Hi Steven, On Wed, Dec 23, 2015 at 12:33:46PM -0500, Steven Rostedt wrote: > On Sun, 6 Dec 2015 10:02:55 +0800 > Li Bin <huawei.libin@xxxxxxxxxx> 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: James Hogan <james.hogan@xxxxxxxxxx> > > Cc: linux-metag@xxxxxxxxxxxxxxx > > Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > > Signed-off-by: Li Bin <huawei.libin@xxxxxxxxxx> > > Hi, can I get a metag maintainer to ack this. Or you can take the patch > too. Yep, sorry for the delay, Acked-by: James Hogan <james.hogan@xxxxxxxxxx> Cheers James > > -- Steve > > > --- > > arch/metag/kernel/ftrace.c | 11 +++++------ > > 1 files changed, 5 insertions(+), 6 deletions(-) > > > > diff --git a/arch/metag/kernel/ftrace.c b/arch/metag/kernel/ftrace.c > > index ed1d685..ac8c039 100644 > > --- a/arch/metag/kernel/ftrace.c > > +++ b/arch/metag/kernel/ftrace.c > > @@ -54,12 +54,11 @@ static int ftrace_modify_code(unsigned long pc, 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. > > - * > > - * No real locking needed, this code is run through > > - * kstop_machine. > > + * Note: > > + * We are paranoid about modifying text, as if a bug was to happen, it > > + * could cause us to read or write to someplace that could cause harm. > > + * Carefully read and modify the code with probe_kernel_*(), and make > > + * sure what we read is what we expected it to be before modifying it. > > */ > > > > /* read the text we want to modify */ >
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