From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 822D5ED5 for ; Tue, 22 Aug 2023 05:22:07 +0000 (UTC) Received: from out-20.mta0.migadu.com (out-20.mta0.migadu.com [91.218.175.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C56E8DB for ; Mon, 21 Aug 2023 22:22:05 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1692681721; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p7OivulQIiYwQDHcgS4MUZiMUDzPvHBUWCHdxzKCuOg=; b=IKqeWJEOY0H3lixphi/D0ubowICn7WaKVQymg5Fxm+6bEi8is7Jcj2+/GwkJQoOliw1sd1 clkVRQi1zRXjgOap/0WpFjEqBzPJFIX1zjXCgXRhGzz0WZ9DnaopCtWSfYGM0AFRX+ZZiN B/7bAw9vME7KxCPUUZBSvmWWu4erthE= Date: Tue, 22 Aug 2023 01:21:59 -0400 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2 bpf-next 7/7] selftests/bpf: Add tests for rbtree API interaction in sleepable progs Content-Language: en-US To: yonghong.song@linux.dev, Dave Marchevsky , bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Kernel Team References: <20230821193311.3290257-1-davemarchevsky@fb.com> <20230821193311.3290257-8-davemarchevsky@fb.com> <7aaa5d24-1377-48c4-1ace-b6a2fc79a2d0@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: David Marchevsky In-Reply-To: <7aaa5d24-1377-48c4-1ace-b6a2fc79a2d0@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On 8/21/23 11:18 PM, Yonghong Song wrote: > > > On 8/21/23 12:33 PM, Dave Marchevsky wrote: >> Confirm that the following sleepable prog states fail verification: >>    * bpf_rcu_read_unlock before bpf_spin_unlock >>       * RCU CS will last at least as long as spin_lock CS > > I think the reason is bpf_spin_lock() does not allow any functions > in spin lock region except some graph api kfunc's. > Yeah, agreed, this test isn't really validating anything with current verifier logic. But, given that spin_lock CS w/ disabled preemption is an RCU CS, do you forsee wanting to allow rcu_read_unlock within spin_lock CS? I'll delete the test if you think it should go, but maybe it's worth keeping with a comment summarizing why it's an interesting example. Also, the existing comment in that test is incorrect, will fix. >> >> Also confirm that correct usage passes verification, specifically: >>    * Explicit use of bpf_rcu_read_{lock, unlock} in sleepable test prog >>    * Implied RCU CS due to spin_lock CS >> >> None of the selftest progs actually attach to bpf_testmod's >> bpf_testmod_test_read. >> >> Signed-off-by: Dave Marchevsky >> --- >>   .../selftests/bpf/progs/refcounted_kptr.c     | 71 +++++++++++++++++++ >>   .../bpf/progs/refcounted_kptr_fail.c          | 28 ++++++++ >>   2 files changed, 99 insertions(+) >> >> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr.c b/tools/testing/selftests/bpf/progs/refcounted_kptr.c >> index c55652fdc63a..893a4fdb4b6e 100644 > [...] >> diff --git a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c >> index 0b09e5c915b1..1ef07f6ee580 100644 >> --- a/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c >> +++ b/tools/testing/selftests/bpf/progs/refcounted_kptr_fail.c >> @@ -13,6 +13,9 @@ struct node_acquire { >>       struct bpf_refcount refcount; >>   }; >>   +extern void bpf_rcu_read_lock(void) __ksym; >> +extern void bpf_rcu_read_unlock(void) __ksym; >> + >>   #define private(name) SEC(".data." #name) __hidden __attribute__((aligned(8))) >>   private(A) struct bpf_spin_lock glock; >>   private(A) struct bpf_rb_root groot __contains(node_acquire, node); >> @@ -71,4 +74,29 @@ long rbtree_refcounted_node_ref_escapes_owning_input(void *ctx) >>       return 0; >>   } >>   +SEC("?fentry.s/bpf_testmod_test_read") >> +__failure __msg("function calls are not allowed while holding a lock") >> +int BPF_PROG(rbtree_fail_sleepable_lock_across_rcu, >> +         struct file *file, struct kobject *kobj, >> +         struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) >> +{ >> +    struct node_acquire *n; >> + >> +    n = bpf_obj_new(typeof(*n)); >> +    if (!n) >> +        return 0; >> + >> +    /* spin_{lock,unlock} are in different RCU CS */ >> +    bpf_rcu_read_lock(); >> +    bpf_spin_lock(&glock); >> +    bpf_rbtree_add(&groot, &n->node, less); >> +    bpf_rcu_read_unlock(); >> + >> +    bpf_rcu_read_lock(); >> +    bpf_spin_unlock(&glock); >> +    bpf_rcu_read_unlock(); >> + >> +    return 0; >> +} >> + >>   char _license[] SEC("license") = "GPL";