Re: [PATCH 1/1] fix 31-bit s390 checkpoint/restart wrappers

[Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>]

Got it

Serge E. Hallyn wrote:
> This patch makes it possible to compile with CONFIG_COMPAT=y.  It
> also refuses checkpoint of a 31-bit task, or restart from a 31-bit
> task.  That's just a temporary restriction as there won't be time
> to get 31-bit support for v19.
> 
> Signed-off-by: Serge E. Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> ---
>  arch/s390/kernel/checkpoint.c     |    9 +++++++++
>  arch/s390/kernel/compat_wrapper.S |   12 +++++++-----
>  arch/s390/kernel/process.c        |   12 ++++++++++++
>  arch/s390/kernel/syscalls.S       |    2 +-
>  4 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/s390/kernel/checkpoint.c b/arch/s390/kernel/checkpoint.c
> index 40dd417..8ec12c6 100644
> --- a/arch/s390/kernel/checkpoint.c
> +++ b/arch/s390/kernel/checkpoint.c
> @@ -83,6 +83,11 @@ static void s390_mm(int op, struct ckpt_hdr_mm_context *h,
>  
>  int checkpoint_thread(struct ckpt_ctx *ctx, struct task_struct *t)
>  {
> +	/* we will eventually support this, as we do on x86-64 */
> +	if (test_tsk_thread_flag(t, TIF_31BIT)) {
> +		ckpt_err(ctx, -EINVAL, "checkpoint of 31-bit task\n");
> +		return -EINVAL;
> +	}
>  	return 0;
>  }
>  
> @@ -143,6 +148,10 @@ int checkpoint_mm_context(struct ckpt_ctx *ctx, struct mm_struct *mm)
>  
>  int restore_thread(struct ckpt_ctx *ctx)
>  {
> +	if (test_tsk_thread_flag(current, TIF_31BIT)) {
> +		ckpt_err(ctx, -EINVAL, "restart from 31-bit task\n");
> +		return -EINVAL;
> +	}
>  	return 0;
>  }
>  
> diff --git a/arch/s390/kernel/compat_wrapper.S b/arch/s390/kernel/compat_wrapper.S
> index 8d0ba6a..bb38630 100644
> --- a/arch/s390/kernel/compat_wrapper.S
> +++ b/arch/s390/kernel/compat_wrapper.S
> @@ -1869,11 +1869,13 @@ sys_checkpoint_wrapper:
>  	lgfr	%r2,%r2			# pid_t
>  	lgfr	%r3,%r3			# int
>  	llgfr	%r4,%r4			# unsigned long
> -	jg	compat_sys_checkpoint
> +	lgfr	%r5,%r5			# int
> +	jg	sys_checkpoint
>  
> -	.globl sys_restore_wrapper
> -sys_restore_wrapper:
> -	lgfr	%r2,%r2			# int
> +	.globl sys_restart_wrapper
> +sys_restart_wrapper:
> +	lgfr	%r2,%r2			# pid_t
>  	lgfr	%r3,%r3			# int
>  	llgfr	%r4,%r4			# unsigned long
> -	jg	compat_sys_restore
> +	lgfr	%r5,%r5			# int
> +	jg	sys_restart
> diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
> index a7cb6bc..61b469f 100644
> --- a/arch/s390/kernel/process.c
> +++ b/arch/s390/kernel/process.c
> @@ -258,6 +258,18 @@ SYSCALL_DEFINE4(restart, pid_t, pid, int, fd, unsigned long, flags,
>  {
>  	return do_sys_restart(pid, fd, flags, logfd);
>  }
> +#else
> +SYSCALL_DEFINE4(checkpoint, pid_t, pid, int, fd, unsigned long, flags,
> +		int, logfd)
> +{
> +	return -ENOSYS;
> +}
> +
> +SYSCALL_DEFINE4(restart, pid_t, pid, int, fd, unsigned long, flags,
> +		int, logfd)
> +{
> +	return -ENOSYS;
> +}
>  #endif
>  
>  SYSCALL_DEFINE4(eclone, unsigned int, flags_low, struct clone_args __user *,
> diff --git a/arch/s390/kernel/syscalls.S b/arch/s390/kernel/syscalls.S
> index ff222e1..a29f9e1 100644
> --- a/arch/s390/kernel/syscalls.S
> +++ b/arch/s390/kernel/syscalls.S
> @@ -342,4 +342,4 @@ SYSCALL(sys_rt_tgsigqueueinfo,sys_rt_tgsigqueueinfo,compat_sys_rt_tgsigqueueinfo
>  SYSCALL(sys_perf_event_open,sys_perf_event_open,sys_perf_event_open_wrapper)
>  SYSCALL(sys_eclone,sys_eclone,sys_eclone_wrapper)
>  SYSCALL(sys_checkpoint,sys_checkpoint,sys_checkpoint_wrapper)
> -SYSCALL(sys_restart,sys_restart,sys_restore_wrapper)
> +SYSCALL(sys_restart,sys_restart,sys_restart_wrapper)