From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F31C419EEC2; Tue, 10 Feb 2026 13:36:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770730619; cv=none; b=N/j/bx3EgyHFaXFDOynoqdVS7zH+v+N7DS9rkTAt8hhoX/3qwwqF99eAoEIk0QNX5R4/SFfV/pCos1Q9InBy6MBs9RbID/19HsnXCFd11agBljHmQ5zlt6gnj/ydy6io3QZBx3y01w6+yiNdx05HQVWqdGGyS/IQYogVyD6/Iak= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770730619; c=relaxed/simple; bh=GOmRG864vY6D1kESbwlYap6WaTBduydOxPqdZeAjT0E=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=b/rx3mOAHlkyQrGSO5AOYG8iQckSHmEaQfSasQstAHiKFk37VA7YyZw2t6guy1qQVpFCn2EUawNglpIV8Es+sMpacK5QD9OcE2lje7m7nSHpGTD/Kd83SRW2r8wmjmIbc2Ja8XocrtSeFdD4ydOMkfW78Bpwz2u9MPQh8GBZPxs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kg2ktQKz; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kg2ktQKz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC6F7C116C6; Tue, 10 Feb 2026 13:36:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770730618; bh=GOmRG864vY6D1kESbwlYap6WaTBduydOxPqdZeAjT0E=; h=From:To:Cc:Subject:Date:From; b=kg2ktQKz46NlVdh6c9xC28x1MGfPXrueSd/nKViP1SVfld23AytZL6hT/N1kYEYvv +rdLk+PSE92FpkQIUlcFXZ51nONGyxSnuv9H+1cTl87OlfpThwiiu6lJb0NM+eWizk 2Q42di9odcL6s2j/fAmEctCMyQgk/XO71SKRXOJ88aR/uiwN+Ffs+WIiWhX8Rz7+Uv 606XYl2LsBiUxXDyMLkBrwKdbGcj6OhbqE2tOCM5CdYMUGcb3V2Zk9y/uSS18Bfd9T UEGt46JvNPEouM6NE/AySds0WzCUmB39E87XAMkdLk+/2umMP5o9DZlXHn14vkft8F 3v+wfnFKIAuEw== From: Jiri Olsa To: Andrii Nakryiko Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Song Liu , Yonghong Song , John Fastabend Subject: [PATCHv2 bpf-next 0/5] libbpf: Make optimized uprobes backward compatible Date: Tue, 10 Feb 2026 14:36:44 +0100 Message-ID: <20260210133649.524292-1-jolsa@kernel.org> 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: 8bit hi, we can currently optimize uprobes on top of nop5 instructions, so application can define USDT_NOP to nop5 and use USDT macro to define optimized usdt probes. This works fine on new kernels, but could have performance penalty on older kernels, that do not have the support to optimize and to emulate nop5 instruction. This patchset adds support to workaround the performance penalty on older kernels that do not support uprobe optimization, please see detailed description in patch 2. v1: https://lore.kernel.org/bpf/20251117083551.517393-1-jolsa@kernel.org/ v2 changes: - after more investigation we realized there are some versions of bpftrace and stap that does not work with solution suggested in version 1, so we decided to switch to following solution: - change USDT macro [1] emits nop,nop5 instructions combo by default - libbpf detects nop,nop5 instructions combo for USDT probe, if there is and if uprobe syscall is detected libbpf installs usdt probe on top of nop5 instruction to get it optimized - added usdt trigger benchmarks [Andrii] - several small fixes on uprobe syscall detection, tests and other places [Andrii] - true usdt.h source [1] updated [Andrii] - compile usdt_* objects unconditionally [Andrii] thanks, jirka [1] https://github.com/libbpf/usdt --- Jiri Olsa (5): libbpf: Add uprobe syscall feature detection libbpf: Add support to detect nop,nop5 instructions combo for usdt probe selftests/bpf: Emit nop,no5 instructions combo for x86_64 arch selftests/bpf: Add test for checking correct nop of optimized usdt selftests/bpf: Add usdt trigger bench tools/lib/bpf/features.c | 24 ++++++++++++++++++++++++ tools/lib/bpf/libbpf_internal.h | 2 ++ tools/lib/bpf/usdt.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++---- tools/testing/selftests/bpf/.gitignore | 2 ++ tools/testing/selftests/bpf/Makefile | 5 ++++- tools/testing/selftests/bpf/bench.c | 4 ++++ tools/testing/selftests/bpf/benchs/bench_trigger.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ tools/testing/selftests/bpf/benchs/run_bench_uprobes.sh | 2 +- tools/testing/selftests/bpf/prog_tests/usdt.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ tools/testing/selftests/bpf/progs/test_usdt.c | 9 +++++++++ tools/testing/selftests/bpf/progs/trigger_bench.c | 10 +++++++++- tools/testing/selftests/bpf/usdt.h | 2 ++ tools/testing/selftests/bpf/usdt_1.c | 18 ++++++++++++++++++ tools/testing/selftests/bpf/usdt_2.c | 16 ++++++++++++++++ 14 files changed, 287 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/bpf/usdt_1.c create mode 100644 tools/testing/selftests/bpf/usdt_2.c