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Tue, 13 Oct 2026 01:20:26 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:44::]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-830384c4985sm11295972a34.8.2026.10.13.01.20.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Oct 2026 01:20:24 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , Ihor Solodrai , Tejun Heo , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v2 03/13] compiler_types: Add __arena and __nullable BTF type tag qualifiers Date: Tue, 13 Oct 2026 10:19:58 +0200 Message-ID: <20261013082012.1107446-4-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261013082012.1107446-1-memxor@gmail.com> References: <20261013082012.1107446-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2184; h=from:subject; bh=t7Ln/IuDVwV2Gh/NYDdesfc2WRWqWh0L7iicESGQ0i0=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIevsy3lnf1a/7q+zTNTm1ntvGSPmlDopfurR/rCKlMQlN2+t my/XUcrCIMbFICumyFLyfx+T8YnK34G2y7hh5rAygQxh4OIUgIns+MnIsL59So1gcOX7XbfEVs9nV5 lWF1He6GjLeHg2z85GEdkaY4Z/BquTs/evbdOT5O2ZZXZO7vt8586Tu3n8Vh2zrJ7V/vwyIwA= X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit Kernel structures increasingly want to publish pointers into a BPF arena to the BPF programs they are shared with, and some pointer members that reach programs as trusted are legitimately NULL at times. Neither can be expressed today: a pointer member reaches the program as an ordinary kernel pointer, and sched_ext resorts to a plain u64 holding a pre-translated arena address that programs cast before use. Define __arena and __nullable as BTF type tags, the way __user, __rcu and __percpu already are, so that tagged members survive into vmlinux and module BTF and the verifier can act on them. To kernel code and to sparse the qualifiers are empty: the pointers are ordinary kernel pointers. The verifier side follows in the next patches. Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/compiler_types.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index c5921f139007..e97ee2d4d1df 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -51,6 +51,8 @@ # define __iomem __attribute__((noderef, address_space(__iomem))) # define __percpu __attribute__((noderef, address_space(__percpu))) # define __rcu __attribute__((noderef, address_space(__rcu))) +# define __arena +# define __nullable static inline void __chk_user_ptr(const volatile void __user *ptr) { } static inline void __chk_io_ptr(const volatile void __iomem *ptr) { } /* other */ @@ -70,6 +72,14 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { } # define __iomem # define __percpu __percpu_qual BTF_TYPE_TAG(percpu) # define __rcu BTF_TYPE_TAG(rcu) +/* + * Qualifiers for the BPF verifier rather than address spaces: __arena marks + * a pointer into a BPF arena, __nullable a pointer that may be NULL. They + * reach BPF programs as BTF type tags on kernel struct members; to kernel + * code the pointers are ordinary. + */ +# define __arena BTF_TYPE_TAG(arena) +# define __nullable BTF_TYPE_TAG(nullable) # define __chk_user_ptr(x) (void)0 # define __chk_io_ptr(x) (void)0 -- 2.53.0-Meta