[PATCH 1/4] powerpc: convert to copy_thread_tls

[Christophe Leroy]

Le 27/08/2019 à 05:30, Nicholas Piggin a écrit :
> Commit 3033f14ab78c3 ("clone: support passing tls argument via C rather
> than pt_regs magic") introduced the HAVE_COPY_THREAD_TLS option. Use it
> to avoid a subtle assumption about the argument ordering of clone type
> syscalls.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/Kconfig          | 1 +
>   arch/powerpc/kernel/process.c | 9 +++++----
>   2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index d8dcd8820369..7477a3263225 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -182,6 +182,7 @@ config PPC
>   	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
>   	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
>   	select HAVE_CONTEXT_TRACKING		if PPC64
> +	select HAVE_COPY_THREAD_TLS
>   	select HAVE_DEBUG_KMEMLEAK
>   	select HAVE_DEBUG_STACKOVERFLOW
>   	select HAVE_DYNAMIC_FTRACE
> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 8fc4de0d22b4..24621e7e5033 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1600,8 +1600,9 @@ static void setup_ksp_vsid(struct task_struct *p, unsigned long sp)
>   /*
>    * Copy architecture-specific thread state
>    */
> -int copy_thread(unsigned long clone_flags, unsigned long usp,
> -		unsigned long kthread_arg, struct task_struct *p)
> +int copy_thread_tls(unsigned long clone_flags, unsigned long usp,
> +		unsigned long kthread_arg, struct task_struct *p,
> +		unsigned long tls)
>   {
>   	struct pt_regs *childregs, *kregs;
>   	extern void ret_from_fork(void);
> @@ -1642,10 +1643,10 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
>   		if (clone_flags & CLONE_SETTLS) {
>   #ifdef CONFIG_PPC64

is_32bit_task() exists and always returns 1 on PPC32 so this gross ifdef 
in the middle of an if/else is pointless, it should be dropped.

>   			if (!is_32bit_task())
> -				childregs->gpr[13] = childregs->gpr[6];
> +				childregs->gpr[13] = tls;
>   			else
>   #endif
> -				childregs->gpr[2] = childregs->gpr[6];
> +				childregs->gpr[2] = tls;
>   		}
>   
>   		f = ret_from_fork;
> 

Christophe