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. -- 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 */ -- To unsubscribe from this list: send the line "unsubscribe linux-metag" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
