Messages in this thread |  | | Date | Tue, 05 Nov 2013 12:15:05 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on func_ptr_is_kernel_text |
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(2013/11/05 11:00), Steven Rostedt wrote: > On Fri, 01 Nov 2013 11:25:37 +0000 > Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote: > >> Prohibit probing on func_ptr_is_kernel_text(). >> Since the func_ptr_is_kernel_text() is called from >> notifier_call_chain() which is called from int3 handler, >> probing it may cause double int3 fault and kernel will >> reboot. >> >> This happenes when the kernel built with CONFIG_DEBUG_NOTIFIERS=y. >> >> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de> >> Cc: Borislav Petkov <bp@suse.de> >> Cc: Ingo Molnar <mingo@kernel.org> >> --- >> kernel/extable.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/extable.c b/kernel/extable.c >> index 832cb28..022fb25 100644 >> --- a/kernel/extable.c >> +++ b/kernel/extable.c >> @@ -129,7 +129,7 @@ int kernel_text_address(unsigned long addr) >> * pointer is part of the kernel text, we need to do some >> * special dereferencing first. >> */ >> -int func_ptr_is_kernel_text(void *ptr) >> +int nokprobe func_ptr_is_kernel_text(void *ptr) >> { >> unsigned long addr; >> addr = (unsigned long) dereference_function_descriptor(ptr); >> > > One thing I worry about the "nokprobe" annotation, is that it moves the > location of the function out of local. This function no exists in > the section with its users. Same with the debug functions in the > other patch. > > Now these may be a slow path where we really don't care, but if the > nokprobe expands this can cause issues. > > The "nokprobe" works differently than "notrace" as "notrace" is just an > attribute that tells gcc not to add mcount to it. The "nokprobe" > actually moves the function into a different section.
Well, in that case, I can put it in the opt-out type blacklist(kprobe_blacklist). :) Hmm, I think if I can list nokprobe functions up at build time, we can almost remove the .kprobes.text (Note that some of entry functions in asm still require it.)
Thank you,
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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