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Date: Tue, 13 Aug 2019 12:15:59 +0200
From: Micha Nelissen <nelissen.micha@...il.com>
To: musl@...ts.openwall.com
Subject: Re: Re: size of executable

On 12-08-2019 20:23, Rich Felker wrote:
> On Mon, Aug 12, 2019 at 11:16:39AM -0700, Khem Raj wrote:
>> On Mon, Aug 12, 2019 at 10:19 AM Rich Felker <dalias@...c.org> wrote:
>>> On Mon, Aug 12, 2019 at 05:55:28PM +0100, Jorge Almeida wrote:
>>>> On Mon, Aug 12, 2019 at 5:48 PM Jorge Almeida <jjalmeida@...il.com> wrote:
>>>>> I get 16768 bytes (not stripped) and 12324 (stripped).
>>>
>>> This is a binutils regression from a dubious anti-ROP feature, -z
>>> separate-code. Add -Wl,-z,noseparate-code and it will go away.
>>
>> is this still so with latest release as well.
> 
> The breakage that caused separate-code to crash at runtime was fixed
> between 2.31 and 2.32, but the size and performance regression
> remains. With separate-code, a couple extra pages of memory and disk
> are needed, with corresponding runtime cost to mmap them properly.
> 
> All to avoid ROP gadgets, when every single dynamic-linked program has
> a nice ROP gadget named "system" (among many others) in it...

I'm curious. Jorge reports that the executable goes from 12k to 4k. That 
suggests two pages saved? But if I look at documentation for this 
separate-code option, then it says to allocate a separate code PT_LOAD 
segment. (PT_LOAD just means loadable?) That would suggest up to 4k more 
usage, not 8k right? One extra page necessary. Are by default rodata and 
code combined but with separate-code those are separated? Or something 
more happening?

Thanks, Micha

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