From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 117E73F928E for ; Fri, 4 Sep 2026 05:10:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=66.220.144.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498612; cv=none; b=WDmMu/WEggumbDat8FDosfq4m4Wx9bNNfoDcb5fXAH6GqN5EL6KEgyF1fBeGsQE6pFJjluE3HlqOYj0i27rOwhw/wMONWxeBYi5n/iQ61lrNUYqzld8VgInyfxvIuzGFf4enhyo7wU+ST2pc+jBQyI56muogtza7HWyeGA4XdHY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498612; c=relaxed/simple; bh=Gznkp0qjUJd1rgFs7tiTsQkyKeKL3014HZbIsvVUwgQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=u4CczCQ6bS9hWsBiv2EWz56qP14eG3jdDjL6KY7ME7ShQeQMnRRABfVWI+cK+eepeHBJFyyetvQtqsEwC9vIEXW3It1Wd6O6EeUJdycXup1EjIDiidJYmqU8NREVOeIVbqeBdh1dtGrtQy9MV1r6a3lKAR0PdYAw2Yj9DGC8ZQQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=66.220.144.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devvm16039.vll0.facebook.com (Postfix, from userid 128203) id B341A28813164B; Thu, 3 Sep 2026 22:09:57 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , kernel-team@fb.com Subject: [PATCH bpf-next 00/12] bpf: Support by-value struct and __int128 arguments Date: Thu, 3 Sep 2026 22:09:57 -0700 Message-ID: <20260904050957.3976119-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable A global function or a kfunc taking a struct or union by value is rejecte= d today: Arg#1 type STRUCT in tar() is not supported yet. Unrecognized R2 type STRUCT and an __int128 argument is accepted but mis-counted: the compiler passes it in two registers while the verifier gives it one, so every argument after it is checked against the wrong register and the program is rejecte= d for a register its source never names. The compiler passes such a value in one argument register per eightbyte, so a value of at most 16 bytes arrives in one or two consecutive registers. This series teaches the verifier to describe that: sub->args[] gains one entry per argument slot rather than one per BTF parameter, and the kfunc argument walk counts slots the same way. A value may only be composed of scalars, as a pointer would reach the callee as an opaque scalar, losing the provenance and reference tracking that make it safe to use. A global function still has no stack arguments, so all of its slots have to fit in the argument registers. For a kfunc the two calling conventions have to agree, and they do not always. Where the BPF convention splits a value between the last argument register and the stack, SysV moves the whole of it to the stack and gives the register to the argument that follows, while AAPCS64 rounds the register number up to an even one for a 16-byte aligned value and gives n= o register to anything once one has gone to the stack. The JITs move the eightbytes the two conventions place differently, and bpf_jit_supports_kfunc_arg_slot() asks the JIT whether it can, defaulting to no, so such an argument is refused on an architecture that has not implemented the placement: Function f arg#5 type STRUCT cannot be passed at argument slot 5 on thi= s architecture Patch 1 records the __int128 failure as it stands today, which patch 4 turns into a success. Patches 2 to 4 index the arguments of a global function by slot and accept a by-value struct and an __int128. Patch 5 does the same for a kfunc call. Patches 6 to 9 place the arguments per th= e kernel calling convention in the x86-64 and arm64 JITs. Patches 10 to 12 are the tests. Tested on x86-64 and arm64 with test_progs. The by-value struct tests are built with clang, as GCC passes an aggregate by invisible reference, and some of them need __BPF_FEATURE_STACK_ARGUMENT. Yonghong Song (12): selftests/bpf: Add a test for an __int128 by-value argument bpf: Index global function arguments by argument slot bpf: Support by-value struct arguments up to 16 bytes bpf: Support __int128 as a by-value function argument bpf: Support by-value struct and __int128 kfunc arguments bpf: Add a JIT helper for the outgoing stack of kfunc calls bpf, x86: Place kfunc arguments per the SysV calling convention bpf: Record a 16-byte argument alignment in the function model bpf, arm64: Place kfunc arguments per AAPCS64 selftests/bpf: Add C tests for by-value arguments up to 16 bytes selftests/bpf: Add inline-asm tests for by-value arguments selftests/bpf: Add tests for by-value kfunc arguments arch/arm64/net/bpf_jit_comp.c | 112 +++++++++- arch/x86/net/bpf_jit_comp.c | 185 +++++++++++++++- include/linux/bpf.h | 3 + include/linux/bpf_verifier.h | 1 + include/linux/filter.h | 3 + kernel/bpf/btf.c | 98 +++++++-- kernel/bpf/core.c | 42 ++++ kernel/bpf/verifier.c | 200 ++++++++++++++++-- .../selftests/bpf/prog_tests/aggregate_arg.c | 11 + .../selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/aggregate_arg_func.c | 155 ++++++++++++++ .../selftests/bpf/progs/aggregate_arg_kfunc.c | 106 ++++++++++ .../testing/selftests/bpf/progs/arena_kfunc.c | 16 ++ .../selftests/bpf/progs/stack_arg_fail.c | 10 - .../selftests/bpf/progs/verifier_int128_arg.c | 195 +++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 40 ++++ .../bpf/test_kmods/bpf_testmod_kfunc.h | 22 ++ 17 files changed, 1151 insertions(+), 50 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/aggregate_arg.= c create mode 100644 tools/testing/selftests/bpf/progs/aggregate_arg_func.= c create mode 100644 tools/testing/selftests/bpf/progs/aggregate_arg_kfunc= .c create mode 100644 tools/testing/selftests/bpf/progs/verifier_int128_arg= .c --=20 2.53.0-Meta