On Fri, 11 Oct 2019 17:39:29 +0900 Masami Hiramatsu <mhira...@kernel.org> wrote:
> Hi Steve, > > On Thu, 10 Oct 2019 17:52:16 -0400 > Steven Rostedt <rost...@goodmis.org> wrote: > > > From: Steven Rostedt (VMware) <rost...@goodmis.org> > > > > I noticed some of my old tests failing on kprobes, and realized that > > this was due to black listing irq_entry functions on x86 from being > > used by kprobes. IIRC, this was due to the cr2 being corrupted and > > such, and I believe other things were to cause. But black listing all > > irq_entry code is a big hammer to this. > > OK, I think if we can use ftrace for hooking, probing on "that address" > is good, but the function body still can not be probed. > > > > > (See commit 0eae81dc9f026 "x86/kprobes: Prohibit probing on IRQ > > handlers directly" for more details) > > > > Anyway, if kprobes is using ftrace as a hook, there shouldn't be any > > problems here. If we white list ftrace locations in the range of > > kprobe_add_area_blacklist(), it should be safe. > > Agreed. > > > > > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > > --- > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index d9770a5393c8..9d28a279282c 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -2124,6 +2124,11 @@ int kprobe_add_area_blacklist(unsigned long start, > > unsigned long end) > > int ret = 0; > > > > for (entry = start; entry < end; entry += ret) { > > +#ifdef CONFIG_KPROBES_ON_FTRACE > > + /* We are safe if using ftrace */ > > + if (ftrace_location(entry)) > > + continue; > > +#endif > > Have you tested the patch? it doesn't measure the entry function's size. > (kprobe_add_ksym_blacklist(entry) returns the function size) Yeah, I tested the patch, but it is obviously buggy. It fixed the issue I was having (was able to test against do_IRQ ;-) > > Could you do this in kprobe_add_ksym_blacklist()? > Instead of continue, increment ent->start_addr by MCOUNT size(?) will be OK. > (Note that since each blacklist symbol is managed independently, you can make > a "gap" between them as a safe area) OK, I'll move it to kprobe_add_ksym_blacklist. -- Steve > > Thank you, > > > ret = kprobe_add_ksym_blacklist(entry); > > if (ret < 0) > > return ret; > >