Messages in this thread |  | | Date | Tue, 05 Nov 2013 15:59:06 +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 15:09), Ingo Molnar wrote: > > * Steven Rostedt <rostedt@goodmis.org> 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. > > Well, it's a bit like noinline, that changes the position of the function > as well. So it's not true that 'noxyz' attributes don't affect function > placement - they often don't, but some do. > > The more important aspect is that 'noprobe' makes it really, really > apparent what the tag is about, at first sight. > > _How_ the 'non probing' is achived is an implementational detail when > kprobes are enabled: right now it puts a function into a separate section, > but we could just a much build a list of function names and check against > it at probe insertion time.
Actually, kprobes already has it -- kprobes_blacklist. Currently the list is manually maintained in kprobes.c separated from the function definition. I hope to build the list when the kernel build time if possible... Would you have any idea to classify some annotated(but no side-effect) functions?
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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