Re: [PATCH 5/5] ptrace: remove PTRACE_SEIZE_DEVEL bit

[Oleg Nesterov <oleg@redhat.com>]

On 02/10, Denys Vlasenko wrote:
>
> PTRACE_SEIZE code is tested and ready for production use,
> remove the code which requires special bit in data argument
> to make PTRACE_SEIZE work.
>
> Strace team prepares for a new release of strace, and we
> would like to ship the code which uses PTRACE_SEIZE,
> preferably after this change goes into released kernel.
>
> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

Personally I agree with this change. PTRACE_SEIZE_DEVEL complicates
the testing/development for the user-space.

Tejun, do you agree?

Acked-by: Oleg Nesterov <oleg@redhat.com>

-
>  include/linux/ptrace.h |    5 +----
>  kernel/ptrace.c        |   15 ---------------
>  2 files changed, 1 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
> index ec6571c..6dffe18 100644
> --- a/include/linux/ptrace.h
> +++ b/include/linux/ptrace.h
> @@ -51,9 +51,6 @@
>  #define PTRACE_INTERRUPT	0x4207
>  #define PTRACE_LISTEN		0x4208
>  
> -/* flags in @data for PTRACE_SEIZE */
> -#define PTRACE_SEIZE_DEVEL	0x80000000 /* temp flag for development */
> -
>  /* Wait extended result codes for the above trace options.  */
>  #define PTRACE_EVENT_FORK	1
>  #define PTRACE_EVENT_VFORK	2
> @@ -64,7 +61,7 @@
>  /* Extended result codes which enabled by means other than options.  */
>  #define PTRACE_EVENT_STOP	128
>  
> -/* options set using PTRACE_SETOPTIONS */
> +/* Options set using PTRACE_SETOPTIONS or using PTRACE_SEIZE @data param */
>  #define PTRACE_O_TRACESYSGOOD	1
>  #define PTRACE_O_TRACEFORK	(1 << PTRACE_EVENT_FORK)
>  #define PTRACE_O_TRACEVFORK	(1 << PTRACE_EVENT_VFORK)
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 99a18a0..32846f7 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -237,25 +237,10 @@ static int ptrace_attach(struct task_struct *task, long request,
>  	bool seize = (request == PTRACE_SEIZE);
>  	int retval;
>  
> -	/*
> -	 * SEIZE will enable new ptrace behaviors which will be implemented
> -	 * gradually.  SEIZE_DEVEL bit is used to prevent applications
> -	 * expecting full SEIZE behaviors trapping on kernel commits which
> -	 * are still in the process of implementing them.
> -	 *
> -	 * Only test programs for new ptrace behaviors being implemented
> -	 * should set SEIZE_DEVEL.  If unset, SEIZE will fail with -EIO.
> -	 *
> -	 * Once SEIZE behaviors are completely implemented, this flag
> -	 * will be removed.
> -	 */
>  	retval = -EIO;
>  	if (seize) {
>  		if (addr != 0)
>  			goto out;
> -		if (!(flags & PTRACE_SEIZE_DEVEL))
> -			goto out;
> -		flags &= ~(unsigned long)PTRACE_SEIZE_DEVEL;
>  		if (flags & ~(unsigned long)PTRACE_O_MASK)
>  			goto out;
>  		flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
> -- 
> 1.7.7.6
>