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Sat, 07 Feb 2026 18:49:03 -0800 (PST) Received: from localhost.localdomain ([113.218.252.53]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a9521b9f5esm67194715ad.51.2026.02.07.18.48.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 07 Feb 2026 18:49:02 -0800 (PST) From: Chengkaitao To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, yangfeng@kylinos.cn, alexei.starovoitov@gmail.com Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Kaitao Cheng Subject: [PATCH v6 0/5] bpf/verifier: Expand the usage scenarios of bpf_kptr_xchg Date: Sun, 8 Feb 2026 10:48:41 +0800 Message-ID: <20260208024846.18653-1-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Kaitao Cheng When using bpf_kptr_xchg, we triggered the following error: 31: (85) call bpf_kptr_xchg#194 function calls are not allowed while holding a lock bpf_kptr_xchg can now be used in lock-held contexts, so we extended its usage scope in [patch 1/5]. When writing test cases using bpf_kptr_xchg and bpf_rbtree_*, the following approach must be followed: bpf_spin_lock(&lock); rb_n = bpf_rbtree_root(&root); while (rb_n && can_loop) { rb_n = bpf_rbtree_remove(&root, rb_n); if (!rb_n) goto fail; tnode = container_of(rb_n, struct tree_node, node); node_data = bpf_kptr_xchg(&tnode->node_data, NULL); if (!node_data) goto fail; data = node_data->data; /* use data to do something */ node_data = bpf_kptr_xchg(&tnode->node_data, node_data); if (node_data) goto fail; bpf_rbtree_add(&root, rb_n, less); if (lookup_key < tnode->key) rb_n = bpf_rbtree_left(&root, rb_n); else rb_n = bpf_rbtree_right(&root, rb_n); } bpf_spin_unlock(&lock); The above illustrates a lock-remove-read-add-unlock workflow, which exhibits lower performance. To address this, we introduced support for a streamlined lock-read-unlock operation in [patch 2/5] and [patch 4/5]. Changes in v6: - allow using bpf_kptr_xchg even if the MEM_RCU flag is set - Add test case Changes in v5: - add lastname Changes in v4: - Fix the dead logic issue in the test case Changes in v3: - Fix compilation errors Changes in v2: - Allow using bpf_kptr_xchg even if the NON_OWN_REF flag is set - Add test case Link to v5: https://lore.kernel.org/all/20260203022712.99347-1-pilgrimtao@gmail.com/ Link to v4: https://lore.kernel.org/all/20260202090051.87802-1-pilgrimtao@gmail.com/ Link to V3: https://lore.kernel.org/all/20260202055818.78231-1-pilgrimtao@gmail.com/ Link to V2: https://lore.kernel.org/all/20260201031607.32940-1-pilgrimtao@gmail.com/ Link to V1: https://lore.kernel.org/all/20260122081426.78472-1-pilgrimtao@gmail.com/ Kaitao Cheng (5): bpf/verifier: allow calling bpf_kptr_xchg while holding a lock bpf/verifier: allow using bpf_kptr_xchg even if the NON_OWN_REF flag is set selftests/bpf: Add supplementary tests for bpf_kptr_xchg bpf/verifier: allow using bpf_kptr_xchg even if the MEM_RCU flag is set selftests/bpf: Add test case for rbtree nodes that contain both bpf_refcount and kptr fields. kernel/bpf/verifier.c | 9 +- .../testing/selftests/bpf/prog_tests/rbtree.c | 6 + tools/testing/selftests/bpf/progs/bpf_misc.h | 4 + .../selftests/bpf/progs/rbtree_search_kptr.c | 290 ++++++++++++++++++ 4 files changed, 307 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/rbtree_search_kptr.c -- 2.50.1 (Apple Git-155)