linux-kernel - Re: [RFC PATCH glibc 4/8] glibc: Perform rseq(2) registration at C startup and thread creation (v15)

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Date:   Thu, 19 Mar 2020 11:56:35 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Florian Weimer <fw@...eb.enyo.de>
Cc:     libc-alpha <libc-alpha@...rceware.org>, carlos <carlos@...hat.com>,
        Rich Felker <dalias@...c.org>,
        linux-api <linux-api@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ben Maurer <bmaurer@...com>, Dave Watson <davejwatson@...com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul <paulmck@...ux.vnet.ibm.com>, Paul Turner <pjt@...gle.com>,
        Joseph Myers <joseph@...esourcery.com>
Subject: Re: [RFC PATCH glibc 4/8] glibc: Perform rseq(2) registration at C
 startup and thread creation (v15)

----- On Mar 19, 2020, at 10:53 AM, Florian Weimer fw@...eb.enyo.de wrote:

> * Mathieu Desnoyers via Libc-alpha:
> 
>> Changes since v14:
>> - Update copyright range to include 2020.
>> - Introduce __ASSUME_RSEQ defined for --enable-kernel=4.18.0 and higher.
>> - Use ifdef __ASSUME_RSEQ rather than ifdef __NR_rseq to discover rseq
>>   availability. This is necessary now that the system call numbers are
>>   integrated within glibc.
> 
> It's not quite clear to me why you need __ASSUME_RSEQ.

This is how I noticed other Linux features were being integrated,
so I figured this is how I should do it. Monkey see, monkey do. ;-)

> Can you use __has_include in <sys/rseq.h>, with a copy of the kernel
> definitions if the kernel header is not available?

Sure. Should I pull a verbatim copy of uapi linux/rseq.h into glibc ?
If so, where should I put it ?

Thanks,

Mathieu




-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com