Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault

[Steven Rostedt]

On Wed, 20 Feb 2019 14:57:31 +0100
Jann Horn <jannh@xxxxxxxxxx> wrote:

> > (*) BTW, there is another concern to use _from_user APIs in kprobe. Are those
> > APIs might sleep??  
> 
> If you want to access userspace without sleeping, and ignore data in
> non-present pages, you can do `pagefault_disable(); err =
> __copy_from_user_inatomic(...); pagefault_enable();`. (Actually, maybe
> the kernel should have a helper for that...)

I was about to say pretty much the same thing (about using
_inatomic()), but yeah, we should also have a helper function if we
don't already to include the page_fault_disable/enable() too.

-- Steve