Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760672AbYGQHgH (ORCPT ); Thu, 17 Jul 2008 03:36:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759996AbYGQHbh (ORCPT ); Thu, 17 Jul 2008 03:31:37 -0400 Received: from mx1.redhat.com ([66.187.233.31]:53639 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759986AbYGQHbg (ORCPT ); Thu, 17 Jul 2008 03:31:36 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit From: Roland McGrath To: Andrew Morton , Linus Torvalds Cc: Ingo Molnar , linux-kernel@vger.kernel.org X-Fcc: ~/Mail/linus Subject: [PATCH 18/23] tracehook: TIF_NOTIFY_RESUME In-Reply-To: Roland McGrath's message of Thursday, 17 July 2008 00:25:41 -0700 <20080717072541.F390E15411D@magilla.localdomain> References: <20080717072541.F390E15411D@magilla.localdomain> X-Antipastobozoticataclysm: Bariumenemanilow Message-Id: <20080717073101.E62B515411D@magilla.localdomain> Date: Thu, 17 Jul 2008 00:31:01 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2704 Lines: 68 This adds tracehook.h inlines to enable a new arch feature in support of user debugging/tracing. This is not used yet, but it lays the groundwork for a debugger to be able to wrangle a task that's possibly running, without interrupting its syscalls in progress. Each arch should define TIF_NOTIFY_RESUME, and in their entry.S code treat it much like TIF_SIGPENDING. That is, it causes you to take the slow path when returning to user mode, where you get the full user-mode state accessible as for signal handling or ptrace. The arch code should check TIF_NOTIFY_RESUME after handling TIF_SIGPENDING. When it's set, clear it and then call tracehook_notify_resume(). In future, tracing code will call set_notify_resume() when it wants to get a callback in tracehook_notify_resume(). Signed-off-by: Roland McGrath --- include/linux/tracehook.h | 34 ++++++++++++++++++++++++++++++++++ 1 files changed, 34 insertions(+), 0 deletions(-) diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index 43bc51b..32867ab 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -537,4 +537,38 @@ static inline void tracehook_report_death(struct task_struct *task, { } +#ifdef TIF_NOTIFY_RESUME +/** + * set_notify_resume - cause tracehook_notify_resume() to be called + * @task: task that will call tracehook_notify_resume() + * + * Calling this arranges that @task will call tracehook_notify_resume() + * before returning to user mode. If it's already running in user mode, + * it will enter the kernel and call tracehook_notify_resume() soon. + * If it's blocked, it will not be woken. + */ +static inline void set_notify_resume(struct task_struct *task) +{ + if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_RESUME)) + kick_process(task); +} + +/** + * tracehook_notify_resume - report when about to return to user mode + * @regs: user-mode registers of @current task + * + * This is called when %TIF_NOTIFY_RESUME has been set. Now we are + * about to return to user mode, and the user state in @regs can be + * inspected or adjusted. The caller in arch code has cleared + * %TIF_NOTIFY_RESUME before the call. If the flag gets set again + * asynchronously, this will be called again before we return to + * user mode. + * + * Called without locks. + */ +static inline void tracehook_notify_resume(struct pt_regs *regs) +{ +} +#endif /* TIF_NOTIFY_RESUME */ + #endif /* */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/