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From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Florian Weimer <fw@deneb.enyo.de>, wangboshi <wangboshi@huawei.com>
Cc: nd@arm.com, libc-alpha@sourceware.org
Subject: Re: [RFC][PATCH] AArch64: use movz/movk instead of literal pools in start.S
Date: Mon, 11 Sep 2017 08:58:00 -0000	[thread overview]
Message-ID: <59B65010.4020807@arm.com> (raw)
In-Reply-To: <877exalool.fsf@mid.deneb.enyo.de>

On 07/09/17 12:43, Florian Weimer wrote:
>> eXecute-Only Memory (XOM) is a protection mechanism against some ROP
>> attacks. XOM sets the code as executable and unreadable, so the
>> access to any data, like literal pools, in the code section causes
>> the fault with XOM. The compiler can disable literal pools for C
>> source files, but not for assembly files, so I use movz/movk instead
>> of literal pools in start.S for XOM.
> 
> Isn't the main goal of XOM to make it more difficult for the
> legitimate device owner to view running machine code?
> 
> | Execute-only memory allows you to protect your intellectual property
> | by preventing executable code being read by users. For example, you
> | can place firmware in execute-only memory and load user code and
> | drivers separately. Placing the firmware in execute-only memory
> | prevents users from trivially reading the code.
> 
> <http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471m/chr1368698326509.html>
> 
> I don't think it's in the interests of the GNU projet to support such
> a thing.
> 

even if that's the main use of xom, there might be other uses
and removing data from text might have other uses than xom
(reduce rop gadget possibility?) so i don't think this should
be a problem (the gnu project already supports gazillion
features that can do harm).

  reply	other threads:[~2017-09-11  8:58 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-07  7:34 wangboshi
2017-09-07 11:43 ` Florian Weimer
2017-09-11  8:58   ` Szabolcs Nagy [this message]
2017-09-11  9:09 ` Andrew Pinski
2017-09-11  9:24   ` Szabolcs Nagy
2017-09-12  8:54   ` Boshi Wang
2017-09-11  9:11 ` Szabolcs Nagy
     [not found]   ` <336560e5-c9de-08bc-c850-28994cac2c33@huawei.com>
2017-09-14  8:35     ` Szabolcs Nagy
2017-09-15  1:16       ` Boshi Wang
2017-09-18 17:21         ` Szabolcs Nagy

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