From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Date: Fri, 04 Dec 2015 12:44:27 +0000 Subject: Re: [PATCH 4/5] sh: ftrace: fix the comments for ftrace_modify_code Message-Id: <56618AAB.2000202@cogentembedded.com> List-Id: References: <1449214067-12177-1-git-send-email-huawei.libin@huawei.com> <1449214067-12177-5-git-send-email-huawei.libin@huawei.com> In-Reply-To: <1449214067-12177-5-git-send-email-huawei.libin@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Li Bin , rostedt@goodmis.org, mingo@redhat.com Cc: linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org Hello. On 12/4/2015 10:27 AM, Li Bin wrote: > There is no need to worry about module and __init text disappearing > case, because that ftrace has a module notifier that is called when > a module is being unloaded and before the text goes away and this > code grabs the ftrace_lock mutex and removes the module functions > from the ftrace list, such that it will no longer do any > modifications to that module's text, the update to make functions > be traced or not is done under the ftrace_lock mutex as well. > And by now, __init section codes should not been modified > by ftrace, because it is black listed in recordmcount.c and > ignored by ftrace. > > Cc: linux-sh@vger.kernel.org > Suggested-by: Steven Rostedt > Signed-off-by: Li Bin > --- > arch/sh/kernel/ftrace.c | 13 ++++++------- > 1 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c > index 079d70e..b696f92 100644 > --- a/arch/sh/kernel/ftrace.c > +++ b/arch/sh/kernel/ftrace.c > @@ -212,13 +212,12 @@ static int ftrace_modify_code(unsigned long ip, unsigned char *old_code, > unsigned char replaced[MCOUNT_INSN_SIZE]; > > /* > - * Note: Due to modules and __init, code can > - * disappear and change, we need to protect against faulting > - * as well as code changing. We do this by using the > - * probe_kernel_* functions. > - * > - * No real locking needed, this code is run through > - * kstop_machine, or before SMP starts. > + * Note: > + * We are paranoid about modifying text, as if a bug were to happen, it s/were/was/. [...] MBR, Sergei