From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-212.mta1.migadu.com [95.215.58.212]) (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 0F2C424336D for ; Fri, 16 Oct 2026 00:00:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.212 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792108858; cv=none; b=sUEUmP45mP8XCKy7B6EFQO7Rz8vshw/oYP2l17Pa1P1HC0huHDkoQHyBdh9g1q2nYc4mi3C3mJ+bJYe0+c764kJ+wvdUzkEJk1M2KvZh44V/sI4XTNyFPXaFQlgQ7mRXDxbVWcON9N/X/T3wGgmwaAA9vK8mVN5ZiAbK2dga1aA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792108858; c=relaxed/simple; bh=G2+IUDy8673k/kbHpMQY5gxm/ffx9qGTVTzH4ALcoWA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PeQIExVdi8UwEx93OEpL/2GOa85xx4U27+/6TQ6K2sXcRnLEDQJ08/tjQVZqHck9rAgPeSproeuJl7UR3+IPfptB29UWsP5zqUtpG3UCyjBj0OE/j+MjfbzH7/7vPqQUNIXOAItuAbim+a0c4gXqvQvPXcLniHkId2iVMWSA5Qw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=JeAioSIx; arc=none smtp.client-ip=95.215.58.212 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) header.d=linux.dev header.i=@linux.dev header.b="JeAioSIx" X-Envelope-To: bpf@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=G2+IUDy8673k/kbHpMQY5gxm/ffx9qGTVTzH4ALcoWA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792108854; v=1; x=1792713654; b=JeAioSIxCCf3l2zNaCh1a5ifWM9LsiOOUHZGY8A48Md18Sdx7L4KeRlAWkVx3NjKudcsRU5m BWI0A6q+vFmu5e2zMwJVaBGIjTP+p91uiuC2EWg7luRYml6QuLmIwB7sd8vNsXnUVD8er8UtmnJ muJRpwMARTrB+8Tkmw5JKhe0= X-Envelope-To: bpf@vger.kernel.org Received: by mta12.migadu.com with ESMTPS id 2df58a9dde94a004; Fri, 16 Oct 2026 00:00:54 +0000 X-Mizu-Trace-ID: 2df58a9dde94a004 X-Migadu-Flow: FLOW_OUT From: Ihor Solodrai To: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Kumar Kartikeya Dwivedi , Quentin Monnet Cc: bpf@vger.kernel.org, Alan Maguire , Cupertino Miranda , David Faust , Ian Rogers , "Jose E . Marchesi" , Vineet Gupta , Yonghong Song Subject: [PATCH bpf-next v1 5/8] bpftool: Emit __bpf_core_pso on verifier-rewritten context types Date: Thu, 15 Oct 2026 17:00:09 -0700 Message-ID: <20261016000012.2232059-6-ihor.solodrai@linux.dev> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261016000012.2232059-1-ihor.solodrai@linux.dev> References: <20261016000012.2232059-1-ihor.solodrai@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The verifier translates accesses to some UAPI context and socket types into accesses to kernel structures. These accesses require an unmodified base and an immediate field offset. Leaving preserve_access_index off does not stop the compiler from merging loads at different field offsets into one load through an adjusted pointer. The verifier rejects the resulting program. preserve_static_offset, available since Clang 18, preserves static field offsets in load and store instruction immediates. Apply it to the 13 types that need static offsets through __bpf_core_pso. Eduard introduced PSO in Clang and proposed annotating BPF context types in 2023 [1]. His v3 RFC [2] left pt_regs annotations in architecture headers unresolved. However since commit de6c7d99f898 ("bpf: Relax fixed offset check for PTR_TO_CTX"), program types without convert_ctx_access() accept fixed offsets from modified context pointers. pt_regs can now keep PAI, while PSO on bpf_perf_event_data covers its regs member. PSO creates no CO-RE relocations, so BPF_NO_PRESERVE_ACCESS_INDEX does not disable it. Clang 18 through 23 crash on __builtin_preserve_field_info over a PSO record, including bpf_core_field_*() and the CO-RE bitfield helpers. -D__bpf_core_pso= can disable PSO for affected programs. [1]: https://lore.kernel.org/bpf/20231208000531.19179-1-eddyz87@gmail.com/ [2]: https://lore.kernel.org/bpf/20231220133411.22978-1-eddyz87@gmail.com/ Signed-off-by: Ihor Solodrai --- tools/bpf/bpftool/btf.c | 16 ++++++++++++++-- .../bpf/bpftool_btf_dump_sorted.expected | 8 ++++++++ .../bpf/bpftool_btf_dump_unsorted.expected | 8 ++++++++ 3 files changed, 30 insertions(+), 2 deletions(-) diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 30f30314ec29..fff2ea0a5c7e 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -1203,12 +1203,17 @@ static int btf_c_annotate_records(struct btf *btf) for (i = 1; i < cnt; i++) { const struct btf_type *t = btf__type_by_id(btf, i); + const char *attr; if (!btf_is_composite(t)) continue; - if (test_bit(i, no_pai)) + if (!test_bit(i, no_pai)) + attr = "__bpf_core_pai"; + else if (btf_c_needs_static_offset(btf, t)) + attr = "__bpf_core_pso"; + else continue; - err = btf__add_decl_attr(btf, "__bpf_core_pai", i, -1); + err = btf__add_decl_attr(btf, attr, i, -1); if (err < 0) goto out; } @@ -1251,6 +1256,13 @@ static int dump_btf_c(const struct btf *btf, printf("#define __bpf_core_pai\n"); printf("#endif\n"); printf("#endif\n\n"); + printf("#ifndef __bpf_core_pso\n"); + printf("#if __has_attribute(preserve_static_offset)\n"); + printf("#define __bpf_core_pso preserve_static_offset\n"); + printf("#else\n"); + printf("#define __bpf_core_pso\n"); + printf("#endif\n"); + printf("#endif\n\n"); printf("#ifndef __ksym\n"); printf("#define __ksym __attribute__((section(\".ksyms\")))\n"); printf("#endif\n\n"); diff --git a/tools/testing/selftests/bpf/bpftool_btf_dump_sorted.expected b/tools/testing/selftests/bpf/bpftool_btf_dump_sorted.expected index 02c8fe8b4859..7da4df1da207 100644 --- a/tools/testing/selftests/bpf/bpftool_btf_dump_sorted.expected +++ b/tools/testing/selftests/bpf/bpftool_btf_dump_sorted.expected @@ -9,6 +9,14 @@ #endif #endif +#ifndef __bpf_core_pso +#if __has_attribute(preserve_static_offset) +#define __bpf_core_pso preserve_static_offset +#else +#define __bpf_core_pso +#endif +#endif + #ifndef __ksym #define __ksym __attribute__((section(".ksyms"))) #endif diff --git a/tools/testing/selftests/bpf/bpftool_btf_dump_unsorted.expected b/tools/testing/selftests/bpf/bpftool_btf_dump_unsorted.expected index 9b6589d2bda3..f082da51d630 100644 --- a/tools/testing/selftests/bpf/bpftool_btf_dump_unsorted.expected +++ b/tools/testing/selftests/bpf/bpftool_btf_dump_unsorted.expected @@ -9,6 +9,14 @@ #endif #endif +#ifndef __bpf_core_pso +#if __has_attribute(preserve_static_offset) +#define __bpf_core_pso preserve_static_offset +#else +#define __bpf_core_pso +#endif +#endif + #ifndef __ksym #define __ksym __attribute__((section(".ksyms"))) #endif -- 2.56.0