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b=qlN1u4IC0r99kFwuTyEvvgpnKtlQXJhQIiaVSYFWhKt0guvQX5I2wtbi4wfjdPRvw jDFjhzprkgEX63ncvKL/SeVUECu5nBFrH5IIY6d1J0MCbZyKD4hvs92/xS0keDVZQs TFtKR1zDQLVPE6z4xgr19Hx8bgMXlNKLzKD8s4AXc3Zou8yXuts/LhS2JxwColr0Fi fduCMr+IhO1XWtSdTYu8QRP94FyJ6/NBxH/2Rikk8e8Rhc+wQF8y4V/m2u6N5if3Jo hNV01hbozoSnECH8E9jJAUxO0tNxkNOo8ENRWVrSeDbk237tgY7YRxY8eo8almgf5b VESCjGrbNaDNQ== Date: Thu, 3 Oct 2024 22:31:44 -0700 From: Namhyung Kim To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf@vger.kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Arnaldo Carvalho de Melo , Kees Cook Subject: Re: [PATCH v4 bpf-next 2/3] mm/bpf: Add bpf_get_kmem_cache() kfunc Message-ID: References: <20241002180956.1781008-1-namhyung@kernel.org> <20241002180956.1781008-3-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241002180956.1781008-3-namhyung@kernel.org> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: BA01D80004 X-Stat-Signature: a87999b544ipta1cyeh1m4ujuosyocat X-Rspam-User: X-HE-Tag: 1728019907-169042 X-HE-Meta: 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 p3T4VMiV WAycP2/Vd+D0O+I8D4WZvMdzizkDMZOG6P0EzIq/vBVcO37XcDRlzLvvPsx/Ynxi7VecejeZoY25KQtEWnPVjWVo7j1oTxHYqFABjICRyWHxecWAyXlNOdtAB5x1cKg4KnPlufkgCFgS8DyNhgHJzmEeZOrSONQ3xsoCWBLcNwFX7TCOmQkabrpxzGj+sihkJnp28kkNkNxk8EpJOFvETAfkpOeArHWX1KZBzMxrHSi0HKA2ak1eIxXQPf5RidYoumb1/6j/eKz1ZzaPM7OLJ/zVTaUb6eIy0CFjwSche7SRksKqvsglnrEgI+EM2dLmBlJeQWzpQD4liadsGHPYdXje5czffFg2QjdkLoBpCfNq8E1cgA7CEJrsoL0Xr5sU0IF56fWctRGLKYuWvymkhsyjOjxW6iJ/5xdGRPCPoslBpVIU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 02, 2024 at 11:09:55AM -0700, Namhyung Kim 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 intended use case for now is to > symbolize locks in slab objects from the lock contention tracepoints. > > Suggested-by: Vlastimil Babka > Acked-by: Roman Gushchin (mm/*) > Acked-by: Vlastimil Babka #mm/slab > Signed-off-by: Namhyung Kim > --- > kernel/bpf/helpers.c | 1 + > mm/slab_common.c | 19 +++++++++++++++++++ > 2 files changed, 20 insertions(+) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 4053f279ed4cc7ab..3709fb14288105c6 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -3090,6 +3090,7 @@ BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW) > BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY) > BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_get_kmem_cache, KF_RET_NULL) > BTF_KFUNCS_END(common_btf_ids) > > static const struct btf_kfunc_id_set common_kfunc_set = { > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 7443244656150325..5484e1cd812f698e 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1322,6 +1322,25 @@ size_t ksize(const void *objp) > } > EXPORT_SYMBOL(ksize); > > +#ifdef CONFIG_BPF_SYSCALL > +#include > + > +__bpf_kfunc_start_defs(); > + > +__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr) > +{ > + struct slab *slab; > + > + if (!virt_addr_valid(addr)) Hmm.. 32-bit systems don't like this. Is it ok to change the type of the parameter (addr) to 'unsigned long'? Or do you want to keep it as u64 and add a cast here? Thanks, Namhyung > + return NULL; > + > + slab = virt_to_slab((void *)(long)addr); > + return slab ? slab->slab_cache : NULL; > +} > + > +__bpf_kfunc_end_defs(); > +#endif /* CONFIG_BPF_SYSCALL */ > + > /* Tracepoints definitions. */ > EXPORT_TRACEPOINT_SYMBOL(kmalloc); > EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc); > -- > 2.46.1.824.gd892dcdcdd-goog >