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Subject: Re: [PATCH] ia64: enable HAVE_COPY_THREAD_TLS, switch to
 kernel_clone_args
To:     Christian Brauner <christian.brauner@ubuntu.com>
Cc:     "Luck, Tony" <tony.luck@intel.com>,
        "Yu, Fenghua" <fenghua.yu@intel.com>,
        "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Qais Yousef <qais.yousef@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20200513204848.1208864-1-christian.brauner@ubuntu.com>
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 <20200514101914.fu7xhgaxtb5fy2ky@wittgenstein>
From:   John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
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Message-ID: <4aad9ad5-b0e9-12b0-0ad2-ac23fceae87b@physik.fu-berlin.de>
Date:   Thu, 14 May 2020 12:21:13 +0200
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 5/14/20 12:19 PM, Christian Brauner wrote:
> Scratch that. It's even worse. On ia64 it is _invalid_ to pass a NULL
> stack. That's at least what the glibc assembly assumes:
> 
> 	cmp.eq p6,p0=0,in0
> 	cmp.eq p7,p0=0,in1
> 	mov r8=EINVAL
> 	mov out0=in3		/* Flags are first syscall argument.	*/
> 	mov out1=in1		/* Stack address.			*/
> (p6)	br.cond.spnt.many __syscall_error	/* no NULL function pointers */
> (p7)	br.cond.spnt.many __syscall_error	/* no NULL stack pointers */
> 	;;
> 	mov out2=in2		/* Stack size.				*/
> 
> so newer systemd just works by accident on ia64 if at all correctly
> afaict.

Hmm, interesting. I really wasn't aware of that. Thanks for the heads-up.

I'll ask Michael whether he can come up for a solution for that problem.

Maybe that's also why systemd crashes.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913