From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C5C418C31; Wed, 9 Oct 2024 00:58:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=167.114.26.122 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728435531; cv=none; b=M7CaheHNIFfKSgGj8CQF/erL6gFQhXWzpBHSMcwxPKOM5+qhrjS54QjvAfAIs0yXkWfIHAY8JqZiDRCQn5ns1Gk7C2RPIFnxBDm7SuNj1qIUkQ1R7Yttlhpi0UraJgLSd5x+pHC4dioFRtDIgWpe7awduzgDvDJDkYioTjRZ4hA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728435531; c=relaxed/simple; bh=94+ST9p9ZEZx/gYVfmyH38elST3i1/AeA9RBXiRn/eg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gdv43cjn4PHwODWFpIDgTvpbr8cHJW4X2GW+9htvLYWyeM7XEGppzoYwpUEid+/OQlUY5+gZRgTm1S+ZoGIOlgCN/4MWXqy7kvTpPCF8uA5Ixd24wcvdVPL2Hk/4449USUsue/kjA71JZFLCxrOPxy+Uf9xWberr6bQU/h9rZdM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=er78mva5; arc=none smtp.client-ip=167.114.26.122 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="er78mva5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1728435528; bh=94+ST9p9ZEZx/gYVfmyH38elST3i1/AeA9RBXiRn/eg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=er78mva5H84qSS+DrO+FFLZNhR6jQFx4KMWPz9soeRQZ1fLAEPm6MEUMEC4Ze/SGF wUVzFJH+Xw0XxOABG7guUjARHKUWLG8MxK0tMC+WpG8Y0aZiZFSnFu3UWTSGU1uaJW +ZwIsefYapDwzZjExa2ES9TDmJxWarAQBZdMM+eZ8xCWQ9juQ4+tRicjkab0ztNnQz i8tg5mzqU7dlpLVuuLWEoWGLpHtUuZz+f2JEMVIFrTtSxHq+i+8aNg0dQ800EuZKJq syMSJNpfB2Ul/I0lRhXff9vmXs3TT5mWlcecYo3XGHCkVIBr5Y1P2H2zZ5NKKham3b G6cVapbPHUnqQ== Received: from [IPV6:2606:6d00:100:4000:cacb:9855:de1f:ded2] (unknown [IPv6:2606:6d00:100:4000:cacb:9855:de1f:ded2]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4XNZJm1FWfzSRw; Tue, 8 Oct 2024 20:58:48 -0400 (EDT) Message-ID: <74d621a3-5b82-4831-a875-7c04e56dec7b@efficios.com> Date: Tue, 8 Oct 2024 20:56:51 -0400 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/8] tracing: Allow system call tracepoints to handle page faults To: Steven Rostedt Cc: Masami Hiramatsu , linux-kernel@vger.kernel.org, Peter Zijlstra , Alexei Starovoitov , Yonghong Song , "Paul E . McKenney" , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Namhyung Kim , Andrii Nakryiko , bpf@vger.kernel.org, Joel Fernandes , linux-trace-kernel@vger.kernel.org, Michael Jeanson References: <20241004145818.1726671-1-mathieu.desnoyers@efficios.com> <20241004145818.1726671-6-mathieu.desnoyers@efficios.com> <20241008192334.54180520@gandalf.local.home> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: <20241008192334.54180520@gandalf.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-10-09 01:23, Steven Rostedt wrote: > On Fri, 4 Oct 2024 10:58:15 -0400 > Mathieu Desnoyers wrote: > >> Use Tasks Trace RCU to protect iteration of system call enter/exit >> tracepoint probes to allow those probes to handle page faults. >> >> In preparation for this change, all tracers registering to system call >> enter/exit tracepoints should expect those to be called with preemption >> enabled. >> >> This allows tracers to fault-in userspace system call arguments such as >> path strings within their probe callbacks. >> >> Signed-off-by: Mathieu Desnoyers >> Cc: Michael Jeanson >> Cc: Steven Rostedt >> Cc: Masami Hiramatsu >> Cc: Peter Zijlstra >> Cc: Alexei Starovoitov >> Cc: Yonghong Song >> Cc: Paul E. McKenney >> Cc: Ingo Molnar >> Cc: Arnaldo Carvalho de Melo >> Cc: Mark Rutland >> Cc: Alexander Shishkin >> Cc: Namhyung Kim >> Cc: Andrii Nakryiko >> Cc: bpf@vger.kernel.org >> Cc: Joel Fernandes >> --- >> include/linux/tracepoint.h | 12 ++++++++++-- >> init/Kconfig | 1 + >> 2 files changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h >> index 014790495ad8..cefd44b7c91f 100644 >> --- a/include/linux/tracepoint.h >> +++ b/include/linux/tracepoint.h >> @@ -17,6 +17,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> >> @@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod, >> #ifdef CONFIG_TRACEPOINTS >> static inline void tracepoint_synchronize_unregister(void) >> { >> + synchronize_rcu_tasks_trace(); >> synchronize_rcu(); >> } >> #else >> @@ -204,11 +206,17 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) >> if (!(cond)) \ >> return; \ >> \ >> - preempt_disable_notrace(); \ > > Should add a comment somewhere stating that the syscall version is to allow faults. I plan to add this comment on top of __TO_TRACE: + * + * With @syscall=0, the tracepoint callback array dereference is + * protected by disabling preemption. + * With @syscall=1, the tracepoint callback array dereference is + * protected by Tasks Trace RCU, which allows probes to handle page + * faults. Thanks, Mathieu > > -- Steve > >> + if (syscall) \ >> + rcu_read_lock_trace(); \ >> + else \ >> + preempt_disable_notrace(); \ >> \ >> __DO_TRACE_CALL(name, TP_ARGS(args)); \ >> \ >> - preempt_enable_notrace(); \ >> + if (syscall) \ >> + rcu_read_unlock_trace(); \ >> + else \ >> + preempt_enable_notrace(); \ >> } while (0) >> >> /* >> diff --git a/init/Kconfig b/init/Kconfig >> index fbd0cb06a50a..eedd0064fb36 100644 >> --- a/init/Kconfig >> +++ b/init/Kconfig >> @@ -1984,6 +1984,7 @@ config BINDGEN_VERSION_TEXT >> # >> config TRACEPOINTS >> bool >> + select TASKS_TRACE_RCU >> >> source "kernel/Kconfig.kexec" >> > -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com