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From: Knut Omang <knut.omang@oracle.com>
To: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org,
	Shuah Khan <shuah@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Shreyans Devendra Doshi <0xinfosect0r@gmail.com>,
	Alan Maguire <alan.maguire@oracle.com>,
	Brendan Higgins <brendanhiggins@google.com>,
	Kevin Hilman <khilman@baylibre.com>,
	Hidenori Yamaji <hidenori.yamaji@sony.com>,
	Frank Rowand <frowand.list@gmail.com>,
	Timothy Bird <Tim.Bird@sony.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	"Theodore Ts'o" <tytso@mit.edu>, Daniel Vetter <daniel@ffwll.ch>,
	Stephen Boyd <sboyd@kernel.org>,
	Knut Omang <knut.omang@oracle.com>
Subject: [RFC 05/19] ktf: Implementation of ktf support for overriding function entry and return.
Date: Tue, 13 Aug 2019 08:09:20 +0200
Message-ID: <1fccfe3062ba6c7a2c8171df8e41975e28dae9ec.1565676440.git-series.knut.omang@oracle.com> (raw)
In-Reply-To: <cover.92d76bb4f6dcedc971d0b72a49e8e459a98bca54.1565676440.git-series.knut.omang@oracle.com>

From: Alan Maguire <alan.maguire@oracle.com>

This is a very powerful and yet simple way to verify or modify
behaviour of kernel calls. It uses the same technique as the error
injection framework in kernel/fail_function.c to to override function
entry and return. In addition to error injection, this is very useful
to for instance verify that a particular API actually ends up being
called, and in the right way, as an effect of a test.

ktf_override.c:  support for overriding function entry.
ktf_override.h:  Function override support interface for KTF.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Knut Omang <knut.omang@oracle.com>
---
 tools/testing/selftests/ktf/kernel/ktf_override.c | 45 ++++++++++++++++-
 tools/testing/selftests/ktf/kernel/ktf_override.h | 15 +++++-
 2 files changed, 60 insertions(+)
 create mode 100644 tools/testing/selftests/ktf/kernel/ktf_override.c
 create mode 100644 tools/testing/selftests/ktf/kernel/ktf_override.h

diff --git a/tools/testing/selftests/ktf/kernel/ktf_override.c b/tools/testing/selftests/ktf/kernel/ktf_override.c
new file mode 100644
index 0000000..7f046c8
--- /dev/null
+++ b/tools/testing/selftests/ktf/kernel/ktf_override.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ *    Author: Alan Maguire <alan.maguire@oracle.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ *
+ * ktf_override.c: support for overriding function entry.
+ */
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include "ktf.h"
+#include "ktf_override.h"
+
+asmlinkage void ktf_just_return_func(void);
+
+asm(
+	".type ktf_just_return_func, @function\n"
+	".globl ktf_just_return_func\n"
+	"ktf_just_return_func:\n"
+	"	ret\n"
+	".size ktf_just_return_func, .-ktf_just_return_func\n"
+);
+
+void ktf_post_handler(struct kprobe *kp, struct pt_regs *regs,
+		      unsigned long flags)
+{
+	/*
+	 * A dummy post handler is required to prohibit optimizing, because
+	 * jump optimization does not support execution path overriding.
+	 */
+}
+EXPORT_SYMBOL(ktf_post_handler);
+
+void ktf_override_function_with_return(struct pt_regs *regs)
+{
+	KTF_SET_INSTRUCTION_POINTER(regs, (unsigned long)&ktf_just_return_func);
+}
+EXPORT_SYMBOL(ktf_override_function_with_return);
+NOKPROBE_SYMBOL(ktf_override_function_with_return);
+
+int ktf_register_override(struct kprobe *kp)
+{
+	return register_kprobe(kp);
+}
+EXPORT_SYMBOL(ktf_register_override);
diff --git a/tools/testing/selftests/ktf/kernel/ktf_override.h b/tools/testing/selftests/ktf/kernel/ktf_override.h
new file mode 100644
index 0000000..8a9cf39
--- /dev/null
+++ b/tools/testing/selftests/ktf/kernel/ktf_override.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ *    Author: Alan Maguire <alan.maguire@oracle.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ *
+ * ktf_override.h: Function override support interface for KTF.
+ */
+#include <linux/kprobes.h>
+#include "ktf.h"
+
+void ktf_post_handler(struct kprobe *kp, struct pt_regs *regs,
+		      unsigned long flags);
+void ktf_override_function_with_return(struct pt_regs *regs);
+int ktf_register_override(struct kprobe *kp);
-- 
git-series 0.9.1

