linux-kernel - Re: [PATCH 4/7] openrisc: Add thread-local storage (TLS) support

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Date:   Mon, 19 Sep 2016 16:25:08 +0200
From:   Jonas Bonn <jonas@...thpole.se>
To:     Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Christian Svensson <blue@....nu>
Subject: Re: [PATCH 4/7] openrisc: Add thread-local storage (TLS) support

On 09/16/2016 04:43 PM, Stafford Horne wrote:
> From: Christian Svensson <blue@....nu>
>
> Historically OpenRISC GCC has reserved r10 which we now use to hold
> the thread pointer for thread-local storage (TLS).
I know this was proposed by way of this patch, but we deferred accepting 
this until the OpenRISC spec could be updated accordingly.  Has this 
been done now?  If not, still NAK.

/Jonas

>
> Signed-off-by: Christian Svensson <blue@....nu>
> Signed-off-by: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
> Signed-off-by: Stafford Horne <shorne@...il.com>
> ---
>   arch/openrisc/kernel/process.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
> index 7095dfe..277123b 100644
> --- a/arch/openrisc/kernel/process.c
> +++ b/arch/openrisc/kernel/process.c
> @@ -173,6 +173,19 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
>   
>   		if (usp)
>   			userregs->sp = usp;
> +
> +		/*
> +		 * For CLONE_SETTLS set "tp" (r10) to the TLS pointer passed to sys_clone.
> +		 *
> +		 * The kernel entry is:
> +		 *	int clone (long flags, void *child_stack, int *parent_tid,
> +		 *		int *child_tid, struct void *tls)
> +		 *
> +		 * This makes the source r7 in the kernel registers.
> +		 */
> +		if (clone_flags & CLONE_SETTLS)
> +			userregs->gpr[10] = userregs->gpr[7];
> +
>   		userregs->gpr[11] = 0;	/* Result from fork() */
>   
>   		kregs->gpr[20] = 0;	/* Userspace thread */