linux-kernel - Re: [RFC5 PATCH v6 00/21] ILP32 for ARM64

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Date:	Mon, 21 Mar 2016 21:43:12 +0300
From:	Yury Norov <ynorov@...iumnetworks.com>
To:	"Zhangjian (Bamvor)" <bamvor.zhangjian@...wei.com>
CC:	Alexander Graf <agraf@...e.de>, Andreas Schwab <schwab@...e.de>,
	<arnd@...db.de>, <catalin.marinas@....com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <pinskia@...il.com>,
	<Prasun.Kapoor@...iumnetworks.com>, <broonie@...nel.org>,
	<heiko.carstens@...ibm.com>, <klimov.linux@...il.com>,
	<jan.dakinevich@...il.com>, <schwidefsky@...ibm.com>,
	<Nathan_Lynch@...tor.com>, <joseph@...esourcery.com>,
	<christoph.muellner@...obroma-systems.com>,
	Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>,
	"dingtianhong@...wei.com" <dingtianhong@...wei.com>
Subject: Re: [RFC5 PATCH v6 00/21] ILP32 for ARM64

On Mon, Mar 21, 2016 at 07:23:28PM +0800, Zhangjian (Bamvor) wrote:
> >>So this most probably means that ilp32 code doesn't handle one of cloned
> >>item properly. I have already discovered a bug where child processes
> >>used parent TLS,
> >It is a kernel bug or glibc bug? Could you please explain it or show the patch?
> >The current ILP32 patches looks good to me. Recently, I backport these patches
> >to our 4.1 kernel. And I saw crash frequently even if I only do a single print
> >or infinite loop. There is some small changes about tls register after 4.1. I
> >am not sure if it is a similar issue. It is great if you have some suggestions/
> >ideas.
> My issue is because I forget to change is_compat_task to
> is_a32_compat_task in arch/arm64/kernel/process.c such piece of code
> is delete after commit d00a3810c162 ("arm64: context-switch user tls
> register tpidr_el0 for compat tasks). It is not exist in upstream
> kernel, never mind.
> 
> Meanwhile, I found that it seem that there is another is_compat_task
> in tls_thread_flush. Is it relative the issue you mentioned?
> 
> ```
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 432b094..9ab968c 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -209,7 +209,7 @@ static void tls_thread_flush(void)
>  {
>         asm ("msr tpidr_el0, xzr");
> 
> -       if (is_compat_task()) {
> +       if (is_a32_compat_task()) {
>                 current->thread.tp_value = 0;
> 
>                 /*
> ```
> 
> Regards
> 
> Bamvor

Hi,

This fix looks correct, though doesn't fix issue.
Thank you.

Yury.