(2013/11/05 11:00), Steven Rostedt 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.
>
> 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...@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/
