips.org>, <cernekee@gmail.com>,
        <Zubair.Kakakhel@imgtec.com>, <geert+renesas@glider.be>,
        <david.daney@cavium.com>, <peterz@infradead.org>,
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Subject: Re: [PATCH v4 3/3] MIPS: set stack/data protection as non-executable
References: <20150805234348.20722.71740.stgit@ubuntu-yegoshin> <20150805234936.20722.60927.stgit@ubuntu-yegoshin> <20150805235543.GG2057@NP-P-BURTON> <55C2A50A.50805@imgtec.com> <55C2A6FE.1020003@caviumnetworks.com> <55C2A91B.1090704@imgtec.com> <55C2AC5B.50408@caviumnetworks.com> <55C2AE7B.4040805@imgtec.com>
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On 08/05/2015 05:46 PM, Leonid Yegoshin wrote:
> On 08/05/2015 05:37 PM, David Daney wrote:
>> This just means that your userspace is broken.
>>
>> If GLibC cannot do the right thing then it should be fixed.
>
> Let's skip this until you explain how to create a fully
> non-executable-stack process.

Build almost any program with a gcc/glibc from a recent Cavium SDK 
toolchain.

Something like this:

   mips64-octeon-linux-gnu-gcc -o myprogram myprogram.c


>
>>
>>
>> You cannot change the default setting for executable stack just
>> because you have created a broken userspace.
>
> Please give me at least one example, one existing application which
> would suffer.

Anything compiled with gcj that uses java.lang.reflect.Method.invoke()

Anything that uses gcc nested functions.

Anything that uses libffi

Where an older toolchain that doesn't set PT_GNU_STACK was used.

>
> I remember that people already wrote here that this kind of apps (which
> is based on eXecutable stack and doesn't announce it in PT_GNU_STACK)
> need to be eliminated.
>
>>
>> The ability of legacy userspace to continue functioning cannot be
>> sacrificed.
>>
>
> Not at any price.
>
> However, this switch is a separate patch from others. It can be not
> applied or it can be applied, depending from prevailing mind - what is
> more significant, some (unknown) app or non-executable stack protection.
>
> - Leonid.

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