linux-kernel - Re: [PATCH 3/7] arm: Implement copy_thread

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Date:   Thu, 2 Jan 2020 19:02:43 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Amanieu d'Antras <amanieu@...il.com>, will.deacon@....com
Cc:     linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>,
        stable@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/7] arm: Implement copy_thread_tls

On Thu, Jan 02, 2020 at 06:24:09PM +0100, Amanieu d'Antras wrote:
> This is required for clone3 which passes the TLS value through a
> struct rather than a register.
> 
> Signed-off-by: Amanieu d'Antras <amanieu@...il.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: <stable@...r.kernel.org> # 5.3.x

Again, looks good to me but I'd like an ack from someone closer to the
architecture itself.
Acked-by: Christian Brauner <christian.brauner@...ntu.com>

> ---
>  arch/arm/Kconfig          | 1 +
>  arch/arm/kernel/process.c | 6 +++---
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index ba75e3661a41..96dab76da3b3 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -72,6 +72,7 @@ config ARM
>  	select HAVE_ARM_SMCCC if CPU_V7
>  	select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
>  	select HAVE_CONTEXT_TRACKING
> +	select HAVE_COPY_THREAD_TLS
>  	select HAVE_C_RECORDMCOUNT
>  	select HAVE_DEBUG_KMEMLEAK
>  	select HAVE_DMA_CONTIGUOUS if MMU
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index cea1c27c29cb..46e478fb5ea2 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -226,8 +226,8 @@ void release_thread(struct task_struct *dead_task)
>  asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
>  
>  int
> -copy_thread(unsigned long clone_flags, unsigned long stack_start,
> -	    unsigned long stk_sz, struct task_struct *p)
> +copy_thread_tls(unsigned long clone_flags, unsigned long stack_start,
> +	    unsigned long stk_sz, struct task_struct *p, unsigned long tls)
>  {
>  	struct thread_info *thread = task_thread_info(p);
>  	struct pt_regs *childregs = task_pt_regs(p);
> @@ -261,7 +261,7 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start,
>  	clear_ptrace_hw_breakpoint(p);
>  
>  	if (clone_flags & CLONE_SETTLS)
> -		thread->tp_value[0] = childregs->ARM_r3;
> +		thread->tp_value[0] = tls;
>  	thread->tp_value[1] = get_tpuser();
>  
>  	thread_notify(THREAD_NOTIFY_COPY, thread);
> -- 
> 2.24.1
>