On Sun, 6 Dec 2015 10:02:58 +0800 Li Bin <[email protected]> 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: Thomas Gleixner <[email protected]> > Cc: "H. Peter Anvin" <[email protected]> > Cc: [email protected] > Suggested-by: Steven Rostedt <[email protected]> > Signed-off-by: Li Bin <[email protected]> > --- > arch/x86/kernel/ftrace.c | 12 +++++------- > 1 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c > index 311bcf3..db0f6b1 100644 > --- a/arch/x86/kernel/ftrace.c > +++ b/arch/x86/kernel/ftrace.c > @@ -106,13 +106,11 @@ ftrace_modify_code_direct(unsigned long ip, unsigned > const 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 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. > */ Thomas, This has been now fixed. You want to ack it and I take it, or can you take it. Or is there something else that should be fixed? -- Steve > > /* read the text we want to modify */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
