From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.13 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793145905; b=vKZK394eTPkCAma6NTfzssG3XxKzxort8XTd3k2PYXP3Opw632Qn9iDVyt68WYgf57rS FpR7U9ky+MivAlm38nr8j/BLL/5EVs1us0HCeO9Dab7//EFJ4h186Jji8bfp//AZIJgJ2 GR2T0bvBR7WhMcWWljWGHw+0JMX+pi4kF3dhwGZybrlehU0w/gGcQm44kQEfb9Y6MdUx9 ii0jMaATv9SX6pjM4eDoSE2z2KGcEPa6jWCJrrCUtlNev92x9bkcSIf9J0j3/DPI8H6Ta 2eEIQGxM7fn0oI9IZvf+8RZ6AttLlUVMtJTr074i0gg2xvKccecOs76tWfLDQVv70CA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793145905; 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:MIME-Version:Content-Transfer-Encoding; bh=ah4gzw5OiHfYj57lOarZOXCU6RfDPS1zY+caCBQQGnA=; b=f//sSc4Z+Mcp98fKxEdmBWU2EpyMFyCFFcunaLSAlJE6xuJkOOLGnxFOHz80sBRcQSRv EKLNA3aAQyTSGCZPFXyROej66av1oRcclL3V/c9ycDlhNQKc+SZoKg0U2eBAwZxJWdh1S yTbOHvZ82y991r0dwbIOAapAUIiqOHRV/gFbpyllQqrdAAtHjNOwV6Vu4WfBN1V097tm9 1qQvxhmdjjXuQ7WBP6P7VYC6ciaAjC2gT0aA+6YaOfEWSnRU5Iejd5i+C8LwiE7rQLAEG rtxFao7zqaB06AWoPMeARoXsPE5rrQnrI7ifUvOPlRvVOVhoGabcEZlbu5wsCRznwmg== 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=TwGC2TzJ; arc=none smtp.remote-ip=91.218.175.13 Received: from mta0.migadu.com (out-13.mta0.migadu.com [91.218.175.13]) (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 4FC83606A31E for ; Wed, 28 Oct 2026 00:05:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 4FC83606A31E 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=TwGC2TzJ X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=psa7zx1Xe6yGIkcQOpjXlYI3zz/TQ9U0VkcLjx2WVoI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793145902; v=1; x=1793750702; b=TwGC2TzJdfwSNEmrRrDbN7E/YKUglZXDJk93kXtg8RHIHAsB5m6nJKHM5O2fwADzREZrrYNI EoFK+ZeF5WsLxVfkw1cRmFH0xwWGSJoPMOgfP1kzmrkGczu+YNoLm68CPpmEy8THreaVszS5E2e AckDE179ZO0DtezqI8nkMtZI= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 84ceb785ec4e11b7; Wed, 28 Oct 2026 00:05:02 +0000 X-Mizu-Trace-ID: 84ceb785ec4e11b7 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 v1 6/7] selftests/bpf: cast explicitly in the arena subprog and callback faults Date: Tue, 27 Oct 2026 17:04:10 -0700 Message-ID: <20261028000411.4010967-7-vineet.gupta@linux.dev> X-Mailer: git-send-email 2.56.0 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 Four stream tests fail with BPF_GCC: test_stream_arena_fault_address:FAIL:stream__open_and_load unexpected error: -13 #479 stream_oversize:FAIL #480 stream_partial_read:FAIL #482 stream_syscall:FAIL 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. Fifteen results go FAIL -> OK -- every test that loads this object, not just the arena ones: stream_arena_fault_address stream_oversize stream_fd stream_fd/blocking stream_partial_read stream_fd/edge stream_fd/empty stream_success stream_fd/hup stream_fd/nmi_epoll stream_success/stream_arena_callback_fault stream_fd/open stream_fd/nonblock stream_success/stream_arena_subprog_fault stream_syscall and the five stream_arena_fault_address subtests become visible for the first time (read, write, xchg, cmpxchg and load_acquire faults). Signed-off-by: Vineet Gupta --- tools/testing/selftests/bpf/progs/stream.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c index 1ae015c4e6b4..dc56779cac06 100644 --- a/tools/testing/selftests/bpf/progs/stream.c +++ b/tools/testing/selftests/bpf/progs/stream.c @@ -5,7 +5,6 @@ #include #include "bpf_misc.h" #include "bpf_experimental.h" -#include struct arr_elem { struct bpf_res_spin_lock lock; @@ -381,9 +380,10 @@ 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; } @@ -404,9 +404,10 @@ 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