On Tue, Dec 08, 2015 at 06:56:23PM +0100, Dmitry Vyukov wrote: > On Tue, Dec 8, 2015 at 6:54 PM, Alexei Starovoitov > <alexei.starovoi...@gmail.com> wrote: > > On Tue, Dec 08, 2015 at 05:12:04PM +0100, Dmitry Vyukov wrote: > >> On Tue, Dec 8, 2015 at 4:24 AM, Alexei Starovoitov > >> <alexei.starovoi...@gmail.com> wrote: > >> > On Mon, Dec 07, 2015 at 05:09:21PM +0100, Dmitry Vyukov wrote: > >> >> > So it would be _awesome_ if we could somehow extend this callchain to > >> >> > include the site that calls call_rcu(). > >> >> > >> >> We have a patch for KASAN in works that adds so-called stack depot > >> >> which allows to map a stack trace onto uint32 id. Then we can plumb > >> > > >> > I was hacking something similar to categorize stack traces with u32 id. > >> > How are you planning to limit the number of such stack traces ? > >> > and what is the interface for user space to get stack trace from an id? > >> > >> > >> We don't limit number of stack traces. Kernel does not seem to use > >> data-driven recursion extensively, so there is limited number of > >> stacks. Though, probably we will need to strip non-interrupt part for > >> interrupt stacks, otherwise that can produce unbounded number of > >> different stacks. > >> There is no interface for user-space, it is used only inside of kernel > >> to save stacks for memory blocks (rcu callbacks, thread pool items in > >> the future). > >> The design is based on what we successfully and extensively use in > >> user-space sanitizers for years. Current code is here: > >> https://github.com/ramosian-glider/kasan/commit/fb0eefd212366401ed5ad244233ef379a27bfb46 > > > > why did you pick approach to never free accumulated stacks? > > That limits usability a lot, since once kasan starts using it only > > reboot will free the memory. ouch. > > what worked for user space doesn't work for kernel. > > > Freeing and reusing will slow down and complicate code significantly. > And it is not yet proved to be necessary.
It's a joke, right? allocating kernel pages without ability to free?! -- 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/