On Mon, Oct 14, 2024 at 06:50:49PM -0700, Alexei Starovoitov wrote: > On Mon, Oct 14, 2024 at 11:13 AM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > > > Hi Alexei, > > > > On Fri, Oct 11, 2024 at 12:14:14PM -0700, Namhyung Kim wrote: > > > On Fri, Oct 11, 2024 at 11:35:27AM -0700, Alexei Starovoitov wrote: > > > > On Thu, Oct 10, 2024 at 4:25 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote: > > > > > > > > > > The bpf_get_kmem_cache() is to get a slab cache information from a > > > > > virtual address like virt_to_cache(). If the address is a pointer > > > > > to a slab object, it'd return a valid kmem_cache pointer, otherwise > > > > > NULL is returned. > > > > > > > > > > It doesn't grab a reference count of the kmem_cache so the caller is > > > > > responsible to manage the access. The returned point is marked as > > > > > PTR_UNTRUSTED. And the kfunc has KF_RCU_PROTECTED as the slab object > > > > > might be protected by RCU. > > > > > > > > ... > > > > > +BTF_ID_FLAGS(func, bpf_get_kmem_cache, KF_RCU_PROTECTED) > > > > > > > > This flag is unnecessary. PTR_UNTRUSTED can point to absolutely any memory. > > > > In this case it likely points to a valid kmem_cache, but > > > > the verifier will guard all accesses with probe_read anyway. > > > > > > > > I can remove this flag while applying. > > > > > > Ok, I'd be happy if you would remove it. > > > > You will need to update the bpf_rcu_read_lock/unlock() in the test code > > (patch 3). I can send v6 with that and Vlastimil's Ack if you want. > > Fixed all that while applying. > > Could you please follow up with an open-coded iterator version > of the same slab iterator ? > So that progs can iterate slabs as a normal for/while loop ? I'm not sure I'm following. Do you want a new test program to iterate kmem_caches by reading list pointers manually? How can I grab the slab_mutex then? Thanks, Namhyung
