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

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Date:   Mon, 19 Sep 2016 23:43:03 +0900 (JST)
From:   Stafford Horne <shorne@...il.com>
To:     Jonas Bonn <jonas@...thpole.se>
cc:     Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Christian Svensson <blue@....nu>
Subject: Re: [PATCH 4/7] openrisc: Add thread-local storage (TLS) support



On Mon, 19 Sep 2016, Jonas Bonn wrote:

> 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.

Hi Jonas,

Thanks for your review, I do not believe the spec has been updated. I will 
look into seeing what I can do and update the patch if needed.

-Stafford

>>
>>  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 */
>
>
>