Re: [PATCH v1 1/9] uretprobes: Introduce uprobe_consumer->ret_handler()

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

* Anton Arapov <anton@redhat.com> [2013-04-03 18:00:31]:

> Enclose return probes implementation, introduce ->ret_handler() and update
> existing code to rely on ->handler() *and* ->ret_handler() for uprobe and
> uretprobe respectively.
> 
> v1 changes:
> * add bp_vaddr argument to ->ret_handler()
> 
> RFCv5 changes:
> * don't remove uprobe in case there are no uprobe consumer(handler),
>   see handler_chain() changes.
> 
> RFCv3 changes: (the patch is introduced in v3)
> * check whether at least one of the consumer's handlers were set.
> * a 'TODO' cap that will be removed once return probes be implemented.
> * introduce ->ret_handler().
> 
> Signed-off-by: Anton Arapov <anton@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
>  include/linux/uprobes.h |  3 +++
>  kernel/events/uprobes.c | 17 ++++++++++++++---
>  2 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 02b83db..4042cad 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -46,6 +46,9 @@ enum uprobe_filter_ctx {
> 
>  struct uprobe_consumer {
>  	int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
> +	int (*ret_handler)(struct uprobe_consumer *self,
> +				unsigned long func,
> +				struct pt_regs *regs);
>  	bool (*filter)(struct uprobe_consumer *self,
>  				enum uprobe_filter_ctx ctx,
>  				struct mm_struct *mm);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 21d8a65..27c964b 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -815,6 +815,14 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
>  	struct uprobe *uprobe;
>  	int ret;
> 
> +	/* Uprobe must have at least one set consumer */
> +	if (!uc->handler && !uc->ret_handler)
> +		return -EINVAL;
> +
> +	/* TODO: Implement return probes */
> +	if (uc->ret_handler)
> +		return -ENOSYS;
> +
>  	/* Racy, just to catch the obvious mistakes */
>  	if (offset > i_size_read(inode))
>  		return -EINVAL;
> @@ -1473,10 +1481,13 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
> 
>  	down_read(&uprobe->register_rwsem);
>  	for (uc = uprobe->consumers; uc; uc = uc->next) {
> -		int rc = uc->handler(uc, regs);
> +		int rc = 0;
> 
> -		WARN(rc & ~UPROBE_HANDLER_MASK,
> -			"bad rc=0x%x from %pf()\n", rc, uc->handler);
> +		if (uc->handler) {
> +			rc = uc->handler(uc, regs);
> +			WARN(rc & ~UPROBE_HANDLER_MASK,
> +				"bad rc=0x%x from %pf()\n", rc, uc->handler);
> +		}
>  		remove &= rc;
>  	}
> 
> -- 
> 1.8.1.4
> 

-- 
Thanks and Regards
Srikar Dronamraju