linux-kernel - Re: [PATCH v3 2.6.39-rc1-tip 18/26] 18: uprobes: commonly used filters.

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Date:	Tue, 19 Apr 2011 15:57:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	SystemTap <systemtap@...rces.redhat.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2.6.39-rc1-tip 18/26] 18: uprobes: commonly used
 filters.

On Fri, 2011-04-01 at 20:06 +0530, Srikar Dronamraju wrote:
> Provides most commonly used filters that most users of uprobes can
> reuse.  However this would be useful once we can dynamically associate a
> filter with a uprobe-event tracer.
> 
> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
>  include/linux/uprobes.h |    5 +++++
>  kernel/uprobes.c        |   50 +++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 26c4d78..34b989f 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -65,6 +65,11 @@ struct uprobe_consumer {
>  	struct uprobe_consumer *next;
>  };
>  
> +struct uprobe_simple_consumer {
> +	struct uprobe_consumer consumer;
> +	pid_t fvalue;
> +};
> +
>  struct uprobe {
>  	struct rb_node		rb_node;	/* node in the rb tree */
>  	atomic_t		ref;
> diff --git a/kernel/uprobes.c b/kernel/uprobes.c
> index cdd52d0..c950f13 100644
> --- a/kernel/uprobes.c
> +++ b/kernel/uprobes.c
> @@ -1389,6 +1389,56 @@ int uprobe_post_notifier(struct pt_regs *regs)
>  	return 0;
>  }
>  
> +bool uprobes_pid_filter(struct uprobe_consumer *self, struct task_struct *t)
> +{
> +	struct uprobe_simple_consumer *usc;
> +
> +	usc = container_of(self, struct uprobe_simple_consumer, consumer);
> +	if (t->tgid == usc->fvalue)
> +		return true;
> +	return false;
> +}
> +
> +bool uprobes_tid_filter(struct uprobe_consumer *self, struct task_struct *t)
> +{
> +	struct uprobe_simple_consumer *usc;
> +
> +	usc = container_of(self, struct uprobe_simple_consumer, consumer);
> +	if (t->pid == usc->fvalue)
> +		return true;
> +	return false;
> +}

Pretty much everything using t->pid/t->tgid is doing it wrong.

> +bool uprobes_ppid_filter(struct uprobe_consumer *self, struct task_struct *t)
> +{
> +	pid_t pid;
> +	struct uprobe_simple_consumer *usc;
> +
> +	usc = container_of(self, struct uprobe_simple_consumer, consumer);
> +	rcu_read_lock();
> +	pid = task_tgid_vnr(t->real_parent);
> +	rcu_read_unlock();
> +
> +	if (pid == usc->fvalue)
> +		return true;
> +	return false;
> +}
> +
> +bool uprobes_sid_filter(struct uprobe_consumer *self, struct task_struct *t)
> +{
> +	pid_t pid;
> +	struct uprobe_simple_consumer *usc;
> +
> +	usc = container_of(self, struct uprobe_simple_consumer, consumer);
> +	rcu_read_lock();
> +	pid = pid_vnr(task_session(t));
> +	rcu_read_unlock();
> +
> +	if (pid == usc->fvalue)
> +		return true;
> +	return false;
> +}

And there things go haywire too.

What you want is to save the pid-namespace of the task creating the
filter in your uprobe_simple_consumer and use that to obtain the task's
pid for matching with the provided number.



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