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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