[PATCH v6 09/22] powerpc/exec: Set thread.regs early during exec

[Christophe Leroy]

Le 25/11/2020 à 06:16, Aneesh Kumar K.V a écrit :
> In later patches during exec, we would like to access default regs.amr to
> control access to the user mapping. Having thread.regs set early makes the
> code changes simpler.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> ---
>   arch/powerpc/include/asm/thread_info.h |  2 --
>   arch/powerpc/kernel/process.c          | 37 +++++++++++++++++---------
>   2 files changed, 25 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> index 46a210b03d2b..de4c911d9ced 100644
> --- a/arch/powerpc/include/asm/thread_info.h
> +++ b/arch/powerpc/include/asm/thread_info.h
> @@ -77,10 +77,8 @@ struct thread_info {
>   /* how to get the thread information struct from C */
>   extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>   
> -#ifdef CONFIG_PPC_BOOK3S_64
>   void arch_setup_new_exec(void);
>   #define arch_setup_new_exec arch_setup_new_exec
> -#endif
>   
>   #endif /* __ASSEMBLY__ */
>   
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index d421a2c7f822..b6b8a845e454 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1530,10 +1530,32 @@ void flush_thread(void)
>   #ifdef CONFIG_PPC_BOOK3S_64
>   void arch_setup_new_exec(void)
>   {
> -	if (radix_enabled())
> -		return;
> -	hash__setup_new_exec();
> +	if (!radix_enabled())
> +		hash__setup_new_exec();
> +
> +	/*
> +	 * If we exec out of a kernel thread then thread.regs will not be
> +	 * set.  Do it now.
> +	 */
> +	if (!current->thread.regs) {
> +		struct pt_regs *regs = task_stack_page(current) + THREAD_SIZE;
> +		current->thread.regs = regs - 1;
> +	}
> +
> +}
> +#else
> +void arch_setup_new_exec(void)
> +{
> +	/*
> +	 * If we exec out of a kernel thread then thread.regs will not be
> +	 * set.  Do it now.
> +	 */
> +	if (!current->thread.regs) {
> +		struct pt_regs *regs = task_stack_page(current) + THREAD_SIZE;
> +		current->thread.regs = regs - 1;
> +	}
>   }
> +
>   #endif

No need to duplicate arch_setup_new_exec() I think. radix_enabled() is defined at all time so the 
first function should be valid at all time.

>   
>   #ifdef CONFIG_PPC64
> @@ -1765,15 +1787,6 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
>   		preload_new_slb_context(start, sp);
>   #endif
>   
> -	/*
> -	 * If we exec out of a kernel thread then thread.regs will not be
> -	 * set.  Do it now.
> -	 */
> -	if (!current->thread.regs) {
> -		struct pt_regs *regs = task_stack_page(current) + THREAD_SIZE;
> -		current->thread.regs = regs - 1;
> -	}
> -
>   #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
>   	/*
>   	 * Clear any transactional state, we're exec()ing. The cause is
>