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Re: [PATCH glibc 2.31 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v12)
- From: Rich Felker <dalias at libc dot org>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: Carlos O'Donell <carlos at redhat dot com>, Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha at sourceware dot org, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, linux-kernel at vger dot kernel dot org, linux-api at vger dot kernel dot org
- Date: Wed, 11 Sep 2019 16:08:18 -0400
- Subject: Re: [PATCH glibc 2.31 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v12)
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On Wed, Sep 11, 2019 at 09:54:23PM +0200, Florian Weimer wrote:
> * Carlos O'Donell:
> > On 9/11/19 3:08 PM, Florian Weimer wrote:
> >> * Carlos O'Donell:
> >>> It would be easier to merge the patch set if it were just an unconditional
> >>> registration like we do for set_robust_list().
> >> Note that this depends on the in-tree system call numbers list, which I
> >> still need to finish according to Joseph's specifications.
> > Which work is this? Do you have a URL reference to WIP?
> I think realistically this is needed for the Y2038 work as well if we
> want to support building glibc with older kernel headers. “glibc 2..31
> will have Y2038 support and rseq support, but only if it runs on a
> current and it happens to have been built against sufficiently recent
> kernel headers” is a bit difficult to explain. The current kernel part
> is easy enough to understand, but the impact of the kernel headers on
> the feature set has always been tough to explain. Especially if you
> factor in vendor kernels with system call backports.
I'm in favor of in-tree syscall numbers list. If you don't want O(n)
per-arch work, though, you could just define the 'base number' for
each arch and use the fact that all the new syscalls share a common
numbering (i.e. base + constant depending only on syscall). I think
including the list with glibc is more robust though, and would
eliminate the need to check for definitions of older (pre-unification)
syscalls glibc wants to use.