From: Cary Coutant <ccoutant@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: gnu-gabi@sourceware.org
Subject: Re: gABI extension proposal: PT_SHMMAP
Date: Sun, 01 Jan 2017 00:00:00 -0000 [thread overview]
Message-ID: <CAJimCsEpJ00Ss7uZ7X0puS=Cs_FevxaZow6-XzEVBq_WFW+U4g@mail.gmail.com> (raw)
In-Reply-To: <5d71c4e4-19d2-3861-e212-5e86d29c53fc@zytor.com>
> I would like to propose an extension to the ELF gABI, which is analogous
> to PT_LOAD except that it requests that the underlying file be
> memory-mapped with MAP_SHARED, rather than MAP_PRIVATE as used for
> PT_LOAD. PT_SHARED or PT_SHLOAD would be other possible names.
>
> The main motivation for this is to allow the Linux kernel vDSO to
> finally become as close to an "ordinary" ELF DSO as is possible. The
> vDSO depends on having its kernel-provided data page(s) at a specific
> offset from the vDSO code; this is currently done by ad hoc memory
> areas, which has a number of problems, especially for mixed-mode programs.
>
> The idea is to convert the vdso to a proper file in one of the
> kernel-provided filesystems (e.g. /proc or /sys); by defining this type,
> an ELF parser would be able to create the appropriate mappings without
> any ad hoc code.
>
> This may be usable for other operating systems or perhaps even in
> userspace. However, if there is no such interest then it would be
> possible for Linux to use one of the PT_*OS constants; however, I
> generally believe it is better to try to be as inclusive as possible.
I'd prefer not to add a new PT_ value that, for the most part, means
the same thing as PT_LOAD. It would be more appropriate to use a
PT_LOAD segment with a new p_flag value, say PF_SHARED. Would that
work?
-cary
next prev parent reply other threads:[~2017-06-01 19:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-01 0:00 H. Peter Anvin
2017-01-01 0:00 ` Cary Coutant [this message]
2017-01-01 0:00 ` hpa
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H. Peter Anvin
2017-01-01 0:00 ` James Y Knight via gnu-gabi
2017-01-01 0:00 ` Cary Coutant
2017-01-01 0:00 ` H. Peter Anvin
2017-01-01 0:00 ` Suprateeka R Hegde
2017-01-01 0:00 ` H. Peter Anvin
2017-01-01 0:00 ` Suprateeka R Hegde
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