(2013/11/05 15:09), Ingo Molnar wrote:
>
> * Steven Rostedt <rost...@goodmis.org> wrote:
>
>> On Fri, 01 Nov 2013 11:25:37 +0000
>> Masami Hiramatsu <masami.hiramatsu...@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...@hitachi.com>
>>> Cc: Andrew Morton <a...@linux-foundation.org>
>>> Cc: "Uwe Kleine-König" <u.kleine-koe...@pengutronix.de>
>>> Cc: Borislav Petkov <b...@suse.de>
>>> Cc: Ingo Molnar <mi...@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...@hitachi.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
