From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.203 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793729965; b=QiHiwsIqvrvL3EwAXdElFNhK0II+QS6pvewtw91QWXjY85pc+WM+9qN4PINiQha5thTO t3dypMRmmAfkznXFrc0GId/7NgJeAHsz41OtHNW3GpNp3YsFztU3L/XFOLtCSteOWQGFv Hngrm0SqZ5Rp9vI28HbXXdEtPL78jCGWAYh2hv1amHknpvYKdo6+06Z+okICFrmAXrRTx DUFvvgXqBrLy3mjdYqjATruCuGLF0v7RJ+5WfwDwIxZGQBW683dh8HkGlx0wVEAfOeIXi z+RDD6hqTsCTev0dTB7blkcDSSlVQbpjMQJKRwtgO0fb0WBP/ss/CW/cN4//obqrsvg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793729965; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=cy5NVa4zy9qS6Mga9ltUsUEtCniHJojXVPr9zJunu6w=; b=Xmfpo2c9d0Ho3bZ83t+tZ2prbT3u9FbhGuIUp2r2j/KyK297HGxDOnWpz+mvO2oiYAfw QWL3Gd63wlUkhXthpp2xpKwHoAiAYkGmMrUVzTsznEkhYgeK7UJBgHbWi4HugbvbpSvIz L6U6WcsMnXvl5Ygmtr75CQU0BG1/mgpyGyLDhHxT/ZLaTdEDyJ6zd5TNrNzalQZKGqH9o +w94Vd/13BYOZ2CKcuEP3hXsnsSETk3+l4aWLjmeOX0CDA/ZMSZQk4CfOuoSnj/4DuxMb vyqrz09slX2kVupwCBhPVzd89JKM8BYLaiodjlg6b9KjAX+B41wR8sfdiGPBiNtYwYg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=wG6CV3Gj; arc=none smtp.remote-ip=91.218.175.203 Received: from mta0.migadu.com (out-203.mta0.migadu.com [91.218.175.203]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04C4C606EE97 for ; Tue, 3 Nov 2026 18:19:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 04C4C606EE97 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=wG6CV3Gj X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=q/ovGyzi7R6zckhCMNiZ94Ym7wcqVfK/WB2DmfreLvE=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793729962; v=1; x=1794334762; b=wG6CV3GjvIJcnzS8uuv6N0bGjfTxLRFRQU7Bm7+tTALamOvLkvRQX5O2Ao75S25YdPf+butm NFU+j4fHQYBhxOus7INUPkcqkAQRbl2Tklzr6Qr12le4YBlRGkaGnwlRJAwDlHFJXWehEIM79kh l6lhRrAT7hnl+9ByiUPhSAVE= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id a72f377556df3c9b; Tue, 03 Nov 2026 18:19:21 +0000 X-Mizu-Trace-ID: a72f377556df3c9b X-Migadu-Flow: FLOW_OUT From: Vineet Gupta To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, john.fastabend@gmail.com, shuah@kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, jose.marchesi@oracle.com, david.faust@oss.qualcomm.com, Vineet Gupta Subject: [PATCH bpf-next v4 8/8] selftests/bpf: cast explicitly in the arena subprog and callback faults Date: Tue, 3 Nov 2026 10:18:16 -0800 Message-ID: <20261103181816.254686-9-vineet.gupta@linux.dev> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261103181816.254686-1-vineet.gupta@linux.dev> References: <20261103181816.254686-1-vineet.gupta@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Stream tests fail with BPF_GCC, e.g. test_stream_arena_fault_address:FAIL:stream__open_and_load unexpected error: -13 They call stream__open_and_load(), which loads every program in the object, and two of those do not verify: #481/11 stream_success/stream_arena_subprog_fault:FAIL #481/12 stream_success/stream_arena_callback_fault:FAIL Both dereference an arena pointer and leave the cast to the compiler: int __arena *addr = (int __arena *)0xdeadbeef; *addr = 1; Without arena support __arena is only btf_type_tag("arena"), so no addr_space_cast is emitted and the store is to a scalar, which the verifier rejects. GCC splits it into byte stores, 0xdeadbeef not being aligned: r2=3735928559 ll *(u8*)(r2+0)=1 <- plain store, no cast Their siblings in the same file do not rely on the compiler; they use bpf_addr_space_cast(), which emits the instruction byte by byte and works anywhere. Do the same here. The address space has to come off the local as well. Left on, a compiler that supports arenas casts a second time for the dereference, on a pointer the explicit cast has already converted: r2 = addr_space_cast(r2, 0, 1) r3 = addr_space_cast(r2, 0, 1) *(u32*)(r3+0)=1 With it off, GCC with and without arena support and clang all emit the same thing, which is what the test wants: r2 = addr_space_cast(r2, 0, 1) *(u32*)(r2+0)=1 What these two assert is the fault report, not how the pointer was produced, so nothing they were testing is lost. Measured on bpf-next with a stock bpf-gcc, test_progs before and after. Every test that loads this object recovers, not just the arena ones: stream_arena_fault_address FAIL -> OK stream_fd FAIL -> OK stream_fd/blocking FAIL -> OK stream_fd/edge FAIL -> OK stream_fd/empty FAIL -> OK stream_fd/hup FAIL -> OK stream_fd/nmi_epoll FAIL -> OK stream_fd/nonblock FAIL -> OK stream_fd/open FAIL -> OK stream_oversize FAIL -> OK stream_partial_read FAIL -> OK stream_success FAIL -> OK stream_success/stream_arena_callback_fault FAIL -> OK stream_success/stream_arena_subprog_fault FAIL -> OK stream_syscall FAIL -> OK and the subtests of the object that failed to load appear for the first time: stream_arena_fault_address/read_fault -> OK stream_arena_fault_address/write_fault -> OK stream_arena_fault_address/xchg_fault -> OK stream_arena_fault_address/cmpxchg_fault -> OK stream_arena_fault_address/load_acquire_fault -> OK Signed-off-by: Vineet Gupta --- v3 -> v4: was 6/8. No longer drops #include , which the arena_base() patch now needs in this file. tools/testing/selftests/bpf/progs/stream.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c index b4d88d0e01ad..8c49a130150b 100644 --- a/tools/testing/selftests/bpf/progs/stream.c +++ b/tools/testing/selftests/bpf/progs/stream.c @@ -341,9 +341,10 @@ int stream_arena_cmpxchg_fault(void *ctx) static __noinline void subprog(void) { - int __arena *addr = (int __arena *)0xdeadbeef; + int *addr = (int *)0xdeadbeef; arena_ptr = &arena; + bpf_addr_space_cast(addr, 0, 1); *addr = 1; } @@ -364,9 +365,10 @@ int stream_arena_subprog_fault(void *ctx) static __noinline int timer_cb(void *map, int *key, struct bpf_timer *timer) { - int __arena *addr = (int __arena *)0xdeadbeef; + int *addr = (int *)0xdeadbeef; arena_ptr = &arena; + bpf_addr_space_cast(addr, 0, 1); *addr = 1; return 0; } -- 2.53.0-Meta