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Re: Official Linux system wrapper library?
- From: Dave Martin <Dave dot Martin at arm dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: Andy Lutomirski <luto at amacapital dot net>, Daniel Colascione <dancol at google dot com>, "Michael Kerrisk (man-pages)" <mtk dot manpages at gmail dot com>, linux-kernel <linux-kernel at vger dot kernel dot org>, Joel Fernandes <joelaf at google dot com>, Linux API <linux-api at vger dot kernel dot org>, Willy Tarreau <w at 1wt dot eu>, Vlastimil Babka <vbabka at suse dot cz>, Carlos O'Donell <carlos at redhat dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Thu, 15 Nov 2018 10:33:57 +0000
- Subject: Re: Official Linux system wrapper library?
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On Wed, Nov 14, 2018 at 12:40:44PM +0100, Florian Weimer wrote:
> * Dave Martin:
> > Fair points, though this is rather what I meant by "sane essentials".
> > Because there are strict limits on what can be done in the vDSO, it may
> > be more bloat-resistant and more conservatively maintained.
> > This might provide a way to push some dumb compatibility kludge code
> > that receives little ongoing maintenance outside the privilege wall,
> > whereas it has to sit in the kernel proper today.
> > In theory we could opt to advertise new syscalls only via vDSO entry
> > points, and not maintain __NR_xxx values for them (which may or may
> > not upset ptrace users.) Anyway, I digress...
> Is the vDSO available across all architectures? (I don't think we use
> it on all architectures in glibc.)
It's probably not available on all arches.
> If not, a vDSO-based approach would merely lead to even more variance
> between architectures, which can't be a good thing.
That's a fair concern.
Channeling syscalls through the vDSO could allow for a uniform syscall
interface at the ELF linkage level, but only those arches that have a
vDSO. There may be other issues too.
Also, I don't say that we should definitely do this, just that it's