Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD73FC433F5 for ; Wed, 12 Jan 2022 14:04:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353926AbiALOEY (ORCPT ); Wed, 12 Jan 2022 09:04:24 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:42816 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353897AbiALOED (ORCPT ); Wed, 12 Jan 2022 09:04:03 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AFD2860ECE; Wed, 12 Jan 2022 14:04:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47834C36AEA; Wed, 12 Jan 2022 14:03:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1641996242; bh=b5cSC0Voo0MtqAVukvSA69tutmiwlNEMrP3tolpDRq4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fEfBpAL0fs4u2zH1JVob4yS11dT6illLKu2wHy3jXU1zrLD8vD4nZgcN3P/1Bhh3Q FO5EWszPAKnTczfrFwS2b2ub0qUQM3aGfT4zlwVVtFBKOFHAAkG7WmYKe2a8HIaK6I 3qs0SOgy97EGIDxar/VJep/NmJ32PKacy/DWH0q56DApgqCBv+zhAiCiO9m281jc98 WacrJGa+MxUxvnXKEYYMfrhrdRjOHrpAVDHEQfSSX69eyMLs9ye8ahhiq0nPvDscjg l6j527jqSRUG3cW61GRRqG6k/N2Os9MzYBUxr6BR0ItmYCUWJp+qpFspyal7eLzQVK aacdNj3WOG4Qw== From: Masami Hiramatsu To: Jiri Olsa , Alexei Starovoitov Cc: Daniel Borkmann , Andrii Nakryiko , Masami Hiramatsu , netdev@vger.kernel.org, bpf@vger.kernel.org, lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Steven Rostedt , "Naveen N . Rao" , Anil S Keshavamurthy , "David S . Miller" Subject: [RFC PATCH v2 6/8] fprobe: Add sample program for fprobe Date: Wed, 12 Jan 2022 23:03:56 +0900 Message-Id: <164199623581.1247129.9124741655034911016.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <164199616622.1247129.783024987490980883.stgit@devnote2> References: <164199616622.1247129.783024987490980883.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a sample program for the fprobe. Signed-off-by: Masami Hiramatsu --- Changes in v2: - Fix infinit loop for multiple symbols. - Fix memory leaks for copied string and entry array. - Update for new fprobe APIs. - Fix style issues. --- samples/Kconfig | 7 +++ samples/Makefile | 1 samples/fprobe/Makefile | 3 + samples/fprobe/fprobe_example.c | 103 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 114 insertions(+) create mode 100644 samples/fprobe/Makefile create mode 100644 samples/fprobe/fprobe_example.c diff --git a/samples/Kconfig b/samples/Kconfig index 43d2e9aa557f..e010c2c1256c 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -73,6 +73,13 @@ config SAMPLE_HW_BREAKPOINT help This builds kernel hardware breakpoint example modules. +config SAMPLE_FPROBE + tristate "Build fprobe examples -- loadable modules only" + depends on FPROBE && m + help + This builds a fprobe example module. This module has an option 'symbol'. + You can specify a probed symbol or symbols separated with ','. + config SAMPLE_KFIFO tristate "Build kfifo examples -- loadable modules only" depends on m diff --git a/samples/Makefile b/samples/Makefile index 4bcd6b93bffa..4f73fe7aa473 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -32,3 +32,4 @@ obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/ subdir-$(CONFIG_SAMPLE_WATCHDOG) += watchdog subdir-$(CONFIG_SAMPLE_WATCH_QUEUE) += watch_queue obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak/ +obj-$(CONFIG_SAMPLE_FPROBE) += fprobe/ diff --git a/samples/fprobe/Makefile b/samples/fprobe/Makefile new file mode 100644 index 000000000000..ecccbfa6e99b --- /dev/null +++ b/samples/fprobe/Makefile @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0-only + +obj-$(CONFIG_SAMPLE_FPROBE) += fprobe_example.o diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c new file mode 100644 index 000000000000..c28320537f98 --- /dev/null +++ b/samples/fprobe/fprobe_example.c @@ -0,0 +1,103 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Here's a sample kernel module showing the use of fprobe to dump a + * stack trace and selected registers when kernel_clone() is called. + * + * For more information on theory of operation of kprobes, see + * Documentation/trace/kprobes.rst + * + * You will see the trace data in /var/log/messages and on the console + * whenever kernel_clone() is invoked to create a new process. + */ + +#define pr_fmt(fmt) "%s: " fmt, __func__ + +#include +#include +#include +#include + +#define MAX_SYMBOL_LEN 4096 +struct fprobe sample_probe; +static char symbol[MAX_SYMBOL_LEN] = "kernel_clone"; +module_param_string(symbol, symbol, sizeof(symbol), 0644); + +static void sample_entry_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs) +{ + pr_info("Enter <%pS> ip = 0x%p\n", (void *)ip, (void *)ip); +} + +static void sample_exit_handler(struct fprobe *fp, unsigned long ip, struct pt_regs *regs) +{ + unsigned long rip = instruction_pointer(regs); + + pr_info("Return from <%pS> ip = 0x%p to rip = 0x%p (%pS)\n", + (void *)ip, (void *)ip, (void *)rip, (void *)rip); +} + +static char *symbuf; + +static int __init fprobe_init(void) +{ + const char **syms; + char *p; + int ret, count, i; + + sample_probe.entry_handler = sample_entry_handler; + sample_probe.exit_handler = sample_exit_handler; + + if (strchr(symbol, ',')) { + symbuf = kstrdup(symbol, GFP_KERNEL); + if (!symbuf) + return -ENOMEM; + p = symbuf; + count = 1; + while ((p = strchr(++p, ',')) != NULL) + count++; + } else { + count = 1; + symbuf = symbol; + } + pr_info("%d symbols found\n", count); + + syms = kcalloc(count, sizeof(char *), GFP_KERNEL); + if (!syms) { + ret = -ENOMEM; + goto error; + } + + p = symbuf; + for (i = 0; i < count; i++) + syms[i] = strsep(&p, ","); + + sample_probe.syms = syms; + sample_probe.nentry = count; + + ret = register_fprobe(&sample_probe); + if (ret < 0) { + pr_err("register_fprobe failed, returned %d\n", ret); + goto error; + } + pr_info("Planted fprobe at %s\n", symbol); + return 0; + +error: + if (symbuf != symbol) + kfree(symbuf); + return ret; +} + +static void __exit fprobe_exit(void) +{ + unregister_fprobe(&sample_probe); + + kfree(sample_probe.syms); + if (symbuf != symbol) + kfree(symbuf); + + pr_info("fprobe at %s unregistered\n", symbol); +} + +module_init(fprobe_init) +module_exit(fprobe_exit) +MODULE_LICENSE("GPL");