linux-kernel - Re: [PATCH] m68k: Implement copy_thread

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Date:   Tue, 14 Jan 2020 11:55:06 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Amanieu d'Antras <amanieu@...il.com>,
        Christian Brauner <christian@...uner.io>,
        Kars de Jong <jongk@...ux-m68k.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
        linux-next@...r.kernel.org
Subject: Re: [PATCH] m68k: Implement copy_thread_tls()

Hi Geert,

On 13/1/20 8:30 pm, Geert Uytterhoeven wrote:
> This is required for clone3(), which passes the TLS value through a
> struct rather than a register.
> 
> As do_fork() is only available if CONFIG_HAVE_COPY_THREAD_TLS is set,
> m68k_clone() must be changed to call _do_fork() directly.
> 
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Looks good for ColdFire too. I compiled for both MMU and non-MMU
targets and no regressions (I did not test clone3() itself though).

Acked-by: Greg Ungerer <gerg@...ux-m68k.org>

Regards
Greg


> ---
> This is a dependency for the combination of commits
> e8bb2a2a1d51511e ("m68k: Wire up clone3() syscall") in m68k/for-next,
> dd499f7a7e342702 ("clone3: ensure copy_thread_tls is implemented") in
> v5.5-rc6.
> ---
>   arch/m68k/Kconfig          |  1 +
>   arch/m68k/kernel/process.c | 31 ++++++++++++++++++++++---------
>   2 files changed, 23 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index 6663f1741798e83f..6ad6cdac74b3dc42 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -14,6 +14,7 @@ config M68K
>   	select HAVE_AOUT if MMU
>   	select HAVE_ASM_MODVERSIONS
>   	select HAVE_DEBUG_BUGVERBOSE
> +	select HAVE_COPY_THREAD_TLS
>   	select GENERIC_IRQ_SHOW
>   	select GENERIC_ATOMIC64
>   	select HAVE_UID16
> diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
> index 22e6b8f4f9582aa4..8f0d9140700f09ad 100644
> --- a/arch/m68k/kernel/process.c
> +++ b/arch/m68k/kernel/process.c
> @@ -108,16 +108,28 @@ void flush_thread(void)
>    * on top of pt_regs, which means that sys_clone() arguments would be
>    * buried.  We could, of course, copy them, but it's too costly for no
>    * good reason - generic clone() would have to copy them *again* for
> - * do_fork() anyway.  So in this case it's actually better to pass pt_regs *
> - * and extract arguments for do_fork() from there.  Eventually we might
> - * go for calling do_fork() directly from the wrapper, but only after we
> - * are finished with do_fork() prototype conversion.
> + * _do_fork() anyway.  So in this case it's actually better to pass pt_regs *
> + * and extract arguments for _do_fork() from there.  Eventually we might
> + * go for calling _do_fork() directly from the wrapper, but only after we
> + * are finished with _do_fork() prototype conversion.
>    */
>   asmlinkage int m68k_clone(struct pt_regs *regs)
>   {
>   	/* regs will be equal to current_pt_regs() */
> -	return do_fork(regs->d1, regs->d2, 0,
> -		       (int __user *)regs->d3, (int __user *)regs->d4);
> +	struct kernel_clone_args args = {
> +		.flags		= regs->d1 & ~CSIGNAL,
> +		.pidfd		= (int __user *)regs->d3,
> +		.child_tid	= (int __user *)regs->d4,
> +		.parent_tid	= (int __user *)regs->d3,
> +		.exit_signal	= regs->d1 & CSIGNAL,
> +		.stack		= regs->d2,
> +		.tls		= regs->d5,
> +	};
> +
> +	if (!legacy_clone_args_valid(&args))
> +		return -EINVAL;
> +
> +	return _do_fork(&args);
>   }
>   
>   /*
> @@ -130,8 +142,9 @@ asmlinkage int m68k_clone3(struct pt_regs *regs)
>   	return sys_clone3((struct clone_args __user *)regs->d1, regs->d2);
>   }
>   
> -int copy_thread(unsigned long clone_flags, unsigned long usp,
> -		 unsigned long arg, struct task_struct *p)
> +int copy_thread_tls(unsigned long clone_flags, unsigned long usp,
> +		    unsigned long arg, struct task_struct *p,
> +		    unsigned long tls)
>   {
>   	struct fork_frame {
>   		struct switch_stack sw;
> @@ -166,7 +179,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
>   	p->thread.usp = usp ?: rdusp();
>   
>   	if (clone_flags & CLONE_SETTLS)
> -		task_thread_info(p)->tp_value = frame->regs.d5;
> +		task_thread_info(p)->tp_value = tls;
>   
>   #ifdef CONFIG_FPU
>   	if (!FPU_IS_EMU) {
>