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Re: vdso handling
- From: Alan Modra <amodra at gmail dot com>
- To: Mark Wielaard <mjw at redhat dot com>
- Cc: Cary Coutant <ccoutant at google dot com>, Doug Evans <dje at google dot com>, "Metzger, Markus T" <markus dot t dot metzger at intel dot com>, "gdb at sourceware dot org" <gdb at sourceware dot org>, "binutils at sourceware dot org" <binutils at sourceware dot org>
- Date: Thu, 13 Mar 2014 23:33:22 +1030
- Subject: Re: vdso handling
- Authentication-results: sourceware.org; auth=none
- References: <A78C989F6D9628469189715575E55B230AA884EB at IRSMSX104 dot ger dot corp dot intel dot com> <20140312071701 dot GW26922 at bubble dot grove dot modra dot org> <CADPb22SAmK5JB3muW_nCvuHN5L-aOcdyzYNR+OtnM3bA1x_OJg at mail dot gmail dot com> <CAHACq4o=HmdCo1FPFL-96raf2UN805jvM=VZM-9dbKrmzJFJTw at mail dot gmail dot com> <20140313010147 dot GZ26922 at bubble dot grove dot modra dot org> <1394704336 dot 11818 dot 115 dot camel at bordewijk dot wildebeest dot org>
On Thu, Mar 13, 2014 at 10:52:16AM +0100, Mark Wielaard wrote:
> On Thu, 2014-03-13 at 11:31 +1030, Alan Modra wrote:
> > It wouldn't
> > help in the vdso case anyway, since the problem there is that you only
> > have the loaded part of the original ELF file.
> Note that the vdso is often special, compared to other ELF dsos, because
> the loaded part is just the complete ELF image in memory. Since they are
> very simple they will just have one PT_LOAD at offset zero and if the
> image is smaller than the page size then the whole file is just simply
> mapped into memory completely. So by fetching the vdso ELF image from
> remote memory you should be able to get the section headers and the
> not-allocated sections too.
Yes, but if the vdso does not fit in a page (which incidentally is
inferred by program header p_align), then you may lose the section
headers. I was assuming this was the case.
Australia Development Lab, IBM