  parent reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-13  6:09 [RFC 00/19] Integration of Kernel Test Framework (KTF) into the kernel tree Knut Omang
2019-08-13  6:09 ` [RFC 01/19] kbuild: Fixes to rules for host-cshlib and host-cxxshlib Knut Omang
2019-08-13 14:01   ` Masahiro Yamada
2019-08-13 16:19     ` Knut Omang
2019-08-14  2:02       ` Masahiro Yamada
2019-08-14  5:50         ` Knut Omang
2019-08-14  5:52         ` Knut Omang
2019-08-14 12:52           ` Knut Omang
2019-08-21  1:47             ` Masahiro Yamada
2019-08-21  4:03               ` Knut Omang
2019-08-13  6:09 ` [RFC 02/19] ktf: Introduce the main part of the kernel side of ktf Knut Omang
2019-09-09  1:23   ` Brendan Higgins
2019-09-10  6:15     ` Knut Omang
2019-08-13  6:09 ` [RFC 03/19] ktf: Introduce a generic netlink protocol for test result communication Knut Omang
2019-09-09  1:28   ` Brendan Higgins
2019-09-10  6:30     ` Knut Omang
2019-08-13  6:09 ` [RFC 04/19] ktf: An implementation of a generic associative array container Knut Omang
2019-08-13  6:09 ` Knut Omang [this message]
2019-08-13  6:09 ` [RFC 06/19] ktf: A simple debugfs interface to test results Knut Omang
2019-08-13  8:21   ` Greg Kroah-Hartman
2019-08-14 17:17     ` Knut Omang
2019-08-15  8:49       ` Greg Kroah-Hartman
2019-08-15 10:35         ` Knut Omang
2019-08-15 10:52           ` Greg Kroah-Hartman
2019-08-13  6:09 ` [RFC 07/19] ktf: Simple coverage support Knut Omang
2019-08-13  6:09 ` [RFC 08/19] ktf: Configurable context support for network info setup Knut Omang
2019-08-13  6:09 ` [RFC 09/19] ktf: resolve: A helper utility to aid in exposing private kernel symbols to KTF tests Knut Omang
2019-08-13  6:09 ` [RFC 10/19] ktf: Add documentation for Kernel Test Framework (KTF) Knut Omang
2019-08-13  6:09 ` [RFC 11/19] ktf: Add a small test suite with a few tests to test KTF itself Knut Omang
2019-08-13  6:09 ` [RFC 12/19] ktf: Main part of user land library for executing tests Knut Omang
2019-08-13  6:09 ` [RFC 13/19] ktf: Integration logic for running ktf tests from googletest Knut Omang
2019-08-13  6:09 ` [RFC 14/19] ktf: Internal debugging facilities Knut Omang
2019-08-13  6:09 ` [RFC 15/19] ktf: Some simple examples Knut Omang
2019-08-13  6:09 ` [RFC 16/19] ktf: Some user applications to run tests Knut Omang
2019-08-13  6:09 ` [RFC 17/19] ktf: Toplevel ktf Makefile/makefile includes and scripts to run from kselftest Knut Omang
2019-08-13  6:09 ` [RFC 18/19] kselftests: Enable building ktf Knut Omang
2019-08-13  6:09 ` [RFC 19/19] Documentation/dev-tools: Add index entry for KTF documentation Knut Omang
2019-08-13  8:10 ` [RFC 00/19] Integration of Kernel Test Framework (KTF) into the kernel tree Brendan Higgins
2019-08-13  8:17 ` Brendan Higgins
2019-08-13 11:29   ` Knut Omang
2019-08-13 17:50     ` Brendan Higgins
2019-08-13  8:23 ` Greg Kroah-Hartman
2019-08-13  9:51   ` Knut Omang
2019-08-13 17:02     ` Brendan Higgins

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