Re: [PATCH v2 06/11] uprobes: Export struct return_instance, introduce arch_uretprobe_is_alive()

[Anton Arapov <arapov@gmail.com>]

On Tue, Jul 07, 2015 at 03:22:54AM +0200, Oleg Nesterov wrote:
> Add the new "weak" helper, arch_uretprobe_is_alive(), used by the next
> patches. It should return true if this return_instance is still valid.
> The arch agnostic version just always returns true.
> 
> The patch exports "struct return_instance" for the architectures which
> want to override this hook. We can also cleanup prepare_uretprobe() if
> we pass the new return_instance to arch_uretprobe_hijack_return_addr().
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <arapov@gmail.com>

> ---
>  include/linux/uprobes.h |   10 ++++++++++
>  kernel/events/uprobes.c |   14 +++++---------
>  2 files changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 60beb5d..50d2764 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -92,6 +92,15 @@ struct uprobe_task {
>  	unsigned int			depth;
>  };
>  
> +struct return_instance {
> +	struct uprobe		*uprobe;
> +	unsigned long		func;
> +	unsigned long		orig_ret_vaddr; /* original return address */
> +	bool			chained;	/* true, if instance is nested */
> +
> +	struct return_instance	*next;		/* keep as stack */
> +};
> +
>  struct xol_area;
>  
>  struct uprobes_state {
> @@ -128,6 +137,7 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
>  extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
>  extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
>  extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs);
> +extern bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs);
>  extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
>  extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>  					 void *src, unsigned long len);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 98e4d97..1c71b62 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -86,15 +86,6 @@ struct uprobe {
>  	struct arch_uprobe	arch;
>  };
>  
> -struct return_instance {
> -	struct uprobe		*uprobe;
> -	unsigned long		func;
> -	unsigned long		orig_ret_vaddr; /* original return address */
> -	bool			chained;	/* true, if instance is nested */
> -
> -	struct return_instance	*next;		/* keep as stack */
> -};
> -
>  /*
>   * Execute out of line area: anonymous executable mapping installed
>   * by the probed task to execute the copy of the original instruction
> @@ -1818,6 +1809,11 @@ bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
>  	return false;
>  }
>  
> +bool __weak arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
> +{
> +	return true;
> +}
> +
>  /*
>   * Run handler and ask thread to singlestep.
>   * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
> -- 
> 1.5.5.1
>