On Mon 2016-06-27 17:17:17, Torsten Duwe wrote: > Once gcc is enhanced to optionally generate NOPs at the beginning > of each function, like the concept proven in > https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01671.html > (sans the "fprintf (... pad_size);", which spoils the data structure > for kernel use), the generated pads can nicely be used to reroute > function calls for tracing/profiling, or live patching. > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index ebecf9a..917065c 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -39,6 +39,12 @@ static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, > if (aarch64_insn_read((void *)pc, &replaced)) > return -EFAULT; > > + /* If we already have what we'll finally want, > + * report success. This is needed on startup. > + */ > + if (replaced == new) > + return 0; This looks strange. I wonder if it actually hides a real bug that we modify the code twice or so. I wanted to try it myself but I haven't succeeded with creating an ARM test system yet. Best Regards, Petr -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
